The Effect of Horizontal Buoyancy on Turbulent Thermal Convection*

We study the effect of horizontal buoyancy on heat transport in turbulent thermal convection system. Experimentally, a condition of increasing horizontal buoyancy ($Ra_H=\alpha g\sin\beta\Delta H^3/\nu\kappa$) under fixed vertical thermal driving strength ($Ra_V=\alpha g\cos\beta\Delta H^3/\nu\kappa$) is achieved by simultaneously titling the convection cell by an angle $\beta$ and increasing the imposed global temperature difference $\Delta$. Furthermore, we propose a vector formed Nusselt number $\textbf{\textit{Nu}}$ to quantify the global heat transport. For fixed vertical buoyancy, we find that the vertical heat transport increase monotonically with the horizontal buoyancy and the horizontal heat transport is also non-negligible. We also conduct direct numerical simulations, the results of which confirm our experimental findings and highlights the richness in convective transport.