GeoChemFoam: Operator Splitting based time-stepping for efficient Volume-Of-Fluid simulation of capillary-dominated two-phase flow
GeoChemFoam: Operator Splitting based time-stepping for efficient Volume-Of-Fluid simulation of capillary-dominated two-phase flow
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发表时间：
2021-05
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通讯作者：
J. Maes;H. Menke
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作者：
J. Maes;H. Menke
我们提出了一种新的时间步进方法，称为毛细管松弛算子分裂（OSCAR），有效的体积流体模拟毛细管占主导地位的两相流。OSCAR使用算子分裂方法来分离粘性阻力和表面张力。不同的时间步长用于粘性阻力步骤，由注射速度控制，并用于毛细松弛步骤，由毛细波的速度控制。虽然OSCAR诱导一个额外的数值误差的顺序0的时间导致的分裂，它是非常适合在低毛细管数的模拟。首先，分裂误差随着毛细管数而减小，并且在低毛细管数下，松弛步骤在到达其最后一次迭代之前收敛，与标准时间步进方法相比，导致大幅加速（这里高达250倍）。该方法在我们基于OpenFOAM的CFD求解器GeoChemFoam中实现。收敛性，准确性和效率证明了三个基准情况下：（1）在一个直的2D微通道中的气泡的稳定运动，（2）在一个3D收缩通道中的超临界CO2的注射，导致一个折断，和（3）在一个2D油湿微观模型表示多孔介质排水。
We present a novel time-stepping method, called Operator Splitting with Capillary Relaxation (OSCAR), for efficient Volume-Of-Fluid simulations of capillary-dominated two-phase flow. OSCAR uses operator splitting methods to separate the viscous drag and the surface tension forces. Different timesteps are used for the viscous drag steps, controlled by the injection velocity, and for the capillary relaxation steps, controlled by the velocity of capillary waves. Although OSCAR induces an additional numerical error of order 0 in time resulting from the splitting, it is well suited for simulations at low capillary number. First, the splitting error decreases with the capillary number and at low capillary number, the relaxation steps converge before reaching their last iteration, resulting in a large speed-up (here up to 250×) compared to standard time-stepping methods. The method is implemented in GeoChemFoam, our OpenFOAM-based CFD solver. Convergence, accuracy and efficiency are demonstrated on three benchmark cases: (1) the steady motion of an air bubble in a straight 2D microchannel, (2) injection of supercritical CO2 in a 3D constricted channel leading to a snap-off, and (3) water drainage in a 2D oil-wet micromodel representing a porous media.