In this study,the performance of a twin-screw propeller under the influence of the wake field of a fully appended ship was investigated using a coupled Reynolds-averaged Navier–Stokes(RANS)/boundary element method(BE...In this study,the performance of a twin-screw propeller under the influence of the wake field of a fully appended ship was investigated using a coupled Reynolds-averaged Navier–Stokes(RANS)/boundary element method(BEM)code.The unsteady BEM is an efficient approach to predicting propeller performance.By applying the time-stepping method in the BEM solver,the trailing vortex sheet pattern of the propeller can be accurately captured at each time step.This is the main innovation of the coupled strategy.Furthermore,to ascertain the effect of the wake field of the ship with acceptable accuracy,a RANS solver was developed.A finite volume method was used to discretize the Navier–Stokes equations on fully unstructured grids.To simulate ship motions,the volume of the fluid method was applied to the RANS solver.The validation of each solver(BEM/RANS)was separately performed,and the results were compared with experimental data.Ultimately,the BEM and RANS solvers were coupled to estimate the performance of a twin-screw propeller,which was affected by the wake field of the fully appended hull.The proposed model was applied to a twin-screw oceanography research vessel.The results demonstrated that the presented model can estimate the thrust coefficient of a propeller with good accuracy as compared to an experimental self-propulsion test.The wake sheet pattern of the propeller in open water(uniform flow)was also compared with the propeller in a real wake field.展开更多
To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this pap...To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this paper,a coupled BEM(Boundary Element Method)/RANS(Renolds-Averaged Navier−Stokes)solver is used to simulate propeller behind the hull in the self-propulsion test.The motivation of this work is to develop a practical tool to design marine propulsion system without suffering long computational time.An unsteady boundary element method which is also known as panel method is chosen to estimate the propeller forces.Propeller wakes are treated using a time marching wake alignment method.Also,a RANS code coupled with VoF equation is developed to consider the ship motions and wake field effects in the problem.A coupling algorithm is developed to interchange ship wake field to the potential flow solver and propeller thrust to the RANS code.Based on the difference between hull resistance and the propeller thrust,a PI controller is developed to compute the propeller RPM in every time step.Verification of the solver is carried out using the towing tank test report of a 50 m oceanography research vessel.Wake factor and trust deduction coefficient are estimated numerically.Also,the wake rollup pattern of the propeller in open water is compared with the propeller in real wake field.展开更多
A series of experiments was carried out to study the flow behaviour behind a rotationally oscillating cylinder at a low Reynolds number （Re=300） placed in a recirculation water channel. A stepper motor was used to r...A series of experiments was carried out to study the flow behaviour behind a rotationally oscillating cylinder at a low Reynolds number （Re=300） placed in a recirculation water channel. A stepper motor was used to rotate the cylinder clockwise- and- counterclockwise about its longitudinal axis at selected frequencies. The particle image velocimetry （PIV） technique was used to capture the flow field behind a rotationally oscillating cylinder. Instantaneous and time-averaged flow fields such as the vorticity contours, streamline topologies and velocity distributions were analyzed. The effects of four rotation angle and frequency ratios Fr （Fr=fn/fv, the ratio of the forcing frequency fn to the natural vortex shedding frequency fv） on the wake in the lee of a rotationally oscillating cylinder were also examined. The significant wake modification was observed when the cylinder undergoes clockwise-and-counterclockwise motion with amplitude of π, especially in the range of 0.6≤Fr≤1.0.展开更多
文摘In this study,the performance of a twin-screw propeller under the influence of the wake field of a fully appended ship was investigated using a coupled Reynolds-averaged Navier–Stokes(RANS)/boundary element method(BEM)code.The unsteady BEM is an efficient approach to predicting propeller performance.By applying the time-stepping method in the BEM solver,the trailing vortex sheet pattern of the propeller can be accurately captured at each time step.This is the main innovation of the coupled strategy.Furthermore,to ascertain the effect of the wake field of the ship with acceptable accuracy,a RANS solver was developed.A finite volume method was used to discretize the Navier–Stokes equations on fully unstructured grids.To simulate ship motions,the volume of the fluid method was applied to the RANS solver.The validation of each solver(BEM/RANS)was separately performed,and the results were compared with experimental data.Ultimately,the BEM and RANS solvers were coupled to estimate the performance of a twin-screw propeller,which was affected by the wake field of the fully appended hull.The proposed model was applied to a twin-screw oceanography research vessel.The results demonstrated that the presented model can estimate the thrust coefficient of a propeller with good accuracy as compared to an experimental self-propulsion test.The wake sheet pattern of the propeller in open water(uniform flow)was also compared with the propeller in a real wake field.
文摘To design a propeller for ship power plant,the interaction between ship hull and propeller must be taken into account.The main concern is to apply the wake effect of ship stern on the propeller performance.In this paper,a coupled BEM(Boundary Element Method)/RANS(Renolds-Averaged Navier−Stokes)solver is used to simulate propeller behind the hull in the self-propulsion test.The motivation of this work is to develop a practical tool to design marine propulsion system without suffering long computational time.An unsteady boundary element method which is also known as panel method is chosen to estimate the propeller forces.Propeller wakes are treated using a time marching wake alignment method.Also,a RANS code coupled with VoF equation is developed to consider the ship motions and wake field effects in the problem.A coupling algorithm is developed to interchange ship wake field to the potential flow solver and propeller thrust to the RANS code.Based on the difference between hull resistance and the propeller thrust,a PI controller is developed to compute the propeller RPM in every time step.Verification of the solver is carried out using the towing tank test report of a 50 m oceanography research vessel.Wake factor and trust deduction coefficient are estimated numerically.Also,the wake rollup pattern of the propeller in open water is compared with the propeller in real wake field.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51409231,51479175,and51679212)Zhejiang Provincial Natural Science Foundation of China(Grant Nos.LY14E090009 and LR16E090002)+2 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,the Ministry of Education(Grant No.1685[2014])the State Key Laboratory of Ocean Engineering(Shanghai Jiao Tong University)(Grant No.1312)China
文摘A series of experiments was carried out to study the flow behaviour behind a rotationally oscillating cylinder at a low Reynolds number （Re=300） placed in a recirculation water channel. A stepper motor was used to rotate the cylinder clockwise- and- counterclockwise about its longitudinal axis at selected frequencies. The particle image velocimetry （PIV） technique was used to capture the flow field behind a rotationally oscillating cylinder. Instantaneous and time-averaged flow fields such as the vorticity contours, streamline topologies and velocity distributions were analyzed. The effects of four rotation angle and frequency ratios Fr （Fr=fn/fv, the ratio of the forcing frequency fn to the natural vortex shedding frequency fv） on the wake in the lee of a rotationally oscillating cylinder were also examined. The significant wake modification was observed when the cylinder undergoes clockwise-and-counterclockwise motion with amplitude of π, especially in the range of 0.6≤Fr≤1.0.
