ABSTRACT For the numerical investigation of re-entry phenomena the modeling of gas-surface intera... more ABSTRACT For the numerical investigation of re-entry phenomena the modeling of gas-surface interactions is crucial. Mission relevant phenomena are catalysis i.e. the surface material dependent recombination of atomic species and the oxidation processes of ceramic thermal protection systems. The latter is closely related to the following questions: What is the size of available surface area for catalysis? What is the dominating process at peak heating during the atmospheric entry maneuver – active or passive oxidation? In this work we will discuss the two main catalysis mechanisms, the Eley-Rideal and the Langmuir-Hinshelwood process. We give a brief introduction to this topic and discuss relevant implementations in catalysis related numerical tools. Also, we present some details on oxidation modeling and its implementation in the URANUS 2D code.
... during STARDUST and ATV1 re-entry Stefan Löhle Ricarda Wernitz Georg Herdrich Markus Fe... more ... during STARDUST and ATV1 re-entry Stefan Löhle Ricarda Wernitz Georg Herdrich Markus Fertig Hans-Peter Röser Heiko Ritter Received: 11 August 2009 / Revised: 26 September 2010 / Accepted: 27 September 2010 Ó CEAS 2010 ...
In the frame of the ESA flight experiment EXPERT the major aerothermodynamic phenomena around two... more In the frame of the ESA flight experiment EXPERT the major aerothermodynamic phenomena around two control surfaces and their cavities have been investigated with experimental and numerical methods. The flow upstream of the flap is characterized by Payload 7 of CIRA using heat flux sensors. The instrumentation of the C/SiC flap and cavity will allow measuring the surface temperature, pressure and the heat flux rate using high temperature sensors (Payload 6 of DLR). The rear surface temperature distribution of one of the flaps will be measured with an infrared (IR) camera (Payload 8 of RUAG). This data will be used to compute the front surface heat flux distribution using an inverse method analysis. Characterization tests in the SCIROCCO facility will allow calibrating the complete measurement system and data reduction software, since in contrast to the flight the front surface temperature of the flap will be measured with an additional IR camera of the facility.
Catalytic heating can be a significant portion of the thermal load experienced by a body during r... more Catalytic heating can be a significant portion of the thermal load experienced by a body during re-entry. Under the auspices of the NATO Research and Technology Organisation Applied Vehicle Technologies Panel Task Group AVT-136 an assessment of the current state-of-the-art in the experimental characterization and numerical simulation of catalysis on high-temperature material surfaces has been conducted. This paper gives an
This document describes the DLR CFD based evaluation of the blackout phenome-non around a 30 cm s... more This document describes the DLR CFD based evaluation of the blackout phenome-non around a 30 cm spherical re-entry performed in the frame of the "Characterisation of the radio transmission black-out phenomenon due to plasma flow" project. Three different flow conditions from the reference trajectory have been simulated employing the DLR CFD code TAU in order to determine the plasma frequencies at around peak heating conditions of a spherical re-entry vehicle. The flow-field was discretized employing hybrid grids. For each flow condition the grid was adapted several times to obtain grid converged results. An 11 component model accounting for N2, O2, NO, N, O, N2+, O2+, NO+, N+, O+ and e- in combination with a two-temperature thermal nonequilibrium model accounting for a separate electron temperature was employed to determine the electron number density around the capsule accurately. The plasma frequencies were determined based on the computed electron number densities. The maximum plasma frequency which is considered the minimal transmission frequency for unhindered transmission was determined along radial straights. The results indicate radio transmission black-out for all of the investigated flow conditions. However, while the radio wave attenuation is 13 orders of magnitude at peak heating conditions it drops to a factor of 70 at peak dynamic pressure. Therefore, radio communication should be possible at slightly lower altitude.
