JPH0557959B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a turret mooring ship, and particularly aims to reduce the mooring force thereof.

[Prior art and its problems]

Around the world, offshore oil fields are being developed in deep-water areas, areas with poor sea conditions, or abandoned locations with low reserves. A simple so-called turret muling ship is attracting attention.

As shown in Fig. 8, this ship has a turret 50 inserted near the bow on the ship's axis, which serves as the center axis of rotation of the ship, and mooring lines 51 and anchors 52 are lowered radially from the turret 50. 50 is fixedly moored directly above an oil well, and excavation etc. are carried out using an oil country pipe lowered through the inside of the turret 50.

In such a turret-maring ship, for example, when a storm acts on the hull, the wind pressure on the structure toward the stern is greater than the position of the turret 50. By rotating and pointing the bow toward the windward direction, the wind pressure acting on the hull is reduced, and the mooring force is reduced (weathervane effect).

However, the rotational force is not sufficient, so conventionally a propulsion device called a thruster was installed at the bottom of the ship, and this thruster was used to forcibly direct the bow in the direction in which the external force was applied. However, equipping such a thruster had problems, such as the manufacturing cost and the need for a high-output power source.

Therefore, the present inventors conducted various experiments and found the following findings from wind tunnel experiments in which wind acted on an object having a plate attached to a cylinder.

FIG. 9 shows the aerodynamic characteristics of a cylinder with vanes. α is the angle at which the wind hits the cylinder, C _D is the drag coefficient, and C _L is the lift coefficient. It can be seen that the lift force that cannot be generated by a simple cylinder (without blades) is large. Recognize.

Therefore, by providing the cylinder with the wing plates on the hull, lift can be effectively utilized.

For example, as shown in FIG. 10, the moment M at which the aerodynamic force acting on the ground flare 60 behind the deck contributes to the weathervane effect is
If the blade 61 is not attached to the blade, there is only a drag force D, and M=D·l _D.

However, the ground flare 60 with the wing plate 61
Since lift force L is generated, M=D・l _D +L・l _L
becomes. If the resultant force of drag and lift is C, then M=
It can also be expressed as C・l _C. As a result, the lift force generated by the effect of the blades 61 serves to increase the drag force D to the resultant force C, increase the arm length _lD to _lC , and increase the moment M.

[Problem that the invention seeks to solve]

As described above, the method of attaching a plate to the ground flare is a very effective method that uses the yawing moment caused by wind pressure to change the direction of the ship so that the mooring force is reduced. This method cannot be used unless the ground flare is located far away from the center of action of the moment (usually near the stern), and in that case, it will be necessary to install a new ground flare such as a cylindrical structure near the stern. There's a problem. Furthermore, since the plate is fixed, its performance cannot be controlled as originally set. In other words, the plates are installed so as to obtain the specified performance using wave force, tidal current force, and wind force set at the time of design, but in sea areas where the combination of these external forces differs, it is not always the best direction (the direction where the mooring force is minimum). There is no guarantee that the hull will be facing the same direction. This is because the characteristics of the mooring force, the drag force that determines the direction of the ship, and the yawing moment with respect to the wind direction angle are different. For example, in sea areas where wind pressure is predominant, the ship faces upwind due to the yawing moment caused by the wind pressure, and as a result, the mooring force due to wave force and tidal current force increases, and the overall mooring force is not minimized. Become.

The present invention was proposed as a result of repeated studies to solve these problems.

[Means for solving problems]

As shown in FIG. 1, the present invention provides an airfoil that can be rotated against the wind and is mounted on the stern (or bow) of a ship that rotates around a turret, for example on the deck 1. It has two sails erected. A swingable aileron may be attached to this airfoil sail 2, or the wing area of the sail 2 may be made variable.

[Effect]

In order to improve the weathervane effect described above, as shown in Fig. 2, the turret 5, which is the central axis of rotation
It is necessary to increase the horizontal internal rotational moment coefficient C _MZ around 0.

The present invention attempts to change the direction of the ship by utilizing the lifting force acting on the sails of conventional sailboats and the like for propulsion of the ship, as the yawing moment of the ship. That is, the attempt is made to increase the rotational moment coefficient C _MZ in the horizontal plane by using the lift force acting on the sail 2 attached near the stern (or bow).

〔Example〕

Figure 3 shows an airfoil sail 20 that has the above-mentioned effect.
This shows the pillar 3 installed on the stern deck.
Fixed above 0.

