The generation of unsteady interfacial gravity waves by a singularity immersed in two semi-infinite fluids was analytically investigated in detail by the methods of integral transform and of stationary-phase analysis....The generation of unsteady interfacial gravity waves by a singularity immersed in two semi-infinite fluids was analytically investigated in detail by the methods of integral transform and of stationary-phase analysis. The fluids were assumed to be initially stationary, immiscible, inviscid and incompressible. The disturbed flows, generated by an impulsive and oscillatory source/dipole immersed above or be neath the interface, were governed by the I.aplace equations. The kinematic and dynamic boundary conditions on the interface were linearized for the small-amplitude waves. By means of the stationary phase analysis on the exact integral form solutions, the asymptotic representations for the interracial waves were derived for large time with a fixed distance to time ratio. The relation between a submerged singularity and a sur face pressure point was discussed. It is found that the local wavelength and the local wave period of the interracial waves are elongated in comparison with those of free-surface waves for a single fluid.展开更多
采用全浮区模型数值研究旋转磁场作用下不同辐射加热温度时熔区内热毛细对流流动特性。研究发现,B0=1 m T的旋转磁场产生的洛伦兹力不足以控制熔区中的热毛细对流,熔体内流场呈现周期性旋转振荡特征,振荡频率随辐射温度的增加而减小,并...采用全浮区模型数值研究旋转磁场作用下不同辐射加热温度时熔区内热毛细对流流动特性。研究发现,B0=1 m T的旋转磁场产生的洛伦兹力不足以控制熔区中的热毛细对流,熔体内流场呈现周期性旋转振荡特征,振荡频率随辐射温度的增加而减小,并与Ma数成线性关系。当Ma数较小时,温度场主要由扩散作用决定,呈二维轴对称分布;随着Ma数的增加,熔体中的温度场受对流影响,亦呈周期性振荡,且振荡主频与对流振荡主频相同。保持旋转磁场的频率不变,适当增加磁场强度,熔体内的三维振荡流将转变为准二维的旋转轴对称流,热毛细对流关于中截面镜面对称。对于Ma=21.8、32.9和43.7的熔体,分别施加2、3和5 m T的旋转磁场,熔体中的温度及速度波动被有效抑制。展开更多
Similar to the capillary phenomenon of liquid, granular particles can move up to a certain height along a vertically vibrating tube. The certain height, which is called the equilibrium height, is related to some param...Similar to the capillary phenomenon of liquid, granular particles can move up to a certain height along a vertically vibrating tube. The certain height, which is called the equilibrium height, is related to some parameters, e.g., the inner diameter of the tube, the amplitude, and the vibration frequency. In this paper, a theoretical model is proposed to explain the physical origin of the capillary phenomenon and the effects of the inner diameter of the tube, the amplitude, and the vibration frequency on the equilibrium height. In this model, the volumes of the inflowing and outflowing particles in a vibration period are calculated, which can significantly broaden our understanding in the flow of particles in the bottom of the tube. In order to prove the assumption of this physical model that the particles in the bottom of the tube move in the form of sine, several experiments are conducted. The granular climbing heights at different granular positions and different time stages are measured. The results show that granules move in the form of sine, which almost coincides with the motion of the tube. Moreover, motivated by the sampling on the asteroid regolith based on this mechanism, the sampling efficiencies for various vibration amplitudes and frequencies are discussed based on the new proposed model. It is found that there is an optimum frequency at which sampling is the most effective.展开更多
文摘The generation of unsteady interfacial gravity waves by a singularity immersed in two semi-infinite fluids was analytically investigated in detail by the methods of integral transform and of stationary-phase analysis. The fluids were assumed to be initially stationary, immiscible, inviscid and incompressible. The disturbed flows, generated by an impulsive and oscillatory source/dipole immersed above or be neath the interface, were governed by the I.aplace equations. The kinematic and dynamic boundary conditions on the interface were linearized for the small-amplitude waves. By means of the stationary phase analysis on the exact integral form solutions, the asymptotic representations for the interracial waves were derived for large time with a fixed distance to time ratio. The relation between a submerged singularity and a sur face pressure point was discussed. It is found that the local wavelength and the local wave period of the interracial waves are elongated in comparison with those of free-surface waves for a single fluid.
文摘采用全浮区模型数值研究旋转磁场作用下不同辐射加热温度时熔区内热毛细对流流动特性。研究发现,B0=1 m T的旋转磁场产生的洛伦兹力不足以控制熔区中的热毛细对流,熔体内流场呈现周期性旋转振荡特征,振荡频率随辐射温度的增加而减小,并与Ma数成线性关系。当Ma数较小时,温度场主要由扩散作用决定,呈二维轴对称分布;随着Ma数的增加,熔体中的温度场受对流影响,亦呈周期性振荡,且振荡主频与对流振荡主频相同。保持旋转磁场的频率不变,适当增加磁场强度,熔体内的三维振荡流将转变为准二维的旋转轴对称流,热毛细对流关于中截面镜面对称。对于Ma=21.8、32.9和43.7的熔体,分别施加2、3和5 m T的旋转磁场,熔体中的温度及速度波动被有效抑制。
基金Project supported by the National Natural Science Foundation of China for Distinguished Young Scholars(No.11525208)
文摘Similar to the capillary phenomenon of liquid, granular particles can move up to a certain height along a vertically vibrating tube. The certain height, which is called the equilibrium height, is related to some parameters, e.g., the inner diameter of the tube, the amplitude, and the vibration frequency. In this paper, a theoretical model is proposed to explain the physical origin of the capillary phenomenon and the effects of the inner diameter of the tube, the amplitude, and the vibration frequency on the equilibrium height. In this model, the volumes of the inflowing and outflowing particles in a vibration period are calculated, which can significantly broaden our understanding in the flow of particles in the bottom of the tube. In order to prove the assumption of this physical model that the particles in the bottom of the tube move in the form of sine, several experiments are conducted. The granular climbing heights at different granular positions and different time stages are measured. The results show that granules move in the form of sine, which almost coincides with the motion of the tube. Moreover, motivated by the sampling on the asteroid regolith based on this mechanism, the sampling efficiencies for various vibration amplitudes and frequencies are discussed based on the new proposed model. It is found that there is an optimum frequency at which sampling is the most effective.
