High-Accuracy Near-Surface Large-Eddy Simulation with Planar Topography
Final rept. 1 Jul 2004-28 Sep 2009
PENNSYLVANIA STATE UNIV STATE COLLEGE
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Large-eddy simulation LES has been plagued by an inability to predict the law-of-the-wall LOTW in mean velocity in the surface layer at high Reynolds numbers. Brasseur Wei developed a theory that explains the source of the difficulty and a framework within which LES can be designed to rectify the problem. The essential difficulty lies in nonphysical frictional content within the discretized dynamical system and the extent to which that frictional content interferes with the inertial scaling that underlies LOTW. Practical models replace inertial flux with dissipative dynamics, so part of this frictional content enters through the subfilter-scale SFS model. However, this spurious content also enters through the surface stress model, the structure of the grid and dissipation within the numerical algorithm. The research program was directed at discovering the essential nature of the difficulty and specific issues surrounding deviations from LOTW. As a result of a number of key breakthroughs we were successful and were able to propose framework within which LES can be designed to overcome the error. Whereas the essential issues are independent of SFS model, details of the SFS and surface stress models affect the prediction of the von K rm n constant, and likely details of the grid required to capture LOTW with LES.
- Electricity and Magnetism