AUGMENTATION OF A HIGH-FIDELITY SOLVER TO RESOLVE UNSTEADY FLOW PHENOMENON IN SUPERSONIC RETROPROPULSION FLOWFIELDS

Abstract

A scale-resolving solver is augmented to incorporate adaptive mesh refinement to reduce the computational expense of application flowfields by over an order of magnitude. This new capability, after a validation effort, was successfully deployed on supersonic retropropulsion (SRP) test cases to provide a large, complete dataset of quantities of interest for the EDL and computational fluid dynamics communities.

Augmentations to the in-house CRoCCo codebase are made to enable high-fidelity simulations of complex applications such as SRP. Adaptive mesh refinement is implemented on generalized curvilinear coordinates to enable wall-resolved simulations with careful considerations to preserve the bandwidth-resolving efficiencies of the underlying numerical methods. The newly developed CRoCCo-AMR codebase is validated through direct numerical simulation (DNS) and wall-resolved large eddy simulation (WRLES) of shock wave and turbulent boundary layer interactions (STBLI) at supersonic conditions. This validation exercise demonstrates a 40% for DNS and 27% for WRLES reduction in grid points. AMR validation shows strong agreement for the mean flow variables, turbulent intensities, and spectral quantities of existing datasets. This dissertation provides in-depth discussion and defense of decisions, implementation, and validation of scale-resolving simulation capabilities in the pursuit of deploying such methods on SRP flowfields to improve the state-of-the-art simulation capabilities for human-class exploration of Mars.

High-fidelity simulations of nozzle flows relevant to supersonic retropropulsion environments are conducted using CRoCCo-AMR. The computational approach is discussed in detail. Initial results are presented for a single-nozzle condition with comparison to available experimental data. Two additional single-nozzle retropropulsion configurations are simulated with reductions in grid size of an order of magnitude. Strong agreement is demonstrated in key regions of the flowfield. Mean and statistical analyses are performed to characterize unsteady, turbulence quantities present in the canonical retropropulsion environment. This study provides new and important insight into the behavior of the vortex shedding present within the SRP flowfields. A detailed accounting of unsteadiness and frequency content is provided in a novel analysis coupling the effects of off-body wake flow to fluctuations in wall quantities.