气液两相分层流剪切应力的不确定度分析

基于水平气液两相分层流的压力梯度、波状液层和气壁剪切应力实验数据,对两流体剪切应力进行不确定度计算,分析各不确定度分量对液壁和气液界面剪切应力结果的影响。由剪切应力可以直接计算分层流动量平衡方程的本构参数,对本构参数的关联作了合理的解释。气液界面剪切应力受液层高度和压力梯度的准确性影响较大,而液壁剪切应力却相反,和气液界面剪切应力最大程度相关。通过和实验数据对比发现,液壁摩擦因子无法像气壁摩擦因子那样可以用单相管流的指数型关系式来描述,而是应该结合气液界面摩擦因子建立一个基于两相各流体特征参数的有效关联式。

An uncertainty analysis to shear stresses in horizontal gas-liquid stratified flow

An uncertainty analysis is applied to liquid-wall and gas-liquid interface shear stresses measurement in horizontal gas-liquid stratified flow.The uncertainty contribution rates of three components,the axial pressure gradient,mean liquid height and gas wall shear stress,are examined respectively.The analysis shows that the measured axial pressure gradient and mean liquid height significantly influence the accuracy of gas-liquid interface shear stress,while the liquid wall shear stress is largely relative to the appropriateness of gas-liquid interface shear stress.As constitutive relations to closure two-fluid momentum balance equations,the friction factors deduced from relevant shear stresses are compared with previous empirical formula.Unlike an appropriate exponential correlation for gas wall friction factor,a new correlation involving two-phase flow characteristic parameters is presented to describe liquid wall friction factor.Prediction has been found to be in good agreement with measured data.