Papers by Sebastien Paris
Transitional shock-wave/boundary-layer interactions in hypersonic flow
Journal of Fluid Mechanics, 2014
Strong interactions of shock waves with boundary layers lead to flow separations and enhanced hea... more Strong interactions of shock waves with boundary layers lead to flow separations and enhanced heat transfer rates. When the approaching boundary layer is hypersonic and transitional the problem is particularly challenging and more reliable data is required in order to assess changes in the flow and the surface heat transfer, and to develop simplified models. The present contribution compares results for transitional interactions on a flat plate at Mach 6 from three different experimental facilities using the same instrumented plate insert. The facilities consist of a Ludwieg tube (RWG), an open-jet wind tunnel (H2K) and a high-enthalpy free-piston-driven reflected shock tunnel (HEG). The experimental measurements include shadowgraph and infrared thermography as well as heat transfer and pressure sensors. Direct numerical simulations (DNS) are carried out to compare with selected experimental flow conditions. The combined approach allows an assessment of the effects of unit Reynolds ...
Design of boundary layer probe payload for EXPERT program
Characteristics of a hyperboloid-flare configuration at high Reynolds numbers
Thermophysics and Aeromechanics, Dec 1, 2006
ABSTRACT Results on a hyperboloid-flare model tested in a new hypersonic wind tunnel with adiabat... more ABSTRACT Results on a hyperboloid-flare model tested in a new hypersonic wind tunnel with adiabatic compression AT-303 based at ITAM SB RAS at M∞ = 10 and 15 and in a wide range of Reynolds numbers are presented. Pressure and heat-flux distributions along the model are compared with data obtained previously in various European hypersonic wind tunnels (Longshot — Belgium, HEG — Germany) and with results of numerical computations. Pressure and heat-flux coefficients measured in the attached flow region are demonstrated to be in good qualitative agreement. Reasons for the differences in results measured in regions of flow separation and reattachment are discussed. Significant viscous effects on characteristics of the flow around the model are demonstrated; a particularly strong effect is exerted on the heat-flux distribution. This fact confirms that it is important to model real Reynolds numbers in wind-tunnel testing of aerospace plane models.
Predicted & Measured Capability of the VKI 1. 2 MW Plasmatron Regarding Re-Entry Simulation
In-Flight Hypersonic Roughness Induced Transition Experiment
46th AIAA Aerospace Sciences Meeting and Exhibit, Jan 7, 2008
The development of an hypersonic isolated roughness induced transition experiment has been carrie... more The development of an hypersonic isolated roughness induced transition experiment has been carried out based on experiments and numerical computations. This experiment has been developed in the frame of the European EXPERT program, which has been developed to carry multiple flight experiments aimed at improving the understanding of critical aerothermodynamic phenomena. The design of this experiment consist in the in the cho ice of the isolated roughness element and the inflight instrumentation. The choice of the roughness shape and dimensions has been made experimentally in a Mach-6 facility and are based r espectively on aerodynamic considerations and on wind-tunnel validated transition criteria. Some numerical thermal computations have been performed for the verification of the roughness des ign and of the ability of the instrumentation to detect transition. Finally, a fundamental investiga tion of the flow-field around and downstream of isolated roughness has been done for preparing the post-flight analysis.
Comparison of plexiglas and vespel materials for heat flux measurements by infrared thermography at hypersonic conditions
Proceedings of the 2002 International Conference on Quantitative InfraRed Thermography, 2002
The VKI Plasmatron Characteristics and Performance
The von Karman Institute (VKI) recently completed the commissioning of a new inductively-coupled ... more The von Karman Institute (VKI) recently completed the commissioning of a new inductively-coupled plasma wind tunnel ("Plasmatron") devoted to the simulation of thermal re-entry conditions as applicable to TPS materials used on real flight trajectories. In the context of the commissioning, two main intrusive measurement techniques, the Pitot tube and the calorimetric heat flux probe, were developed and extensively used to record the performance in order to compare them with the specifications. During the commissioning phase, other techniques were being developed in another VKI facility, the Minitorch, a small inductively-coupled plasma torch used as the instrumental test bench for the Plasmatron. This paper presents the Plasmatron facility to the reader, then describes in detail the probes that were used, the test methodology that was followed, and the results that were obtained during the commissioning phase. The technique of laser Doppler velocimetry (LDV), which is curre...
Contributions to Plasma Physics, 2004
The paper presents an overview of the aerothermal plasma simulation facilities in use at the von ... more The paper presents an overview of the aerothermal plasma simulation facilities in use at the von Karman Institute for Fluid Dynamics and the main research topics that have been followed during 10 years of work in the field. Both numerical simulation of plasma flows and experimental techniques are addressed, with an emphasis of the methodology which allows to relate measurements in the facilities to flight conditions of a space vehicle (re‐)entering a planetary atmosphere. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Infrared thermography equipment is used to measure the temperature rise at a surface of a model s... more Infrared thermography equipment is used to measure the temperature rise at a surface of a model simulating a deflected flap of a re-entry vehicle. The model is tested in the VKI-H3 hypersonic wind tunnel with a flow at Mach 6 at different Reynolds numbers and temperatures. Examining the rise of temperature on the interested surface, it is possible to visualize the flow topology on the surface and to infer the heat flux on the model. By heating artificially the model before the tests it is possible to evaluate the effects of the wall temperature on heat flux and flow topology.
