Internal Energy Transfer and Dissociation Model Development using Accelerated First-Principles Simulations of Hypersonic Flow Features
Final rept. 15 Apr 2010-14 Apr 2013
MINNESOTA UNIV MINNEAPOLIS OFFICE SPONSORED PROJECTS ADMINISTRATION
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All-atom computational chemistry molecular dynamics MD simulation of normal shock waves is demonstrated and validated with experimental data for shock structure. The only model input into such simulations is the potential energy surface PES that governs individual atomic interaction forces. In contrast to existing rotational energy models, we found that the rotational relaxation rate depends strongly on the initial degree of nonequilibrium and the direction towards the equilibrium state. Compressing flows involve fast excitation whereas expanding flows involve slow relaxation for the same equilibrium temperature. We developed a new rotation model for both DSMC and CFD simulation. At high temperatures we found clear evidence of rotational-vibrational energy coupling. In contrast to existing models, we propose that a coupled ro-vib relaxation time is required to model direct energy transfer between rotation and vibration at high temperatures and we present a new ro-vibrational model. Finally, we develop a numerical method that replaces the collision model in DSMC with MD trajectories. We verify that the new method exactly reproduces pure MD results. This advancement enables the simulation of axisymmetric and even 3D flows with the accuracy of pure MD.
- Fluid Mechanics