A turbulence dissipation inhomogeneity scaling in the wake of two side-by-side square prisms
Résumé
We experimentally study how the turbulent energy dissipation rate scales in the cross-stream direction of turbulent wake flows generated by two side-by-side square prisms. We consider three different such turbulent flows with gap ratios $G/H=1.25$ , $2.4$ and $3.5$ , where $G$ is the distance between the prisms and $H$ is the prism width. These three flows have a very different dynamics, inhomogeneities and large-scale features. The measurements were taken with a multi-camera particle image velocimetry system at several streamwise locations between $2.5H$ and $20H$ downstream of the prisms. After removing the large-scale most energetic coherent structures, the normalised turbulence dissipation coefficient $C'_{\epsilon }$ of the remaining incoherent turbulence is found to scale as $C'_{\epsilon } \sim (\sqrt {Re_{L}}/Re'_{\lambda })^{3/2}$ along the highly inhomogeneous cross-stream direction for all streamwise locations tested in all three flows and for all three inlet Reynolds numbers considered; $Re'_{\lambda }$ and $Re_{L}$ are, respectively, a Taylor length-based and an integral length-based Reynolds number of the remaining incoherent turbulence.
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