The effect of waveform shape, Womersley number, and pulsation amplitude on transitional pulsatile pipe flow: a 4D PTV study

Previous studies have shown that pulsatile pipe flow mimics steady flow at high Womersley numbers (Wo>10), highlighting that a “critical Womersley number” likely exists, beyond which on transition is no longer influenced by Womersley number-specific effects. However, inconsistencies regarding the specific effects of Womersley number on transitional pulsatile pipe flow have been reported across literature indicating that underlying factors likely have yet to be completely studied. In this study, we use volumetric particle tracking velocimetry (PTV) to investigate the isolated effects of relevant parameters like waveform shape and pulsation amplitude. Additionally, we study their combined effects with changing Womersley number across laminar, transitional, and turbulent flow regimes. We compute turbulent kinetic energy, turbulence intensity, and phase lag. Through this analysis, we evaluate the underlying trends and interactive relations between waveform shape, Womersley number, and pulsation amplitude. This work will provide a wholistic picture of how these axial flow factors affect transition in an effort to resolve the conflicting results across the literature.