This document describes the numerical rebuilding of the wind tunnel testing per-formed in DLR H2K... more This document describes the numerical rebuilding of the wind tunnel testing per-formed in DLR H2K facility performed in the frame of the Planetary Probe Standard Model Testing project. Two different flow conditions investigated experimentally in H2K under 0°, 6° and 12° angle of attack have been simulated employing the DLR CFD code TAU in order to determine the prediction accuracy of the rear cover heat-ing results. For these runs the steady state solver with local time stepping was em-ployed. In this case the time step for each volume cell is determined based on the local characteristic time and user defined CFL number. Hence, the steady state solv-er is not time accurate. One of the experimental conditions was simulated time re-solved employing the dual time-stepping scheme implemented in TAU with second order accuracy in time. Two initial grids have been used in order to resolve the boundary layer and the sur-face conditions properly. All grids were adapted several times to obtain grid con-verged results. None of the stationary simulations assuming laminar flow converged in the base flow region. This indicates that the wake flow for all of the experimental conditions was instationary. However, the flow cases with angle of attack show only small variations of rear cover heat flux such that a time resolved computation under angle of attack does not seem necessary. With turbulence model applied the flow becomes stationary.
This paper describes the methodology of determining the recombination coefficients for candidate ... more This paper describes the methodology of determining the recombination coefficients for candidate materials of the catalytic based sensor system PHLUX. The methodology was broadened in terms of evaluation of the specific heat flux on catalytic surfaces. This leads to the possibility of calculating species concentration and atom net fluxes on and at the surface directly. Recombination coefficients with an indication of temperature and pressure level at which they were determined is given. Total emissivities for these materials for temperatures up to 2300K are provided.
In this paper an overview is given on a numerical simulation program for applied field magnetopla... more In this paper an overview is given on a numerical simulation program for applied field magnetoplasmadynamic (AF–MPD) thrusters, which is currently under development at the Institute of Space Systems (IRS). The program allows the simulation of argon plasma flows under thermal and chemical non–equilibrium. The code is based on an axisymmetric finite volume method on unstructured, adaptive meshes. An externally applied magnetic field can be taken into account employing the vector potential formulation. Azimuthal velocity and magnetic field are handled by a quasi–three dimensional approach with vanishing azimuthal derivatives. Besides the numerical analysis, a radiation–cooled laboratory model of an AF– MPD thruster is under development at IRS. The thruster model is to be assembled into a thrust balance. The modular design allows adjustments of the electrode and magnetic field configuration to find an optimized thruster geometry based on numerical and experimental results.
9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 2006
ABSTRACT In order to model the transient plasma flow inside an instationary magnetoplasmadynamic ... more ABSTRACT In order to model the transient plasma flow inside an instationary magnetoplasmadynamic (IMPD) thruster, also known as pulsed plasma thruster (PPT), a cooperation between IRS (Institute of Space Systems, University of Stuttgart), IAG (Institute for Aerodynamics and Gas Dynamics, University of Stuttgart), HLRS (High Performance Computing Center Stuttgart) and IHM (Institute for Pulsed Power and Microwave Technology, Research Center Karlsruhe) has been formed. Within the project "Modeling and Simulation on High Performance Computers", which is funded by the Landesstiftung BadenWiirttemberg, a scheme for approximately solving the Boltzmann equation for rarefied, non-continuum plasma flows is under development, making use of well known approaches from PlC (Particle in Cell) and DSMC (Direct Simulation Monte Carlo). The current development status will be reported and required computational resources will be estimated
This document describes the DLR supersonic and hypersonic CFD activities performed in the frame o... more This document describes the DLR supersonic and hypersonic CFD activities performed in the frame of the EXOMARS 2018 project. Eighteen different flow conditions from the reference trajectory have been simulated employing the DLR CFD code TAU in order to determine the aerodynamic coefficients as well as heating rates at hypersonic speed of the EXOMARS 2018 vehicle. Two initial grids have been used in order to resolve the boundary layer and the surface conditions properly. All grids were adapted several times to obtain grid converged results. However, especially the surface heating results show some scatter which is based on the usage of unstructured grids. Therefore, smoothed heating results are shown in the report in addition.
