Accession Number : ADA190405

Title :   Unsteady Flow in Supersonic Inlet Diffuser.

Descriptive Note : Final technical rept. 14 Aug 84-14 Sep 87,

Corporate Author : MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING

Personal Author(s) : Adamson, T C , Jr ; Messiter, A F

PDF Url : ADA190405

Report Date : Nov 1987

Pagination or Media Count : 13

Abstract : A supersonic inlet diffuser with flow at supercritical conditions has been analyzed using a combination of analytical and numerical methods of solution. Analytical solutions for the flow variables are presented for the inviscid part of the unsteady flow field. Instantaneous displacement thickness distributions found numerically for both separated and unseparated flows allow definition of the effective wall shape for the analytical solutions. An equation describing the unsteady motion of the passages shock caused by variations in back pressure and/or wall shape has been derived. Results have been compared with those found numerically, both for inviscid and viscous flow fields; agreement is excellent in phase and good in amplitude. In example calculations, parameters are varied separately to show how they may cause shock disgorgement (engine unstart) when back pressure oscillations are impressed upon the flow. A mechanism by which shock wave oscillations may be selfsustaining has been proposed and illustrated by example. Parametric effects upon the magnitude and frequency of the self sustained oscillations and upon shock disgorgement are illustrated by numerical examples with given inlet. The work on inlet buzz, although not completed, has led to studies of high resolution schemes for capturing both shock and slip surface discontinuities in numerical algorithms, reported in two papers. This is still an active area of research.

Descriptors :   *OSCILLATION, *SUPERSONIC DIFFUSERS, *SUPERSONIC INLETS, *UNSTEADY FLOW, ALGORITHMS, BACK PRESSURE, DISPLACEMENT, DISTRIBUTION, EQUATIONS, FLOW FIELDS, FLOW SEPARATION, HIGH RESOLUTION, INLETS, INVISCID FLOW, NUMERICAL METHODS AND PROCEDURES, PARAMETRIC ANALYSIS, SHAPE, SHOCK WAVES, SOLUTIONS(GENERAL), SUPERCRITICAL FLOW, THICKNESS, VARIABLE PRESSURE, VARIABLES, VISCOUS FLOW, WALLS, NUMERICAL ANALYSIS, PHASE, AMPLITUDE, DISCONTINUITIES

Subject Categories : Fluid Mechanics
      Numerical Mathematics
      Jet and Gas Turbine Engines

Distribution Statement : APPROVED FOR PUBLIC RELEASE