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A growing interest has been devoted to the contra-rotating propellers (CRPs) due to their high propulsive efficiency, torque balance, low fuel consumption, low cavitations, low noise performance and low hull vibration. Compared with the single-screw system, it is more difficult for the open water performance prediction because forward and aft propellers interact with each other and generate a more complicated flow field around the CRPs system. The current work focuses on the open water performance prediction of contra-rotating propellers by RANS and sliding mesh method considering the effect of computational time step size and turbulence model. The validation study has been performed on two sets of contra-rotating propellers developed by David W Taylor Naval Ship R & D center. Compared with the experimental data, it shows that RANS with sliding mesh method and SST k-ω turbulence model has a good precision in the open water performance prediction of contra-rotating propellers, and small time step size can improve the level of accuracy for CRPs with the same blade number of forward and aft propellers, while a relatively large time step size is a better choice for CRPs with different blade numbers. 相似文献
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进入2009年11月以来,北半球极地冷空气偏强,位置偏西,欧亚大陆大气环流的经向度加大,造成冷空气活动频繁、强度增强。蒙西山地聚集的强冷空气东移路径由原来经蒙古中部影响我国东北地区变为经河套及华北大部爆发南下影响我国长江以北的大部地区,从而导致2009年11月上旬末至中旬鄂尔多斯市大部地区的强降雪及雪后持续低温天气,11月中旬鄂尔多斯市各地平均气温在-10.8～-8.0℃之间,较正常年份同期偏低5～9℃,为有气象记录以来同期最低值,11月的平均气温为1986年以来同期最低值。低温暴雪天气给鄂尔多斯市各地的居民生活、交通运输及农牧业种养殖等造成严重影响。 相似文献
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The horseshoe vortex generated around the sail-body junction of submarine has an important influence on the non-uniformity of submarine wake at propeller disc.The flow characteristics in the horseshoe vortex generated area are analyzed,and a new method of vortex control baffler is presented.The influence of vortex control baffler on the flow field around submarine main body with sail is numerically simulated.The wind tunnel experiment on submarine model is carried out,and it is proved that the vortex control baffler can weaken the horseshoe vortex and decrease the non-uniformity of the wake at propeller disc.It is shown from the experiment results that the effect of vortex control baffler depends on its installation position;with a proper installation position,the non-uniform coefficient of submarine wake would be declined by about 50%;the Reynolds number of submarine model has an influence on the effect of vortex control baffler too,and the higher the Reynolds number is,the better the effect of the vortex control baffler is. 相似文献
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The hydrodynamic performance of a hybrid CRP pod propulsion system was studied by RANS method with SST turbulence model and sliding mesh. The effect of axial spacing on the hydrodynamic performance of the hybrid CRP pod propulsion system was investigated numerically and experimentally. It shows that RANS with the sliding mesh method and SST turbulence model predicts accurately the hydrodynamic performance of the hybrid CRP pod propulsion system. The axial spacing has little influence on the hydrodynamic performance of the forward propeller, but great influence on that of the pod unit. Thrust coefficient of the pod unit declines with the increase of the axial spacing, but the trend becomes weaker, and the decreasing amplitude at the lower advance coefficient is larger than that at the higher advance coefficient. The thrust coefficient and open water efficiency of the hybrid CRP pod propulsion system decrease with the increase of the axial spacing, while the torque coefficient keeps almost constant. On this basis, the design principle of axial spacing of the hybrid CRP pod propulsion system was proposed. 相似文献
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