Simulation of Magnetohydrodynamic Effects on an Ionised Hypersonic Flow by Using the TAU Code

In the present investigation the DLR TAU code is extended to support future experimental investigations of magnetohydrodynamic effects in high temperature hypersonic flows. According to the conditions in the High Enthalpy Shock Tunnel Goettingen (HEG) the first steps in enhancing the TAU code are the implementation of a source term formulation of electromagnetic forces and the calculation of the electrical conductivity of air as a gas mixture in chemical non equilibrium. To verify the source term implementation a perfect gas study related to numerical simulations from Poggie and Gaitonde is conducted and shows reasonable agreement. Applied to the experimental conditions the model predicts a noticeable increase of the shock stand off distance

Sensitivity of scale resolving aft-body flow simulations to numerical model parameter variations

The sensitivity of hybrid RANS-LES methods like Improved Delayed Detached Eddy Simulation (IDDES) to numerical model parameter variations related to generic space launch vehicle aft-body flows is investigated. In particular the changes resulting from the choice of the time step size, the turbulence model, the fluid modelling, the circumferential grid resolution, the filter length definition and the data collection period is considered. The results are also compared to experimental and numerical data taken from the available literature. The sensitivity to the time step size and the turbulence model is minuscule with respect to the obtained mean flow field, wall pressure distributions, azimuthal modes and wall pressure frequency spectra. However, circumferential resolution, fluid model and filter length definition affect the solution to a higher extent. Buffeting spectra are very sensitive to the data collection period

Sensitivity Analysis Study of Expanding Hypersonic Flows of Nitrogen and Oxygen

Sensitivity analysis studies of expanding high-enthalpy binary flows of nitrogen and oxygen in hypersonic nozzles are carried out for a variety of conditions. The polynomial chaos expansion (PCE) methodology is utilised to assess the sensitivity of the free-stream conditions to vibrational and chemical relaxation rates, as well as the reservoir conditions. It is shown that for high-enthalpy conditions, the main contributors to uncertainty in the free-stream flow are uncertainties in the vibrational and chemical relaxation rates for molecule-atom collisions, as well as uncertainties in the reservoir conditions. The impact of high- temperature vibrational relaxation time corrections and the vibrational-chemical coupling was found to be negligible for the investigated cases. A preliminary analysis on the potential influence of ionization was also performed, which was found to have an insignificant effect on the free-stream conditions in nitrogen

Uncertainty Quantification of Expanding High-Enthalpy Air Flows

In the present work, we study the sensitivity of expanding hypersonic air flows in the HEG facility with respect to the thermochemical relaxation rates and reservoir conditions, along with the impact of uncertainties in the rates and reservoir conditions on uncertainties of the free-stream parameters. A simplified 1-D formulation of the flow equations is utilized to allow for simultaneous variation of a large number (10) of uncertain parameters. The simulation results show large uncertainties in the vibrational temperature of oxygen and molar fractions of oxygen-containing species, mainly due to uncertainties in the reservoir parameters and data on thermochemical relaxation rates of molecular oxygen

Numerical and Experimental Investigations of a Generic Rocket Launcher Configuration with Cold Plume in Hypersonic Flow

A generic rocket launcher geometry is studied experimentally and numerically at hypersonic flow conditions including a cold plume. The experiments are conducted in a hypersonic Ludwieg tube while numerical calculations are performed with a finite-volume Navier-Stokes solver using the Detached-Eddy Simulation technique. Good agreement for the mean flow field is obtained. However, discrepancies between the spectral analysis of the computed and measured pressure fluctuations are observed

About the Assessment of Heat Flux and Skin Friction of the DLR TAU-code for Turbulent Supersonic Flows

The correct prediction of skin friction and surface heat flux by CFD tools is an important prerequisite for the design of hypersonic flight vehicles. Results of a test campaign of a flow past a flat plate configuration with an impinging oblique shock carried out in the Ludwieg Tube Facility of DLR Göttingen were used to assess the applicability and accuracy of the DLR TAU-code at respective flow conditions. A shock-wave/turbulent boundary layer interaction (SWTBLI) on the flat plate model was created with a planar shock generator at different incidence angles. This two dimensional test case involving the flat plate flow and the interaction of an oblique shock with the turbulent boundary layer is well documented with various measurements like wall pressure, boundary layer velocity profiles, skin friction, and heat flux, and offers a good basis for the assessment of the two latter variables for the DLR TAU-code. The assessment includes grid studies, the influence of various turbulence models as well as the external turbulence intensity set in the calculations

Simulation von Hochenthalpieströmungen

Charkaterisierung von Hochenthalpieströmungen, Rückblick auf gemeinsame Projekte mit B. Esser, Ausblick auf potentielle Weiterentwicklungen basierend auf vorhandenen Projektergebnissen

KW TURBULENCE MODEL: SHOCK UNSTEADINESS MODIFICATION

Introduction of the author's DLR department and the kw turbulence model modifications to improve the turbulent energy production term in the vicinity of a shock. Shock sensors are discussed to provide the location and strength of the shocks in a compression ramp flowfiled and a shock-wave-boundary-layer-interaction flowfield