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Flow over cube arrays of different packing densities

Flow over cube arrays of different packing densities
Flow over cube arrays of different packing densities
Measurements by 120° x-wire anemometry over uniform urban-type surfaces of two different area densities were performed in a wind tunnel, together with direct measurements of the surface drag. The aerodynamic characteristics of each surface were determined and compared, the influence of area density and array geometry on these parameters was examined. Various approaches were discussed for the determination of the roughness length (z0) for a given surface. The surface shear stress (determined from form drag measurements by pressure tapping a roughness element or from the total surface drag determined by a floating drag balance) and the shear stress (determined from spatially averaged vertical profiles of Reynolds shear stress) were compared. The surface shear stress was found to be about 25% greater than the measured Reynolds shear stress in the inertial sub-layer over the surfaces. There was, however, no constant stress region and extrapolation of the shear stress profiles in the inertial sub-layer to the zero-plane displacement provided a much better estimate of the surface shear stress. The results did not support the argument put forward in the literature that the zero-plane displacement could be reliably predicted from the height of the centre of drag force. Finally, the accuracy of existing geometrical methods of determining the aerodynamic properties of rough surfaces was shown to be limited by the use of inappropriate wind tunnel data in their formulation.
0167-6105
715-740
Cheng, H.
de8f13f3-1d85-48b6-a9da-54fa69571688
Hayden, P.
4824ded5-2d41-4df4-a715-7ff9dec849d7
Robins, A.G.
e522c3af-6028-4e6a-b34c-146487afc10d
Castro, I.P.
66e6330d-d93a-439a-a69b-e061e660de61
Cheng, H.
de8f13f3-1d85-48b6-a9da-54fa69571688
Hayden, P.
4824ded5-2d41-4df4-a715-7ff9dec849d7
Robins, A.G.
e522c3af-6028-4e6a-b34c-146487afc10d
Castro, I.P.
66e6330d-d93a-439a-a69b-e061e660de61

Cheng, H., Hayden, P., Robins, A.G. and Castro, I.P. (2007) Flow over cube arrays of different packing densities. Journal of Wind Engineering and Industrial Aerodynamics, 95 (8), 715-740. (doi:10.1016/j.jweia.2007.01.004).

Record type: Article

Abstract

Measurements by 120° x-wire anemometry over uniform urban-type surfaces of two different area densities were performed in a wind tunnel, together with direct measurements of the surface drag. The aerodynamic characteristics of each surface were determined and compared, the influence of area density and array geometry on these parameters was examined. Various approaches were discussed for the determination of the roughness length (z0) for a given surface. The surface shear stress (determined from form drag measurements by pressure tapping a roughness element or from the total surface drag determined by a floating drag balance) and the shear stress (determined from spatially averaged vertical profiles of Reynolds shear stress) were compared. The surface shear stress was found to be about 25% greater than the measured Reynolds shear stress in the inertial sub-layer over the surfaces. There was, however, no constant stress region and extrapolation of the shear stress profiles in the inertial sub-layer to the zero-plane displacement provided a much better estimate of the surface shear stress. The results did not support the argument put forward in the literature that the zero-plane displacement could be reliably predicted from the height of the centre of drag force. Finally, the accuracy of existing geometrical methods of determining the aerodynamic properties of rough surfaces was shown to be limited by the use of inappropriate wind tunnel data in their formulation.

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flow_over_cube_arrays_of_different_packing_densitites.pdf - Accepted Manuscript
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Published date: August 2007

Identifiers

Local EPrints ID: 64350
URI: https://eprints.soton.ac.uk/id/eprint/64350
ISSN: 0167-6105
PURE UUID: 1813b7a5-f97e-4ef7-a1cf-62b0f98736c5

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Date deposited: 19 Dec 2008
Last modified: 13 Mar 2019 20:22

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Contributors

Author: H. Cheng
Author: P. Hayden
Author: A.G. Robins
Author: I.P. Castro

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