Hostname: page-component-cd9895bd7-8ctnn Total loading time: 0 Render date: 2024-12-28T04:41:14.956Z Has data issue: false hasContentIssue false
  • English
  • Français

Test flow disturbances in an expansion tube

Published online by Cambridge University Press:  26 April 2006

A. Paull  and
R. J. Stalker
A. Paull
Affiliation:
Mechanical Engineering Department, University of Queensland, Brisbane, Qld 4072, Australia
R. J. Stalker
Affiliation:
Mechanical Engineering Department, University of Queensland, Brisbane, Qld 4072, Australia
Get access Rights & Permissions [Opens in a new window]

Abstract

The operation of an expansion tube is investigated with particular attention given to the test flow disturbances which have limited their utility in the past. Theoretical bounds for the duration of uniform test flow are first explored using one-dimensional ideal-gas relations, together with shock-tube boundary-layer entrainment effects. It is seen that test flow duration is limited either by the arrival of the downstream edge of the test-gas unsteady expansion or by the arrival of the upstream edge of this expansion after it has been reflected from the driver–test gas interface. These bounds are seen to be in good agreement with measurements made with large driver-gas expansion ratios. For small expansion ratios additional disturbances are observed in the test gas. Similar disturbances are also observed in the driver gas. It is postulated that these disturbances first appear in the driver gas and are transmitted into the test gas before the test gas is expanded. These disturbances remain with the test gas as it is expanded and subsequently produce unsteady conditions at the test section. Theoretical calculations for the range of frequencies which occur in the test gas before the expansion are obtained by modelling the disturbances as acoustic waves. It is shown that only the high-frequency components of the disturbances in the driver gas can penetrate the driver–test gas interface and this provides a mechanism for suppressing disturbances in the test gas. Additional analytical calculations for the shift in frequency produced as an acoustic wave traverses an unsteady expansion are also presented and it is shown that all frequencies of a given acoustic wave mode converge to one frequency. This focusing of frequencies is seen to occur in three different facilities.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 245 , December 1992 , pp. 493 - 521
Copyright
© 1992 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Godunov S. K. 1959 A difference method for numerical calculation of discontinues solutions of the equation of hydrodynamics. Mat. Sb. 47, 271–306.Google Scholar
Levine M. A. 1970 Turbulent mixing at the contact surface in a driven shock wave. Phys. Fluids 13, 116–117.Google Scholar
Liepmann, H. W. & Roshko A. 1957 Elements of Gas Dynamics. Wiley.
Lordi J. A., Mates, R. E. & Moselle J. R. 1966 Computer program for numerical solution of nonequilibrium expansions of reacting gas mixtures. NASA CR-472.Google Scholar
McIntosh M. K. 1968 Computer program for the numerical calculation of frozen and equilibrium conditions in shock tunnels. Dept. of Physics, ANU Canberra.
Miller C. G. 1977 Operational experience in the Langley expansion tube with various test gases. NASA Tech. Mem. 78637.Google Scholar
Mirels H. 1964 Shock tube test time limitation due to turbulent-wall boundary layer. AIAA J. 2, 84–93.Google Scholar
Neely A. J., Stalker, R. J. & Paull A. 1991 High enthalpy, hypervelocity flows of air and argon in an expansion tube. Aeronaut. J.Google Scholar
Norfleet G. D., Lacey, J. J. & Whitfield J. D. 1965 Results of an experimental investigation of the performance of an expansion tube. Fourth Hypervelocity Tech. Symp., AEDC Tullahoma, Tennessee, Nov., pp. 49–110.
Paull, A. & Stalker R. J. 1991 The effect on an acoustic wave as it traverses an unsteady expansion Phys. Fluids A 3, 717–719.Google Scholar
Spurk J. H. 1965 Design, operation, and preliminary results of the BRL expansion tube. Fourth Hypervelocity Tech. Symp., A.E.D.C. Tullahoma, Tennessee, Nov., pp. 111–144.
Stalker R. J. 1966 The free piston shock tunnel. Aeronaut. Q. 17, 351–370.Google Scholar
Trimpi R. L. 1962 A preliminary theoretical study of the expansion tube, a new device for producing high-enthalpy short-duration hypersonic gas flows. NASA TR R-133.Google Scholar
Whitham G. B. 1974 Linear and Nonlinear waves. Wiley.