Assessment of Immersed Boundary Methods for Hypersonic Flows with Gas-Surface Interactions

TL;DR

This paper evaluates immersed boundary methods with adaptive mesh refinement for hypersonic atmospheric entry flows, focusing on chemical nonequilibrium and gas-surface interactions, and compares their accuracy against traditional body-fitted grid solutions.

Contribution

It provides a comprehensive assessment of conservative and non-conservative immersed boundary methods in hypersonic flow simulations with chemical and surface interaction complexities.

Findings

Conservative cut-cell IB method matches body-fitted grid accuracy.

Ghost-cell IB methods show mass conservation errors at high gradients.

IB methods generally agree well with reference solutions.

Abstract

Immersed boundary (IB) methods with adaptive mesh refinement (AMR) techniques are assessed for atmospheric entry applications, including effects of chemical nonequilibrium (CNE) and gas-surface interactions (GSI). The performance of a conservative cut-cell and two non-conservative ghost-cell IB methods is assessed in comparison with analytical solutions, data from literature, and results obtained with a reference solver that operates on body-fitted grids. All solvers use the same external thermochemistry library so that all observed differences can be attributed to the underlying numerical methods. Results from eight benchmark cases are reported. Four cases are selected to verify the implementation of chemistry, transport properties, catalytic boundary conditions, and shock capturing. Four validation cases consider blunt geometries with adiabatic/isothermal and inert/catalytic/ablative boundary conditions. Overall, the results obtained with the IB solvers are in very good agreement with the reference data. Discrepancies arise with ghost-cell methods for cases with large temperature or concentration gradients at the wall and are attributed to mass conservation errors. Only a strictly conservative cut-cell IB method is on par with body-fitted grid methods.