Boundary-layer disruption and heat-transfer enhancement in convection turbulence by oscillating deformations of boundary

Turbulent convection driven by unstable temperature gradients in the direction of gravity exists in many natural flows and engineering applications, such as atmosphere, mantle and indoor temperature control, etc. The way to regulate and enhance the convective heat transfer efficiency has important theoretical and practical value. Here we report a new mechanism for improving the efficiency of turbulent convective heat transfer, saying by using boundary vibration deformation. Specifically, vibration deformations in the form of standing waves are introduced at boundaries. The results indicate that, to significantly increase the heat transfer, the boundary vibration amplitude needs to be comparable to the boundary layer thickness. And this enhancement happens when the wavenumber is large enough. For a moderate frequency, the nondimensional heat flux, i.e. the Nusselt number can be more than doubled compared to the uncontrolled flow. Since boundary layer is the bottleneck of heat transfer for the parameters explored here, the method proposed here can strongly disturb the original boundary layer and enhance the heat flux. This also leads to the dependence of the Nusselt number on the Rayleigh number approaching the scaling law for the so-called ultimate regime.