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NUMERICAL SIMULATION OF PARTICLE SET EVOLUTION IN OSCILLATING FLUID IN MICROGRAVITY CONDITION

机译：微重力条件下振荡流体中颗粒集演化的数值模拟

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Investigations of different mechanical, physical and chemical processes in microgravity conditions, which play a very important role in modern space science, often require in calculation of evolution of particle set weighted in surrounding liquid. Such situations can be observed not only onboard space vehicles in free flight. Effective microgravity takes place in case of weighted enough small particles in any conditions, if surface forces acting on them are sufficiently more than mass (for example, gravitational) forces. Thus investigations of the considered particle systems are actual for many fields of science. A specific feature of the microgravity condition differs it from any other multiphase media; in particular, the considered particles can be not so small as for usual disperse phase objects. As a result, hydro-dynamic interaction force can influence more sufficiently on the particle motions under host fluid flow than in traditional multiphase flow with extremely small particles. It was shown in previous work of the authors, that the hydrodynamic interaction forces bring together the particles in direction perpendicular to fluid motion and push apart the particles in direction of fluid flow velocity. For enough high frequency oscillating fluid flow, an ideal fluid flow model can be used for the flow calculation and, correspondingly to quantitatively determine the considered hydrodynamic interaction forces. Boundary clement method is applied as numerical tool for flow calculation in the present work. All particles in calculations here arc assumed spherical. Motion of any particle is described by Cauchy problem for material point motion equations (second order ordinary differential equations), which are solved numerically by Euler scheme. The hydrodynamic interaction forces at every time step is calculated using Cauchy-Lagrange integral. Several examples are calculated numerically to illustrate the considered problem. Different positions of particles in translational oscillating fluid motions and fluid motions due to oscillating point source are analysed. An opportunity to use the oscillating flows as control tool for multiphase media in microgravity conditions is discussed as item of future investigations.
机译：在微重力条件下对不同的机械，物理和化学过程的研究在现代空间科学中起着非常重要的作用，这通常需要计算加权在周围液体中的粒子集的演化。不仅可以在自由飞行的机载航天器上观察到这种情况。如果在任何条件下称重足够小的颗粒，只要作用在其上的表面力远远大于质量（例如重力）力，就会产生有效的微重力。因此，对于许多科学领域来说，对所考虑的粒子系统的研究都是实际的。微重力条件的一个特定特征与任何其他多相介质不同。特别地，所考虑的颗粒可以不如通常的分散相物体那么小。结果，与具有极小颗粒的传统多相流相比，流体动力相互作用力可以更有效地影响主流体流动下的颗粒运动。在作者的先前工作中表明，流体动力相互作用力将颗粒沿垂直于流体运动的方向聚集在一起，并沿流体流速的方向推开颗粒。对于足够的高频振荡流体流量，可以将理想的流体流量模型用于流量计算，并相应地定量确定所考虑的流体动力相互作用力。本文采用边界元法作为数值计算的数值工具。计算中所有粒子均假定为球形。对于质点运动方程（二阶常微分方程），柯西问题描述了任何粒子的运动，并通过Euler方案对其进行了数值求解。使用柯西-拉格朗日积分计算每个时间步的流体动力相互作用力。数值计算了几个例子来说明所考虑的问题。分析了平移振荡流体运动和由于振荡点源引起的流体运动中颗粒的不同位置。作为未来研究的项目，讨论了在微重力条件下使用振荡流作为多相介质控制工具的机会。

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