Effects of the Reynolds number on a scale-similarity model of Lagrangian velocity correlations in isotropic turbulent flows |
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Authors: | Zhaoyu Shi Jincai Chen Guodong Jin |
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Affiliation: | 1. State Key Laboratory of Nonlinear Mechanics(LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China;2. School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China;3. School of Engineering, Sun Yat-sen University, Guangzhou 510275, China |
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Abstract: | A scale-similarity model of a two-point two-time Lagrangian velocity correlation (LVC) was originally developed for the relative dispersion of tracer particles in isotropic turbulent flows (HE, G. W., JIN, G. D., and ZHAO, X. Scale-similarity model for Lagrangian velocity correlations in isotropic and stationary turbulence. Physical Review E, 80, 066313 (2009)). The model can be expressed as a two-point Eulerian space correlation and the dispersion velocity V. The dispersion velocity denotes the rate at which one moving particle departs from another fixed particle. This paper numerically validates the robustness of the scale-similarity model at high Taylor micro-scale Reynolds numbers up to 373, which are much higher than the original values (Rλ = 66, 102). The effect of the Reynolds number on the dispersion velocity in the scale-similarity model is carefully investigated. The results show that the scale-similarity model is more accurate at higher Reynolds numbers because the two-point Lagrangian velocity correlations with different initial spatial separations collapse into a universal form compared with a combination of the initial separation and the temporal separation via the dispersion velocity. Moreover, the dispersion velocity V normalized by the Kolmogorov velocity Vη ≡ η/τη in which η and τη are the Kolmogorov space and time scales, respectively, scales with the Reynolds number Rλ as (V/V_etapropto{R_lambda^{1.39}}) obtained from the numerical data. |
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Keywords: | thick workpiece slip line field parametric integration analytical solution Lagrangian velocity correlation turbulent mixing relative dispersion dispersion velocity Reynolds number effect scalesimilarity model |
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