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Seminar by Richard Morgan |
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Date: September 23, 2005
Time: 1:00pm
Location: NIA, Rm 101
Expansion Tube Investigations of Planetary Entry Aerothermodynamics
Richard Morgan, The University of Queensland
This talk will discuss the use of expansion tubes for generating aerothermodynamic data pertaining to the conditions encountered during high speed entry into planetary atmospheres. These facilities have the capability of generating very high total enthalpies and pressures for test times of up to ~1 millisecond, and with core flows suitable for aerothermodynamic testing and measurement. This provides a means for reproducing many of the phenomena which occur in hypervelocity flight, such as ionisation and dissociation, and radiation and rarefied gas effects.
Three expansion tubes have been commissioned at the university of Queensland, X1, X2 and X3, with bores from 37 to 182 mm, and with lengths of up to 65m. The tubes are driven by free piston drivers, which give the flexibility to operate over a wide range of conditions from low sub-orbital to speeds ~ 15 km/sec. The facilities are used in 3 primary roles, those of direct simulation of flight vehicles, fundamental studies of basic phenomena and CFD validation. A range of test gases have been used, including air, CO2, N2/CH4, H2/He, H2/Ne, N2 and O2. The models which have been tested include a range of sphere-cone configurations, waveriders, toroidal ballutes, scramjets and various wedge and flat plate combinations for fundamental studies (such as separated flows). Available instrumentation is surface pressure and heat transfer gauges, radiation flux measurement (developmental), 3 component force balance, and various optical diagnostic techniques such as laser interferometry, and measurements of ionisation and temperature levels, and in flow velocity measurement
The results of some of these experiments will be presented, and the techniques used for test flow determination will be discussed. At the higher speed end of the envelope, many of the thermo-physical processes will occur together, and interact with complex compressible flow fields. Under these conditions, full similarity of all relevant parameters is usually not possible, and direct simulation of flight configurations cannot be achieved.
The limits and utility of direct simulation will be discussed, with reference to the FIRE flight experiment which have been partially reproduced in the X1 expansion tube.
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