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ISSN Print: 2152-5102
ISSN Online: 2152-5110
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Influence of the Virtual Origin on the Turbulent Length Scales in the Grid-Generated Turbulence
ABSTRACT
The turbulent flow downstream of a single square grid is being experimentally investigated in a relatively small-sized wind tunnel. 2D LDV (Laser Doppler Velocimetry) measurements are conducted at the centerline of the channel for Reynolds numbers ranging from 8300 to 24870. Two grids are tested with two mesh sizes (M) and the solidity coefficient is always kept constant. We aim at discussing the influence of the position of virtual origin x0 on the turbulent macro (Lf), micro (λf) and Kolmogorov (ηK) length scales. Five possible virtual origins (0 < x0/M < 8) are arbitrary chosen based on a literature review. Whatever x0/M is, we demonstrate that macro, micro and Kolmogorov length scales can be predicted by empirical laws according to some confidence intervals of 30, 20 and 15 % respectively. Comparisons with others experimental data are also provided to validate the model. Best choice for the virtual origin is also provided for the present set of experiments.
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Zheng Y., Nagata K., Watanabe T., Energy dissipation and enstrophy production/destruction at very low Reynolds numbers in the final stage of the transition period of decay in grid turbulence, Physics of Fluids, 33, 3, 2021. Crossref