Extending an Analytical Wall-Function for Turbulent Flows Over Rough Walls

The chapter proposes and validates an extension to the analytical wall-function (AWF) approach that allows for the effects of fine-grain surface to roughness. It is highlighted that relatively simple adaptations of the method result in an approach that does reproduce many of the features of flows over rough surfaces, while retaining the computational efficiency associated with wall-functions. The flow test cases chosen for the validation are internal flows through rough pipes and channels, external flows over rough surfaces and separating flows over a sand dune and a sand-roughened ramp. The overall strategy of the wall function derivation and application is retained, with the wall roughness accounted for by modifying the non-dimensional thickness of the modeled viscous layer immediately adjacent to the wall. The extended scheme is validated in fully developed channel, pipe and developing fiat plate boundary layer flows over a wide range of Reynolds numbers and roughness element heights as well as separating flows over a sand dune and a round ramp. © 2005 Elsevier B.V. All rights reserved.