Transition in Pulsatile Flows: The Role of Pressure Field

Pulsatile flows are of interest because for certain range of characteristic non-dimensional parameters, they display laminar and turbulent behavior at different times of the pulsating cycle. Addressing how turbulence appears, decays and is suppressed is challenging due to the flow unsteadiness and flow-wall interactions. An experiment was setup to replicate pulsatile motion of water in a clear, rigid pipe. The flow is driven by a piston-motor assembly controlled by a computer to induce cyclic motion of the mean flow. Time-Resolved Particle Image Velocimetry (TR-PIV) techniques are used to acquire velocity data on the plane of a CW laser illumination sheet. Pressure sensors were installed along the length of the pipe to monitor the flow and its variation during the transition process. Depending on the Reynolds number the hydrostatic pressure difference along the vertical diameter of the pipe causes the velocity profile to become asymmetric. Time-dependent activities related to transition and turbulence in the near wall are highly asymmetric.