Abstract
For turbulent boundary-layer flow under a uniform freestream speed over a plate of length , covered with uniform roughness of nominal sand-grain scale , the physical behaviors underlying two distinguished limits at large are explored: the fully rough wall flow where is fixed and the long-plate limit where is fixed. For the fully rough limit it is shown that not only is the drag coefficient independent of but that a universal skin-friction coefficient and normalized boundary-layer thickness can be found that depends only on , where is the downstream distance. In the long-plate limit, it is shown that the flow becomes asymptotically smooth at huge at a rate that depends on . Comparisons with wind-tunnel and field data are made.
- Received 7 March 2017
DOI:https://doi.org/10.1103/PhysRevFluids.2.082601
©2017 American Physical Society