圆管层流脉动流动的数值模拟

为研究圆管层流脉动流动特性,建立了二维非稳态轴对称模型,对壁温恒定、入口速度周期性变化的流体进行数值模拟.分析了速度振幅和频率对层流流动的影响,得到了频率和振幅对压力、温度、壁面摩擦系数影响的规律.研究表明:脉动流动时,压力、温度、壁面摩擦系数围绕相同Re下稳态流动时的数值波动;压力与速度之间存在相位差;压力、壁面摩擦系数的波动与速度振幅和频率成正比;温度的波动与速度振幅成正比,与频率呈反比;当流体脉动的频率和振幅足够大时,会在近壁面处出现回流,并且出现回流的时间会随着频率和振幅的增大而增长.

Numerical simulation of laminar pulsating flow in tubes

In order to investigate laminar pulsating flow characteristics in tubes,a two-dimensional unsteady axisymmetric model was established,and the pulsating fluid with constant wall temperature and periodical variation velocity as the entrance boundary condition of the tube was simulated. The influence of velocity amplitude and frequency on laminar flow was analyzed and the effects of velocity amplitude and frequency on pressure,temperature and wall surface friction coefficient were concluded. Numerical simulation results show that the values of pressure,temperature and wall surface friction coefficient for pulsating flow fluctuate around those of the stablestate flow at the same Reynolds number Re. Phase difference exists between pressure and velocity. The pressure amplitude and the wall surface friction coefficient amplitude are both in direct proportion to velocity amplitude and frequency. The temperature amplitude is in direct proportion to velocity amplitude but inversely proportional to frequency. When the velocity amplitude and frequency are large enough,back flow occurs near the inner surface,and the duration for the back flow increases along with the growing of frequency and amplitude.