The area of this sail 20 is determined as follows. As shown in Fig. 4, consider the case of design conditions in which the current, waves, and wind act at an angle β. For simplicity, the waves and wind are assumed to be in the same direction, but the same is true even if they are in different directions.

From the characteristic curve of the action angle of the mooring force (drag force) due to each external force, determine the angle at which the mooring force (drag force) is the minimum, and determine the angle β ₁ (angle between the hull, waves and wind) and β ₂ as shown in Figure 4. Suppose that (the angle between the hull and the current). Next, from the characteristic curve of the yawing moment with respect to the angle of action of the external force, the required magnitude of the yawing moment due to the wind pressure is determined.
If the edge is in the bow direction), from the lift characteristic curve of the sail 20 (Fig. 5 shows an example of the lift characteristic curve for the airfoil type NACA0025), the sail 20 should be adjusted so that the required yawing moment is Find the area.

The airfoil sail 20 is configured to be rotatable around the support 30, and by active control, the lift of the sail 20 can be changed in response to wind at a certain angle with respect to the hull. There is. When performing active control with such a structure, the angle of the sail 20 is adjusted to obtain the optimum yawing moment using the lift characteristic curve, an example of which is shown in Fig. 5, based on moment-by-moment tide, wave, and wind data. Not only can it be set, but it can also accommodate external force conditions that are different from the design conditions.

6 and 7 show a further improved embodiment of the invention.

The configuration of the airfoil sail 21 in FIG.
1a is attached. Furthermore, a guide bar 41 that can be moved while being guided by a guide rail 40 is installed below the auxiliary member 21a. When the ailerons 21a are attached in this manner, the air flow on the surface of the airfoil sail 21 is rectified, the peak level of the lift characteristic curve is further increased, and a high lift coefficient is obtained.

On the other hand, the wing-shaped sail 22 of the embodiment shown in FIG. 7 has a double structure that can be expanded and contracted up and down, so that the wing area can be changed. That is, the wing-shaped sail 22 includes a casing wing-shaped sail 22a, and a storage sail 22 that is stored therein and that can be accessed upwardly from the casing wing-shaped sail 22a.
b, and the whole is rotatably supported by a support 32 on the stern deck. The airfoil sail 22 whose wing area can be changed in this way is
The area of the sail 22 can be set so as to obtain the optimum yawing moment by using the above-mentioned lift characteristic curve based on data on tides, waves, and wind that change from time to time, and more appropriate active control is possible.

〔Effect of the invention〕

As explained above, the present invention has a simple structure in which a wing-shaped sail that can be rotated against the wind is attached to the bow or stern, and the natural wind is used to change the direction of the hull. Therefore, there is no need for special power such as a thruster, and it is easy to attach ailerons to the airfoil sail or create a structure where the wing area can be changed, making active control possible, making it extremely economical. Effects such as being able to be carried out can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of the present invention, Fig. 2 is an explanatory diagram of the rotational moment coefficient C MZ in the present invention, and Fig. 3 is an explanatory diagram of the rotational moment coefficient C _MZ of the present invention.
The figure is a front view showing the shape of a wing-shaped sail according to an embodiment of the present invention, FIG. 4 is an explanatory diagram of a method for setting the area of the wing-shaped sail, and FIG. 5 is an example of the lift characteristic curve of the wing-shaped sail. 6 is a front view showing another embodiment of the wing-shaped sail of the present invention, FIG. 7 is a front view showing still another embodiment, and FIG. 8 is a front view showing another embodiment of the wing sail of the present invention. A schematic diagram, Fig. 9 is a graph showing the aerodynamic characteristics of a cylinder with wing plates, and Fig. 10 is a plan view explaining the principle of mooring force reduction effect by providing a cylinder with wing plates on the hull. be. In the figure, 2, 20, 21, 22 are airfoil sails, 30,
Reference numerals 31 and 32 indicate pillars, respectively.

Claims (1)

[Scope of Claims] 1. A turret muling ship, characterized in that a wing-shaped sail that can be rotated against the wind is installed on the bow or stern of a ship that rotates around a turret. 2. The turret muling ship according to claim 1, wherein the wing-shaped sail is provided with swingable ailerons. 3. The turret muling ship according to claims 1 and 2, characterized in that the wing area of the wing-shaped sail is variable.