三角槽道低Reynolds数脉动流的流动特性分析

Analysis of flow characteristics in triangular grooved channel by pulsating flow at low Reynolds number

以水为工质对三角槽道低Reynolds数脉动流的流动特性进行了实验研究与理论分析。通过流动实验,分析了Reynolds数(Re)、Womersley数(W)、脉动振幅(A)等参数对流动阻力的影响。同时,建立了脉动流压降的数学模型,从理论层面解析了各脉动参数对流动阻力产生影响的作用机理,揭示了瞬时流速曲线与瞬时压降曲线之间相位差产生的原因。研究发现,相较于稳态流,脉动流会增加流动阻力,这是因为脉动流压降方程中存在三角函数项Δp_r,其周期平均值P始终大于0;就脉动参数而言,W对总压降的形阻压降部分影响较为显著,而A与总压降呈正相关;相位差的产生是由于总压降方程中存在加速度压降,而相位差的大小取决于沿程阻力、形阻压降、加速度压降三者对总压降波动的影响程度。

The flow characteristics in the triangular grooved channel by pulsating flow at low Reynolds number has been investigated.The influence of several main parameters on flow resistance is analyzed.The parameters are Reynolds number,Womersley number and pulsating amplitude.The results show that,flow resistance in the triangular grooved channel by pulsating flow is higher than that in steady state.Flow resistance in pulsating state increases with the pulsating amplitude,and there is a Womersley number for the highest flow resistance.It also measures that the imposed pulsating flow causes phase difference between the curve of velocity and the curve of pressure drop.In addition,the phase difference is determined by Womersley number,but irrelevant to the pulsating amplitude.To explore the cause from what has been discussed above,the mathematical model of pressure drop is established.The reason why flow resistance in pulsating state is higher than that in steady state is that,compared with steady state,there is aΔpr in the mathematical formulas of pressure drop in pulsating state,and the average value of theΔpr in a cycle is more than 0.The pressure drop of form drag is mainly affected by Womersley number,and the total pressure drop increases with the pulsating amplitude.The results from theoretical analysis also indicate that,the accelerating pressure drop induces the phase difference,and the value of phase difference is affected by frictional resistance,form drag and accelerating pressure drop.