The TU Wien Turbulent Water Channel: measurements and statistics

Abstract

The statistical properties of a turbulent duct flow are investigated experimentally. Experiments are performed in the TU Wien Turbulent Water Channel at a shear Reynolds number of 370. A high-speed imaging system is used to record the flow and the velocity fields are obtained via three-dimensional particle tracking velocimetry (3D-PTV). Experimental results are first used to compute the first four moments of the velocity distribution and then compared against direct numerical simulations (DNS). It was found that in the duct, the statistics of all velocity components exhibit good agreement with those obtained from DNS. Slight overestimation of the main Reynolds stresses, particularly close to the wall, has been observed. Skewness and flatness of the stream-wise velocity were underestimated in the viscous sub-layer. Moreover, a new method is proposed to correct the misalignment of the measurement volume with respect to the actual flow direction. This method successfully reduced the average span-wise velocity. Finally, we analysed the effect of the width-to-height aspect ratio (AR) on the flow statistics. We analysed DNS of duct flows with 1 ≤ AR ≤ 8 and we observed that, at a shear Reynolds number of 150, a duct with AR ≤ 8 is not sufficient to reproduce the statistical properties observed in a turbulent channel flow (AR = ∞). These findings are significant because they provide evidence of the turbulence characteristics in the TU Wien Turbulent Water Channel.