Development of Variable Space Resolution Hybrid Simulation Technique for Multi-Scale prediction of Multi-Phase Flows

提出了一种混合计算多流体力学（CMFD）方法，用于预测包括大尺度界面、多分散气泡和/或液滴在内的多相流。该方法是一种精确界面跟踪方法（ITM）、三种气泡跟踪方法和基于多流体模型（MFM）的平均方法的混合集成。该集成使我们(1)能够覆盖d^*=d/Δx的广泛范围，其中d为颗粒直径，Ax为网格尺寸；(2)可以使用ITM、BTM和MFM的任意组合进行各种多相CFD，如标准界面跟踪仿真、泡/滴跟踪仿真、多流体仿真和混合仿真。因此，该方法可以看作是一种多用途、多尺度、多相的CFD方法。本文详细介绍了该方法的场方程、本构方程和数值求解算法。利用该混合方法模拟了一个小开口容器内的多分散空气-水气泡流和多个气泡羽流，以证明其潜力。

A hybrid CMFD (computational multi-fluid dynamics) method is proposed for the prediction of multiphase flows including large-scale interface, poly-dispersed bubbles and/or drops. The method is the hybrid integration of an accurate interface tracking method (ITM), three kinds of bubble tracking methods and an averaging method based on a multi-fluid model (MFM). The integration enables us (1)to cover a wide range of d^*=d/Δx, where d is the particle diameter and Ax the grid size, and (2)to perform various kinds of multiphase CFD such as standard interface tracking simulation, bubble/drop tracking simulation, multi-fluid simulations, and hybrid simulations using an arbitrary combination of ITM, BTM and MFM. The developed method can, therefore, be regarded as a multipurpose multi-scale multiphase CFD method. The field equations, constitutive equations and numerical solution algorithms of the proposed method are described in detail in this report. A poly-dispersed air-water bubbly flow and several bubble plumes in a small open vessel are simulated using the proposed hybrid method to demonstrate its potential.