Investigation of pulsatile flow structure in closed-type cavity

Abstract

Pulsatile flow in a channel with sudden expansion and contraction, referred to as a closed-type cavity, is experimentally and numerically investigated in the range of Re = 50–1650, covering laminar and transitional flow regimes. Investigations are performed in the range of pulsation frequencies corresponding to Wo = 0.28–0.62 and at a constant pulsation amplitude. Pulsation frequency influence to time-averaged recirculation zone length and the development of recirculation zone as well as upper and corner eddies during the pulse cycle at different pulsation frequencies are investigated. A fixed amplitude from zero to maximum velocity is chosen to investigate flow behaviour throughout a whole pulsation cycle. The results show that the pulsation effect on the recirculation zone length is insignificant in the laminar flow regime at investigated frequencies. However, in the transitional flow regime, recirculation zone length was shortened, regardless of the Wo. The analysis of recirculation zone and upper eddy dynamics during the pulse cycle revealed that their growth rate depends on Wo. The development lag effect is observed at certain velocity phase angles. The analysis of shear rate and turbulence intensity profiles revealed that increased instabilities are determined by the interaction of recirculation zone, upper eddy and the forward-facing step during the pulse cycle.