JPS6234088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wind tunnel, and more particularly to a wind tunnel that generates a breeze velocity within a shell.

When simulating in a laboratory the effects of wind damage caused by the construction of skyscrapers, pollution caused by harmful gases and heat emitted from chimneys and tunnel exhaust stacks, and other effects not limited to harm caused by the action of wind. A wind tunnel is used.

Figure 1 shows a blow-out type wind tunnel for observing the state of smoke diffusion.

The wind tunnel is continuous and is formed from a variety of differently shaped shells, and a blower 01 is installed at one end of the shell.
The flow of wind generated in the air is expanded in the wind guiding part 02, and is made into a uniform flow in the rectifying part 03 where a rectifying device 04 such as a grid is placed inside the body, and in the contracting part 05 where the cross-sectional area of the body rapidly decreases. rectified.

This uniformly rectified flow is appropriately disturbed by a turbulence generating device 06 as required, enters a measuring section 07, and is finally discharged to the outside of the body through a discharge port 09.

A model 08 is disposed within the measurement section 07, and a tracer gas 010 such as smoke is discharged from the model 08 and its diffusion state is observed or measured.

In wind tunnel experiments, in order to bring phenomena from the natural world into the laboratory, it is necessary to conduct experiments that match the so-called law of similarity. In particular, as the model is reduced in size, the wind hitting the model must be slowed down accordingly. For example, if the scale of the model is 1/100 and we are trying to simulate a wind speed of 5 m/s, the wind speed at measurement section 07 will be is 0.5m/s.

Various problems that can be ignored when the wind speed inside the wind tunnel is high often become major problems at such low wind speeds.

For example, this is a problem in terms of the temperature of the body, and is particularly inconvenient in the rectifying section 03 where the flow path expands and in the measuring section 07 that performs measurements. In other words, it is a problem of convection inside the shell that occurs when heat enters the shell through the walls of the shell or when heat leaves the shell, and when the wind tunnel is affected by direct sunlight or when the ground When the bodies are in contact with each other, if there is an imbalance in which the lower part of the body is cold and the upper part is hot, convection will occur in the vertical direction.
Further, due to the difference in specific gravity due to temperature, the flow velocity in the vertical direction is not uniform. In the rectifying section 03 where the flow path expands and the flow velocity slows down, turbulence occurs and affects the downstream side, and in the measuring section 07, the turbulence itself influences the measurement results.

FIG. 2 is a schematic diagram of the flow from the contraction section 05 to the inlet of the measurement section 07 when the upper part of the shell is higher in temperature than the lower part.

The wind flow F ₁ is directed upward and is biased above the measurement part 07, so the wind speed is faster in the upper part and slower in the lower part.
A vortex 012 may be generated at the bottom of the contraction section 05. In this case, a uniform flow cannot be obtained in the measuring section 07, and the flow ends up having a wind speed distribution.

FIG. 3 is a schematic diagram of the flow from the contraction section 05 to the inlet of the measuring section 07 when, contrary to the above, the lower part of the body is hotter than the upper part.

On the contrary, the wind flow F ₂ is directed downward and is biased below the measuring section 07, resulting in a flow with a wind speed distribution in which the wind speed is slow in the upper part and fast in the lower part.

As described above, in the conventional wind tunnel, a temperature difference occurs between the top and bottom of the shell due to the temperature difference outside the shell, and due to this influence, wind speed distribution and wind direction distribution occur in the measurement section 07, resulting in a constant wind speed,
The wind tunnel's original characteristic of constant wind direction will be lost, making experiments impossible.

The present invention eliminates this drawback, and includes a constriction section that constricts the flow of wind generated in a continuous cylindrical body to create a uniform flow, and a constriction section that creates a uniform flow by constricting the flow of air generated in a continuous cylindrical body. In the wind tunnel, an inner cylinder is provided which is connected to the upstream end of the measurement part and expands and opens toward the upstream side within the contraction part, It is characterized by having an opening in the body and an adjustment mechanism for adjusting the amount of air discharged outside the body through the opening. The purpose of the present invention is to provide a wind tunnel with low wind speeds that allows experiments to be conducted under conditions extremely similar to natural conditions by reducing the wind speed distribution in the wind tunnel measurement section due to inflow and outflow.

As described above, one feature of the present invention is that an inner tube that expands and opens toward the upstream side is provided inside the contraction section, and the downstream end of the inner tube is connected to the measurement section. . In other words, this inner cylinder has an appropriate cross-sectional shape and performs a flow contracting action.

On the other hand, two features of the present invention are that an opening is provided in the contracted flow section. That is, Figures 2 and 3
As shown in the figure, flow velocity changes that are large or vortices that are biased upward or downward at the contraction section are discharged to the outside of the shell through the opening.

Further, the present invention includes an adjustment mechanism that adjusts the amount of air discharged outside the shell through the opening.

