TY - JOUR
T1 - An experimental and computational study of the post-collisional flow induced by an impulsively rotated sphere
AU - Calabretto, Sophie A. W.
AU - Denier, James P.
AU - Levy, Benjamin
PY - 2019/12/25
Y1 - 2019/12/25
N2 - The unsteady flow due to a sphere, immersed in a quiescent fluid, and suddenly rotated, is a paradigm for the development of unsteady boundary layers and their collision. Such a collision arises when the boundary layers on the surface of the sphere are advected towards the equator, where they collide, serving to generate a radial jet. We present the first particle image velocimetry measurements of this collision process, the resulting starting vortex and development of the radial jet. Coupled with new computations, we demonstrate that the post-collision steady flow detaches smoothly from the sphere's surface, in qualitative agreement with the analysis of Stewartson (Grenzschichtforschung/Boundary Layer Research (ed. H. Görtler), Springer, 1958, pp. 60-70), with no evidence of a recirculation zone, contrary to the conjectured structure of Smith & Duck (Q. J. Mech. Appl. Maths, vol. 20, 1977, pp. 143-156).
AB - The unsteady flow due to a sphere, immersed in a quiescent fluid, and suddenly rotated, is a paradigm for the development of unsteady boundary layers and their collision. Such a collision arises when the boundary layers on the surface of the sphere are advected towards the equator, where they collide, serving to generate a radial jet. We present the first particle image velocimetry measurements of this collision process, the resulting starting vortex and development of the radial jet. Coupled with new computations, we demonstrate that the post-collision steady flow detaches smoothly from the sphere's surface, in qualitative agreement with the analysis of Stewartson (Grenzschichtforschung/Boundary Layer Research (ed. H. Görtler), Springer, 1958, pp. 60-70), with no evidence of a recirculation zone, contrary to the conjectured structure of Smith & Duck (Q. J. Mech. Appl. Maths, vol. 20, 1977, pp. 143-156).
KW - boundary layer separation
KW - boundary layer receptivity
KW - absolute/convective instability
UR - http://www.scopus.com/inward/record.url?scp=85074333455&partnerID=8YFLogxK
U2 - 10.1017/jfm.2019.783
DO - 10.1017/jfm.2019.783
M3 - Article
AN - SCOPUS:85074333455
SN - 0022-1120
VL - 881
SP - 772
EP - 793
JO - Journal of Fluid Mechanics
JF - Journal of Fluid Mechanics
ER -