JP6857864B2 - Friction resistance reduction method, structure with reduced friction resistance, and electrode forming method for friction resistance reduction - Google Patents

Description

The present invention relates to a method for reducing frictional resistance of an object for reducing frictional resistance due to a fluid, a structure for reducing frictional resistance, and a method for forming an electrode for reducing frictional resistance.

Among the resistances that work when a ship navigates, there are air lubrication method and microbubble method that generate bubbles in water as a method for reducing frictional resistance, which has a large influence.
For example, Patent Document 1 describes an anode-side conductive coating surface and a cathode-side conductive coating surface formed on the surface of the hull outer panel of the bow below the waterline at predetermined distances, and both coating surfaces. A device for reducing the frictional resistance of the hull by electrolyzing seawater to generate bubbles and causing the bubbles to flow backward is described.
Further, in Patent Document 2, a bubble water mixed fluid is ejected diagonally backward from the submerged surface in a boundary layer formed near the submerged surface of the hull, and the bubbles are more accurately compared to the case of a single bubble alone. Is described as a device for reducing friction by feeding the water into a desired bottom layer in the boundary layer.

Japanese Unexamined Patent Publication No. 9-48389 Japanese Unexamined Patent Publication No. 7-156859

Patent Document 1 electrolyzes seawater to generate oxygen and hydrogen, instead of the conventional technique of forming air bubbles by passing compressed air through a perforated plate and ejecting the air bubbles from a hole provided in the outer plate of the hull. It is generated and flows away from both coating surfaces as bubbles along the hull skin in the direction opposite to the direction of travel of the ship to reduce frictional resistance. Relationships are not considered.
Further, Patent Document 2 attempts to reduce the frictional resistance of the hull by sending a bubble-water mixed fluid into the boundary layer, but the range δ of the relative speed u equal to the navigation speed of the hull is within the range of the boundary layer. The relationship between the viscous bottom layer, the buffer area, and the air bubbles, which is the area near the surface of the hull in the boundary layer, is not considered.

Therefore, the present invention locally realizes a high void ratio or volume concentration of particles by directly acting on the viscous bottom layer and the buffer region, which are regions near the surface of the hull, among the turbulent boundary layers, and turbulence. It is an object of the present invention to provide a friction resistance reducing method for suppressing a flow and reducing the frictional resistance of an object (structure) such as a hull, a structure for reducing the frictional resistance, and an electrode forming method for reducing the frictional resistance. ..

In the method for reducing frictional resistance according to claim 1, an electrode is formed on the surface of an object for reducing frictional resistance due to a fluid, and a flow velocity detecting means for detecting the flow velocity of the fluid or a submerged state of the electrode is detected. The power applied to the electrode is controlled according to the detection result of the submerged state detecting means, and the particles and / or bubbles generated by the electrolysis action are made to act from the surface of the object which is the inner wall surface of the turbulent boundary layer. In order to reduce the frictional resistance due to the fluid of the object, the volume concentration of the particles generated by the electrolysis action in the viscous bottom layer of the turbulent boundary layer and the buffer region is 1.0E-8% or less and 1.0E-6% or more. And / or the void ratio of the bubble is 2% or less and 0.0001% or more .
According to the first aspect of the present invention, since the particles and / or bubbles are generated from the electrodes formed on the inner wall surface (surface of the object) of the turbulent boundary layer, the particles and / or the bubbles are generated at the turbulent boundary. It acts directly on the viscous bottom layer and buffer area, which is the area near the inner wall surface in the layer. Therefore, even if the amount of generated particles or bubbles is small, it is possible to locally realize a high volume concentration of particles or a void ratio of bubbles, suppress turbulence, and reduce frictional resistance due to the fluid of the object. Further, since the diffusion in the turbulent boundary layer is reduced by suppressing the turbulent flow, even a small amount of particles and / or bubbles flow while staying near the inner wall surface. Therefore, the effect of reducing frictional resistance is enhanced. Further, even when used in an environment where the pressure of the fluid is high, particles and / or bubbles can be generated from the inner wall surface of the turbulent boundary layer without requiring special pressurizing means. Further, since the frictional resistance of the object increases or decreases depending on the flow velocity of the fluid, the amount of particles and / or bubbles generated can be adjusted by controlling the electric power according to the flow velocity of the fluid or the submerged state of the electrode. The frictional resistance due to the fluid of the object can be effectively reduced. Further, it is possible to reduce the frictional resistance due to the fluid of the object while suppressing the amount of particles and / or bubbles generated by the electrolysis action.

In the frictional resistance reducing method corresponding to the second aspect, an electrode is formed on the surface of the object for reducing the frictional resistance due to the fluid, and the thickness of the turbulent boundary layer is set to the position from the front edge of the object and the fluid. The power applied to the electrode is controlled according to the thickness of the turbulent boundary layer, and the particles and / or bubbles generated by the electrolysis action are transferred to the inside of the turbulent boundary layer. In order to reduce the frictional resistance due to the fluid of the object by acting from the surface of the object which is the wall surface of the object, the volume concentration of the particles generated by the electrolysis action in the viscous bottom layer of the turbulent boundary layer and the buffer area is 1. It is characterized in that the void ratio of 0E-8% or less and 1.0E-6% or more and / or the bubble is 2% or less and 0.0001% or more.
According to the second aspect of the present invention, since the particles and / or bubbles are generated from the electrodes formed on the inner wall surface (surface of the object) of the turbulent boundary layer, the particles and / or the bubbles are generated at the turbulent boundary. It acts directly on the viscous bottom layer and buffer area, which is the area near the inner wall surface in the layer. Therefore, even if the amount of generated particles or bubbles is small, it is possible to locally realize a high volume concentration of particles or a void ratio of bubbles, suppress turbulence, and reduce frictional resistance due to the fluid of the object. Further, since the diffusion in the turbulent boundary layer is reduced by suppressing the turbulent flow, even a small amount of particles and / or bubbles flow while staying near the inner wall surface. Therefore, the effect of reducing frictional resistance is enhanced. Further, even when used in an environment where the pressure of the fluid is high, particles and / or bubbles can be generated from the inner wall surface of the turbulent boundary layer without requiring special pressurizing means. Further, by controlling the electric power according to the thickness of the turbulent boundary layer to adjust the amount of particles and / or bubbles generated, the frictional resistance due to the fluid of the object can be effectively reduced. Further, it is possible to reduce the frictional resistance due to the fluid of the object while suppressing the amount of particles and / or bubbles generated by the electrolysis action.

