Compressible Cavitating Flow And Its Dynamics In Thermo-sensitive Fluid

In the space industry,the thermo-sensitive cavitating flow is an important fundamental issues in the research of liquid rocket turbopumps.The understanding of thermo-sensitive unsteady cavitating flow characteristics and dynamics is helpful to the performance optimization of turbopump system.Compared with water at room temperature,thermo-sensitive fluid has thermo-sensitive properties,which makes its physical properties more complex.Moreover,when cavitation of a thermo-sensitive fluid occurs,more mass of liquid needs to be vaporized,resulting in a non-negligible latent heat from the phase change.Therefore,the traditional computational approach is no longer applicable.It is extremely important to carry out the exploration of a new approach,which is beneficial to explore its unsteady flow characteristics and has important theoretical significance and engineering applications for the study of liquid rocket turbopumps.To this end,the following main work is carried out in this paper:The Zwart cavitation model is corrected for thermal effects using the heat transfer equation,and then the flow medium is corrected for compressibility using the ideal gas EOS and the Tamman liquid EOS.The empirical coefficients of the vapour-liquid twophase EOS are generalized according to the physical properties of different thermosensitive fluids to ensure the applicability to different thermo-sensitive cavitating flow.In addition,for the original RNG k-ε turbulence model,the filter–based density corrected model(FBDCM)is adopted.The compressible thermal cavitation model is validated using liquid nitrogen flow around 2D hydrofoil and ogive.The results are in good agreement with NASA’s Hord experimental data.The accuracy performance is compared with the predictions of existing cavitation models.The relationship between compressibility and thermal effects in the phase transition process is investigated.The results show that the consideration of thermal compressibility is beneficial to improve the accuracy of numerical simulation of cavitating flow based on thermal effects.In addition,the role of thermal effect and compressibility on the cavitation behavior is investigated in depth.3D unsteady numerical simulations of fluoroketone cavitating flow at different cavitation numbers around NACA0015 were carried out,and the flow characteristics were analyzed in detail.The results show that the time evolution of the vapour volume remains quasi-periodic as the cavitation number rises.However,the cavitation intensity decreases.The Q-criterion analysis shows that the wall-return jet shear effect causes the attached cavity to fall off from the hydrofoil,and the rotation effect causes the collapse of the cloud cavity.Therefore,the shear effect and the rotation effect jointly govern the cavitating flow.The force element formula is used to disentangle the lift and drag forces,and the correlation between the cavitation evolution and the lift drag force is analyzed.The results show that an increase in the cavitation number causes the lift-drag coefficient to rise and then fall.The evolution of transient lift and drag is analyzed in conjunction with the cavity evolution.The results show that the cavity development is accompanied by the growth of positive lift elements,and the collapse of the cloud cavity leads to the disappearance of positive force elements.The growth and collapse rates of both affect the rising and falling of lift drag forces.