Hyperboloid Flare Experiments in the HEG Facility.

Experiments on a Hyperboloid Flare model have been carried out in the HEG at the standard operating Conditions I and III. Pressure and heat transfer profiles have been taken along the model, together with Holographic Interferometry and Schlieren optical techniques. The model was also rotated about its axis to investigate flow non-uniformity. The pressure and heat transfer profiles indicate that the flow is uniform and repeatable for both conditions tested. These profiles together with Schlieren images indicate that the separation region atthe junction of the model body to its flare is larger for Condition III than for Condition I. The separation lengths measured for both conditions are compared with results from other hypersonic facilitiesas a function of the viscous interaction parameter and indicate that there is an enthalpy effect on the flow structure about the model

Phase Step Holographic Interferometry in Hypervelocity, High Temperature Flows

A holographic interferometer with a 300 mm field of view for the flow visualisation in the high enthalpy shock tunnel (HEG) has been installed and upgraded. This world's largest free piston driven shock tunnel is located at the German Aerospace Research Esstablishment (DLR) in Goettingen. Ist interferometer applies the phase step technique. This method enables computerized evaluation of the holograms to create high quality interferograms by increasing the signal to noise ratio. Complete flow field density gradients around two dimensional models are calculated from the interferograms.Because of the high spatial resolution of the holograms, large optical enlargements and Hologram-Schlieren is made possible. Typicalresults which are presented, demonstrate is feasibility and underlinethe demand on optical techniques like the holographic interferometry to study the complex flow phenomena of high temperature reacting flows produced by the tunnel. Thus it is shown that the tunnel works in the desired flow range of nonequilibrium gas state

Cylinder Experiments in the High Enthalpy Tunnel HEG

Fourteen cylinder experiments in the HEG under high enthalpy conditions habe been carried out for four different free-stream conditions in air and one free-stream condition in nitrogen. Schlieren, interferogram and luminosity pictures were obtained. Interferograms have been used to determine the density distribution on the stagnation streamline. The density profile on the stagnation streamline has been compared to results from Navier-Stokes calculations. The sshock wave stand-off distance has been determined using these optical measurements and compared to the shock wave stand-off distance for the ideal gas case. The distance was found to be between the frozen and the equilibrium limit, even though data varies from measurement to measurement technique. At the wall of the cylinder 18 pressure and 17 thermocouple sensors have been installed at five degree steps from -40 to 40 degree relative to the free-stream flow direction

Study of Aerochemistry Around a 70 degree Half Angle Blunted Cone in CO2 Environment in the High Enthalpy Shock Tunnel

Four tests are performed in the HighEnthalpy Tunnel Goettingen (HEG) of the DLR at a free stream Mach number of approximately 10. Three CO2/N2 mixtures and one pare CO2 test gas case were used to study the entry into the Martian atmosphere. A blunted cone model with a cylindrical afterbody (sting)similar to a entry vehicle was investigated. To obtain information on the influence of defined parameters on the body back flow, especially of the reacting gas, the pressure distribution and the heat transfer rate along the body contour was measured with fast response surface thermocouples on the forebody and sensitive thin fil heat transfer gauges on the sting of the model. Flow visualisation of the region on the sting were the seperated fflow is turned by a second shock was imaged with the planar laser induced fluorescence system. Rough information about therotational temperature ratio across this shock was obtained for one run. For a pure CO2 test gas run a holographic interferogram and a laser schlieren picture was obtained

Zwei Charakterisierungen von Gruppensprachen abelscher Gruppen

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