The present invention according to claim 3 is characterized in that the anode and the cathode are arranged so that the lines of electric force formed between the anode and the cathode of the electrode when power is applied intersect the streamlines of the fluid. To do.
According to the third aspect of the present invention, the electrodes can be installed parallel to the streamline of the fluid.

The present invention according to claim 4 is characterized in that the anode and the cathode are arranged so that the electric power line formed between the anode and the cathode of the electrode when power is applied is parallel to the streamline of the fluid. And.
According to the fourth aspect of the present invention, the electrodes can be installed perpendicular to the streamline of the fluid.

The present invention according to claim 5 is characterized in that a plurality of electrodes are formed on the surface of the object, and the entire portion of the object in contact with the fluid for reducing frictional resistance is covered with the plurality of electrodes.
According to the fifth aspect of the present invention, since the entire portion of the object in contact with the fluid can be flowed with a small amount of particles and / or bubbles while staying near the inner wall surface, the effect of reducing frictional resistance is enhanced. Can be done.

The present invention according to claim 6 is characterized in that a metal material that is ionized and eluted by applying electric power is used for the electrode.
According to the sixth aspect of the present invention, particles and bubbles can be generated to reduce the frictional resistance of the object due to the fluid.

The present invention according to claim 7 is characterized in that direct current is used as electric power.
According to the seventh aspect of the present invention, direct current can be applied to the electrodes to perform electrolysis to generate particles and / or bubbles. When direct current is used, for example, the electric power stored in the battery can be directly used, and the power supply device for supplying the electric power can be simplified.

The present invention according to claim 8 is characterized in that alternating current is used as electric power.
According to the eighth aspect of the present invention, since the anode and the cathode can be periodically exchanged for electrolysis, particles and / or bubbles can be generated from the anode and the cathode, for example, and the anode and the cathode can be generated. It is possible to reduce the consumption of the scale and the adhesion of the scale .

The present invention described in請Motomeko 9, characterized in that the fluid is water, sea water or an aqueous solution.
According to the ninth aspect of the present invention, the electrolysis action is promoted by the action of ions contained in water, seawater or an aqueous solution, and the frictional resistance of an object in contact with water, seawater or an aqueous solution due to water, seawater or an aqueous solution. Can be reduced.

The structure having reduced frictional resistance according to claim 10 is characterized in that the frictional resistance reducing method according to claim 9 is applied to a structure in contact with water, seawater or an aqueous solution as an object.
According to the tenth aspect of the present invention, the electrolysis action is promoted by the action of ions contained in water, seawater or an aqueous solution, and the frictional resistance of a structure in contact with water, seawater or an aqueous solution due to water, seawater or an aqueous solution. Can be effectively reduced.

The present invention according to claim 11 is characterized in that the structure is the hull of a ship.
According to the eleventh aspect of the present invention, the frictional resistance of the hull of a ship due to water, seawater or an aqueous solution can be reduced. It is also possible to locally reduce the frictional resistance by selecting a portion of the hull that has a large frictional resistance due to water, seawater or an aqueous solution.

The invention according to claim 12 is characterized in that the structure is a propeller of a ship.
According to the twelfth aspect of the present invention, the frictional resistance of a ship's propeller due to water, seawater or an aqueous solution can be reduced. It is also possible to locally reduce the frictional resistance by selecting a portion of the propeller having a large frictional resistance due to water, seawater or an aqueous solution.

The present invention according to claim 13 is characterized in that the structure is a pipe.
According to the thirteenth aspect of the present invention, the frictional resistance of the pipe due to water, seawater or an aqueous solution can be reduced. It is also possible to locally reduce the frictional resistance by selecting a portion of the pipe that has a large frictional resistance due to water, seawater or an aqueous solution.

The electrode forming method for reducing frictional resistance according to claim 14 is the electrode forming method used in the frictional resistance reducing method according to any one of claims 1 to 9 , wherein the electrode is formed. Was formed by coating, printing, or pasting on the surface of an object using a conductive material.
According to the 14th aspect of the present invention, an electrode can be formed on the surface of the object to reduce the frictional resistance of the object due to the fluid.

According to the frictional resistance reducing method of the present invention, particles and / or bubbles are generated from electrodes formed on the inner wall surface (surface of the object) of the turbulent boundary layer, so that the particles and / or bubbles are generated from the turbulent boundary layer. It acts directly on the viscous bottom layer and buffer area, which is the area near the inner wall surface. Therefore, even if the amount of generated particles or bubbles is small, it is possible to locally realize a high volume concentration of particles or a void ratio of bubbles, suppress turbulence, and reduce frictional resistance due to the fluid of the object. Further, since the diffusion in the turbulent boundary layer is reduced by suppressing the turbulent flow, even a small amount of particles and / or bubbles flow while staying near the inner wall surface. Therefore, the effect of reducing frictional resistance is enhanced. Further, even when used in an environment where the pressure of the fluid is high, particles and / or bubbles can be generated from the inner wall surface of the turbulent boundary layer without requiring special pressurizing means. Further, it is possible to reduce the frictional resistance due to the fluid of the object while suppressing the amount of particles and / or bubbles generated by the electrolysis action.

Further, when the anode and the cathode are arranged so that the electric power line formed between the anode and the cathode of the electrode when power is applied intersects the streamline of the fluid, the electrode becomes the streamline of the fluid. It can be installed parallel to the other.

Further, when the anode and the cathode are arranged so that the electric lines of force formed between the anode and the cathode of the electrode when power is applied are parallel to the streamline of the fluid, the electrode is the streamline of the fluid. Can be installed perpendicular to.

Further, when a plurality of electrodes are formed on the surface of the object to reduce the frictional resistance and the entire portion of the object in contact with the fluid is covered with the plurality of electrodes, the entire portion of the object in contact with the fluid is covered. Since a small amount of particles and / or air bubbles can flow while staying near the inner wall surface, the effect of reducing frictional resistance can be enhanced.

Further, when a metal material that is ionized and eluted by applying electric power is used for the electrode, particles and bubbles can be generated to reduce the frictional resistance due to the fluid of the object.

When direct current is used as electric power, direct current can be applied to the electrodes to perform electrolysis to generate particles and / or bubbles. When direct current is used, for example, the electric power stored in the battery can be directly used, and the power supply device for supplying the electric power can be simplified.

Further, when alternating current is used as electric power, the anode and the cathode can be periodically exchanged to perform electrolysis, so that particles and / or bubbles can be generated from the anode and the cathode, for example, and the anode and the cathode can be generated. It is possible to reduce the consumption of the scale and the adhesion of the scale.

