利用一介面追蹤VOF法於沸騰流動之計算

Abstract

此研究是以有限體積法(Finite Volume Method) 搭配VOF (Volume of fluid) 型式的CISIT介面追蹤法求解雙流體流之質傳與熱傳現象。在模擬兩相流時，採用一擁有連續的速度場的單一流體(Single fluid) 的模型進行模擬，最後可用一組質量、動量之統御方程式組描述此單一流體的模型。在求解兩相流體間的介面相變化時，先利用VOF 的方法計算出介面的位置並將介面的網格中心或網格面上視為一邊界，接著利用介面處的質量與能量的跳躍條件求出介面處的質傳量，並且將相變化所造成的質傳變化量以一源項型式加入連續方程式中，求解動量方程式時同時滿足連續方程式，藉此模擬兩流體間的相變化情形。首先模擬兩個一維具有理論解的相變化測試以驗證相變化的準確性。最後模擬一薄膜沸騰的氣泡生成，可觀察到氣泡的生成與成長過程中對於熱傳及質傳變化的影響。

This study is using finite volume method with a VOF based interface tracking method (CISIT) is used for simulation of two-fluid flows with heat and mass transfer. When simulation of two-fluid flows, using a single-fluid model which have continuous velocity field, finally we can obtaind quality and momentum governing equations to describe the single-fluid model. For solving the phase change of two-fluid flows, first use of VOF method to calculate the interface position and the interface can be viewed as the thermal boundary, and then the mass change across the phase boundary is computed by taking the mass and energy jump conditions at the interface, It is added as a source term in the continuity equation, this continuity equation is used in the pressure-velocity coupling algorithm. After the velocity field obtained from solving the momentum equation the jump condition for the continuity is satisfied. First test two one-dimensional Stefan problems which have exact solution to assess the accuracy of phase change. Finally simulation of film boiling on a horizontal plate is presented. It shows that how the bubble growth affects the heat and mass transfer of the flow.