| Cavitation is widely found in hydropower engineering and ship engineering,which is the phase transition between liquid and vapor caused by low pressure in the local area of liquid.Based on the existing experimental data of cavitation,the open source computational fluid dynamics software OpenFOAM is used to study the cavitation flow of hydrofoils The numerical simulation of the cavitation performance of the 3D wave-like leading edge hydrofoils are carried out,which provides a theoretical basis for the optimal design of hydraulic machinery.The main work is as follows:Firstly,the difference between the velocity field and pressure field of the leading edge of the NACA0009 hydrofoil,the pressure coefficient of the hydrofoil and the lift coefficient of the hydrofoil is compared to find that the SST k-Omega turbulence model and the Kunz cavitation model can better predict the flow field characteristics of the cavitation.Cavity shedding process of the Clark-Y hydrofoil is analyzed.The results show that compared with the SST k-Omega turbulence model,the Rebound modified SST k-Omega model and the large eddy simulation based on the K equation model can better simulate the process of bubble shedding,and predict the frequency of the shedding more accurately.Secondly,using the validated SST k-Omega turbulence model and the Kunz cavitation model,the changes of the cavitation length,the volume of cavity and the lift coefficient of the hydrofoil are investigated under six different cavitation numbers and six different angles of attack,and the cavitation of Clark-Y hydrofoil is analyzed under the condition of the cavitation number of 0.8 and the attack angle of 8°.The variation of cavity shape,velocity field and pressure field with time and the effect of re-entrant jet on cavitation are discussed.Finally,the flow characteristics of the three dimensional wave-like leading edge hydrofoils are introduced and the effect of wavelength and amplitude of wave-like leading edge hydrofoils is studied.The results show that the drag coefficient of wave-like leading edge hydrofoils are larger than the reference hydrofoil.The hydrofoil with larger amplitude and smaller wavelength can restrict the cavitation to the hollow site of the hydrofoils,reducing the total vapor volume in the field.By analyzing the limiting streamline of the hydrofoils,the flow field in the closed area of the cavitation bubbles and the vorticity,it is found that there is a vortex structure in the closed area of the cavity of 3D wave-like leading edge hydrofoils,which inhibits the further development of the cavity,and the strength of the inhibition is related to the vorticity strength. |
