摘要
建立了竖直管中降膜流动的二维模型,液体在重力作用下沿着管壁流下,气体从相反方向进入,采用多相流VOF(Volume of Fluid)模型,在流体力学软件FLUENT求解器中数值求算,模拟其中的液膜流动情况。通过改变液体和气体雷诺数,对于液膜的流体力学特征,包括液膜流动形态、液膜厚度随时间变化、流动方向液膜变化以及液膜中的速度分布等进行了分析。结果发现液膜形成过程主要可分为入口区、发展区和稳定区3个部分,液体雷诺数一定时,逆流气流对液膜形成的影响主要集中在稳定区;气相雷诺数一定时,随着液体雷诺数增大,液膜流动入口区变长,成熟区复合波中光滑液膜所占比例增加。液膜中的速度分布呈半抛物线型,速度随距离壁面距离增加增大,但在接近气液界面处略微下降。根据模拟得到的不同雷诺数的平均液膜厚度,与Nusselt理论预测值进行了比较,发现吻合良好。
A computational fluid dynamic （CFD） simulation of the falling film flow in a vertical tube was presented using the volume of fluid （VOF） model in conjunction with continuum surface force （CSF） model on the software platform of FLUENT 6.3.A set of transient conservation equations of mass and momentum taking surface tension and gravitational force effects into consideration were solved and the VOF method was applied to characterize the behavior of gas-liquid interface movement.The liquid was driven by the gravity along the inner wall of tube and the gas flow in the opposite direction.The hydrodynamic characteristics from 2-D simulations,including liquid volume profile,liquid Reynolds and film thickness,film velocity,as well as the gas Reynolds,were analyzed.The liquid film patterns in entry,developing and developed regions and the transitions of different patterns at different Reynolds were studied.The distribution of liquid film velocity at different gas Reynolds and different entry distances was analyzed.The variations of liquid film thickness with time and liquid film velocity along the flow direction were discussed as well.A comparison between the results obtained for studied water in the same conditions was made.The film thickness of simulated results adheres to Nusselt equation for smooth water films well.
出处
《计算机与应用化学》
CAS
CSCD
北大核心
2014年第6期745-750,共6页
Computers and Applied Chemistry
关键词
降膜
逆流
液膜流态
液膜厚度
液膜速度
falling-film
counter-current
film thickness
film velocity
