Accession Number : ADA184132

Title :   Numerical Simulation of Unsteady Separated Flows.

Descriptive Note : Doctoral thesis,

Corporate Author : NAVAL POSTGRADUATE SCHOOL MONTEREY CA

Personal Author(s) : Mostafa,Samir I

PDF Url : ADA184132

Report Date : Jun 1987

Pagination or Media Count : 141

Abstract : Two unsteady flows dominated by the occurrence of separation are simulated through the use of the discrete vortex model. The first of these is a sinusoidally oscillating flow about a circular cylinder at a Keulegan-Carpenter number of K = 10. The vortex model has been combined with the boundary layer calculations and the positions of the separation and stagnation points, the evolution of the wake, the velocity and pressure distributions, and the instantaneous forces have been calculated and compared, whenever possible, with those obtained experimentally. The model has successfully simulated the occurrence of the transverse half Karman vortex street. The calculated positions of the vortices were found to be in good agreement with those obtained experimentally. The measured and calculated in-line forces and the differential pressure distributions showed reasonably good agreement. The second simulation dealt with a rapidly decelerating flow about a two-dimensional sharp-edged camber. An extensive study of the velocity field in the vicinity of the singular points led to the development of a novel method for the introduction of vorticity at variable time intervals. The measured and calculated characteristics of the flow, such as the evolution of the wake and the forces acting on the camber, were found to be in excellent agreement. Futhermore, the simulation provided a plausible explanation for the cause of parachute collapse, a phenomenon which gave impetus to the numerical and physical experiments described herein.

Descriptors :   *DIGITAL SIMULATION, *FLOW SEPARATION, *UNSTEADY FLOW, BOUNDARY LAYER, COMPUTATIONS, DECELERATION, VORTICES, NUMERICAL METHODS AND PROCEDURES, PHYSICAL PROPERTIES, COLLAPSE, CAMBER, PRESSURE GRADIENTS, EVOLUTION (GENERAL) WAKE, MATHEMATICAL MODELS, NUMERICAL ANALYSIS, OSCILLATION, UNSTEADY FLOW, PRESSURE DISTRIBUTION, HARMONIC ANALYSIS, NAVIER STOKES EQUATIONS, SIMULATION, STAGNATION POINT, EDGES, SHARPNESS, TWO DIMENSIONAL, TIME INTERVALS, VARIABLES, UNSTEADY FLOW, THESIS

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE