TAU Extensions for High Enthalpy Flows Sebastian Karl AS-RF
Contents Motivation Extensions available in the current release: Numerical schemes for super- and hypersonic flow fields Models for gas mixtures, gas properties and chemically reacting flows Exemplary applications Atmospheric entry of spacecraft Ignition of a hydrogen fuelled combustion chamber Brief overview of current developments Folie 2
Motivation Further development of TAU at the Spacecraft Department of the Institute of Aerodynamics and Flow Technology Fluid mechanical problems related to spacecraft require additional modeling capabilities Atmospheric entry of spacecraft Hypersonic flight vehicles Propulsion systems Orbital systems Folie 3
Numerical schemes for super- and hypersonic flows Stable treatment of strong discontinuities (shocks) in the flow field Upwind solvers for inviscid (Euler-) fluxes Mimic the physics of wave propagation in super- (and sub-) sonic flows 8 different solvers available, work horse: AUSMDV Robust capturing of shocks, 2 nd order accurate (gradient reconstruction + limiting) Stability and convergence acceleration Special treatment to avoid carbuncle phenomena Restriction damping for multi-grid method Shock indicator to switch off residual smoothing Modifications of turbulence models (shocks, compressibility effects) Folie 4
Models for gas mixtures, gas properties and chemical reacting flows Available thermo-chemical modeling in TAU covers complete reentry trajectory of spacecraft in the continuum regime Folie 5
Models for gas mixtures, gas properties and chemical reacting flows Baseline: Reacting mixture of thermally perfect gases Set of transport equations for species partial densities with chemical source terms Chemical source terms computed from the law of mass action and detailed Reaction mechanisms (Arrhenius) Species thermodynamic properties computed from partition functions (quantum mechanics) or curve fits Species transport properties obtained from collision integrals (gaskinetic theory) or curve fits (e.g. Sutherland) Mixture transport properties computed from mixture rules Folie 6
Models for gas mixtures, gas properties and chemical reacting flows Extensions: Turbulence-chemistry interaction model (assumed PDF) Thermal non-equilibrium model (vibrational excitation of molecules) Dedicated plasma-diffusion models Simplifications: Models for flows in chemical equilibrium (based on pre-computed lookup tables) Models for non-reacting mixtures (e.g. exhaust gases in air) Available data: Air (O 2, N 2, NO, N, O, O 2+, N 2+, NO +, N +, O +, e - ) Mars and Titan atmospheres Hydrogen combustion (H 2, H 2 O, OH, H, O 2, HO 2, H 2 O 2, N 2 ) Folie 7
Exemplary applications Atmospheric entry of spacecraft Intermediate Experimental Vehicle (IXV), wind tunnel conditions Planned ESA R&T platform for re-usable entry configuration Wind tunnel experiments (DLR), U = 6km/s, = 1.5 g/m 3. Chemical non-equilibrium, t max = 9000K. Heat flux distribution on model surface Surface heat load Folie 8
Exemplary applications Ignition of a subscale combustor Complex multi-stage ignition process of a hydrogen / air flame in a subscale combustor (pre-mixed and diffusion flames) Excellent agreement with experimental data Folie 9
Exemplary applications Ignition of a subscale combustor Complex multi-stage ignition process of a hydrogen / air flame in a subscale combustor (pre-mixed and diffusion flames) Excellent agreement with experimental data Folie 10
Exemplary applications Ignition of a subscale combustor Complex multi-stage ignition process of a hydrogen / air flame in a subscale combustor (pre-mixed and diffusion flames) Excellent agreement with experimental data Folie 11
Current developments Overview Magneto hydrodynamics (MHD) Radiation transport Coupling with DSMC (rarefied flow) Multiphase flow and dense gas thermodynamics (Spray, Sloshing, Cryogenic fluids) Ablation Combustion models (e.g. Flamelet model) Thermal fluid-structure coupling Folie 12
Current developments Dense gas thermodynamics Modified equations of state and thermodynamic models for non-ideal gases (supercritical, high densities) Thermal fluid-structure coupling Example: flow in cooling channels of a rocket engine Folie 13
Current developments Dense gas thermodynamics Folie 14
Current developments Radiative heat transfer Solution of radiation transport equation using Monte-Carlo method Example: FIRE II flight experiment (h=50km, u=11 km/s) TAU fluid model: 11 species, air plasma Folie 15
Current developments Coupling with rarefied flow solvers TAU coupling interface for external statistical gas-kinetics solvers Example: plume flow of a satellite attitude control thruster Navier Stokes + DSMC Navier Stokes Folie 16
Summary Available extensions of TAU include a comprehensive set of models for: Numerical methods for super- and hypersonic flows Re-entry aerothermodynamics Combustion in the ideal gas regime Treatment of general gas mixtures (e.g. mixing of engine exhaust with ambient flow) Folie 17