Numerical Simulation of Hydrodynamic Noise in Centrifugal Pump Based on LES

Abstract

The computational fluid dynamics(CFD) technique combined with the Lighthill acoustic analogy theory are applied to study the hydrodynamic noise caused by the volute surface dipole and the blade rotating dipole in a centrifugal pump.The large eddy simulation method is employed to solve the transient flow field of the pump.The fluid fields show that obvious peak of pressure fluctuations near the tongue is observed at blade passing frequency under different flow conditions,indicating that the interaction between the impeller and the tongue is the main cause of pressure fluctuation near the tongue.The interior boundary element method(BEM) model of pump is constructed,and the sound scattering effect of the volute casing is considered.The direct BEM is applied to solve the interior sound field of the pump.The computational results show good agreements with experimental ones.The validation of the LES combined with the Lighthill method for the hydrodynamic noise computation is verified.The results show that the sound pressure level at the shaft frequency under the design point is lowest,and the level of noise at the blade frequency and its harmonics becomes higher as the flow rate increases.The noise level at the blade frequency and its harmonics can be predicted quantitatively by calculating the blade rotating dipole source.The trend of the noise caused by the volute surface dipole is identical with the experimental trend.Comparing with the design and higher flow rates,the error between simulation and experiment is bigger at partial flow rate.