Abonnement à la biblothèque: Guest
TSFP DL Home Archives Comité de direction

DNS OF TURBULENT CHANNEL FLOW OVER ENGINEERING ROUGH SURFACES

Angela Busse
Faculty of Engineering and the Environment University of Southampton United Kingdom

Chris J. Tyson
Faculty of Engineering and the Environment University of Southampton United Kingdom

Neil D. Sandham
Aerodynamics and Flight Mechanics Group Faculty of Engineering and the Environment, University of Southampton Southampton SO17 1BJ, UK

Mark Lutzner
Institut fur Aerodynamik und Gasdynamik Universitat Stuttgart Germany

Résumé

Most rough surfaces found in engineering applications are irregular and possess features on multiple length scales. In these respects they differ considerably from standard roughness models, such as arrays of cubes, used in most experiments and numerical simulations investigating turbulent flow over rough surfaces. Results from direct numerical simulations of turbulent channel flow at Reτ = 180 over realistic representations of typical engineering rough surfaces are presented in this paper. The surface geometries are based on surface scans of four different materials: graphite, carbon-carbon composite, shotblasted and ground steel. The roughness function ΔU+ shows a strong dependence on the three-dimensional topography of the surfaces and is not solely determined by the physical roughness height. The dependence of the roughness function on various characteristic topological surface parameters has been tested. As expected, the roughness function increases with the surface skewness and the effective slope. It is also found that the roughness function decreases with increasing surface bearing index. The surface anisotropy and the texture direction of the surface with respect to the mean flow direction has an additional effect on the roughness function. Of the normal Reynolds stresses, only the streamwise stress shows a clear correlation to the degree of roughness of the surface. The spanwise and wall-normal stresses are largely unaffected by the degree of roughness and the roughness type outside the roughness sub-layer.