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

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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.