Validation of Hypersonic Flow Simulationsvia Molecular-Scale Physics
Abstract
Hypersonic and re-entry flows are characterized by extreme gradients in key flow quantities, chemical reactions and internal energy excitation, and highly coupled convective and diffusive effects. For example, a re-entry vehicle has a shock layer that is only a few millimeters thick, with temperatures that can exceed 20,000K. Over the past several decades, it has become possible to accurately solve the equations that describe these flows on very large and complex grids. However, all of these computational fluid dynamics (CFD) and Direct SimulationMonte Carlo (DSMC) codes use the same models, based on the same assumptions.There has never been a rigorous evaluation of these models, and there are known deficiencies in their formulation. The Boltzmann equation is the most basic description of a flowing gas, and it can be used to derive the compressible Navier-Stokes equations for a mixture of non-reacting gases. This derivation requires that the velocity distribution function is not far from equilibrium. Kinetic theory provides expressions for the viscosity and mass diffusivity of the gas mixture. It is computationally intensive to use the complete kinetic theory results, and significant simplifications are made in all simulation codes. However, there is no theory-based model for the thermal conductivity of a non-trivial gas mixture. Furthermore, there are no kinetic theory derivations for a reacting gas with an internal energy state that is far from equilibrium. Thus, the overall goal of the proposed research is to use fundamental molecular-scale data to validate, improve, and extend the existing numerical simulation approaches for hypersonic and high-temperature flows. This work will result in more accurate and reliable simulations of Air Force relevant hypersonic flows. The proposed approach will leverage new computational chemistry data and an array of numerical simulation approaches to achieve this goal.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 28, 2017
- Source ID
- FA95501710250
Entities
People
- Graham Vardy Candler
Organizations
- Air Force Office of Scientific Research
- Regents of the University of Minnesota
- United States Air Force