防風垣前後の風に関する研究 (6)

連墻の機能

抄録

As was seen in our previous report, a lot of turbulence in the wind reduces the function of the shelter-hedge. Moreover, some experiments in the wind tunnel clearly show that the multiple shelter-hedge is more affected by the turbulence than the single shelter-hedge.
By our experiments the multiple shelter-hedge of two belts has a higher ratio of wind velocity than the single one by 4 to 8%, as far as 20 times the height of the hedge, on the leeward; the 3-belted one has an increase of 1 to 4% in ratio of wind velocity, as compared with the 2-belted one, the 4-belted one has an increase of 1 to 2% in the ratio, as far as 10 times the height of the hedge, on the leeward, as compared with the 3-belted one. However, within the distance of 10 times the height of the hedge, clear result has not been obtained.
Concerning the vertical distribution of wind velocity, in the single hedge remain the spheres of the turbulence of 120cm, 80cm, and 50cm, respectively at the distance of 5, 10 and 15 times the height of the hedge, on the leeward, while in the multiple hedges the spheres of 100cm, 50cm, 30cm, remain, at the distance of 5, 10, and 15 times, respectively, on the leeward.
As for the turbulence of wind velocity, the 2-belted hedge has an increase of 2% over the single one, at the distance of 15, 20, 25 times the height to the leeward. But the turbulence caused by the multiple hedge seems to be constant when the belts increase in number.