The quantitative description of fluid mixing using Lagrangian- and concentration-based numerical approaches
The quantitative description of fluid mixing using Lagrangian- and concentration-based numerical approaches
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DOI：
10.1016/s0009-2509(98)00169-9
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发表时间：
1999-01-01
影响因子：
4.7
通讯作者：
Saraiva, RMCN
中科院分区：
文献类型：
--
作者：
Mackley, MR;Saraiva, RMCN
我们报告两种数值方法来量化混合方法I是基于运动学混合率（即混合，由于流体力学的速率只）和方法II是基于被动示踪剂的浓度分布的演变。对于方法I，运动学混合率是从无穷小流体线元素被流动拉伸的方式建立的。根据方法II，混合速率由颗粒云浓度的方差降低的速率确定。在混合过程中。对于方法II，通过使用Langevin型方程（即引入随机游走项来模拟分子扩散）跟踪大量扩散颗粒并将域划分为小区域来计算浓度。这两种方法被应用到一个案例研究，振荡流混合（OFM）内折流管，这是一种惯性流，已被证明是一种有效的替代传统的混合过程，是一个可行的候选人的技术应用。该流场的数值解是通过求解完整的轴对称Navier-Stokes方程来计算的，该方程在200阶的振荡雷诺数的值以下是有效的。两种混合方法的结果进行了比较，其适用性和有用性的混合排名的表征。流体振荡条件的影响也被量化，为流场检查。(C)1998爱思唯尔科技有限公司版权所有。
We report on two numerical approaches to quantify mixing-method I is based on kinematic mixing rates (i.e. the mixing, rates due to the fluid mechanics only) and method II is based on the evolution of the concentration distribution of a passive tracer. For method I, kinematic mixing rates are established from the way infinitesimal fluid line elements are stretched by the flow and. from method II, the mixing rate is determined from the rate at which the variance of the concentration of a particle cloud decreased. during the mixing process. For method II, concentrations were calculated by tracking a large number of diffusive particles using a Langevin-type equation (i.e. introducing a random walk term to model molecular diffusion) and by dividing the domain into small regions. The two approaches were applied to a case study, oscillatory flow mixing (OFM) within baffled tubes, which is an inertial flow that has been shown to provide an efficient alternative to conventional mixing processes and is a viable candidate for technological application. A numerical solution for this flow field was calculated by solving the full axisymmetric Navier-Stokes equations which is valid up to a value of the oscillatory how Reynolds number of order 200. The results of the two mixing methods are compared and their applicability and usefulness in the characterisation of the mixing ranked. The effect of fluid oscillation conditions are also quantified, for the flow field examined. (C) 1998 Elsevier Science Ltd. All rights reserved.