Research On Cavitation Performance Of Ship Propeller Based On Improved Delayed Separation Vortex

Cavitation of propellers usually has negative effects on propulsion systems,such as performance degradation,noise,vibration and material damage.However,cavitation is almost inevitable in normal operation of propeller.Therefore,it is necessary to study the cavitation phenomenon of Marine propeller in order to reduce the cavitation phenomenon and maximize the performance.Aiming at the problems of low efficiency and low accuracy of traditional propeller modeling,and low accuracy of computational fluid dynamics(CFD)turbulence model,this paper improved and optimized the model.Firstly,a fast-modeling method for Marine propeller is proposed,which improves the modeling efficiency and precision of propeller.Secondly,the turbulence model in CFD is improved.Finally,the improved turbulence model can calculate the cavitation performance of propeller more comprehensively and accurately through numerical simulation results.Aiming at the complex and tedious problems of the commonly used 3d modeling methods of Marine propeller,this paper,based on the GSD module embedded in the 3D modeling software CATIA,uses the given programs Star Loft and End Loft of the module to transform the coordinates of the type value points at different radius sections of the propeller,and import the calculated data into CATIA through recording macros.A fast modeling method from point to line and from line to surface is obtained,which is more efficient than the traditional CAD propeller modeling method,and effectively improves the modeling efficiency and accuracy of Marine propeller.In order to better predict the phenomenon of blade cavitation and tip vortex cavitation when ship propeller is running.The improved Delayed vortex separation method(IDDES),which is modified from the delayed vortex separation method(DDES)in the computational fluid dynamics software STAR-CCM+,is used as the turbulence model.Based on this model,the open water performance of PPTC propeller was verified numerically,and the thrust coefficient,torque coefficient and open water performance curve were calculated.Schnerr-Sauer cavitation model based on Rayleigh-Plesset was used to calculate the axial velocity distribution cloud images of PPTC blade cavitation,wake tip vortex cavitation and Y=0 plane under three different conditions.The numerical results agree well with the experimental data,which verifies the accuracy of the model.Using the method of a big fishing boat propeller cavitation performance calculation,detailed analysis of the simulation data and the visualization images,the results show that by improving the propeller in speed,blade with the propeller cavitation area into the speed increase and decrease,when increases to a critical moment,blade cavitation will shift from the blade suction surface area to the pressure of the blade surface area.The cavitation at the leading edge of the blade decreased significantly than that at the edge of the blade.As for the propeller tail tip vortex,there is an inward bending structure in the blade tip region,so a branch vortex will be generated in the tip vortex region.At low advance speed,the propeller tail tip vortices are closely arranged and can quickly fuse with each other.With the increase of velocity coefficient,the fusion of branch vortex and outer vortex gradually decreases and begins to fuse with hub vortex.