Date of Award

3-21-2019

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Jeffrey R. Komives, PhD

Abstract

Direct numerical simulation (DNS) computational fluid dynamic (CFD) calculations were performed on a 30° slice of 7° half-angle cones with increasing nose radii bluntness at Mach 10 while simulating a distributed roughness pattern on the cone surface. These DNS computations were designed to determine if the non-modal transition behavior observed in testing performed at the Arnold Engineering Development Center (AEDC) Hypervelocity Wind Tunnel 9 was induced via distributed surface roughness. When boundary layer transition is dominated by second mode instabilities, an increase in nose radius delays the transition location downstream. However, blunt nose experiments indicated that as the nose radius continued to increase from sharp to blunt, the transition location was no longer second mode dominated and the transition location failed to continue to move downstream. The cause of this non-modal transition phenomenon is unknown but is hypothesized to be due to distributed roughness on the surface of the test articles. The DNS grids utilized in this research effort simulated distributed roughness along the surface of the cone by moving the nodes on the surface according to a normal distribution centered on the maximum roughness height and having the nodes in the direction normal to the cone move in a hyperbolic tangent descent. The results showed that the distributed surface roughness was not suffcient to cause transitional flow by itself. Distributed surface roughness may still be an influencing factor for the non-modal transition observed in the blunt nose cone experiments performed by the AEDC Tunnel 9 but an additional forcing function would have needed to be present to cause transitional flow.

AFIT Designator

AFIT-ENY-MS-19-M-211

DTIC Accession Number

AD1073574

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