增强Euler-Lagrange跟踪下Taylor-Couette流中的可变形椭球气泡
Deformable ellipsoidal bubbles in Taylor-Couette flow with enhanced Euler-Lagrange tracking
摘要：
在这项工作中，我们提出的数值模拟$10^5$亚Kolmogorov变形气泡分散在泰勒-库埃特流（壁有界剪切系统）旋转的内圆筒和外圆筒在休息。我们研究了两相系统中气泡的变形能力对载流流体引起的总阻力的影响。我们发现，在变形的气泡的结果在增强减阻由于一个更显着的积累附近的驱动内壁变形的气泡的增加。这种优先积累是由气泡在壁法线方向上的运动阻力增加引起的。增加的阻力与靠近壁的气泡的强烈变形有关，这使它们长形（沿一个轴拉伸）并沿流向定向。驱动壁附近气泡的浓度越大，意味着它们在削弱羽流喷射方面越有效，从而导致更强的减阻效果。这些模拟实际上是不可能的完全解决的技术是通过耦合的亚网格变形模型与双向耦合欧拉-拉格朗日跟踪分散在一个湍流领域，这是通过直接数值模拟解决亚Kolmogorov气泡。气泡被认为是椭圆形的形状和它们的变形是由一个演变方程，这取决于当地的流动条件和它们的表面张力。
英文摘要：
In this work we present numerical simulations of $10^5$ sub-Kolmogorov deformable bubbles dispersed in Taylor-Couette flow (a wall-bounded shear system) with rotating inner cylinder and outer cylinder at rest. We study the effect of deformability of the bubbles on the overall drag induced by the carrier fluid in the two-phase system. We find that an increase in deformability of the bubbles results in enhanced drag reduction due to a more pronounced accumulation of the deformed bubbles near the driving inner wall. This preferential accumulation is induced by an increase in the resistance on the motion of the bubbles in the wall-normal direction. The increased resistance is linked to the strong deformation of the bubbles near the wall which makes them prolate (stretched along one axes) and orient along the stream-wise direction. A larger concentration of the bubbles near the driving wall implies that they are more effective in weakening the plume ejections which results in stronger drag reduction effects. These simulations which are practically impossible with fully resolved techniques are made possible by coupling a sub-grid deformation model with two-way coupled Euler-Lagrangian tracking of sub-Kolmogorov bubbles dispersed in a turbulent flow field which is solved through direct numerical simulations. The bubbles are considered to be ellipsoidal in shape and their deformation is governed by an evolution equation which depends on the local flow conditions and their surface tension.
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