加速管道流瞬态壁面摩擦阻力及湍流行为实验研究

Experimental Study of Wall Shear Stress and Turbulent Behavior in Accelerating Pipe Flows

通过对加速管道流瞬态壁面摩擦阻力及湍流行为的实验研究,并将改进的统计平均法应用于实验数据的处理。结果表明,加速管道流瞬态时均壁面切应力较稳态壁面切应力存在明显差异,工况1中最大差值接近于稳态值的2倍。流动加速率的降低和初始流量的增加缩短了湍流的滞后段,减小了瞬态壁面切应力与稳态值的差别。瞬态壁面切应力及湍流的发展可分为4个典型阶段,前2个阶段为湍流的滞后期,流动惯性占据主导地位,后2个阶段为湍流的发展阶段。

An experimental study was carried out on wall shear stress and turbulent behavior in accelerating pipe flows.A modified ensemble averaging mean method was used for the experimental data.Results showed that the transient mean wall shear stress is significantly different from that of steady flow,where a maximum of twice is observed in case 1.The decrease of acceleration and the improvement of initial flowrate would alleviate the turbulence delay and reduce the difference of wall shear stress.The mean wall shear stress and turbulent behovior are shown to respond to an imposed acceleration in four stages.Turbulence delay is seen in the first two stages and flow inertia plays a dominant role during this period.Then the effect of the development of turbulence is in the last two stages.