Computational Math Seminar: Mike Sprague

Coupling meso-scale and micro-scale fluid dynamics codes for wind-energy computing: A two-dimensional study  

Mike Sprague

National Renewable Energy Laboratory

Date and time: 

Tuesday, October 29, 2013 - 10:00am

Location: 

Grandview Conference Room

Abstract: 

Enabled by peta-scale supercomputing, the next generation of computer models for wind energy will simulate a vast range of scales and physics, spanning from wind-turbine structural dynamics and blade-scale turbulence to meso-scale atmospheric flow. This work focuses on new interface conditions and computational algorithms for coupling meso-scale numerical-weather-prediction codes with micro-scale turbine-vicinity fluid-dynamics codes.  Here, an inherent challenge exists when the weather code is based on the compressible Euler equations, while the turbine-vicinity flow is modeled by the incompressible Navier-Stokes (NS) equations.  We propose partial-boundary and projection coupling for one- and two-way code coupling.  In partial-boundary coupling, NS-domain inflow and outflow boundary conditions are derived from the mean component of the meso-scale flow. In projection coupling, an incompressible-flow solution is found through projection of the compressible-flow solution, from which boundary conditions for the NS domain are extracted.  In both approaches, two-way coupling is achieved through loose coupling, where the Euler-domain solution is overwritten by the NS solution in the overlapping domain. These approaches are implemented in a two-dimensional testing platform composed of two in-house codes: (1) a finite-difference code that mimics the weather research and forecasting (WRF) solver and (2) an embedded-domain code based on a common finite-volume approach.  Numerical experiments show that the two approaches provide comparable performance in one-way coupling, but projection is superior for two-way coupling.