Further, since the electric power is controlled according to the flow velocity of the fluid or the submerged state of the electrode, the frictional resistance of the object increases or decreases depending on the flow velocity of the fluid. By controlling the electric power to adjust the amount of particles and / or the amount of bubbles generated, the frictional resistance of the object due to the fluid can be effectively reduced.

Further, since the electric power is controlled according to the thickness of the turbulent boundary layer, it is effective to control the electric power according to the thickness of the turbulent boundary layer to adjust the amount of particles and / or bubbles generated. In addition, the frictional resistance due to the fluid of the object can be reduced .

Also, when the fluid is water, sea water or aqueous solution, water, promotes electrolytic action by the action of ions contained in sea water or an aqueous solution, of an object in contact water, seawater or an aqueous solution, water, seawater or The frictional resistance due to the aqueous solution can be reduced.

Further, when the frictional resistance reducing method is applied to a structure in contact with water, seawater or an aqueous solution as an object, the electrolysis action is promoted by the action of ions contained in water, seawater or an aqueous solution, and water, seawater or water or seawater or The frictional resistance of a structure in contact with an aqueous solution due to water, seawater or an aqueous solution can be effectively reduced.

Further, when the structure is the hull of a ship, the frictional resistance of the hull of the ship due to water, seawater or an aqueous solution can be reduced. It is also possible to locally reduce the frictional resistance by selecting a portion of the hull that has a large frictional resistance due to water, seawater or an aqueous solution.

Further, when the structure is a ship propeller, the frictional resistance of the ship propeller due to water, seawater or an aqueous solution can be reduced. It is also possible to locally reduce the frictional resistance by selecting a portion of the propeller having a large frictional resistance due to water, seawater or an aqueous solution.

Further, when the structure is a pipe, the frictional resistance of the pipe due to water, seawater or an aqueous solution can be reduced. It is also possible to locally reduce the frictional resistance by selecting a portion of the pipe that has a large frictional resistance due to water, seawater or an aqueous solution.

Further, when the electrode is formed by coating, printing, or pasting on the surface of the object using a conductive material, the electrode can be formed on the surface of the object to reduce the frictional resistance due to the fluid of the object. ..

Schematic configuration diagram showing a ship to which the frictional resistance reduction method according to the embodiment of the present invention is applied. Schematic diagram of electrodes used in the same frictional resistance reduction method Schematic configuration diagram showing a ship to which the frictional resistance reduction method according to another embodiment of the present invention is applied. Schematic diagram of electrodes used in the same frictional resistance reduction method Schematic configuration diagram showing a ship to which the frictional resistance reduction method according to still another embodiment of the present invention is applied. Schematic configuration diagram showing a ship to which the frictional resistance reduction method according to still another embodiment of the present invention is applied. Partial horizontal cross-sectional view of the hull 11 using the frictional resistance reduction method according to still another embodiment of the present invention. Schematic configuration diagram showing a propeller to which the frictional resistance reducing method according to still another embodiment of the present invention is applied. Schematic configuration diagram showing a pipe to which the frictional resistance reduction method according to still another embodiment of the present invention is applied. Overall view of the small high-speed flow path used in the experiment Configuration diagram of the electrodes used in the experiment Photograph of the formation of precipitates in the same experiment The figure which shows the height part on the downstream side of the anode of the electrode used in the experiment. Schematic diagram of the measurement unit used in the experiment Photograph taken during the measurement of the experiment Average velocity distribution map in the mainstream direction by the same experiment Turbulence intensity distribution map in the mainstream direction by the same experiment Data rate distribution map from the same experiment Average velocity distribution map in the mainstream direction by the same experiment Turbulence intensity distribution map in the mainstream direction by the same experiment Data rate distribution map from the same experiment

Hereinafter, a method for reducing frictional resistance, a structure for reducing frictional resistance, and a method for forming electrodes for reducing frictional resistance according to the embodiment of the present invention will be described.

FIG. 1 is a schematic configuration diagram showing a ship to which the frictional resistance reducing method according to the embodiment of the present invention is applied, and FIG. 2 is a schematic diagram of electrodes used in the frictional resistance reducing method.
The structure as an object for reducing the frictional resistance due to the fluid X is the hull 11 of the ship 10. Vessel 10 is navigating in the direction indicated by the white arrow in FIG. The fluid X is water, seawater or an aqueous solution. The hull 11, which is a structure, is in contact with the fluid X (water, seawater, or aqueous solution).
When the ship 10 navigates, a turbulent boundary layer is formed on a portion of the outer panel surface of the hull 11, which is a structure, that is submerged in water. The turbulent boundary layer has regions called a viscous bottom layer, a buffer region, and a law of the wall region in order from the side closest to the outer plate surface of the hull 11. The viscous bottom layer and the buffer region together are about several tens of μm to several hundreds of μm.
For example, the calculation results of the viscous bottom layer and buffer area calculated for an actual ship are as follows: Captain L = 300 m, ship speed 12 kt, about 270 μm (corresponding to large ocean-going vessels such as tankers), L = 300 m, 24 kt. It was about 150 μm (corresponding to a large high-speed ocean-going vessel such as a container ship), L = 70 m, 10 kt, and about 270 μm (small coastal cargo ship).

A plurality of electrodes 20 formed so that the longitudinal direction is horizontal are provided on the portion of the outer plate surface of the hull 11 that is in contact with the fluid X (the portion below the waterline Y). Each electrode 20 is composed of an anode 21 and a cathode 22. One end of the anode 21 and the cathode 22 is located on the bow 12 side, and the other end is located on the stern 13 side. As described above, the entire surface of the hull 11 in contact with the fluid X (the portion below the waterline Y) is covered with the plurality of electrodes 20. The anode 21 and the cathode 22 may be divided into a plurality of electrodes from the bow portion 12 side to the stern portion 13 side instead of one electrode each. Further, the electrode 20 can be formed only on the portion of the outer surface of the hull 11 having a large frictional resistance.
A power supply device 30 is connected to the electrode 20. Direct current is used as the electric power of the power supply device 30. When direct current is used, there is an advantage that the electric power stored in the battery can be directly used and the power supply device 30 can be simplified. The power supply of the power supply device 30 is controlled by the control device 40. It is also possible to use alternating current as the electric power of the power supply device 30, and in this case, the anode and the cathode can be periodically exchanged to perform electrolysis. When alternating current is used, particles and / or bubbles can be generated from the anode and the cathode, and consumption of the anode and the cathode and adhesion of scale can be reduced.

