周期性沟槽通道内自激振荡流及换热特性

Self-sustained oscillatory flow and heat transfer characteristics in periodically grooved channel

应用数值模拟方法分析了以周期性方式布置不同结构通道内产生的周期性自振荡流动现象,并研究了自激振荡流对下壁面物块传热特性的影响。计算采用低Reynolds数、二维、非稳态层流模型。采用布置斜板和布置两个不同弯曲方向叶片3种方式来诱导自激振荡流。分别对不同结构通道内流体的流场、温度场、Nusselt数和表面摩擦系数变化规律进行了对比分析。计算结果发现:3种结构由稳态过渡到自振荡流时对应的临界Reyn-olds数都很低,分别为620、480、400,并且有较低临界Reynolds数的通道结构对应较强烈的振荡,表现为沟槽区域的强烈涡结构运动,及由此带来的更好的换热效果。此外,表面摩擦系数因通道涡结构相异而有不同的变化趋势。

A numerical investigation on the heat transfer characteristics and the self-sustained oscillation flow is conducted in a periodically grooved channel with different structures.The unsteady two-dimensional laminar flow at low Reynolds number（400—1600） was analyzed.Three structures with oblique plate and two curve vanes with different directions were used to induce the self-sustained oscillation flow.A comparison among different channels was made for streamlines,temperature filed,Nusselt number and friction factor.It was found that the critical Reynolds number was low,with the values of 620,480,and 400 for the three structures.In the channel with lower critical Reynolds number,the oscillation was more drastic and the vortex movement was more violent in the groove areas,resulting in better heat transfer.For the same Reynolds number,the oscillation periods of three kinds of channel were roughly equal,but the self-sustained oscillation characteristics were different.The friction factor had different trend because of different vortices in the channel.When the Reynolds number was over 800,the friction coefficients of two channel structures were three times that of the third channel structure,while their heat transfer had the same trend.