Hybrid DSMC/CFD Method Development for High-Altitude Hypersonic Flows
Abstract
Hypersonic flows produce extreme conditions, including chemical reactions and gas-surface interactions. In addition, the strong gradients in these flows can cause the continuum governing equations to break down, particularly at high altitudes where the air density is low. At these conditions, there can also be strong viscous-inviscid interactions that affect aerodynamic performance and control surface effectiveness. This regime is not well understood because thecontinuum equations of motion are not valid, but particle-simulation methods are too expensive to use. Therefore, the research project will develop a hybrid continuum/particle simulation method that combines the efficiency of the continuum Navier-Stokes equations with the accuracy of the Direct Simulation Monte Carlo (DSMC) approach. The basic concept is to start a flow field simulation with the continuum solver, and then detect regions where thecontinuum equations fail and switch to the DSMC method in those regions. Required data are passed between the two methods so that the simulation is completely consistent between the formulations. The proposed work builds on several recent advances and leverages previous theoretical research on the development of hybrid continuum/particle methods. In particular, ahighly flexible, scalable, and efficient adaptive mesh refinement (AMR) capability has recently been implemented in the University of Minnesota US3D computational fluid dynamics code. This makes the US3D code the ideal framework for the development of a hybrid method; grid elements can be refined based on the requirements of the continuum solver or based on thoseof the DSMC method, as dictated by the local state of the flow. Recent and ongoing work is making detailed comparisons between continuum and DSMC simulations so as to rigorously validate the methods and to ensure consistency between all aspects of the simulations. It has only recently become possible to run DSMC into the continuum regime so that this validation can be carried out. Previous work also provides a clear approach for passing data between theformulations so that continuum data can be obtained from statistical particle-based data, and vice versa. Therefore, the background research has been completed and it is now possible to develop a hybrid continuum/particle simulation tool for high Mach number flows. Initial work will focus on the development of a non-reacting gas model; as this becomes complete, a fullthermochemical nonequilibrium model will be implemented in US3D. Emphasis will be given to code efficiency and scaling so that the hybrid code will be of practical utility. The research will enable new high-fidelity simulations of complex-geometry hypersonic flows in the viscous interaction regime and under conditions where the continuum governing equations fail. This will result in more accurate predictions and improved understanding of high-altitudeaerodynamic performance and control surface effectiveness. The hybrid simulation capability will be transitioned to the US3D user community for application to national hypersonic programs.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 26, 2018
- Source ID
- N000141812521
Entities
People
- Graham Vardy Candler
Organizations
- Office of Naval Research
- Regents of the University of Minnesota
- United States Navy