ABSTRACT For the numerical investigation of re-entry phenomena the modeling of gas-surface intera... more ABSTRACT For the numerical investigation of re-entry phenomena the modeling of gas-surface interactions is crucial. Mission relevant phenomena are catalysis i.e. the surface material dependent recombination of atomic species and the oxidation processes of ceramic thermal protection systems. The latter is closely related to the following questions: What is the size of available surface area for catalysis? What is the dominating process at peak heating during the atmospheric entry maneuver – active or passive oxidation? In this work we will discuss the two main catalysis mechanisms, the Eley-Rideal and the Langmuir-Hinshelwood process. We give a brief introduction to this topic and discuss relevant implementations in catalysis related numerical tools. Also, we present some details on oxidation modeling and its implementation in the URANUS 2D code.
... during STARDUST and ATV1 re-entry Stefan Löhle Ricarda Wernitz Georg Herdrich Markus Fe... more ... during STARDUST and ATV1 re-entry Stefan Löhle Ricarda Wernitz Georg Herdrich Markus Fertig Hans-Peter Röser Heiko Ritter Received: 11 August 2009 / Revised: 26 September 2010 / Accepted: 27 September 2010 Ó CEAS 2010 ...
In the frame of the ESA flight experiment EXPERT the major aerothermodynamic phenomena around two... more In the frame of the ESA flight experiment EXPERT the major aerothermodynamic phenomena around two control surfaces and their cavities have been investigated with experimental and numerical methods. The flow upstream of the flap is characterized by Payload 7 of CIRA using heat flux sensors. The instrumentation of the C/SiC flap and cavity will allow measuring the surface temperature, pressure and the heat flux rate using high temperature sensors (Payload 6 of DLR). The rear surface temperature distribution of one of the flaps will be measured with an infrared (IR) camera (Payload 8 of RUAG). This data will be used to compute the front surface heat flux distribution using an inverse method analysis. Characterization tests in the SCIROCCO facility will allow calibrating the complete measurement system and data reduction software, since in contrast to the flight the front surface temperature of the flap will be measured with an additional IR camera of the facility.
Catalytic heating can be a significant portion of the thermal load experienced by a body during r... more Catalytic heating can be a significant portion of the thermal load experienced by a body during re-entry. Under the auspices of the NATO Research and Technology Organisation Applied Vehicle Technologies Panel Task Group AVT-136 an assessment of the current state-of-the-art in the experimental characterization and numerical simulation of catalysis on high-temperature material surfaces has been conducted. This paper gives an
This document describes the DLR CFD based evaluation of the blackout phenome-non around a 30 cm s... more This document describes the DLR CFD based evaluation of the blackout phenome-non around a 30 cm spherical re-entry performed in the frame of the "Characterisation of the radio transmission black-out phenomenon due to plasma flow" project. Three different flow conditions from the reference trajectory have been simulated employing the DLR CFD code TAU in order to determine the plasma frequencies at around peak heating conditions of a spherical re-entry vehicle. The flow-field was discretized employing hybrid grids. For each flow condition the grid was adapted several times to obtain grid converged results. An 11 component model accounting for N2, O2, NO, N, O, N2+, O2+, NO+, N+, O+ and e- in combination with a two-temperature thermal nonequilibrium model accounting for a separate electron temperature was employed to determine the electron number density around the capsule accurately. The plasma frequencies were determined based on the computed electron number densities. The maximum plasma frequency which is considered the minimal transmission frequency for unhindered transmission was determined along radial straights. The results indicate radio transmission black-out for all of the investigated flow conditions. However, while the radio wave attenuation is 13 orders of magnitude at peak heating conditions it drops to a factor of 70 at peak dynamic pressure. Therefore, radio communication should be possible at slightly lower altitude.
