论文标题
在稀疏流条件下建模椭圆形颗粒的阻力系数
Modelling drag coefficients of ellipsoidal particles in rarefied flow conditions
论文作者
论文摘要
准确捕获具有复杂形状和稀有气流的颗粒之间的双向耦合相互作用的重要性在不同的实际应用中迅速增加,例如航空航天行业和半导体制造。在这些条件下颗粒的运输通常是通过欧拉 - 拉格朗日点粒子方法对颗粒进行建模的,在这种情况下,通过现象学坎宁安校正对粒子经历的阻力力的校正,包括稀疏效应。在点粒子接近时,通常会忽略与颗粒,形状,方向和动量适应系数的有限大小的任何明确关系。在这项工作中,我们旨在通过完全分辨的DSMC模拟来弥补这一差距,即作用于具有不同纵横比的椭圆形颗粒上的阻力模型的启发式模型。我们在模型中包括通过切向动量容纳系数(TMAC)预测与气体表面相互作用相关的效果的能力。在标准的欧拉 - 拉格朗日点颗粒粒子中,衍生模型可以用作校正(包括形状,方向和TMAC效应)。此外,我们表明,在粒子接近固体壁的情况下,所获得的拖放校正正式有效,适用于无界气体流动。我们通过研究近壁对岩体椭圆形颗粒的阻力的影响来做到这一点。由于限制效果,与无限制的情况相比,阻力增加,但是对于大$ kN $,在与固体壁接触的情况下,这种效果通常可以忽略不计。
The importance of accurately capturing two-way coupled interactions between particles with complex shapes and rarefied gas flows is rapidly rising in different practical applications such as aerospace industry and semiconductor manufacturing. The transport of particles in these conditions is often modelled via an Euler-Lagrangian Point-Particles approach, where rarefaction effects are included through the phenomenological Cunningham corrections on the drag force experienced by the particles. In Point-Particles approaches, any explicit relation to the finite size of the particles, shape, orientation and momentum accommodation coefficient is typically neglected. In this work we aim to cover this gap by deriving, from fully-resolved DSMC simulations, heuristic models for the drag force acting on ellipsoidal particles with different aspect ratios. We include in the models the capability to predict effects related to gas-surface interactions via the tangential momentum accommodation coefficient (TMAC). The derived models can be used as corrections (to include shape, orientation and TMAC effects) in standard Euler-Lagrangian Point Particles simulations in rarefied gas flows. Additionally, we show that the obtained drag corrections, formally valid for unbounded gas flows, can potentially be applied also in cases where the particle moves in proximity to a solid wall. We do so by investigating near-wall effects on the drag of a prolate ellipsoidal particle. Due to confinement effects, the drag increases when compared to the unbounded case, but such effects are typically negligible for large $Kn$ also in cases in which the particle is in contact with the solid wall.