エルボ下流の乱れに及ぼすレイノルズ数の影響(流体工学,流体機械)

Measurements of turbulence intensities downstream from a 90 degree elbow of circular cross section in the case of 1.1, 2 and 4 radius ratios were obtained using a laser-Doppler velocimeter at Reynolds numbers of 5×104-1×106 in order to clarify the Reynolds number effect on turbulence downstream from the elbow. The cross-sectionally averaged turbulence intensity decreased slightly with increasing Reynolds number. The effect of Reynolds number on it near the elbow was smaller than that for fully developed turbulent flow and decreased with decreasing radius ratio. The power spectrum of the turbulence intensity downstream near the elbow with any radius ratio had a distinct peak at the reduced frequency of about 0.5. No marked effect was observed of the Reynolds number on it.