温度梯度对平板边界层转捩影响的数值模拟

Numerical simulation of temperature gradient influence on flat plate boundary layer transition

为了研究温度梯度对边界层转捩的影响,在对有/无压力梯度的T3系列平板转捩实验进行数值模拟获得满意结果的基础上,对原型实验进行重新设计,以在平板边界层内形成不同温度梯度并进行数值模拟。计算结果表明随着温度梯度的增大,转捩位置向下游推延发生,平板相同位置边界层的形状参数和壁面切应力系数也相应大幅增高,边界层湍流脉动得到抑制,这是因为温度梯度形成的密度分层,湍流能量为了克服因为密度分层形成的法向浮力而被逐渐耗散,但是温度梯度对转捩影响与其它流动特性对转捩的影响相比较弱。

To investigate the influence of high temperature gradient on transition in boundary layer, Coupland＇s T3 flat plate experiments at zero and non-zero pressure gradient are adapted with different temperature gradient in boundary layer by numerical simulation, and are validated by experiments. The results show that the higher temperature gradient can delay transition process and postpone the onset location of transition to backward position, wall skin-friction coefficient and shape factor of boundary layer with temperature gradient are higher than that with no temperature gradient in the same place of plate. The turbulent pulse of mainstream is weakened because of density gradient caused by temperature gradient. The turbulent energy is dissipated by the vertical buoyancy caused by the density gradient in boundary layer. The influence on transition by temperature gradient is weaker than mainstream hydrokinetics properties, such as turbulence intensity, inlet velocity and pressure gradient.