Unsteady Boundary Layer Separation.
MARTIN MARIETTA LABS BALTIMORE MD
Pagination or Media Count:
A new separation criterion for two-dimensional unsteady boundary layers is proposed here. This criterion is derived by analogy, from its counterpart for steady, three-dimensional boundary layer. Analogous limiting streamlines for the unsteady, two-dimensional case are first defined, and an envelope of these streamlines is used to signify unsteady separation. To demonstrate this procedure, two previously studied problems are recalculated here. These are the unsteady responses to 1 a sudden change in velocity in Howarths problem, and 2 an impulsively-started circular cylinder. Our conclusion regarding separation for the cylinder problem disagrees with that of the Telionis and Tsahalis based on the singularity criterion, but appears to be consistent with the prediction of Proudman and Johnson. Finally, we propose a three-dimensional, unsteady separation criterion on the basis of repeated applications of either the steady, three-dimensional separation criterion at successive times or the unsteady, two-dimensional separation criteion at fixed coordinate planes. Author
- Fluid Mechanics