Masters Theses

Date of Award

12-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

C.F. Lo

Committee Members

Ahmad D. Vakili, Frank G. Collins

Abstract

It has been shown in the past that the turbulent boundary layer of supersonic wind tunnel nozzle and test section walls affects adversely the transition Reynolds number on models in the wind tunnel. If the boundary layer of the nozzle and test section is kept laminar, the boundary layer disturbance can be eliminated. Two different computational methods are used to study the effects of heating and cooling strips on the stability of the laminar boundary layer of the nozzles and test section walls of the Laminar Flow Supersonic Wind Tunnel (LFSWT) and the 1/8 scale of the LFSWT called the Proof of Concept (POC) Supersonic Wind Tunnel at NASA Ames Research Center. The first method used is the Stability Modifiers Method, which examines the second derivative of velocity near the wall to study stability of the boundary layer. The second method is the eN Method, where eN is a exponential function of N and N is known as the N Factor. The N Factor value is used to investigate boundary layer stability. Results of this study indicate that heating applied upstream of the location of instability on-set can enhance boundary layer stability. Applying cooling near the point of the on-set of instability and downstream increases boundary layer stability. When cooling is applied upstream and heating is applied downstream of the on-set points of instability, the boundary layer becomes more destabilized. The effects of heating and cooling are predicted by the methods of the present study and can be utilized to model the actual temperature distribution of experiments.

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