壁面温度在多参数下对平板边界层的影响研究

为了得到壁面温度在不同来流速度、不同湍流强度条件下对边界层转捩与减阻的影响规律,本文采用Transitionk-kl-ω模型对低来流速度下无压力梯度的光滑平板进行了数值模拟。结果表明,随着来流速度的升高,壁温升高所起到的减阻效果更好,即高来流速度对壁面温度更为敏感。当来流处于中高湍流强度下时,壁温升高能起到推迟转捩的作用,且随着湍流强度的升高,转捩推迟的效果越好,但减阻效果正好相反;当来流处于低湍流强度下时,壁温升高会使得转捩提前发生。壁温升高抑制了边界层内流体的脉动程度,使得层流的稳态不易被破坏,流动更加稳定;同时,壁温升高使得边界层内流体的速度梯度减小,从而降低了壁面摩擦系数,故壁温升高能起到推迟边界层转捩与减阻的作用。

Study on the influence of wall temperature on the boundary layer of flat plate under multi-parameters

In order to obtain the influence of wall temperature on the boundary layer transition and drag reduction under different inflow velocities and different turbulence intensities,the Transition k-kl-ωmodel is used to simulate the smooth plate without pressure gradient at low inflow velocity.Numerical simulations mainly lead to the following conclusions:As the velocity of the incoming flow increases,effect of reducing the wall temperature is better,that is,the high flow velocity is more sensitive to the wall temperature.When the incoming flow is at the mid-high turbulence intensity,the wall temperature rise can play a role in delaying the transition,and as the turbulence intensity increases,effect of delaying the transition is better,but the drag reduction effect is just the opposite.At low turbulence levels,an increase in wall temperature causes the transition to occur earlier.The increase of wall temperature suppresses the degree of pulsation of the fluid in the boundary layer,so that the steady state of the laminar flow is not easily destroyed,and the flow is more stable.At the same time,the wall temperature rises,so that the velocity gradient of the fluid in the boundary layer is reduced,thereby reducing the wall friction coefficient,so the increase in wall temperature can delay the transition of the boundary layer and reduce drag.