The recession of an ablative heat shield could significantly modify the nominal outer shape of a ... more The recession of an ablative heat shield could significantly modify the nominal outer shape of a re-entry capsule and affect its aerodynamic behavior during the flight through the atmosphere. To quantify this effect, an experimental activity was carried out in the Mach-6 hypersonic wind tunnel H3 at the von Karman Institute for Fluid Dynamics. Subscale models of the European Space Agency hypervelocity entry demonstrator Phoebus, equipped with a heat shield made of a low-temperature ablator to promote the surface recession in the low-enthalpy conditions, were tested to record simultaneously the heat-shield recession and the aerodynamic loads. This paper describes the theoretical conception of this activity, details the preparation of the experimental test campaign and presents a first analysis of the experimental results.
The operation of the VKI Longshot hypersonic gun tunnel strongly depends on its compression proce... more The operation of the VKI Longshot hypersonic gun tunnel strongly depends on its compression process by which high-pressure and high-temperature gases are generated in the nozzle reservoir. The main part of this process takes place in a driven tube where a light supersonic piston compresses the test gas nearly adiabatically. In order to provide an experimental database for numerical simulations of the compression process, the present work characterizes this process by means of fast-response pressure sensors fitted at several locations along the driven tube. Moreover, the transient pressure measurements are used to determine the piston motion. Finally, the initial conditions prior to a test and the final reservoir conditions are also monitored.
Review of the VKI Longshot Hypersonic Tunnel Operation for Martian Entries
AIAA Scitech 2019 Forum, 2019
Proceedings of the 2004 International Conference on Quantitative InfraRed Thermography, 2004
Transition on the boundary layer of a hypersonic vehicle can result from many factors, among whic... more Transition on the boundary layer of a hypersonic vehicle can result from many factors, among which one of the most important is the presence of discontinuities (roughness) on its surface. For experiments performed in ground facilities, not all the in-flight conditions can be reproduced resulting in a mismatch between the data obtained from experimentation and the real flight conditions. This work represents an initial investigation of the parameters for transition in the Mach 6 H3 VKI wind tunnel using infrared thermography and on Kheops model. Three different kinds of discontinuities are considered: distributed roughness, gaps between different sections and isolated roughness elements. Results from the H3 tests are found to be in good agreement with ballistics range results plotted with PANT criterion parameters.
Characterization of CO2 flow in a hypersonic impulse facility using DLAS
Experiments in Fluids, 2016
AbstractThis work documents diode laser absorption measurements of CO2 flow in the free stream of... more AbstractThis work documents diode laser absorption measurements of CO2 flow in the free stream of the Longshot hypersonic impulse facility at Mach numbers ranging from 10 to 12. The diode laser sensor was designed to measure absorption of the P12 (30013) $$\leftarrow$$← (00001) transition near 1.6 $$\upmu$$μm, which yields relatively weak direct absorption levels (3.5 % per meter at peak Longshot free-stream conditions). Despite this weak absorption, measurements yielded valuable flow property information during the first 20 ms of facility runs. Simultaneous measurements of static temperature, pressure, and velocity were acquired in the inviscid core flow region using a laser wavelength scanning frequency of 600 Hz. The free-stream values obtained from DLAS measurements were then compared to Longshot probe-derived values determined from settling chamber and probe measurements. This comparison enabled an assessment of the traditional method of flow characterization in the facility, which indicated negligible influence from possible vibrational freezing of reservoir gases.
This work is part of the EXPERT project lead by ESA aiming to study phenomena occurring during Ea... more This work is part of the EXPERT project lead by ESA aiming to study phenomena occurring during Earth reentry for hypersonic vehicles. Transition from laminar to turbulent flows due to distributed roughness on the non-ablative nose of a blunt vehicle can be a big issue for the thermal protection system. Experiments are carried out with different distributed roughness densities, locations and sizes in the Longshot short duration facility (free-stream Mach number of 14, low enthalpy, Reynolds number about 13.10 6 /m) at the VKI. Wall temperature measurements with thermocouples on the scaled EXPERT model allow the determination of heat flux and Stanton number. Comparison between experimental and theoretical Stanton numbers allows the detection of transition. Pressure measurements support the transition investigation. Following a complementary approach, empirical correlations (Reda and Reshotko) are evaluated from CFD results to determine the distributed roughness critical height leading...
Utilization of Low-=Speed Experiments in Transonic Capsule Stability Research
Journal of Spacecraft and Rockets, 1999
Sensors, 2010
Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypers... more Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship's Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow.
… InfraRed Thermography, 2010
Space vehicles that make an entry through the atmosphere of a planet suffer tremendously because ... more Space vehicles that make an entry through the atmosphere of a planet suffer tremendously because of extreme heating of the vehicle. The design of thermal protection systems for space vehicles involves multidisciplinary topics and is a very critical stage of space vehicles. The qualification of thermal protection systems on ground is very important for a safe space flight and the protection of critical payloads. At von Karman Institute, several ground facilities are used for the characterisation and qualification of thermal protection systems and materials. Infrared thermography is one of the most important measurement techniques used to monitor surface temperature and heat flux imposed on the thermal protection material, thus enabling the researchers to analyse the structural and thermal behaviour of tested materials.
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Papers by Sebastien Paris