Browsing by Author "Jiang, Yuntao"

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    A Divergence-free Mixture Model for Multiphase Fluids
    (The Eurographics Association and John Wiley & Sons Ltd., 2020) Jiang, Yuntao; Li, Chenfeng; Deng, Shujie; Hu, Shi-Min; Bender, Jan and Popa, Tiberiu
    We present a novel divergence free mixture model for multiphase flows and the related fluid-solid coupling. The new mixture model is built upon a volume-weighted mixture velocity so that the divergence free condition is satisfied for miscible and immiscible multiphase fluids. The proposed mixture velocity can be solved efficiently by adapted single phase incompressible solvers, allowing for larger time steps and smaller volume deviations. Besides, the drift velocity formulation is corrected to ensure mass conservation during the simulation. The new approach increases the accuracy of multiphase fluid simulation by several orders. The capability of the new divergence-free mixture model is demonstrated by simulating different multiphase flow phenomena including mixing and unmixing of multiple fluids, fluid-solid coupling involving deformable solids and granular materials.
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    A Dynamic Mixture Model for Non-equilibrium Multiphase Fluids
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Jiang, Yuntao; Lan, Yingjie; Zhang, Fang-Lue and Eisemann, Elmar and Singh, Karan
    We present a dynamic mixture model for simulating multiphase fluids with highly dynamic relative motions. The previous mixture models assume that the multiphase fluids are under a local equilibrium condition such that the drift velocity and the phase transport can be computed analytically. By doing so, it avoids solving multiple sets of Navier-Stokes equations and improves the simulation efficiency and stability. However, due to the local equilibrium assumption, these approaches can only deal with tightly coupled multiphase systems, where the relative speed between phases are assumed stable. In this work we abandon the local equilibrium assumption, and redesign the computation workflow of the mixture model to explicitly track and decouple the velocities of all phases. The phases still share the same pressure, with which we enforce the incompressibility for the mixture. The phase transport is calculated with drift velocities, and we propose a novel correction scheme to handle the transport at fluid boundaries to ensure mass conservation. Compared with previous mixture models, the proposed approach enables the simulation of much more dynamic scenarios with negligible extra overheads. In addition, it allows fluid control techniques to be applied to individual phases to generate locally dynamic and visually interesting effects.