Therefore, the air sent to the measuring section is only the air that enters from the tip of the inner cylinder and has a small change in velocity, and is contracted in the inner cylinder, resulting in a uniform flow.

The present invention will be described below with respect to an embodiment of the wind tunnel shown in FIG. 4 and FIG. Since it has the same structure as the one with , the explanation will be omitted.

Reference numeral 11 denotes an inner cylinder disposed within the body forming the flow contraction section 5, the trailing end of which is connected to the inner wall of the measurement section 7, and the enlarged upstream end disposed within the rectification section 3. The current reaches the rectifying device 4. This inner cylinder 1
1 is composed of a thin plate, and its shape is approximately similar to the shape of the inner wall of the contraction section.

Reference numerals 12a and 12b are openings having an appropriate cross-sectional area, which are provided through the upper and lower body walls of the contracting portion 5, respectively.

Exhaust fans 1 are provided in the openings 12a and 12b, respectively.
3a and 13b, and the rotational speed of the exhaust fans 13a and 13b is controlled by a controller 15 that receives the outputs of temperature sensors 14a and 14b installed in the measurement section 7 of the wind tunnel and outputs a control signal. Ru. These exhaust fans 13a and 13b, temperature sensors 14a and 14b, and controller 15 constitute an adjustment mechanism.

Now, if a temperature difference occurs between the upper part and the lower part of the air guide pipe section 2 due to some cause such as sunlight or the influence of ambient temperature, a temperature difference will also occur in the internal air flow.

When the upper part of the wind has a high temperature and the lower part has a low temperature, the upper part of the body is generally accelerated. (It is shown by the dotted line in Figure 5.) Therefore, there is a difference in the temperature of the wind inside the measuring section 7 measured by the pair of temperature sensors 14a and 14b, and the output of the upper temperature sensor 14a is large, while the output of the lower temperature sensor 14a is large. The output of the temperature sensor 14b becomes smaller.

In such a case, the controller 15 controls the temperature sensor 14 so as to keep the vertical wind speed distribution constant.
In response to the difference in output between a and 14b, the exhaust fan 13a
The rotation speed of the upper part is increased to increase the amount of exhaust from the opening 12a, and the lower part of the exhaust fan 13b is
By lowering the rotation speed of the lower opening 12b.
Reduce emissions from As a result, a more uniform wind speed distribution as shown in the experiment in FIG. 5 is obtained.

Note that the average wind speed in this case is adjusted by a blower in a wind tunnel (not shown).

As described above, the wind tunnel contraction section 5 of this embodiment
By providing openings 12a and 12b on the upper and lower walls and providing exhaust fans 13a and 13b, the wind flows in the high temperature layer, that is, the acceleration region layer, and the wind in the low temperature layer, that is, the low speed region layer, respectively, as required. The volume is adjusted and discharged outside the body, and the flow contracting part 5
The opening 12 is opened by an inner cylinder 11 provided inside the opening 12.
Since the wind flowing out to a and 12b and the wind flowing to the measuring part 7 are stably separated, even when there is a temperature difference between the upper and lower parts of the body at a slight wind speed, an air flow of a constant speed and a constant wind direction can be obtained. It will be done.

In the above embodiment, the openings 12 were provided only in the upper and lower walls of the contraction section 5, and the inner cylinders 11 having a double structure were provided only at the top and bottom, but the inner cylinders having a double structure were provided throughout the circumference of the body. Of course, it may be inserted and an appropriate opening may also be made on the side.

Further, the air volume passing through the openings 12a and 12b may be adjusted by changing the opening area by using a valve or the like instead of using the exhaust fans 13a and 13b.

[Brief explanation of the drawing]

Figure 1 is an overall explanatory diagram of a conventional wind tunnel, Figures 2 and 3 are diagrams showing the flow inside a conventional wind tunnel, and Figure 4 is a longitudinal section showing only the main parts of a wind tunnel according to an embodiment of the present invention. The top view and FIG. 5 are graphs showing the wind speed at the entrance of the measuring section. 3: Rectifier section, 4: Rectifier device, 5: Contraction section, 7:
Measuring part, 11: inner cylinder, 12a, 12b: opening,
13a, 13b: Exhaust fan, 14a, 14b:
Temperature sensor, 15: Controller.

Claims (1)

[Claims] 1. It has a constriction section that constricts the flow of wind generated in a continuous cylindrical body to create a uniform flow, and a measurement section that is continuous with the constriction section and introduces the uniform air. In the wind tunnel, an inner cylinder is provided that is connected to the upstream end of the measurement section and expands toward the upstream side in the contraction section, and an opening is provided in the contraction section, and the opening is opened in the contraction section. A wind tunnel characterized by being equipped with an adjustment mechanism that adjusts the amount of air that passes through the tunnel and is discharged outside the body.