Date of Award
Spring 5-2024
Degree Name
Master of Science (MS)
Degree Type
Thesis
Abstract
This thesis consists of two related parts. The first part is the study of supersonic/hypersonic flow in compression corners. The compression corners are simple geometries but rich in flow-features that can be challenging for accurate prediction of their flow fields in high-speed compressible flow using the Reynold-Averaged Navier-Stokes (RANS) equations in conjunction with a turbulence model. At higher degrees of corner angles, there exists a shock-boundary layer interaction region which includes a significant recirculation zone in the corner. In this thesis, experimentally available test cases for compression corner at Mach 3, 8, and 11 at various corner angles are modeled as 2D planar geometries and are simulated using the ANSYS Fluent. Results are compared to the experimental studies for the same flow conditions from Settles et al. and Smits and Muck at Mach 2.85 and from Holden et al. at Mach 8 and Mach 11 for various corner angles. The Spalart-Allmaras (SA), SST k-ω, and Wray-Agarwal (WA) turbulence models are employed in the study. The surface static pressure, heat transfer rate, and separation bubble in the corner are compared between the simulations and the experiments. Generally, it was found that the SA model’s accuracy begins to falter at the higher corner angles (> 20+ degrees). It was found that SST k-ω and WA models are suitable for these flow conditions, as they can reproduce the trends seen in the experimental static pressure measurements. Additionally, it was found that the WA model shows good behavior in generating the major recirculation region that is present in the corner for the higher corner angles (>20+ degrees).
The second part of the thesis consists of a hypersonic flow study of atmospheric entry of Mars Science Laboratory (MSL) Capsule. The MSL spacecraft architecture constituted the design of the Curiosity and Perseverance rover missions. The heat shield of the MSL capsule used a tiled PICA (Phenolic Impregnated Carbon Ablator) TPS (Thermal Protection System), with gap-filler material applied in the space between the tiles. During atmospheric entry at high Mach numbers, the instrumentation of the MSL heatshield reported a sharp rise in the net heating rate of the heatshield, which indicated an earlier-than-expected onset of turbulent flow over the heatshield. A CFD investigation was conducted to determine if the protrusion of the gap-filler after a period of ablation could be a significant factor in the onset of turbulent flow over the heat shield. The case was run using the resources of NASA Ames Research Center’s Advanced Supercomputing Division and employed NASA’s DPLR hypersonic CFD code. The results obtained suggest that the gap-filler protrusion is a significant factor.
Language
English (en)
Chair
Ramesh K. Agarwal
Committee Members
David A. Peters, Swami Karunamoorthy