The paper presents a quaternion approach of giving a closed form solution of the motion in a central force field relative to a rotating reference frame. This new method involves two quaternion operators: the first one...The paper presents a quaternion approach of giving a closed form solution of the motion in a central force field relative to a rotating reference frame. This new method involves two quaternion operators: the first one transforms the motion from a non-inertial reference frame to a inertial one with a very significant consequence of vanishing all the non-inertial terms (Coriolis and centripetal forces);the second quaternion operator provides the solution of the motion in the noninertial reference frame by applying it to the solution in the inertial reference frame. This process will govern the inverse transformation of the motion and is proved on two particular cases, the Foucault Pendulum and Keplerian motions problems relative to rotating reference frames.展开更多
One of the solutions to reduce fuel consumption of diesel generators (DG) is to adapt the rotational speed to mechanical torque of the crankshaft. When load power decreases, a reduction in both mechanical torque and r...One of the solutions to reduce fuel consumption of diesel generators (DG) is to adapt the rotational speed to mechanical torque of the crankshaft. When load power decreases, a reduction in both mechanical torque and rotational speed of the diesel engine will maintain the combustion efficiency near the levels of the nominal regime. Accordingly, the generator itself should operate at a variable speed which normally requires power electronics converters. In this paper, we are exploring a new generator concept that uses a stator rotating in opposite direction to the rotor such as the relative velocity between the two components remains constant when diesel engine slows down. The stator itself is driven by a compensator synchronous motor (CM) such as the relative velocity of the rotor is constant, eliminating as such sophisticated power electronics. The model developed for the synchronous machine with a rotating stator is based on Park’s transformation. This new concept was modelled using MATLAB software. Experimental analysis has been conducted using a 500-kW diesel GENSET equipped with a permanent magnet synchronous generator (PMSG). The numerical and experimental results are in good agreement and demonstrate that fuel consumption is reduced with a rotating-mode stator for PMSG during low electrical loads.展开更多
Ocean energy has a potential of providing a large amount of renewable energy around the world. One of the forms of ocean energy, tidal stream power is widely recognized as the continuous, predictable and eco-friendly ...Ocean energy has a potential of providing a large amount of renewable energy around the world. One of the forms of ocean energy, tidal stream power is widely recognized as the continuous, predictable and eco-friendly ocean energy source. Unique tandem propellers that can counter-rotate have been designed to generate electric power effectively from a tidal stream. This type of power unit has several advantages compare to the conventional unit with a single propeller. At the design of the tidal stream power unit, it is important to investigate the structure of the tip vortex tubes shedding to predict the load of the propeller. In this research, we investigated the tip vortex shedding using the CFD method for the conventional single propeller and counter-rotating type tandem propellers and estimated the performance efficiency using RANS (Reynolds Averaged Navier-Stokes) model and we confirmed the limitation of RANS model on the calculation of the tip vortex stretching.展开更多
We have developed a path integral formalism of the quantum mechanics in the rotating frame of reference, and proposed a path integral description of spin degrees of freedom, which is connected to the Schwinger bosons ...We have developed a path integral formalism of the quantum mechanics in the rotating frame of reference, and proposed a path integral description of spin degrees of freedom, which is connected to the Schwinger bosons realization of the angular momenta. We have also given several important examples for the applications in the rotating frames.展开更多
采用虚拟的旋转不同角度左、右手模型,构建"左右手判断(Left and right hand judgment:LR)"任务和"相同-不同判断(same and different judgment:SD)"任务,考察这两种实验任务是否都存在内旋效应和角度效应,以此推...采用虚拟的旋转不同角度左、右手模型,构建"左右手判断(Left and right hand judgment:LR)"任务和"相同-不同判断(same and different judgment:SD)"任务,考察这两种实验任务是否都存在内旋效应和角度效应,以此推论被试采用何种旋转策略。结果发现:(1)两种实验任务结果均表现出显著的角度效应;(2)在LR任务条件下,存在显著的内旋效应,而在SD任务中不存在内旋效应。从而表明当人手图片作为心理旋转材料时,它具有双重角色。被试心理旋转加工时究竟选用何种参照系的旋转策略,与实验材料和实验任务两者都密不可分。展开更多
文章基于RANS方程,对计及自由面影响的双桨转动情况下的舰船旋臂试验(RAT)粘性流场数值模拟方法进行了研究。在旋臂试验的数值模拟中,根据旋臂试验的特点,采用分区混合网格,结合MRF方法和滑移网格方法,解决船体圆运动及螺旋桨定轴旋转...文章基于RANS方程,对计及自由面影响的双桨转动情况下的舰船旋臂试验(RAT)粘性流场数值模拟方法进行了研究。在旋臂试验的数值模拟中,根据旋臂试验的特点,采用分区混合网格,结合MRF方法和滑移网格方法,解决船体圆运动及螺旋桨定轴旋转运动的叠合难题。文中以ITTC推荐的MARIN model no.7967船模为对象,对其在四组转动半径下的旋臂试验进行了数值计算,并将结果与权威水池试验结果进行了对比,吻合良好。文中提出的方法可获得全附体船模旋转流场水动力性能参数,可以较真实地模拟其流场特性,获取包括船—舵—桨干扰在内的流场信息。该文的工作是可行的、有效的,可为深入研究舰船自由旋回试验及非定常操纵运动的数值模拟提供基础。展开更多
文摘The paper presents a quaternion approach of giving a closed form solution of the motion in a central force field relative to a rotating reference frame. This new method involves two quaternion operators: the first one transforms the motion from a non-inertial reference frame to a inertial one with a very significant consequence of vanishing all the non-inertial terms (Coriolis and centripetal forces);the second quaternion operator provides the solution of the motion in the noninertial reference frame by applying it to the solution in the inertial reference frame. This process will govern the inverse transformation of the motion and is proved on two particular cases, the Foucault Pendulum and Keplerian motions problems relative to rotating reference frames.
