窄环隙内层流脉动流动特性分析

Flow Characteristics of Laminar Pulsating Flow in Narrow Annulus

为分析脉动流动状态下的热工水力特性,通过建立数学模型,对窄环隙流道内的层流脉动流动特性进行分析。研究结果表明,脉动流对环隙内速度及相位差径向分布有较大影响。当脉动频率较小时,窄环隙内的速度径向分布与稳定流动相同,相位差在整个流道截面为恒定值;随着脉动频率增大,速度径向分布出现"环状效应",相位差沿径向呈现近似抛物线型分布;且脉动频率及流动尺寸越大、或流体粘性越小,脉动对速度及相位差的径向分布影响越明显,而脉动振幅变化对速度及相位差的径向分布没有影响。

In the purpose of analysis the thermal hydraulics in pulsating flow, the mathematical models were established to study the flow characteristics of pulsating laminar flow in narrow annulus. The results show that the pulsating＇ significantly influences the velocity and phase lag axial distribution. As the pulsating frequency is small, the velocity axial distribution is similar to the steady flow, and the phase hag in the axial direction is a constant value. However, as the pulsating frequency becomes large enough, the maximum axial velocity occurs near the wall, which is the ＂annular effect＂. Furthermore, the phase lag appears as a parabolic in the axial direction. Moreover, the bigger the pulsating frequency or the annulus geometry is, the larger the effect of pulsation is. On the contrary, the bigger the viscosity is, the smaller the effect of pulsation is. Nevertheless, the variation of pulsation amplitude does not affect the axial distribution of velocity and phase lag.