A Theoretical and Numerical Study of 2D and 3D Flow over Dynamically Tall Mountain Ranges

University Of California-San Diego Scripps Inst Of Oceanography, La Jolla CA

Investigators

Abstract

This research will use a combination of theory and numerical simulation to study the role of stratified air flow over simulated, dynamically varying mountain range heights to determine when the flow must be characterized by fully 3-dimensional flow and when a 2-dimensional framework will suffice to model this flow. The broader impact of this research will serve the Mountain Meteorology community in the areas of aviation and fire safety, as well as micrometeorology of small scale flows. The proposed research seeks to use a Computational Fluid Dynamics (CFD) approach to simulate 3-dimensional flow over dynamically tall mountain ranges. Numerical results will be analyzed to determine when and why these flows split. The proposal includes a refinement of earlier theories on these flow splits and potentially the development of a new theoretical basis; particularly for the along-ridge flow variability. Recent theoretical analyses have shown the quantitative connection between blocked flow upstream and asymmetric, supercritical, downslope flow in the lee. Simulations that resolve viscous boundary layers, flow separation and non-hydrostatic shear instabilities suggest these flows separate from the ridge and form an internal hydraulic pump downstream of the separation point. This study will investigate this separation point as a function of dimensionless mountain height and certain thermal characteristics such as the cold pool in the valley between mountain ranges.