Validation of Turbulence Models for the Beggar Code in Unsteady Flows

摘要

Validation of the turbulence models in the CFD code Beggar for unsteady turbulent flow are discussed. Six validation cases of the code are considered, three cases with the intent of validating the code without the turbulence model and three cases to validate the turbulence model itself. Finally, a more realistic simulation of a simplified store is examined. The turbulence models considered are the Baldwin-Lomax, Spalart-Allmaras, and a DES model. The conclusions made deal with necessary prerequisites to properly simulating unsteady turbulent flow and model selection. The prerequisites necessary in the Beggar code are a second order temporal discretization and the calculation of at least three Newton dt-iterations per time step. Baldwin-Lomax overpredicts unsteady effects. The Spalart-Allmaras model was found to not properly simulate unsteady turbulent flow and is possible written incorrectly in Beggar. A recommendation of whether to use the DES model or not cannot be made due to time and computational constraints and temporary problems within the Beggar code.