Scalar Transport in flow past finite circular patches of tall roughness

Wangsawijaya, Dea Daniella, Nicolai, Claudia and Ganapathisubramani, Bharathram (2022) Scalar Transport in flow past finite circular patches of tall roughness. 12th International Symposium on Turbulence and Sher Flow Phenomena, , Osaka, Japan. 19 - 22 Jul 2022. pp. 1-6 .

Abstract

Simultaneous particle image velocimetry-planar laserinduced fluorescence (PIV-PLIF) measurements are conducted of the flow around and downstream of patches of tall cylinders with various solidity φ ≡ N_c(d/D)², where N_c is the number of cylinders in a patch, d and D are the diameters of the cylinder and the patch, respectively. Results suggest that the bleeding and scalar concentration in the wake and above the patches are dependent upon φ. Recirculation bubble appears at the trailing edge (TE) of the patch, limiting the flow from convecting downstream and forcing the flow (and the scalar) to escape vertically from the top of the patch. Above the wake, a shear layer generated by the velocity difference shields the near-wake region. The net effect is the appearance of an elongated patch as φ decreases and a taller patch as φ increases. In terms of scalar transport, both advective and turbulent vertical scalar transport are enhanced as φ increases. High advective vertical scalar transport CV is concentrated around the canopy (above the canopy due to vertical bleeding and at the TE due to high scalar concentration), while high turbulent transport c′v′largely coincides with the shear layer. Joint probability density function (PDF) calculated at few selected points show that there is an entrainment of turbulent flows from the shear layer towards the wake of the patch below this layer, followed by scalar diffusion the the same direction and further downstream
of the patch.

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Contributors

Author: Dea Daniella Wangsawijaya

Author: Bharathram Ganapathisubramani

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