Experimental Investigation of the Effect of Propeller Slipstream on the Behavior of Boundary Layers at Low Reynolds Number

Date of Award

Winter 2001

Document Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical & Aerospace Engineering


Aerospace Engineering

Committee Director

Colin P. Britcher

Committee Member

Osama A. Kandil

Committee Member

Stanley J. Miley

Committee Member

P. Balakumar


The emphasis in this work is on the effects of the propeller slipstream on the behavior of boundary layers at low Reynolds number. High altitude unmanned aerial vehicles used for scientific research are the applications in mind. Three different models are used to provide different types of flows. A laminar flow airfoil and two-dimensional inlet airfoil are used to provide two different types of boundary layers. The laminar flow airfoil is used as a benchmark case in order to refine the measurement techniques used in the study. Computational data obtained by the MSES code is compared to the corresponding experimental data when appropriate. The two-dimensional inlet airfoil designed to serve as a root section of the wing of a high altitude unmanned aircraft of the ERAST class, is used extensively to explore the effects of the periodic turbulence produced by the propeller slipstream on its boundary layer at a chord Reynolds number of 500,000. Pressure measurements, hot-film traces, and velocity profiles for both mean and turbulent quantities are measured using hot-wire probes in the constant temperature mode. Also, the profile drag of the two-dimensional inlet airfoil is measured using the momentum deficit method. The measurements show that the periodic disturbance provided by the propeller slipstream penetrates right though the boundary layer and modifies its character periodically and promotes an earlier transition process. A physical model of the slipstream disturbance is introduced and supported by the current measurements.

Also, the effect of the propeller slipstream on the external diffusion of a two-dimensional inlet that was designed as a low drag configuration of a heat exchanger installation is investigated. The propeller slipstream seems not to change the mean flow entering the inlet. On the other hand, the turbulence intensity of the flow entering the inlet is modified. The higher turbulence level associated with the slipstream should work on improving the mixing process and consequently enhancing the performance of the inlet.





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