Aerothermodynamics and hypersonic flows involve complex multi-disciplinary physics, including finite-rate gas-phase kinetics, finite-rate internal energy relaxation, gas-surface interactions with finite-rate oxidation and sublimation, transition to turbulence, large-scale unsteadiness, shock-boundary layer interactions, fluid-structure interactions, and thermal protection system ablation and thermal response. Many of the flows have a large range of length and time scales, requiring large computational grids, implicit time integration, and large solution run times. The University of Minnesota / NASA US3D code was designed for the simulation of these complex, highly-coupled flows. It has many of the features of NASA's well-established DPLR code, but uses unstructured grids and has many advanced numerical capabilities and physical models for multi-physics problems. The main capabilities of the code are described, the physical modeling approaches are discussed, the different types of numerical flux functions and time integration approaches are outlined, and the parallelization strategy is overviewed. Comparisons between US3D and the NASA DPLR code are presented, along with several advanced simulations to illustrate some novel features of the code.

A method for performing dynamic simulations of entry vehicles is developed. This capability uses existing infrastructure within the US3D flow solver, developed for doing fluid structure interaction (FSI) simulations, to allow for up to six degree of freedom (6-DoF) simulations. Inviscid, free-to-oscillate simulations of the Mars Science Laboratory (MSL) capsule at Mach 2.5 and 3.5 are used to evaluate di↵erent data reduction methods. It is found that many simulations may be required to get reliable data. The computed pitch damping coe cients show comparable trends to ballistic range data, though they di↵er in magnitude, particularly at high angles of attack. Preliminary viscous simulation results are presented, and show improved agreement with experimental data compared to the inviscid analysis.

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The method used for coupling US3D to a structural solver for the purpose of simulating fluid-structure interactions (FSI) is detailed. An overview of the solver components is provided, with an explanation of the necessary modification to US3D. Component level validation is undertaken against analytic solutions for both the structure to fluid and the fluid to structure parts of the FSI capabilities. The coupled solver is used on two instructive model problems to demonstrate FSI phenomena, and a full scale tension cone is also simulated to show the usefulness of a coupled solver in design evaluation.

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