FIG. 2 is a schematic view of the electrode 20. The black arrow indicates the direction of fluid flow.
The anode 21 and the cathode 22 of the electrode 20 are arranged so that the electric lines of force F formed between the anode 21 and the cathode 22 when power is applied intersect the streamline Z of the fluid X.
For the electrode 20, a metal material that is ionized and eluted by applying electric power is used. For example, metal materials that generate particles include Ag (silver), Sn (tin), Zn (zinc), solder, and baby metal, and metal materials that generate oxygen and hydrogen include Ag, Sn, Zn, and solder. , Babit metal, etc., Fe (iron), Ni (nickel), Be (berylium), Pt (platinum), Co (cobalt), Ir (iridium), Au (gold), Pd (palladium), Cd ( Conductivity of cadmium), Ru (ruthenium), Cu (copper), In (indium), W (tungsten), Mo (molybdenum), Al (aluminum), Pb (lead), Rh (lodium), Cr (chromium), etc. There are synthetic metals, alloys such as brass, bronze and stainless steel, and conductive alloys such as aluminum alloys. Particles and bubbles can be generated by using such a metal material. In addition, you may generate only air bubbles by using the material which does not generate particles.
The electrodes 20 are formed by applying a conductive paint to the surface of the hull 11. By forming the electrode 20 by applying the conductive paint, it is possible to reduce the unevenness and prevent the electrode 20 itself from causing an increase in resistance. Instead of coating, it can be formed by printing, pasting, or embedding. Here, printing also includes formation using a 3D printer. It is also possible to use a conductive resin or carbon instead of the conductive paint.

When electric power is applied to the electrode 20 by the power supply device 30, the fluid X is electrolyzed, oxygen and particles are generated from the anode 21, and hydrogen is generated from the cathode 22.
Since the electrode 20 is formed on the outer surface of the hull 11 (the inner wall surface in the turbulent boundary layer), the generated particles, oxygen and hydrogen become bubbles, and the viscous bottom layer in the turbulent boundary layer. And acts directly on the buffer area. In this way, by allowing particles and bubbles generated by electrolysis to act from the surface of the hull 11 which is the inner wall surface of the turbulent boundary layer, a locally high volume concentration of particles or a void ratio of bubbles is realized. , Suppresses turbulence and reduces frictional resistance of the hull 11. Further, since the turbulent flow is suppressed, the diffusion of bubbles and particles in the turbulent boundary layer is reduced, and even a very small amount of bubbles or particles flow backward while staying near the inner wall surface. Therefore, a high resistance reduction effect can be obtained.
As described above, since the effect of reducing frictional resistance can be sufficiently obtained even with a small amount of bubbles or particles, it is generated by electrolysis in order to reduce the amount of particles and bubbles generated and the power consumption. It is preferable that the volume concentration of the particles is 1.0E-8% or less and 1.0E-6% or more, and the void ratio of the bubbles is 2% or less and 0.0001% or more. However, when the amount of particles and bubbles generated is more important, the volume concentration is preferably in the 1.0E-7% range, and the void ratio is preferably less than 2% and 0.001% or more.
As a result of calculating the volume concentration of the particles generated by the electrolysis action in the experiment described later, it was 2.55E-7% to 6.12E-7%.
The reason why the volume concentration of particles is numerically lower than the void ratio is that particles are expected to have an elongated band shape, and even if they are smaller in volume than spherical shapes in the case of bubbles, they are longer. , It is presumed that it is effective in suppressing turbulence.

The control device 40 controls the electric power of the power supply device 30 according to the flow velocity of the fluid X measured by the flow rate detecting means (flow velocity sensor or the like). Since the frictional resistance of the hull 11 increases or decreases depending on the flow velocity of the fluid X, the frictional resistance of the hull 11 can be efficiently increased by controlling the electric power according to the flow velocity of the fluid X to adjust the amount of particles and / or bubbles generated. Can be reduced. That is, the frictional resistance can be efficiently reduced by increasing the amount of particles and / or bubbles generated when the flow velocity is high and decreasing the amount of particles and / or bubbles generated when the flow velocity is slow.
Further, the control device 40 controls the electric power of the power supply device 30 according to the submerged state of the electrode 20 according to the draft and the posture of the hull 11. Since the frictional resistance of the hull 11 increases or decreases depending on the submerged state, the frictional resistance of the hull 11 can be efficiently adjusted by controlling the electric power according to the submerged state of the electrode 20 to adjust the amount of particles and / or bubbles generated. Can be reduced. In addition to the draft meter, inclinometer, and the like, the electrode 20 itself may be used to detect the submerged state. Further, in a state where a part of the electrode 20 is not soaked in water and is dry, no current flows even when electric power is applied, so the electric power is automatically controlled to reduce the amount of particles and / or bubbles generated. It is also possible to adjust.
The control device 40 may control the power of the power supply device 30 according to the thickness of the turbulent boundary layer. The thickness of the turbulent boundary layer is estimated by measuring the position from the front edge of the hull 11, the speed of the ship, and the water temperature, and using, for example, the drag coefficient formula and logarithmic velocity distribution formula of Karman-Schoenherr from the measured values. it can. Therefore, in this case, the calculation means (personal computer or the like) is obtained by the position detecting means for detecting the position of the hull 11 from the front edge, the ship speed measuring means for measuring the ship speed, and the water temperature measuring means for measuring the water temperature. The thickness of the turbulent boundary layer is calculated based on each value, and the control device 40 controls the electric power according to the calculated thickness of the turbulent boundary layer.

Next, a method for reducing frictional resistance, a structure for reducing frictional resistance, and a method for forming electrodes for reducing frictional resistance according to another embodiment of the present invention will be described with reference to FIGS. 3 and 4.
FIG. 3 is a schematic configuration diagram showing a ship to which the friction resistance reduction method according to the present embodiment is applied, and FIG. 4 is a schematic diagram of electrodes used in the friction resistance reduction method.
The present embodiment is different from the above-described embodiment in that a plurality of electrodes 120 formed so that the longitudinal direction is the vertical direction are provided. Other than that, the configuration is the same as that of the above embodiment. The same functional members as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.
Each electrode 120 is composed of an anode 121 and a cathode 122. One end of the anode 121 and the cathode 122 is located on the water line Y side, and the other end is located on the bottom side of the ship. As described above, the entire surface of the hull 11 in contact with the fluid X (the portion below the waterline Y) is covered with the plurality of electrodes 120. When the outer surface has a complicated shape and the local frictional resistance is different, when the reduction of frictional resistance due to bubbles is emphasized, the cathode 122 generates more bubbles, so the cathode 122 is used as the portion having the larger frictional resistance. Better to apply. Further, when the reduction of the frictional resistance by the particles is emphasized, it is better to apply the anode 121 to the portion having a large frictional resistance.

