The tip-clearance flow in a pump-jet propulsor exerts great impacts on the fluctuating pressures and resultant unsteady forces,which are important sources of structural vibrations and radiated noise underwater.The bla...The tip-clearance flow in a pump-jet propulsor exerts great impacts on the fluctuating pressures and resultant unsteady forces,which are important sources of structural vibrations and radiated noise underwater.The blade geometry close to the tip is an important factor determining the vortex strength in the tip-clearance flow.In the open-water condition,the effects of raking the rotor tips on the duct-surface fluctuating pressures and the resultant unsteady forces acting on different components of the propulsor are investigated via physical model experiments and the numerical solution of Reynolds-averaged Navier-Stokes(RANS)equations coupled with the SST k-ωturbulence model.The measured and simulated results of hydrodynamic pressures are consistent to each other,and the simulated flows help better understand why the fluctuating pressures change with the tip geometry.The strong fluctuations of duct-surface pressures are caused by intensive tip separation vortices.The duct-surface pressure fluctuations are effectively reduced by using the rake distribution near the tip towards blade back side and,for the combination of the five-bladed rotor and the seven-bladed stator,the resultant unsteady horizontal(and vertical)forces acting on the duct and stator are also reduced;while increasing rake leads to negative effect on pressure fluctuations and unsteady horizontal(and vertical)forces acting on all the components of the propulsor.展开更多
In this paper,the scale effect of Kappel tip-rake propellers with different end plate designs was studied using computational fluid dynamics.Given the base size of the mesh and the appropriate numerical model for the ...In this paper,the scale effect of Kappel tip-rake propellers with different end plate designs was studied using computational fluid dynamics.Given the base size of the mesh and the appropriate numerical model for the determined simulation,the open-water performance of three Kappel propellers with different bending degrees of the end plate at different scales was calculated.Comparing the scale effect of these propellers,the scale effect of the torque coefficient of a Kappel propeller is more intense than that of the conventional propeller.In addition,the scale effect of the torque coefficient is strong when the bending degree of the end plate increases,dwarfing the scale effect on the thrust coefficient.Following the research on the scale effect of the wake field for the Kappel propeller,the laws that reveal the influence of the scale on the wake field were summarized;that is,the high-speed zone in the wake relatively expands with the increase of the scale in company with a trend of tip cross flow.The research reveals the basic variation trend and rule of the open-water performance and wake distribution for the Kappel propeller under different scales within the Reynolds number range of 4.665×10^(5)-8.666×10^(7)consideringγtransition,as well as the characteristic differences between the Kappel propellers with different end plate designs,which will be of great significance to its optimization design and application to marine vehicles of different scales.展开更多
基金supported by the National Key Project of China for Strengthening Fundamental Research(Grant No.2019-JCJQ-ZD-016-00).
文摘The tip-clearance flow in a pump-jet propulsor exerts great impacts on the fluctuating pressures and resultant unsteady forces,which are important sources of structural vibrations and radiated noise underwater.The blade geometry close to the tip is an important factor determining the vortex strength in the tip-clearance flow.In the open-water condition,the effects of raking the rotor tips on the duct-surface fluctuating pressures and the resultant unsteady forces acting on different components of the propulsor are investigated via physical model experiments and the numerical solution of Reynolds-averaged Navier-Stokes(RANS)equations coupled with the SST k-ωturbulence model.The measured and simulated results of hydrodynamic pressures are consistent to each other,and the simulated flows help better understand why the fluctuating pressures change with the tip geometry.The strong fluctuations of duct-surface pressures are caused by intensive tip separation vortices.The duct-surface pressure fluctuations are effectively reduced by using the rake distribution near the tip towards blade back side and,for the combination of the five-bladed rotor and the seven-bladed stator,the resultant unsteady horizontal(and vertical)forces acting on the duct and stator are also reduced;while increasing rake leads to negative effect on pressure fluctuations and unsteady horizontal(and vertical)forces acting on all the components of the propulsor.
基金Supported by the Ningbo Institute of Materials Technology and Engineering affiliated to Chinese Academy of Sciences(Grant No.829203-I22101)TXC(Ningbo)Co.,Ltd.(Grant No.529203-I22004).
文摘In this paper,the scale effect of Kappel tip-rake propellers with different end plate designs was studied using computational fluid dynamics.Given the base size of the mesh and the appropriate numerical model for the determined simulation,the open-water performance of three Kappel propellers with different bending degrees of the end plate at different scales was calculated.Comparing the scale effect of these propellers,the scale effect of the torque coefficient of a Kappel propeller is more intense than that of the conventional propeller.In addition,the scale effect of the torque coefficient is strong when the bending degree of the end plate increases,dwarfing the scale effect on the thrust coefficient.Following the research on the scale effect of the wake field for the Kappel propeller,the laws that reveal the influence of the scale on the wake field were summarized;that is,the high-speed zone in the wake relatively expands with the increase of the scale in company with a trend of tip cross flow.The research reveals the basic variation trend and rule of the open-water performance and wake distribution for the Kappel propeller under different scales within the Reynolds number range of 4.665×10^(5)-8.666×10^(7)consideringγtransition,as well as the characteristic differences between the Kappel propellers with different end plate designs,which will be of great significance to its optimization design and application to marine vehicles of different scales.
