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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

UNCERTAINTY ESTIMATION FOR THE SPATIAL AND TEMPORAL RESOLUTION IN DETACHED EDDY SIMULATIONS (DES) OF TRANSONIC FLOW OVER AN OPEN CAVITY

Debashis Basu
Fire Technology Department, Chemistry and Chemical Engineering Division, Southwest Research Institute

Kaushik Das
Thermal Modeling and Analysis Systems Engineer, The Giant Magellan Telescope Organization

Abstract

The paper presents a Computational Fluid Dynamics (CFD) analysis of transonic cavity flows and an assessment of numerical uncertainty associated with the computation. Numerical solutions to the three-dimensional (3-D) Navier-Stokes equations are obtained using a third-order Roe scheme and the shear-stress-transport (SST) two-equation-based hybrid turbulence model [Detached Eddy Simulation (DES)] for transonic flow over an open cavity. A detailed assessment of the effects of the computational grid is presented for the unsteady flow field. Results for the vorticity, pressure fluctuations, sound pressure level (SPL) spectra and for modeled and resolved Turbulent Kinetic Energy (TKE) are presented and compared with available experimental data and with Large Eddy Simulations (LES) results. The results demonstrate that both grid resolution and the time step have a significant effect on the resolved scales and the peak amplitude of the unsteady SPL and TKE spectra. Mesh discretization errors are estimated for the simulated open cavity flow using the traditional Grid Convergence Index (GCI) method and the least square (LS) technique. Four levels of computational grids were used in the GCI analysis. The simulated results obtained from the different grid levels showed little variation. The GCI results indicate that the actual order of accuracy realized from the solution is lower compared to the theoretical order specified. Extrapolated pressure obtained from the GCI equations show a relatively nonuniform pattern with mesh refinement. The error estimated using the GCI and LS method are found to be comparable.

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