FIG. 4 is a schematic view of the electrode 120. The black arrow indicates the direction of fluid flow.
The anode 121 and the cathode 122 of the electrode 120 are arranged so that the electric lines of force F formed between the anode 121 and the cathode 122 when power is applied are parallel to the streamline Z of the fluid X.

When electric power is applied to the electrode 120 by the power supply device 30, the fluid X is electrolyzed, oxygen and particles are generated from the anode 121, and hydrogen is generated from the cathode 122.
Since the electrode 120 is formed on the outer surface of the hull 11 (the inner wall surface in the turbulent boundary layer), the generated oxygen and hydrogen become bubbles, and the viscous bottom layer and the buffer area in the turbulent boundary layer Acts directly on.

For the electrode 120, the same metal material as the electrode 20 of the above-described embodiment can be used. Further, the electrode 120 can be formed by coating, printing, pasting, or embedding in the same manner as the electrode 20 of the above-described embodiment.

Next, a method for reducing frictional resistance, a structure for reducing frictional resistance, and a method for forming electrodes for reducing frictional resistance according to still another embodiment of the present invention will be described with reference to FIG.
FIG. 5 is a schematic configuration diagram showing a ship to which the frictional resistance reduction method according to the present embodiment is applied.
This embodiment is different from the above-described embodiment in that a plurality of electrodes 220 formed in a staggered shape (mesh shape) are provided. Other than that, the configuration is the same as that of the above embodiment. The same functional members as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.
Each electrode 220 is composed of an anode 221 and a cathode 222. The electrode 220 is rectangular. The entire surface of the hull 11 in contact with the fluid X (the portion below the waterline Y) is covered with a plurality of electrodes 220.

When electric power is applied to the electrode 220 by the power supply device 30, the fluid X is electrolyzed, oxygen and particles are generated from the anode 221 and hydrogen is generated from the cathode 222.
Since the electrode 220 is formed on the outer surface of the hull 11 (the inner wall surface in the turbulent boundary layer), the generated oxygen and hydrogen become bubbles, and the viscous bottom layer and the buffer area in the turbulent boundary layer Acts directly on.

For the electrode 220, the same metal material as the electrodes 20 and 120 of the above-described embodiment can be used. Further, the electrode 220 can be formed by coating, printing, pasting, or embedding in the same manner as the electrodes 20 and 120 of the above-described embodiment.

Next, a method for reducing frictional resistance, a structure for reducing frictional resistance, and a method for forming electrodes for reducing frictional resistance according to still another embodiment of the present invention will be described with reference to FIG.
FIG. 6A is a schematic configuration diagram showing a ship to which the frictional resistance reduction method according to the present embodiment is applied, and FIGS. 6B and 6C are schematic views of electrodes used in the frictional resistance reduction method.
In the present embodiment, a plurality of electrodes 320 formed in a staggered shape (mesh shape) are provided, and the power supply device 130 connected to the electrodes 320 is individually controlled by the control device 140 to supply electric power to the electrodes 320. It differs from the above embodiment in that. Other than that, the configuration is the same as that of the above embodiment. The same functional members as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.
Each electrode 320 is rectangular. The entire surface of the hull 11 in contact with the fluid X (the portion below the waterline Y) is covered with a plurality of electrodes 320.
Various electrode patterns can be implemented by controlling the power supply to the electrodes 320 formed so as to cover the surface of the hull 11 below the waterline Y in a staggered pattern (mesh pattern). That is, by arbitrarily selecting the electrode 320 to be supplied with power, the apparent electrode shape as an aggregate of the plurality of electrodes 320 can be changed.

When electric power is applied to the electrode 320 by the power supply device 130, the fluid X is electrolyzed, oxygen and particles are generated from the anode, and hydrogen is generated from the cathode.
Since the electrode 320 is formed on the outer surface of the hull 11 (the inner wall surface in the turbulent boundary layer), the generated oxygen and hydrogen become bubbles, and the viscous bottom layer and the buffer area in the turbulent boundary layer Acts directly on.

For the electrode 320, the same metal material as the electrodes 20, 120, 220 of the above-described embodiment can be used. Further, the electrode 320 can be formed by coating, printing, pasting, or embedding in the same manner as the electrodes 20, 120, and 220 of the above-described embodiment.
Further, as the shape of the electrode 320, a spiral electrode as shown in FIG. 6 (b) or a comb-shaped electrode as shown in FIG. 6 (c) may be used. In the spiral electrode shown in FIG. 6B and the comb electrode shown in FIG. 6C, the anode 321 and the cathode 322 can be distributed relatively uniformly, so that the generation of particles and bubbles can be relatively uniform.

Next, a method for reducing frictional resistance, a structure for reducing frictional resistance, and a method for forming electrodes for reducing frictional resistance according to still another embodiment of the present invention will be described with reference to FIG. 7.
FIG. 7 is a partial horizontal cross-sectional view of the hull 11 using the frictional resistance reducing method according to the present embodiment, and the electrodes are schematically shown in the figure. The alternate long and short dash line A is the center line of the hull.
This embodiment differs from the above embodiment in that the electrodes 20, 120, 220, and 320 described above are embedded in the surface layer of the surface 11a of the hull 11 to form the same surface as the surface 11a of the hull 11. Other than that, the configuration is the same as that of the above embodiment. The same functional members as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.
Since the electrodes 20, 120, 220, and 320 are formed on the same surface as the surface 11a of the hull 11, the surface 11a of the hull 11 has irregularities even if the electrodes 20, 120, 220, and 320 are formed. Absent. Therefore, by forming the electrodes 20, 120, 220, and 320 on the surface 11a of the hull 11, it is possible to further prevent the electrodes 20, 120, 220, and 320 themselves from causing an increase in resistance. The electrodes 20, 120, 220, and 320 may be embedded in the material constituting the hull 11, or the anodes 21, 121, 221 and 321 and the cathodes 22, 122, 222, and 222 may be filled with an insulating material on the same surface. It may be configured as.
Further, the electrodes 20, 120, 220 and 320 may be formed so as to project from the surface of the hull 11 below the viscous bottom layer of the turbulent boundary layer. In this case, even if the electrodes 20, 120, 220, and 320 protrude from the hull 11, there is substantially no effect on the increase in frictional resistance, so that the electrodes 20, 120, 220, and 320 themselves cause the increase in resistance. It is possible to further prevent it from happening.

