在高纬电离层,由于受大的对流电场的影响,致使离子的速度分布函数常常会表现为非麦克斯韦分布形式.通过简化玻耳兹曼弛豫碰撞模型下离子速度非麦克斯韦分布函数的积分解,得到了离子呈环形分布的速度分布函数,并模拟和图解分析了离子速度分布函数呈环形分布的特征.同时,基于离子温度各向异性,模拟并分析了当离子速度分布函数呈环形时,不同方向上的离子非相干散射功率谱.理论研究表明,在离子碰撞频率较低的高纬电离层,随着电离层对流电场的增强,离子速度分布函数呈环形分布的特征愈加明显,且考虑离子温度各向异性等因素对功率谱的影响,能更加符合高纬电离层实际.

Considering the relatively strong electric field and small collision frequency between ion and neutral in the high-latitude ionosphere ,the integral solution of the non-Maxwellian ion velocity distribu-tion function for the relaxation collision model is simplified ,the torus distribution function for ion veloc-ity is obtained ,and the characteristic of the torus distribution function is analyzed .Meanwhile ,using the electromagnetic theory of the incoherent scattering proposed by Sheffield ,and taking into account the ion temperature anisotropy and its variation with the electric field ,the incoherent scattering power spectrum of ion in different direction is simulated .The research shows that the ionospheric electric field , the ion-neutral collision frequency and the ion anisotropic temperature distribution is all have an effect on incoherent scatter spectra ,the research content provides a theoretical basis for further understanding the high-latitude ionosphere and improving detecti

主要研究了影响非定常动边界问题的一些基本参数并分析了其与推进力的关系。数值模拟采用格子波尔兹曼方法求解流场信息，并用浸入边界速度修正方法进行边界处速度的修正。研究对象为二维情况下摆动的鱼，影响推进力的参数有鱼体的形状、频率、波长、雷诺数。通过对各个参数的一系列模拟，得出其对推进力的不同影响关系。本文总共选取五种形状的鱼体，其运动模式为鱼体中线以行波的方式做横向摆动。最后，从涡的角度分析鱼的尾尖在不同位置时鱼体表面涡的分布情况，得到旋涡变化与鱼身运动的相互关系。通过研究发现，不同形状的鱼推进力不同，在高频、增大波长、增大雷诺数时，推进力增大。

The current study mainly focuses on some fundamental parameters that affect the unsteady moving boundary problems.The relationships between the propulsion force and these parameters are ana-lyzed.To numerically simulate fish swimming in this work,the Lattice Boltzmann Method (LBM)is applied to obtain the information of flow field.At the same time,the velocity near the body is corrected via the Im-mersed Boundary Velocity Correction Method (IBVCM).Here,a two-dimensional oscillating fish is studied and the factors affecting the fish swimming,which are investigated in current study,are the shape,frequen-cy,wavelength,and Reynolds number as well.After a series of simulations with different parameters,the correspondly effects on the propulsion force are obtained.Five kinds of shapes are selected for the fish body, and its motion mode is that the centerline of fish oscillates transversally in the form of traveling wave.More-over,from the perspective of vortex,the vortex distribution is analy