Numerical Study On Unsteady Hydrodynamic Performance Of Waterjet Impeller

The performance of the waterjet in real working conditions is obviously different from the performance of the independent waterjet.The inlet of the waterjet impeller can be obviously uneven due to the influence of the retardation caused by the hull and duct.The non-uniformity can cause non-niform loads on the surface of the waterjet impeller.In addition,the uneven pressure distribution will bring cavitation and noise on the surface of the duct,which will affect the cavitation and noise performance of the waterjet.The waterjet impeller properly installed on the ship will reflect the significant unsteady hydrodynamic performance.It has a certain theoretical research and practical guiding significance to analysis the unsteady hydrodynamic performance of the waterjet impeller under different working conditions.This article studies the unsteady hydrodynamic performance of the waterjet impeller in real working conditions,which uses the CFD method based on solving RANS equations.We built the model INSEAN2340 installed with two waterjet,and completed the non-steady numerical calculation of the model in three-dimensional viscous flow.The unsteady hydrodynamic performance of the waterjet impeller was analyzed in two stages:the startup stage and the stage with steady flow.Among them,the real rotation was realized by the sliding Mesh Model.We discussed the mesh generation method,the number of grids,the calculation domain,the boundary condition and the choice of the turbulence model,which was based on the sliding Mesh Model.Of course,the accuracy of numerical calculation must be demonstrated.The focus of startup stage focuses on the flow characteristics of the waterjet duct’s water flow in the time domain,and observes the phenomenon of flow characteristics.The degree and variation law of the non-uniformity on the inflow disk of the impeller was reflected through the analysis of axial velocity,planar point vector and streamline’s distribution at different times of the impeller’s inflow disk,and the dynamic performance of the impeller in the startup stage was discussed.The focus of the stage with steady flow focuses on cyclical variation of the impeller’s hydrodynamic performance.Transient pressure coefficient distribution at different blade section of the impeller blade was analyzed.In addition,comparative study should be made on the surface load fluctuation and its law at different blade section and different chord,and it was helpful to complete the comparative analysis of the hydrodynamic performance of the whole impeller and individual blades in a certain period of the stage with steady flow.All in all,the core of the article is to study the unsteady hydrodynamic performance of the waterjet impeller.Method of periodic analysis was taken,and we studied the information of complex internal flow field and the load on the surface of impeller,which belongs to the the startup stage or the stage with steady flow.So,it was beneficial for us to get a more comprehensive understanding of hydrodynamic performance of a waterjet impeller.The model establishment,calculation method,analysis method for internal flow field and the numerical calculation results in numerical calculation and research process are of a certain reference value for the follow-up of other same types of research.