The term bursting refers to the structural change from a strong regular spiral motion to a weaker turbulent motion which can occur at some position along a vortex. Various observations of this phenomenon have been recorded during low-speed tunnel investigations of vortex flows generated from sharp, swept back leading edges. These reveal a sudden deceleration of fluid along the vortex axis and e...

This DNS study is focused on the structure of turbulence in a boundary layer. First, it is not appropriate to call the turbulent flow as a “random” motion. Any mean flow like Blasius solution, which is a Navier-Stokes solution, added by white noise or random perturbation would be rejected by Navier-Stokes equations and the perturbation will be damped quickly. The governing Navier-Stokes equatio...

Area and axial flow variations on rectilinear vortex tubes are considered. The state of the flow is characterized by two dependent variables, a core area, and an azimuthal circulation per unit length, which vary in time and in distance along the length of the tube. Nonlinear integrodifferential equations of motion for these variables are derived by taking certain integrals of the vorticity tran...

An axisymmetric vortex-sheet model is applied to simulate an experiment of Didden (1979) in which a moving piston forces fluid from a circular tube, leading to the formation of a vortex ring. Comparison between simulation and experiment indicates that the model captures the basic features of the ring formation process. The computed results support the experimental finding that the ring trajecto...

A vortex fluidic device (VFD) involving a rapidly rotating tube open at one end forms dynamic thin films at high rotational speed for finite sub-millilitre volumes of liquid, with shear within the films depending on the speed and orientation of the tube. Continuous flow operation of the VFD where jet feeds of solutions are directed to the closed end of the tube provide additional tuneable shear...

We demonstrate and discuss a liquid pumping effect based on the interaction between periodically generated cavitation microbubbles and a millimeter diameter tube. The bubbles are generated by the heat of laser adsorption at the tip of an optical fiber immersed in liquid. When the bubbles are generated well away from the tube, a steady streaming flow with a relatively large and energetic ring vo...