This document describes the numerical rebuilding of the wind tunnel testing per-formed in DLR H2K... more This document describes the numerical rebuilding of the wind tunnel testing per-formed in DLR H2K facility performed in the frame of the Planetary Probe Standard Model Testing project. Two different flow conditions investigated experimentally in H2K under 0°, 6° and 12° angle of attack have been simulated employing the DLR CFD code TAU in order to determine the prediction accuracy of the rear cover heat-ing results. For these runs the steady state solver with local time stepping was em-ployed. In this case the time step for each volume cell is determined based on the local characteristic time and user defined CFL number. Hence, the steady state solv-er is not time accurate. One of the experimental conditions was simulated time re-solved employing the dual time-stepping scheme implemented in TAU with second order accuracy in time. Two initial grids have been used in order to resolve the boundary layer and the sur-face conditions properly. All grids were adapted several times to obtain grid con-verged results. None of the stationary simulations assuming laminar flow converged in the base flow region. This indicates that the wake flow for all of the experimental conditions was instationary. However, the flow cases with angle of attack show only small variations of rear cover heat flux such that a time resolved computation under angle of attack does not seem necessary. With turbulence model applied the flow becomes stationary.
This paper describes the methodology of determining the recombination coefficients for candidate ... more This paper describes the methodology of determining the recombination coefficients for candidate materials of the catalytic based sensor system PHLUX. The methodology was broadened in terms of evaluation of the specific heat flux on catalytic surfaces. This leads to the possibility of calculating species concentration and atom net fluxes on and at the surface directly. Recombination coefficients with an indication of temperature and pressure level at which they were determined is given. Total emissivities for these materials for temperatures up to 2300K are provided.
In this paper an overview is given on a numerical simulation program for applied field magnetopla... more In this paper an overview is given on a numerical simulation program for applied field magnetoplasmadynamic (AF–MPD) thrusters, which is currently under development at the Institute of Space Systems (IRS). The program allows the simulation of argon plasma flows under thermal and chemical non–equilibrium. The code is based on an axisymmetric finite volume method on unstructured, adaptive meshes. An externally applied magnetic field can be taken into account employing the vector potential formulation. Azimuthal velocity and magnetic field are handled by a quasi–three dimensional approach with vanishing azimuthal derivatives. Besides the numerical analysis, a radiation–cooled laboratory model of an AF– MPD thruster is under development at IRS. The thruster model is to be assembled into a thrust balance. The modular design allows adjustments of the electrode and magnetic field configuration to find an optimized thruster geometry based on numerical and experimental results.
9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 2006
ABSTRACT In order to model the transient plasma flow inside an instationary magnetoplasmadynamic ... more ABSTRACT In order to model the transient plasma flow inside an instationary magnetoplasmadynamic (IMPD) thruster, also known as pulsed plasma thruster (PPT), a cooperation between IRS (Institute of Space Systems, University of Stuttgart), IAG (Institute for Aerodynamics and Gas Dynamics, University of Stuttgart), HLRS (High Performance Computing Center Stuttgart) and IHM (Institute for Pulsed Power and Microwave Technology, Research Center Karlsruhe) has been formed. Within the project "Modeling and Simulation on High Performance Computers", which is funded by the Landesstiftung BadenWiirttemberg, a scheme for approximately solving the Boltzmann equation for rarefied, non-continuum plasma flows is under development, making use of well known approaches from PlC (Particle in Cell) and DSMC (Direct Simulation Monte Carlo). The current development status will be reported and required computational resources will be estimated
This document describes the DLR supersonic and hypersonic CFD activities performed in the frame o... more This document describes the DLR supersonic and hypersonic CFD activities performed in the frame of the EXOMARS 2018 project. Eighteen different flow conditions from the reference trajectory have been simulated employing the DLR CFD code TAU in order to determine the aerodynamic coefficients as well as heating rates at hypersonic speed of the EXOMARS 2018 vehicle. Two initial grids have been used in order to resolve the boundary layer and the surface conditions properly. All grids were adapted several times to obtain grid converged results. However, especially the surface heating results show some scatter which is based on the usage of unstructured grids. Therefore, smoothed heating results are shown in the report in addition.
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