Forces on a Sphere in the Presence of Static and Dynamic Roughness Elements
- Creators
- Norman, A. K.
-
McKeon, B. J.
Abstract
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.
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.Attached Files
Published - AIAA-2009-3704-805.pdf
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Additional details
- Eprint ID
- 55469
- Resolver ID
- CaltechAUTHORS:20150303-112614795
- CBET-0747672
- NSF
- Created
-
2015-03-03Created from EPrint's datestamp field
- Updated
-
2021-11-10Created from EPrint's last_modified field
- Caltech groups
- GALCIT
- Other Numbering System Name
- AIAA Paper
- Other Numbering System Identifier
- 2009-3704