| Summary: | 碩士 === 國立交通大學 === 機械工程系所 === 104 === This study is based on a VOF method, is called CISIT, and introduces of the level-set function to improve computation accuracy of surface tension and then simulated different two-phase flows to confirm the applicability of this method. When general VOF method to calculate the curvature of the interface, volume fraction must first be smoothed, in the original CISIT, adopting a treatment of averaging smoother, but in this way that obtained a not accurate surface tension, so we introduced the level-set function to improve its accuracy, this method is called a coupled level-set function and VOF interface tracking method (CLSVOF). In this method, position of interface is defined in volume fraction of 0.5 and level-set of zero, when calculating the level-set function its initial distribution will be converted by volume fraction, and solved re-initialization equation to obtain the distribution, and with the CSF model to calculate the surface tension, coupled velocity and pressure in the flow field is using PISO, finally CISIT is used to predict the motion of the interface. In the two-dimensional flow field, this article tested the accuracy of surface tension and simulated a problem of single bubbles rising in a stationary liquid, and then extended to the three-dimensional flow field, including single bubble rise and two bubble coalescence and droplet collision. Test results show that, compared with CISIT, the result simulated by the CLSVOF, surface tension is more accurately and spurious currents are smaller (a numerical error, spurious currents are caused by CSF model), and in the three-dimensional flow field, the CLSVOF method can present the results closer to the experiments when using coarser grid.
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