Session Ci - Vortex Dynamics.
ORAL session, Sunday, November 23
309, Moscone Center
Impulsive flows exiting non-axisymmetric orifices are examined at two Reynolds numbers (2800 and 23,000). The flow is initiated with a round piston/cylinder apparatus and the cylinder exits are inclined with lengths of 0, D/4, D/2 and D. Instantaneous velocity fields were measured in a number of azimuthal planes with particle image velocimetry (PIV). Due to the inclined exit, the velocity field exiting the cylinder was spatially non-uniform leading to non-axisymmetric entrainment and the formation of a complex vortex structure. The structure consisted of a primary vortex ring with non-uniform circulation around the circumference and branched vortex tubes. The structure migrated off the centerline toward the short cylinder side. With increasing incline angle, the vortex structure migrated further away from the centerline. The flow also became increasingly disorganized resulting in reduced propagation speed and penetration distance. The general flow features were the same for each Re and for varying piston geometry.