JPS6256454B2 - - 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. References ("Wind tunnel experiment for visualizing the phenomenon of exhaust gas diffusion over mountains" Collection of lecture abstracts of the Kyushu branch of the Japan Meteorological Society, No. 5, 1983)
A wind tunnel like the one introduced in

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 a wind speed of 5 m/s is to be simulated, the wind speed at the 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.
Furthermore, the flow velocity in the vertical direction is not uniform due to the difference in specific gravity due to temperature. 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 toward the lower part of the measuring section 07, so that the flow has 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 connected to the upstream end of the measurement part and expands and opens toward the upstream side in the contraction part, and The purpose of this is to reduce the wind velocity distribution in the wind tunnel measurement area due to the flow of heat through the wind guide shell, and to create conditions that are extremely similar to natural conditions. The purpose of this project is to provide a wind tunnel with low wind speeds in which experiments can be conducted.

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.

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

The present invention will be described below with respect to an embodiment of the wind tunnel shown in FIGS. 4 to 6. In this example, too, the present invention is applied to a blow-out type wind tunnel, and those designated by numerals 2 to 7 are shown in FIG. Since they have the same structure as those marked with 02 to 07, their 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 located 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 numeral 12 designates a plurality of openings having appropriate cross-sectional areas, which are provided through the upper and lower body walls of the contracting portion 5.

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.

Figure 6 shows the flow pattern in the above case. In the figure, the dotted line is the flow of the conventional wind, which is the same as that shown in Figure 2, and the solid line is the flow of the wind in the wind tunnel of this example. It shows the flow. Also the 7th
The figure shows the wind speed distribution in the vertical direction in the measurement chamber, where the dotted line is the conventional one and the solid line is the one of this embodiment, as in FIG. 6.

As shown by the dotted line in Figure 6, wind flows gather in the upper layer and even create vortices in the lower layer. Therefore, in the conventional wind tunnel, the wind speed distribution at the measuring section shows a distribution shape in which the upper layer is accelerated and the lower layer is decelerated, as shown by the dotted line in FIG.

On the other hand, in the wind tunnel of this embodiment, the flow of high-temperature and accelerated wind that comes between the upper part, that is, the inlet of the contracting part 5 and the upstream end of the inner cylinder 11, is directed toward the measuring part 7. The flow flows to the opening 12 opened in the contracted flow section 5, where the resistance is lower than that of the flow, and is discharged to the outside of the barrel.

In the case of the lower layer, the provision of the opening 12 makes the flow easier than before, so the upward flow is corrected and the vortex disappears.

On the other hand, if the lower temperature is higher than the upper temperature, the opposite phenomenon occurs.

Furthermore, since the flow inside the cylinder is discharged from the opening 12, it goes without saying that it is necessary to increase the rotational speed of the blower somewhat compared to the conventional blower.

Therefore, the wind speed distribution that was caused by the temperature difference between the top and bottom inside the shell in a slight wind speed region where the wind tunnel wind speed is 0.5 m/s or less, for example, is not suitable for the upper and lower wall surfaces of the contraction section 5 as in the wind tunnel of this embodiment. By providing an appropriate number of openings 12 with a cross-sectional area, the wind in the high temperature layer, that is, the acceleration region layer, and the wind in the low temperature layer, that is, the low velocity region layer in the upper or lower layer are discharged to the outside of the body, and the air flow in the contraction section 5 is discharged. The opening 12 is opened by the inner cylinder 11 provided inside.
Since the wind flowing out to the measuring part 7 is stably separated from the wind flowing to the measurement part 7, an air flow having a constant speed and a constant direction can be obtained even when there is a temperature difference between the upper and lower parts of the body at a low wind speed.

In the above embodiment, the openings 12 are provided only in the upper and lower walls of the contraction section 5, but the openings 12 may be provided all around the circumference of the body.

In addition, the measurement section and the inner cylinder are integrated, and the body wall that forms the conventional flow contraction section is made to cover the inner cylinder, and the rear end of the body wall is made to have a slight gap with the body wall of the measurement section. Alternatively, the opening may be formed using the same method.

[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. 5 is a horizontal sectional view of FIG. 4, FIG. 6 is a diagram showing the wind flowing in the wind tunnel according to an embodiment of the present invention in comparison with the conventional one, and FIG. 7 is a diagram showing the measuring section. It is a graph showing the wind speed at the entrance. 3: Rectifier section, 4: Rectifier device, 5: Contraction section, 7:
Measuring part, 11: inner cylinder, 12: opening.

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 within the contraction section, and an opening is provided in the contraction section. Wind tunnel.