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Turbulent length scales and anisotropy downstream of a wall mounted sphere

Author(s): Sankar Sarkar; Subhasish Dey

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Keywords: Open channel flow; steady flow; turbulence anisotropy; turbulent flow; wake

Abstract: Characteristics of turbulent mixing-length, length scales and anisotropy in the wall-wake flow downstream of a sphere placed on a rough wall are studied. The Prandtl's mixing-length in wall-wake flow increases compared to that in upstream flow, while the Taylor microscale and the Kolmogorov length scale decrease. As the downstream distance increases, the defects (difference between upstream and downstream distributions) in vertical distributions of mixing-length and length scales gradually disappear to recover their distributions in undisturbed upstream flow. These distributions of the defects exhibit some degree of similarity, as they are scaled by their individual peak values and the vertical distance is scaled by the height of occurrence of their individual half-peak defects. In anisotropy analysis, the streamwise, spanwise and vertical components of anisotropy in wall-wake flow are less, more and invariant, compared to their individual upstream trends. However, the former two components recover with an increase in downstream distance.


Year: 2015

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