Next, a method for reducing frictional resistance, a structure for reducing frictional resistance, and a method for forming electrodes for reducing frictional resistance according to still another embodiment of the present invention will be described with reference to FIG.
FIG. 8 is a schematic configuration diagram showing a propeller to which the frictional resistance reducing method according to the present embodiment is applied.
In this embodiment, a plurality of electrodes 420 formed in a staggered shape (mesh shape) are provided on the surface of the propeller 50. Other than that, the configuration is the same as that of the above embodiment. The same functional members as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.
Each electrode 420 is rectangular and is composed of an anode 421 and a cathode 422. The surface of the propeller 50 is covered with a plurality of electrodes 420.

When electric power is applied to the electrodes 420 by the power supply devices 30 and 130, the fluid X is electrolyzed, oxygen and particles are generated from the anode 421, and hydrogen is generated from the cathode 422.
Since the electrode 420 is formed on the surface of the propeller 50 (the inner wall surface in the turbulent boundary layer), the generated oxygen and hydrogen become bubbles and directly enter the viscous bottom layer and the buffer region in the turbulent boundary layer. It works.

For the electrode 420, the same metal material as the electrodes 20, 120, 220, 320 of the above-described embodiment can be used. Further, the electrode 420 can be formed by coating, printing, sticking, or embedding in the same manner as the electrodes 20, 120, 220, and 320 of the above-described embodiment.
The electrode 420 may be selectively provided in a portion of the propeller 50 where the frictional resistance is particularly large.

Next, a method for reducing frictional resistance, a structure for reducing frictional resistance, and a method for forming electrodes for reducing frictional resistance according to still another embodiment of the present invention will be described with reference to FIG.
FIG. 9 is a schematic configuration diagram showing a pipe to which the frictional resistance reducing method according to the present embodiment is applied.
In this embodiment, a plurality of electrodes 520 formed in a staggered shape (mesh shape) are formed on the inner surface of the pipe 60. Other than that, the configuration is the same as that of the above embodiment. The same functional members as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.
Each electrode 520 is rectangular and is composed of an anode 521 and a cathode 522. The inner surface of the pipe 60 is covered with a plurality of electrodes 520.

When electric power is applied to the electrodes 520 by the power supply devices 30 and 130, the fluid X is electrolyzed, oxygen and particles are generated from the anode 521, and hydrogen is generated from the cathode 522.
Since the electrode 520 is formed on the inner surface of the pipe 60 (the inner wall surface in the turbulent boundary layer), the generated oxygen and hydrogen become bubbles in the viscous bottom layer and the buffer area in the turbulent boundary layer. It acts directly. In the case of the pipe 60, an aqueous solution in which various substances are mixed with water such as antifreeze or sewage is often handled.

As the electrode 520, the same metal material as the electrodes 20, 120, 220, 320, 420 of the above-described embodiment can be used. Further, the electrode 520 can be formed by coating, printing, pasting, or embedding in the same manner as the electrodes 20, 120, 220, 320, and 420 of the above-described embodiment.
The electrode 520 may be selectively provided in a portion of the pipe 60 in which frictional resistance becomes large, such as a bent portion, a branch portion, a sudden contraction portion, and a sudden expansion portion. In addition, piping materials such as elbows, bends, cheese, and reducers shall also be included in the piping.

(Experiment)
The experimental results relating to the present invention will be described below.
FIG. 10 is an overall view of the small high-speed flow path used in the experiment. This device realizes a two-dimensional flow (flow between parallel plates) in the test section by driving the test fluid with a pump and performing rectification in the expansion / contraction section. The test section is made of transparent acrylic and has a rectangular cross section (channel). The main dimensions are shown in Table 1. In the test section, the flow becomes a fully developed turbulent flow when the flow velocity increases due to its cross-sectional shape. In addition, there are a total of 5 measurement windows at intervals of 500 mm in the mainstream direction at the top of the test unit, and it is possible to install a measurement lid with a shear force meter attached.

In this experiment, in order to improve the data rate near the wall surface, a method was used in which the insoluble precipitate generated during electrolysis by the electrolytic precipitation method was eluted directly from the wall surface and supplied as a tracer.
The electrolytic precipitation method is a visualization method using an insoluble precipitate generated from an anode when electrolyzing water as a tracer. When metals such as tin, zinc, solder, and babbitt are used as anodes, it is possible to generate clouds of white fine particles without generating oxygen (Koji Ishii: Summary of Flow Visualization Technology, Kyushu University Applied Mechanics Research) Technical Report, No. 8, 2007, pp.142-166.).
An electrode for the electrolytic precipitation method was attached to the measuring lid. FIG. 11 shows the measurement surface side of the measurement lid constructed. The anode was installed so as to be the center in the width direction of the test part, and the cathode was installed on the opposite side where the probe was installed so as not to interfere with the laser beam of the laser Doppler Velocimetry (LDV).
FIG. 12 shows how a precipitate is generated in a flow of several cm / s.

The electrodes were manufactured by applying a conductive silver paint in order to elute the precipitate from the wall surface and to make the construction surface as smooth as possible so as not to disturb the flow. The height distribution on the downstream side of the manufactured anode is shown in FIG. The height of the electrode surface with respect to the construction surface is about 50 μm, but it can be seen that the height of the end is higher than that, especially the downstream end is about 200 μm. The raised edges are due to the masking tape at the time of application.

The laser Doppler velvet is a method of measuring the flow velocity of a fluid by measuring the Doppler frequency change of scattered light of fine particles passing through a measurement volume formed by crossing laser beams. It has features such as non-contact measurement, high spatial resolution and time resolution, and absolute measurement (Laser Measurement Handbook Editorial Committee: Laser Measurement Handbook, 1998, pp.159-161.). Here, Table 2 shows the LDV system installed in the small high-speed flow path. Two-dimensional measurement is possible with this system, but in this experiment, when measuring the vicinity of the wall surface, it was difficult to insert a laser beam that measures the flow velocity in the height direction into the measurement position, so the measurement was performed in one dimension. The probe was placed on the traverser and traversed in the height direction at a minimum interval of 0.01 mm.

