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Forces on a Sphere in the Presence of Static and Dynamic Roughness Elements

Norman, A. K. and McKeon, B. J. (2009) Forces on a Sphere in the Presence of Static and Dynamic Roughness Elements. In: 39th AIAA Fluid Dynamics Conference, 22–25 June 2009, San Antonio, TX.

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Though the effect of distributed roughness on flow over a sphere has been examined in detail, there have been few observations as to the effect of an isolated roughness element on the forces induced on a sphere that is in uniform flow. In this experimental study, we examine how the forces are altered due to both a stationary and dynamic three-dimensional roughness element in the Reynolds number range of 5 x 104 to 5 x 105. It is found that even a small change to the geometry of the sphere, by adding a cylindrical roughness element with a width and height of 1% the sphere diameter, dramatically alters the drag and lateral forces over a wide range of Reynolds numbers. Of particular interest is that the mean of the lateral force magnitude can be increased by a factor of about seven, compared with a stationary stud, by moving the isolated roughness at a constant angular velocity about the sphere. These results can be applied to tripping a laminar boundary layer, steering a bluff body, and increasing the mixing of two fluids, using a minimal amount of energy input. This research is a first step towards understanding the interaction between time dependent surface motion and the subsequent alteration of the location of the boundary layer separation line and wake development.

Item Type:Conference or Workshop Item (Paper)
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URLURL TypeDescription
McKeon, B. J.0000-0003-4220-1583
Additional Information:© 2009 by AK Norman and BJ McKeon. Support from the National Science Foundation under Grant No. 0747672 (Program Manager William W. Schultz) is gratefully acknowledged.
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AIAA Paper2009-3704
Record Number:CaltechAUTHORS:20150303-112614795
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55469
Deposited By: Jamie Sei
Deposited On:03 Mar 2015 22:41
Last Modified:10 Nov 2021 20:46

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