Scalar transport in flow past finite circular patches of tall roughness
Scalar transport in flow past finite circular patches of tall roughness
Simultaneous particle image velocimetry-planar laser-induced fluorescence (PIV-PLIF) measurements are conducted on 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 downstream of the patch boundary, limiting the flow from convecting downstream and forcing it (and the scalar) to escape vertically from the top of the patch. Above the wake, a shear layer generated by the velocity difference between the free flow and the wake itself shields the near-wake region. The net effect of the solidity on the wake topology 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. Octant analysis of the conditionally averaged fluctuating components (u ′, v ′, and c ′) shows an enhanced mixing inside the shear layer and entrainment of turbulent flows between the shear layer, the wake region below and the freestream above this layer. In terms of eddy diffusivity models, the complexity of the eddy diffusivity constant increases with ϕ.
Mixing and dispersion, Mixing enhancement, Turbulent boundary layers, Urban fluid dynamics, Wakes
Wangsawijaya, Dea D.
b9f307f6-2828-416f-bc41-a025ecf49098
Nicolai, Claudia
8bdc34da-efe2-4dd0-b3bc-ece3bbddebff
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
2 June 2023
Wangsawijaya, Dea D.
b9f307f6-2828-416f-bc41-a025ecf49098
Nicolai, Claudia
8bdc34da-efe2-4dd0-b3bc-ece3bbddebff
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
Wangsawijaya, Dea D., Nicolai, Claudia and Ganapathisubramani, Bharathram
(2023)
Scalar transport in flow past finite circular patches of tall roughness.
International Journal of Heat and Fluid Flow, 102 (8), [109167].
(doi:10.1016/j.ijheatfluidflow.2023.109167).
Abstract
Simultaneous particle image velocimetry-planar laser-induced fluorescence (PIV-PLIF) measurements are conducted on 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 downstream of the patch boundary, limiting the flow from convecting downstream and forcing it (and the scalar) to escape vertically from the top of the patch. Above the wake, a shear layer generated by the velocity difference between the free flow and the wake itself shields the near-wake region. The net effect of the solidity on the wake topology 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. Octant analysis of the conditionally averaged fluctuating components (u ′, v ′, and c ′) shows an enhanced mixing inside the shear layer and entrainment of turbulent flows between the shear layer, the wake region below and the freestream above this layer. In terms of eddy diffusivity models, the complexity of the eddy diffusivity constant increases with ϕ.
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Accepted/In Press date: 16 May 2023
e-pub ahead of print date: 2 June 2023
Published date: 2 June 2023
Additional Information:
Funding Information:
The authors gratefully acknowledge the financial support from EPSRC, United Kingdom (Grant Nos: EP/P021476/1 and EP/S013296/1 ).
Keywords:
Mixing and dispersion, Mixing enhancement, Turbulent boundary layers, Urban fluid dynamics, Wakes
Identifiers
Local EPrints ID: 484786
URI: http://eprints.soton.ac.uk/id/eprint/484786
ISSN: 0142-727X
PURE UUID: b978b25c-456e-4ee1-944c-31a443bd9908
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Date deposited: 21 Nov 2023 17:52
Last modified: 18 Mar 2024 04:00
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Author:
Dea D. Wangsawijaya
Author:
Claudia Nicolai
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