板间距对三角槽道脉动流流动阻力的影响

Influence of channel height on resistance characteristics in triangular grooved channel by pulsating flow

以水为工质对不同板间距的三角槽道脉动流流动阻力特性进行了研究。基于受力平衡方程,建立了适用于三角槽道脉动流压降的数学模型,用于理论分析流动阻力的影响因素。通过实验测试与数值模拟,校验数学模型的合理性,并且对三角槽道脉动流流动阻力进行分析。结果表明,流动阻力主要受板间距、涡旋拟"能"两方面因素影响,且与板间距呈反比,与涡旋拟"能"呈正比;板间距的缩小,会使流动阻力增加,当缩小到板间距与槽深比值为1.0时,出现流动阻力的阶越式增长,上升1个数量级;造成流动阻力骤升的主要原因在于:随着板间距的缩小,流场结构逐渐变化,三角槽道内涡旋的影响区域由"三角槽内部"逐渐转变为"整个流道",且主流区壁面出现流动分离,出现涡旋流动与波状流共存现象,使流动阻力大幅提升。

The flow resistance characteristics of the pulsating flow in the triangular channel with different plate spacings were studied with water as the working fluid.Based on the force balance equation,a mathematical model suitable for the pulsating flow pressure drop of the triangular channel is established to theoretically analyze the influencing factors of the flow resistance.Mathematical model shows that flow resistance is mainly affected by channel height and enstrophy.Flow resistance increases as channel height reduces,but increases with enstrophy.In addition,experiment and numerical research have been conducted to investigate correlation among channel height,enstrophy and flow resistance.The experimental results show that flow resistance becomes large as the channel height becomes short.What’s more,when the ratio of channel height and groove depth is less than1.0,the sharp rise of flow resistance occurs.And flow resistance increases ten fold compared with the state that the ratio of channel height and groove depth is more than1.0.Otherwise,no matter how the channel height changes,resistance also increases with pulsating amplitude,and there exists a Womersley number for the highest flow resistance.The numerical results indicate that the reason why flow resistance changes dramatically as the channel height decreases is because flow field changes with the channel height.When the ratio of channel height and groove depth is more than1.0,vortex is mainly located inside the triangle groove.Thus the wall of mainstream can be rarely affected.However,when the ratio of channel height and groove depth is less than1.0,vortex in the triangle groove expands and gradually affects the area of mainstream.Hence the flow separation occurs near the wall of mainstream,which causes wave flow and eddy coexisting.