双圆柱气囊缓冲性能分析

基于有限元法和控制体积法,建立了双圆柱气囊缓冲系统的有限元模型。以着陆速度为6.7m/s,高为2m,直径为1m的圆柱形气囊为例,利用LS-DYNA软件计算气囊缓冲过程中空投设备的速度和加速度,并对影响气囊缓冲性能的织物弹性模量、排气孔开口面积以及气囊初始内压进行了分析。结果表明:(1)当气囊织物的弹性模量E≤0.5GPa时,增大弹性模量可以显著提高气囊的缓冲性能;当气囊织物的弹性模量E0.5GPa时,增大弹性模量对气囊缓冲性能的影响很小。(2)在不超过排气阀门值的范围内,增大气囊的初始内压可以有效地提高气囊的缓冲性能。     

漩涡合并过程中颗粒运动的数值模拟

漩涡合并不仅影响着流场的演化,还制约着颗粒相的运动．基于涡团分裂合并机制,以一种改进的涡核扩散方法(CCSVM)计算了二相流中的漩涡合并与演化,在此基础上采用单颗粒轨道模型计算、分析了漩涡合并过程中的颗粒运动轨迹．研究结果表明:漩涡合并过程中的颗粒轨迹是一条螺旋线,并且保持与漩涡相同的旋转方向,合并后的漩涡中心即为达到稳定状态后的环状颗粒群中心;合并时间与环量初始值、漩涡半径与涡心距比值的初始值有关;特定条件下,颗粒群中会生成一条拉伸的尾迹,尾迹的产生与黏度系数、颗粒与漩涡的相对位置、合并漩涡环量的不对称性有关．     

剥蚀引起的球锥体两相绕流效应

基于多学科理论建立了极端环境下球锥体烧蚀、剥蚀的数理模型。利用离散涡方法计算流场与球锥表面压力分布,采用三方程烧蚀模型计算热化学控制机制下的烧蚀速率;引入颗粒轨道模型求解剥蚀颗粒的运动,编程计算高温高压燃烧室内球锥形烧蚀试件的绕流场及剥蚀颗粒的运动轨迹。研究表明：烧蚀对球锥体的绕流影响显著,球锥体的涡云较快地转变为不对...     

Simulation on motion of particles in vortex merging process

In a two-phase flow, the vortex merging influences both the flow evolution and the particle motion. With the blobs-splitting-and-merging scheme, the vortex merging is calculated by a corrected core spreading vortex method （CCSVM）. The particle motion in the vortex merging process is calculated according to the particle kinetic model. The results indicate that the particle traces are spiral lines with the same rotation direction as the spinning vortex. The center of the particle group is in agreement with that of the merged vortex. The merging time is determined by the circulation and the initial ratio of the vortex radius and the vortex center distance. Under a certain initial condition, a stretched particle trail is generated, which is determined by the viscosity, the relative position between the particles and the vortex, and the asymmetrical circulation of the two merging vortices.