Toward Predictive Modeling of Winds Around Complex Terrain Under Stably Stratified Conditions
MIE Department Seminar
September 24, 2019
11:00 AM - 12:00 PM
Toward Predictive Modeling of Winds Around Complex Terrain Under Stably Stratified Conditions
Presenter: Inanc Senocak, PhD, Associate Professor, University of Pittsburgh Material Science and Engineering
Abstract: Prediction of winds around complex terrain finds several applications in wind energy, agriculture, air quality, and defense operations. Wall-modeled Cartesian immersed boundary technique and turbulent inflow boundary conditions have been coupled to predict winds around complex terrain under neutrally stratified atmospheric conditions with reasonable accuracy. However, neutral stratification of the atmosphere is often the exception rather than the norm. Stable stratification prevails during nighttime and in cold climates. Unlike its well-mixed, unstable counterpart, turbulence in stable stratification is poorly understood due to several mystifying processes such as turbulent bursts, relaminarization and wave-turbulence interactions. This gap in our comprehension of stratified flows hinders progress in developing accurate parameterization of turbulence in computer models of atmospheric flows.
In the first part of my talk, I will present a computational capability to predict winds around arbitrarily complex terrain using a large-eddy simulation paradigm accelerated with graphics processing units. In the second part, I will present a prototype flow problem to better understand katabatic winds. The investigation is centered around a relatively less- known exact solution from Ludwig Prandtl. A linear stability analysis of slope flows, supported with direct numerical simulations, demonstrates that the Prandtl model for katabatic slope flows is prone to transverse and longitudinal modes of instability. The transverse mode manifests itself as stationary vortical flow structures aligned in the along- slope direction, whereas the longitudinal mode emerges as waves propagating in the base-flow direction. The progression of these instabilities toward turbulence is found to depend on the slope angle, the Prandtl number and a newly introduced stratification perturbation parameter. A single Richardson number criteria is deemed ineffective to characterize the stability of stratified slope flows.
Presenter bio: Inanc Senocak is an associate professor of mechanical engineering at the University of Pittsburgh. He earned his PhD degree in aerospace engineering from the University of Florida and his B.Sc. degree in mechanical engineering from the Middle East Technical University in Ankara, Turkey. He conducted postdoctoral studies at the Stanford University and the Los Alamos National Laboratory prior to beginning his faculty career at the Boise State University in 2007. Senocak is a fellow of the American Society of Mechanical Engineers (ASME), an associate fellow of the American Institute of Aeronautics and Astronautics (AIAA) and a past recipient of a CAREER Award from the National Science Foundation.
Host: Dr. Farzad Mashayek
Date posted
Sep 12, 2019
Date updated
Sep 12, 2019