文摘One of the solutions to reduce fuel consumption of diesel generators (DG) is to adapt the rotational speed to mechanical torque of the crankshaft. When load power decreases, a reduction in both mechanical torque and rotational speed of the diesel engine will maintain the combustion efficiency near the levels of the nominal regime. Accordingly, the generator itself should operate at a variable speed which normally requires power electronics converters. In this paper, we are exploring a new generator concept that uses a stator rotating in opposite direction to the rotor such as the relative velocity between the two components remains constant when diesel engine slows down. The stator itself is driven by a compensator synchronous motor (CM) such as the relative velocity of the rotor is constant, eliminating as such sophisticated power electronics. The model developed for the synchronous machine with a rotating stator is based on Park’s transformation. This new concept was modelled using MATLAB software. Experimental analysis has been conducted using a 500-kW diesel GENSET equipped with a permanent magnet synchronous generator (PMSG). The numerical and experimental results are in good agreement and demonstrate that fuel consumption is reduced with a rotating-mode stator for PMSG during low electrical loads.
文摘Ocean energy has a potential of providing a large amount of renewable energy around the world. One of the forms of ocean energy, tidal stream power is widely recognized as the continuous, predictable and eco-friendly ocean energy source. Unique tandem propellers that can counter-rotate have been designed to generate electric power effectively from a tidal stream. This type of power unit has several advantages compare to the conventional unit with a single propeller. At the design of the tidal stream power unit, it is important to investigate the structure of the tip vortex tubes shedding to predict the load of the propeller. In this research, we investigated the tip vortex shedding using the CFD method for the conventional single propeller and counter-rotating type tandem propellers and estimated the performance efficiency using RANS (Reynolds Averaged Navier-Stokes) model and we confirmed the limitation of RANS model on the calculation of the tip vortex stretching.
基金Supported by National Natural Science Foundation of China (10875129, 10525522)
文摘We have developed a path integral formalism of the quantum mechanics in the rotating frame of reference, and proposed a path integral description of spin degrees of freedom, which is connected to the Schwinger bosons realization of the angular momenta. We have also given several important examples for the applications in the rotating frames.
文摘采用虚拟的旋转不同角度左、右手模型,构建"左右手判断(Left and right hand judgment:LR)"任务和"相同-不同判断(same and different judgment:SD)"任务,考察这两种实验任务是否都存在内旋效应和角度效应,以此推论被试采用何种旋转策略。结果发现:(1)两种实验任务结果均表现出显著的角度效应;(2)在LR任务条件下,存在显著的内旋效应,而在SD任务中不存在内旋效应。从而表明当人手图片作为心理旋转材料时,它具有双重角色。被试心理旋转加工时究竟选用何种参照系的旋转策略,与实验材料和实验任务两者都密不可分。
文摘文章基于RANS方程,对计及自由面影响的双桨转动情况下的舰船旋臂试验(RAT)粘性流场数值模拟方法进行了研究。在旋臂试验的数值模拟中,根据旋臂试验的特点,采用分区混合网格,结合MRF方法和滑移网格方法,解决船体圆运动及螺旋桨定轴旋转运动的叠合难题。文中以ITTC推荐的MARIN model no.7967船模为对象,对其在四组转动半径下的旋臂试验进行了数值计算,并将结果与权威水池试验结果进行了对比,吻合良好。文中提出的方法可获得全附体船模旋转流场水动力性能参数,可以较真实地模拟其流场特性,获取包括船—舵—桨干扰在内的流场信息。该文的工作是可行的、有效的,可为深入研究舰船自由旋回试验及非定常操纵运动的数值模拟提供基础。
