Computational Modeling of Fundamental Exchange Processes from Heterogeneous Surfaces over Arbitrarily Complex Terrain
Abstract
A computational and theoretical approach is proposed to elucidate the physics of exchange processes of heat, moisture and momentum in the close proximity of EarthÕs surface. These processes are key driving forces in snow transport, fog formation, forest fires, drought, and air quality. Their parameterization in numerical weather prediction models is of great value as they serve as approximate boundary conditions to the mathematical model. Current parameterization schemes have been developed from a similarity theory of atmospheric flows over flat homogeneous terrain because of a lack of complete theory for complex terrain. Deficiencies in existing parameterization have been known for some time, but those deficiencies cannot be overlooked anymore as the research community is able to afford fine spatial resolutions in numerical weather prediction models, thanks to a new generation of supercomputers. In this project the chief objective is to improve the parameterization of exchange processes through a fundamental understanding of the physics involved, and establish a predictive capability to simulate winds over complex terrain. Direct numerical simulation of idealized slope flows and large-eddy simulation (LES) of winds over complex terrain will be conducted to achieve this objective. The project team will make use of recent field and laboratory experiments to validate new parameterizations. A parametric relation will be developed for separated flows that would take into account adverse pressure gradient and buoyancy effects in the leeward side of complex terrain. Numerical methods to represent arbitrarily complex terrain will be developed that would embody the surface parameterization schemes in them. To uncover the physics of exchange processes, simulations will adopt very fine spatial resolutions that will be supported on high performance computing clusters of graphics processing units. Unlike convective conditions during daytime, stable conditions start with evening transitions and develop into the night time due to radiative cooling. Stably stratified flows have been difficult to simulate even on flat terrain because turbulent motions are not in equilibrium anymore and become intermittent as a result of negative buoyancy that acts to suppress turbulent motions. The prediction problem becomes further difficult with increasing stability and terrain complexity. PI will investigate improvements to the LES technique to simulate stable conditions with better accuracy. Data from recent extensive field experiments conducted in the U.S. and Europe will be used to validate the hypotheses and numerical simulations.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 23, 2018
- Source ID
- W911NF1710564
Entities
People
- Inanc Senocak
Organizations
- Army Contracting Command
- United States Army
- University of Pittsburgh