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Unformatted text preview: x y z SmokeWire (b) (a) Wire r ing Tufts (b) (a) (b) (a) x y z Speed Adjust Laser Doppler Anemomet er Analysis of the flow over a Sphere GROUP 1 ASE – 120K LowSpeed Aerodynamics Laboratory The University of Texas at Austin Department of Aerospace Engineering and Engineering Mechanics Fall, 2010 By signing this form, I acknowledge that I have read this entire document prior to submission, that I approve of all material contained in this document and that it is original and nonplagiarized work of all the members of my group. UT EID Print Full Name Signature Date _________ _________________________________________ ____________________________ ________ _________ _________________________________________ ____________________________ ________ _________ _________________________________________ ____________________________ ________ _________ _________________________________________ ____________________________ ________ _________ _________________________________________ ____________________________ ________ 2 _________ _________________________________________ ____________________________ ________TABLE OF CONTENTS ABSTRACT page 2 INTRODUCTION page 3 APPARATUS & PROCEDURE page 9 RESULTS & DISCUSSION page 14 SUMMARY & CONCLUSIONS page 32 APPENDICES page 34 REFERENCES page 44 3 1. ABSTRACT The coefficient of drag, C d , and the boundary layer associated with a sphere were measured in a wind and water tunnel. Tufts, a smoke wire, and a stethoscope were used in a closed circuit wind tunnel to gain qualitative understanding of the flow over a brass sphere of a diameter of 0.2159 meters to find the angle of separation, , of the flow. I t was found that for Reynolds numbers between 10 θ 4 and 3.5 x 10 5 the angle of separation is relatively independent of the Reynolds number. At a Reynolds number of 1.62 x 10 5 , was found to be 82° using tufts at the surface θ of the sphere. At a Reynolds number of 3.3 x 10 5 , was 100°, which shows that as θ the Reynolds number increases, increases. A dye injection system in a closed θ circuit water tunnel was used to visualize the flow over a glass sphere with diameter 0.0665m. The water tunnel allows for testing at a different range of Reynolds numbers while operating at a lower speed, making the flow visualization process easier. At Reynolds numbers of 8.00 x 10 3 and 2.05 x 10 4 , the flow showed the characteristic vortex shedding on a blunt body. Quantitative measurements were also taken in the wind tunnel to find the coefficient of pressure, C p from which the C d was calculated for several different Reynolds numbers: 1.69 x 10 5 , 2.192 x 10 5 , 2.693 x 10 5 , 3.171 x 10 5 , 3.679 x 10 5 and respectively the C d ’s were: 0.435, 0.406, 0.348, 0.225, 0.221. In the water tunnel, measurements were taken by a Laser Doppler Anemometer, LDA, to characterize the velocity profile of the boundary layer of the sphere. The thickness of the boundary layer was found to be 7% of the diameter of the sphere. Also the velocity in the freestream direction could be diameter of the sphere....
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 Fall '10
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 Fluid Dynamics

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