Next, the experimental method will be described.
The measuring lid with the electrodes was installed in the third measuring window from the upstream. A schematic diagram of the measuring unit is shown in FIG. LDV measurement is performed at the center in the width direction, 3 mm downstream (Pos.1) of the downstream end of the anode, and L / 4 = 23 mm upstream position (Pos.2) from the downstream end, and the height from the upper surface y = 0 mm in the flow path. The flow velocity distribution in the mainstream direction up to the center of the direction y = 10 mm was measured. As shown in FIG. 10, when the downstream end of the condensing portion is x = 0 mm, Pos.1 is x = 1621 mm and x = 1596.5 mm. The state of measurement is shown in FIG.

Next, the measurement results will be described.
First, the measurement results at Pos.1 will be described. The measurement conditions are shown in Table 3. Pos.1-Flat is the case where the electrode is not installed, Pos.1-0.00A / m is the case where the electrode is installed but no current is flowing, Pos.1-0.23A / m, Pos.1- 0.40A / m and Pos.1-0.56A / m are cases where the voltage (Volt.) Is applied to 20, 30, and 40V, respectively. 0.00A / m, 0.23A / m, 0.40A / m, and 0.56A / m are the values obtained by dividing the applied current by the electrode length L = 86mm. Um (m / s) is the average flow velocity in the cross section, and for Pos.1-Flat and Pos.1-0.00A / m, the values obtained from the LDV measurement results, Pos.1-0.23A / m, Pos.1-0.40 At A / m and Pos.1-0.56A / m, the change in the average flow velocity distribution was large, so the same value as Pos.1-0.00A / m was used. T (deg.) Is the water temperature, and Rem is the dimensionless Reynolds number (Rem = Um (2δ) / ν, ν (m ² / s): kinematic viscosity coefficient) with Um and channel height 2δ. is there. Since the flow between parallel plates transitions from about Rem = 3000 to turbulent flow, it can be seen that the measurement conditions are completely developed turbulent flow. _{Reτ is the Reynolds number (Reτ = u τ} (δ) / ν) that is dimensionless with the wall friction velocity u _τ and the half height δ of the channel. The friction velocity u _τ (m / s) is Dean's equation (RB Dean: Reynolds number dependence of skin friction and other bulk flow variables in two-dimensional rectangular duct flow, ASME Trans. J. Fluids Eng, 100, 215, 1978). It was calculated from (c _f = 0.073 × Rem ^-0.25).

The average velocity distribution in the mainstream direction is shown in FIG. 16 (a) is a diagram showing the average velocity distribution in the mainstream direction, FIG. 16 (b) is a diagram in which a long dashed line indicating a decrease in the velocity gradient is additionally shown in FIG. 16 (a), and FIG. 16 (c) is a diagram. It is the figure which showed the part data excerpted from FIG. 16A in an easy-to-read manner. In each figure, the broken line is the DNS calculation result (K. Iwamoto, et al .: Fully Developed 2-D Channel Flow at Re_tau = 650, DNS Database of Turbulence and Heat Transfer, 2002 by Iwamoto et al. , Http://thtlab.jp/DNS/CH12__PG.WL10). LDV measurement was performed for 90 seconds (maximum 5000 samples) for each point. Looking at Pos.1-Flat, it can be seen that the viscous bottom layer, buffer region, and law of the wall region are well captured. Also, compared to DNS, the flow velocity tends to be smaller in the law of the wall region. Looking at Pos.1-0.00A / m, it is almost in agreement with the result of Pos.1-Flat, but it can be seen that the flow velocity decreases at ^{y + = 5 to 40.} Here, looking at FIG. 12, the height of the downstream end of the anode is about 200 μm, which corresponds to about ^{y + = 12 under these measurement conditions.} Since this value coincides with the position where the decrease in the flow velocity of Pos.1-0.00A / m is the largest, it is considered that this decrease in the flow velocity is due to the influence of the shape of the electrode. Looking at Pos.1-0.23A / m, Pos.1-0.40A / m, and Pos.1-0.56A / m, the flow velocity matches Pos.1-0.00A / m where ^{y + = 300 is larger.} It can be seen that the flow velocity drops significantly around ^{y + = 7 to 300.} In the ^{vicinity of y +} = 7 to 20, the decrease in flow velocity increases in the order of Pos.1-0.23A / m, Pos.1-0.40A / m, and Pos.1-0.56A / m. In the ^{vicinity of y +} = 40 to 100, the decrease in flow velocity increases in the order of Pos.1-0.56A / m, Pos.1-0.40A / m, and Pos.1-0.23A / m, and the current increases. Then, it can be seen that the decrease in flow velocity is large. In the ^{vicinity of y +} = 1 to 7, the flow velocity increases in the order of Pos.1-0.56A / m, Pos.1-0.40A / m, and Pos.1-0.23A / m.
As shown in FIG. 16B, at Pos.1-0.23A / m, Pos.1-0.40A / m, and Pos.1-0.56A / m, Pos.1-Flat or Pos.1-0.00 It can be seen that the velocity gradient is greatly reduced compared to A / m. Such a large change in the flow field means that the effect of reducing the frictional resistance is obtained.

The distribution of turbulent intensity (standard deviation of velocity fluctuation, rms value) in the mainstream direction is shown in FIG. It can be seen that Pos.1-Flat has a good match between DNS, peak position, peak value, and ^{the tendency after y + = 10.} It is considered that the large variation between y ⁺ = 1 to 10 is due to the low data rate near the wall surface and the small number of samples acquired. Looking at Pos.1-0.00A / m, it is almost in agreement with the result of Pos.1-Flat, but it is smaller than Pos.1-Flat near ^{y + = 10 to 30.} Looking at Pos.1-0.23A / m, Pos.1-0.40A / m, and Pos.1-0.56A / m, ^{where y +} = 300 is larger, it matches Pos.1-0.00A / m. However, it can be seen that other than that, the value is large as a whole. It can also be seen that the peak position is around y ⁺ = 30, which is outside of Pos.1-0.00A / m. In the ^{vicinity of y +} = 10 to 30, the turbulent flow intensity increases in the order of Pos.1-0.23A / m, Pos.1-0.40A / m, and Pos.1-0.56A / m, which is the average flow velocity. This is consistent with the decreasing trend of flow velocity in this range of distribution.

