Numerical simulations are used to study the formation of vortex rings that are generated by applying a non-conservative force of long duration, simulating experimental vortex ring generation with large stroke ratio. For sufficiently long-duration forces, we investigate the extent to which properties of the leading vortex ring are invariant to the force distribution. The results confirm the exis...

In this paper, we study the influence on the ring-like vortex structure in MVG controlled supersonic ramp flow by different inflow conditions. In front of the MVG, three turbulent inflow profiles with different boundary layer thickness are generated as the inflow. From the shape factors, we can see that these inflows in front of the MVG are fully developed turbulent. It is found that the inflow...

within a larger vortex ring, which includes centres (1) and (3). Counter-rotating centres in the dorsal vortex ring produce jet A; a second jet B develops later as a result of flow induced by the ventral tip vortex. Jets A and B are directed on average at 35° to the freestream flow, before combining to produce a single broad jet C. Initially, little downstream flow is seen between same-sign vor...

The recent work of Gharib, Rambod, and Shariff @J. Fluid Mech. 360, 121 ~1998!# studied vortex rings formed by starting jets generated using a piston-cylinder mechanism. Their results showed that vortex rings generated from starting jets stop forming and pinch off from the generating jet for sufficiently large values of the piston stroke to diameter ratio (L/D), suggesting a maximization princi...

Starting flow through a nozzle or orifice typically results in the transient formation of a leading vortex ring and trailing jet. Experiments are conducted to investigate the dynamics of this process in the case of a temporally variable nozzle exit diameter, with the aim of understanding these flows as they occur in Nature and emerging technologies. By kinematically decoupling the source flow f...

We propose very general vortex nucleation mechanismss1] analogous to a hydrodynamic instability and calculate associated critical velocity in agreement with experiments. The creation of vortices via extrinsic mechanism is driven by a formation of the surface vorticity sheet created by the ow, which reaches a critical size. Such a sheet screens an attraction of a half-vortex ring to the wall, th...

This study investigated the relationship between the pinch-off of axisymmetric vortex rings and the evolution of pressure in the shear layer being entrained into the vortex rings. A piston-cylinder apparatus was used to generate the vortex rings, and five cases of constant piston acceleration over distances ranging from zero (impulsive start) to eight piston diameters were investigated. It was ...

We propose very general vortex nucleation mechanisms[1] analogous to a hydrodynamic instability and calculate associated critical velocity in agreement with experiments. The creation of vortices via extrinsic mechanism is driven by a formation of the surface vorticity sheet created by the flow, which reaches a critical size. Such a sheet screens an attraction of a half-vortex ring to the wall, ...

PURPOSE To evaluate viscous energy loss and the association with three-dimensional (3D) vortex ring formation in left ventricular (LV) blood flow during diastolic filling. THEORY AND METHODS Thirty healthy volunteers were compared with 32 patients with corrected atrioventricular septal defect as unnatural mitral valve morphology and inflow are common in these patients. 4DFlow MRI was acquired...