JPS6123127B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a windbreak fence to be installed at a windward position of bulk materials piled up in the open, such as coal piles, to prevent them from generating dust due to the wind. It is related to.

Conventionally, as shown in FIG. 1, when a sufficiently rigid net-like fence 1 is erected up to a height H, the flow of wind changes as shown by streamlines 2 on the leeward side of the fence 1. In this state, when the mesh opening ratio of the fence 1 is approximately 60%, the wind speed of the surface of the loose material that is about to generate dust, that is, the friction speed, is 2 times higher than the wind speed _V0 on the windward side. The wind speed gradually decreases as shown by curve 4 in the figure, and when the opening ratio is approximately 40%, the deceleration increases as shown by curve 3 in FIG. 2, and the wind speed decreases to 1/10 V ₀ to 1/5 V ₀ . This deceleration value does not occur suddenly from the position immediately downwind of Fens 1;
The wind speed gradually slows down and after a certain point it tends to gradually return to the original speed, and the effective deceleration zone is narrow. In order to enlarge this deceleration section, the height of the fence 1 may be increased, but this increases the wind pressure that the fence 1 receives, necessitating a high-strength fence, and the disadvantage is that the construction cost of the fence increases.

Further, in order to obtain a rapid deceleration effect at a position immediately behind the leeward side of the fence, it is preferable to install a non-porous fence 5 at a height H as shown in FIG. In this case, as shown in FIG. 2, the deceleration curve 8 is immediately after the fence 5 in the opposite wind direction, and the absolute value of the wind speed decreases. However, this is not effective because the wind speed value increases as you move away from the fence 5. This phenomenon is shown in Figure 3.
This occurs because, in addition to the streamlines 6, vortices such as the streamlines 7 are generated on the leeward side of the fence 5. As described above, since the non-porous fence 5 is not effective and the wind pressure that the non-porous fence 5 receives is large, there is a drawback that the construction cost is further increased.

An object of the present invention is to provide a windbreak fence that can rapidly reduce wind speed, expand the deceleration zone, and reduce construction costs.

The main point of the present invention is to provide a non-porous fence in the lower tier.
The basic structure is a composite windbreak fence with a middle fence with a large number of holes and an upper fence with a larger opening ratio than the middle fence, and the turbulence generated on the lee side of the non-porous lower fence. The key point is that the wind speed immediately after the fencing can be rapidly reduced.

An embodiment of the present invention will be described below with reference to FIGS. 4, 5, and 6.

The composite type fence shown in Fig. 6 consists of a non-porous lower fence 9 erected at a height H ₁ from the ground surface, and a middle tier fence 1 erected from the upper end surface of the lower tier fence 9.
0, and an upper fence 11 standing upright from the upper end surface of the middle fence 10.

The height of the middle fence 10 itself is _H2 , the opening ratio is 40%, and the height of the upper fence 11 itself is
The opening ratio is 60% with _H3 . The overall height of the composite fence is H.

The height ratios of the lower middle and upper fences themselves are H ₁ = 1/4H, H ₂ = 1/2H, and H ₃ = 1/4H.

When such a composite fence is erected on the windward side, the wind flow on the leeward side becomes a streamline 12 in FIG. 4 and a vortex 13 immediately after the lower fence 9. This vortex 13 is generated, resulting in a turbulent state, and as a result, the friction velocity is rapidly decelerated with respect to the wind speed V ₀ on the windward side immediately after the composite type fence, as shown by curve 14 in Fig. 5, and the deceleration section reaches the height of the fence. It will expand without increasing it. This has been confirmed through experiments, and the backflow wind due to the vortex 13 immediately after the lower fence 9 cancels out the friction speed, causing the friction speed to sharply decrease. In this way, when the entire fence has an aperture ratio of 40%, the effective deceleration section begins only at three times the fence height H, that is, after 3H, as shown by curve 3 in Figure 2.
In this embodiment, as shown in FIG. 5, the effective deceleration section begins uniformly immediately ahead of 3H, and the effective deceleration section expands. Moreover, since there is no need to increase the height, the wind pressure received is small, and by increasing the aperture ratio of the upper fence 11, which does not have much effect on the friction speed, the wind pressure received is further reduced, and the construction cost of the fence is reduced. .

According to experiments, if the height H ₁ of the lower fence 9 is too high, the backflow becomes intense as shown in Figure 3, which tends to reduce the dustproof effect, so the height H ₁ of the lower fence 9 should not exceed 1/3H. I found that setting it to . In addition, upper fence 1
According to experiments, if the height H ₃ of the upper fence 11 is about 1/2H, the friction speed will be almost the same as when all the fences are composed of the middle fence 10. For this reason, it can be seen that even if the aperture ratio of the upper fence changes considerably, it has almost no effect on the friction velocity on the ground surface side. Furthermore, the sixth
In the composite type windbreak fence shown in the figure, the opening ratio of the middle fence 10 is 30 to less than 50%, and the upper fence 11 is
The opening ratio of the lower fence 10 was set to 50% to 80%, the height _H1 of the lower fence 10 was set to 10% to 35% of the overall height H, and the height of the upper fence 11 was set to 40% to 60% of the overall height H. Compound fences are valid.

As described above, according to the present invention, the basic structure includes a composite fence in which a dense fence with a small opening ratio is placed above a non-porous fence, and a coarse fence with a large opening ratio is further added above the non-porous fence. Then, without increasing the fence, the friction speed is reduced so as to be canceled out by the turbulence generated behind the non-porous fence,
Furthermore, since the wind pressure exerted by the combination of dense and dense fences can be reduced, the effect of expanding the deceleration section by the windbreak fence and the effect of reducing the cost of constructing the fence can be obtained.

[Brief explanation of the drawing]

Figure 1 is a flow line diagram of wind due to mesh fences, Figure 2 is a diagram of friction speed deceleration curves due to various types of fences,
Figure 3 is a flow line diagram of wind due to non-porous fence, Figure 4
The figure is a flow line diagram of wind caused by a composite type windbreak fence according to an embodiment of the present invention, and Fig. 5 is a friction speed deceleration curve diagram due to a composite type windbreak fence according to an embodiment of the present invention.
FIG. 6 is a perspective view of a composite windbreak fence according to an embodiment of the present invention. 9...lower fence, 10...middle fence,
11...Upper fence, 12...Wind streamline, 13
...Vortex, 14...Curve showing the friction speed deceleration situation.

Claims (1)

[Scope of Claims] 1. A non-porous lower fence is installed, a middle fence with a large number of holes is installed at a higher position than the lower fence, and a middle fence is installed at a higher position than the middle fence than the middle fence. A composite windbreak fence consisting of an upper fence with a large opening ratio. 2. The composite windbreak fence according to claim 1, characterized in that a middle fence is erected in contact with the lower fence, and a lower fence is erected in contact with the middle fence.