The distribution of data rates is shown in FIG. It can be seen that the data rate improves as the current increases from ^{y + = 1 to 100.} It can also be seen that there is no significant difference in the data rate where ^{y + = 100 is greater.}

Although the data rate improved in the measurement at Pos.1, the flow field changed significantly. It is considered that this is because oxygen bubbles were generated together with the precipitate in the current passed in this measurement. The tendency that the average velocity decreases and the peak of the turbulent flow intensity moves away from the wall is the same measurement result in the turbulent flow measurement of the microbubble flow (Kitagawa Quartz et al .: Microbubble flow turbulence by the PTV / LIF method). Flow modulation measurement, National Maritime Research Institute 4th Research Presentation Proceedings, 2003) has been obtained.
Therefore, in order to prevent the generation of oxygen, a smaller current was used, and in order to mix the precipitate directly into the measurement volume, measurement was performed at Pos.2, which is directly under the electrode. The experimental conditions are shown in Table 4. Pos.2-0.00A / m is the case where no current is flowing, and Pos.2-0.02A / m is the case where a voltage of 3V, which is about 1/10 of the measurement at Pos.1, is applied. The average flow velocity Um in the cross section was calculated from the measured value at Pos.2-0.00A / m, and the same value was used at Pos.2-0.02A / m.

The average velocity distribution in the mainstream direction is shown in FIG. Since the data rate of LDV measurement was lower overall than that of Pos.1, each point was measured for 180 seconds (maximum 5000 samples). In Pos.2, the electrode surface is y = 0 mm. Looking at Pos.2-0.00A / m, it matches well with Pos.1-Flat, and unlike the shape of the electrode end, the unevenness on the electrode surface does not significantly affect the average flow velocity distribution. Understand. Looking at Pos.2-0.02A / m ^{, the flow velocity is small at y +} = 3 to 20, but the amount of change and the range of change are both smaller than those measured at Pos.1. There is.

The turbulent intensity distribution in the mainstream direction is shown in FIG. Looking at Pos.2-0.00A / m, it matches well with Pos.1-Flat as well as the average flow velocity distribution, and unlike the shape of the electrode end, the unevenness on the electrode surface also affects the turbulent intensity distribution. It can be seen that it does not have a large effect. Looking at Pos.2-0.02A / m, the turbulent flow intensity decreases at ^{y + = 3 to 20.} This is consistent with the range in which the average flow velocity distribution is changing. Also, as with the average flow velocity distribution, the amount of change and the range of change are both smaller than those measured at Pos.1.

The distribution of data rates from y ⁺ = 0 to 20 is shown in FIG. From this, it can be seen that the data rate is improved by about 1.5 to 3 times at Pos.2-0.02A / m. Similar to Pos.1, the range where the data rate changed coincided with the range where the flow field changed, and there was no significant difference in the data rate after ^{y + = 20.}

The frictional resistance reducing method, the structure with reduced frictional resistance, and the electrode forming method for reducing frictional resistance of the present invention include objects and structures (ship hulls, ship propellers, etc.) that are subject to frictional resistance of fluids including water. It can be applied to piping, etc.).

11 Hull (object, structure)
20, 120, 220, 320, 420, 520 Electrodes 21, 121, 221, 321, 421, 521 Anodes 22, 122, 222, 322, 422, 522 Cathodes 30, 130 Power supply devices 40, 140 Control devices 50 Propellers (target) Things, structures)
60 Piping (object, structure)
F Line of electric force X Fluid Z Streamline

Claims (14)

An electrode is formed on the surface of an object for reducing frictional resistance due to a fluid, and the submerged state detecting means for detecting the flow velocity of the fluid or the submerged state detecting means for detecting the submerged state of the electrode is described. By controlling the power applied to the electrodes and allowing particles and / or bubbles generated by the electrolysis action to act from the surface of the object, which is the inner wall surface of the turbulent boundary layer, the fluid of the object causes it. Upon reducing the frictional resistance, before Kiranryu viscosity bottom layer of the boundary layer and below 1.0E-8% the volume concentration of the particles generated by the electrolytic action at the buffer area 1.0E-6% or more and / or A method for reducing frictional resistance, wherein the void ratio of the bubbles is 2% or less and 0.0001% or more. An electrode is formed on the surface of the object to reduce frictional resistance due to the fluid, and the thickness of the turbulent boundary layer is calculated based on the position of the object from the front edge, the velocity of the fluid, and the temperature of the fluid. Then, the power applied to the electrode is controlled according to the thickness of the turbulent boundary layer, and particles and / or bubbles generated by the electrolysis action are transferred to the object which is the inner wall surface of the turbulent boundary layer. by acting from the surface, when reducing the frictional resistance due to the fluid of the object, the volume concentration of the particles generated by the electrolytic action in the viscous bottom layer and a buffer zone before Kiranryu boundary layer 1. A method for reducing frictional resistance, characterized in that the void ratio of 0E-8% or less and 1.0E-6% or more and / or the bubble is 2% or less and 0.0001% or more. The claim is characterized in that the anode and the cathode are arranged so that an electric power line formed between the anode and the cathode of the electrode when the electric power is applied intersects the streamline of the fluid. 1 or the method for reducing frictional resistance according to claim 2. The claim is characterized in that the anode and the cathode are arranged so that the electric power line formed between the anode and the cathode of the electrode when the electric power is applied is parallel to the streamline of the fluid. The method for reducing frictional resistance according to claim 1 or 2. The first aspect of the present invention, wherein a plurality of the electrodes are formed on the surface of the object to reduce frictional resistance, and the entire portion of the object in contact with the fluid is covered with the plurality of electrodes. The method for reducing frictional resistance according to claim 1. The frictional resistance reducing method according to claim 1, wherein a metal material that is ionized and eluted by applying the electric power is used for the electrode. The method for reducing frictional resistance according to claim 1, wherein direct current is used as the electric power. The method for reducing frictional resistance according to claim 1, wherein alternating current is used as the electric power. Frictional resistance reducing method according to one of claims 1 to 8, wherein said fluid is water, sea water or an aqueous solution. A structure having reduced frictional resistance, wherein the method for reducing frictional resistance according to claim 9 is applied to a structure in contact with water, seawater or an aqueous solution as the object. The structure with reduced frictional resistance according to claim 10 , wherein the structure is a hull of a ship. The structure with reduced frictional resistance according to claim 10 , wherein the structure is a propeller of a ship. The structure with reduced frictional resistance according to claim 10 , wherein the structure is a pipe. The method for forming the electrode used in the frictional resistance reducing method according to any one of claims 1 to 9, wherein the electrode is applied to the surface of the object using a conductive material. An electrode forming method for reducing frictional resistance, which is formed by printing, printing, or pasting.

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