Four ships,a twin-propeller naval ship,two single-propeller container ships,and a single-propeller very large crude carrier(VLCC),were studied to investigate the scale effect of the form factor.The viscous flow fields...Four ships,a twin-propeller naval ship,two single-propeller container ships,and a single-propeller very large crude carrier(VLCC),were studied to investigate the scale effect of the form factor.The viscous flow fields of the ships at different scales were solved numerically via the Reynolds-averaged Navier–Stokes method combined with the shear stress transport k–ωturbulence model.The numerical method was validated through comparisons with experimental data,and numerical uncertainty analysis was carried out based on the ITTC recommended procedure.On this basis,scale effects of the form factor were analyzed using different friction lines,and scale effects of flow fields and the mean axial wake fractions were further analyzed in details.The results showed that the form factor exhibited scale effects when adopting the ITTC-1957 line,and it increased with the increase in the Reynolds number.The scale effect of the form factor reduces the prediction precision of the full-scale ship resistance.The friction line has a significant effect on the form factor.The form factor exhibits little dependence on the Reynolds number when using the numerical friction line or the Katsui line,which is useful for full-scale ship resistance predictions.With the increasing Reynolds number,the boundary layer thickness becomes thinner and the axial velocity contour contracts toward the center plane,and there is nearly a linear relationship between the reciprocal of mean axial wake fraction on propeller disc and Reynolds number in logarithmic scale for the three types of ship forms.展开更多
The horseshoe vortex generated around the sail-body junction of a submarine has an important influence on the uniformity of the submarine wake at the propeller disc.In this article,the horseshoe vortex is simulated by...The horseshoe vortex generated around the sail-body junction of a submarine has an important influence on the uniformity of the submarine wake at the propeller disc.In this article,the horseshoe vortex is simulated by the Detached Eddy Simulation（DES） method,and a new method to control the horseshoe vortex by vortex control baffler is proposed.The numerical simulation shows that a kind of attached vortex,with the rotation direction opposite to that of horseshoe vortex,is generated by the vortex control baffler.With the attached vortex,the strength of the horseshoe vortex is significantly reduced.The wind tunnel experiment on a submarine model is carried out,and the axial velocities at the propeller disc of the submarine with and without vortex control baffler are measured by a hot wire anemometer system.It is shown from the experimental results that the vortex control baffler can enhance the uniformity of the wake at the propeller disc,which helps to improve the propeller performance.The engineering applicability of the vortex control baffler is discussed.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.51809273)。
文摘Four ships,a twin-propeller naval ship,two single-propeller container ships,and a single-propeller very large crude carrier(VLCC),were studied to investigate the scale effect of the form factor.The viscous flow fields of the ships at different scales were solved numerically via the Reynolds-averaged Navier–Stokes method combined with the shear stress transport k–ωturbulence model.The numerical method was validated through comparisons with experimental data,and numerical uncertainty analysis was carried out based on the ITTC recommended procedure.On this basis,scale effects of the form factor were analyzed using different friction lines,and scale effects of flow fields and the mean axial wake fractions were further analyzed in details.The results showed that the form factor exhibited scale effects when adopting the ITTC-1957 line,and it increased with the increase in the Reynolds number.The scale effect of the form factor reduces the prediction precision of the full-scale ship resistance.The friction line has a significant effect on the form factor.The form factor exhibits little dependence on the Reynolds number when using the numerical friction line or the Katsui line,which is useful for full-scale ship resistance predictions.With the increasing Reynolds number,the boundary layer thickness becomes thinner and the axial velocity contour contracts toward the center plane,and there is nearly a linear relationship between the reciprocal of mean axial wake fraction on propeller disc and Reynolds number in logarithmic scale for the three types of ship forms.
文摘The horseshoe vortex generated around the sail-body junction of a submarine has an important influence on the uniformity of the submarine wake at the propeller disc.In this article,the horseshoe vortex is simulated by the Detached Eddy Simulation（DES） method,and a new method to control the horseshoe vortex by vortex control baffler is proposed.The numerical simulation shows that a kind of attached vortex,with the rotation direction opposite to that of horseshoe vortex,is generated by the vortex control baffler.With the attached vortex,the strength of the horseshoe vortex is significantly reduced.The wind tunnel experiment on a submarine model is carried out,and the axial velocities at the propeller disc of the submarine with and without vortex control baffler are measured by a hot wire anemometer system.It is shown from the experimental results that the vortex control baffler can enhance the uniformity of the wake at the propeller disc,which helps to improve the propeller performance.The engineering applicability of the vortex control baffler is discussed.
