Large eddy simulation of turbulent cavitating flow in a Venturi-type section with special emphasis on LES errors and pressure fluctuation analyses

Abstract

In this study, large eddy simulation (LES) coupled with the homogeneous cavitation model is used to simulate the turbulent cavitating flow in the venturi with special emphasis on LES errors and pressure fluctuation analysis. The numerical results accurately predict the quasi-periodic behavior and frequency characteristics of the cavitation by comparing them with the experimental observations. The modified one-dimensional model is utilized here to figure out the relationship between cavitation and pressure fluctuation. A good coincidence between the predicted and monitored pressure is obtained to validate the consideration of the geometric and flow factors in the modified model. Further analysis indicated that the cavity volume acceleration is the main source of cavitation excited pressure fluctuation. Moreover, LES Verification and Validation (V&V) are involved to quantify the errors and uncertainties of the numerical results. It is found that the large magnitude of the errors often emerges in the region where the re-entrant jet and shedding cavity occurs, which demonstrates the influence of cavitation on the simulation accuracy. The modeling error has a larger magnitude than the numerical error and both often show opposite signs. To better understand the influence of cavitation on LES V&V, the interaction between cavitation and vortex is also discussed further.