Abstract
A large eddy simulation (LES) of flow in an inducer is carried out under flow rate oscillations. The present study focuses on characteristics of dynamic responses of the backflow and the pressure performance to the flow rate fluctuations under non-cavitation conditions. Results show that the backflow response delays behind the flow rate fluctuation. The pressure performance curve exhibits a closed curve caused by the effect of inertia associated with the flow rate fluctuations. Comparing with one dimensional evaluation of the inertia effects, it was found that the inertial effects obtained by the LES are smaller. Additionally, the averaged negative slope of the performance curve becomes larger under unsteady conditions. From the conservations of angular momentum and energy, an expression useful for the evaluation of unsteady pressure rise was obtained. The examination of each term of this expression shows that the apparent decrease of inertia effects is caused by the response delay of Euler head and that the increase of negative slope is caused by the inertial term associated with the delay of backflow response.
