亂れの減衰に關する一寄與 : 初期亂れの影響に就いて

概要

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The present tests were undertaken to investigate the effect of initial turbulence on tht decay of turbulence produced by a fine mesh grid. Initial turbulence was produced by another large mesh grid. Mesh length of up- and downstream grid were 10.1mm and 1.1mm, and their wire diameters 2.1 and 0.2mm respectively. Distances between two grids were 20, 40 and 70cm. Turbulence intensity measurements behind downstream grid were performed by means of so-called, "heat diffusion method". From the results of the tests, the remarkable effects of the initial turbulence on the intensity and the decay of turbulence produced by the fine mesh grid were confirmed. In appendix, utilizing the rapid decay.of turbulence produced by fine mesh grid the intensity of turbulence of the 1.5mm wind-tunnel of the Institute was reduced, 1mm mesh length grid being inserted downstream of equalizer. The intensity of turbulence and the transition point of the laminar boundary layer along a flat plat were measured. The intensity was reduced from 0.3% to 0.19%, and Reynolds Number Vx/v at the transition point was raised from 1.87×10^6 to 2.14×10^6.
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