Date of Award

Summer 1994

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Surendra N. Tiwari

Committee Director

Richard W. Barnwell

Committee Member

Gregory V. Selby

Committee Member

John J. Korte

Call Number for Print

Special Collections; LD4331.E56P717

Abstract

Accurate prediction of the development of the boundary-layer thickness is essential in designing hypersonic wind tunnel nozzles using computational fluid dynamics (CFD). The nozzle boundary-layer thickness becomes extremely thin at the throat region. Immediately downstream of the throat, as the flow begins to expand, the boundary-layer thickness grows rapidly. Estimates of grid requirements for resolving the turbulent boundary layer in the throat region using a Navier-Stokes solver have shown that the number of grid points is typically an order of magnitude greater than what is needed to resolve the nozzle exit region. Approximately 80% of the total time taken to resolve the flow field in the entire nozzle is consumed at the throat region. In the present study, a combination of an empirical method and a numerical method is used to reduce the grid requirements. The law of the wall and the law of the wake are used to resolve the inner part of the boundary layer to improve the execution time and relax the grid clustering requirements. A compressible defect stream function formulation of the governing equations assuming an arbitrary turbulence model is employed. The energy equation is replaced by the Crocco temperature-velocity relationship. The van Driest's logarithmic law of the wall function and an analytical law developed by Wahls is used as the law of the wake. The defect stream function method has been used to solve compressible nonequilibrium turbulent boundary layers. Solutions are also obtained for the incompressible and compressible equilibrium turbulent boundary layers.

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DOI

10.25777/y42d-j166

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