A numerical study based on three-dimensional direct numerical simulations are performed to investigate horizontal thermal convection in a long channel at a large Rayleigh number, Ra. Differential thermal forcing is applied at the bottom boundary over two equal regions. The steady-state circulation is achieved after the net heat flux from the boundary becomes zero. A stable ther-mocline forms above the cooled base and is advected over the heated part of the base, confining small-scale three-dimensional convection to the heated base and end wall region. At the end-wall a narrow turbulent plume rises through the full depth of the channel. The less energetic return flow is downward in the interior, upon which eddy motions are imposed. This work, for the first time, focuses on the three dimensional instabilities and structures of the flow. The conversions of mechanical energy are examined in different regions of the flow (boundary layer, plume and interior) and help to understand overall circulation dynamics.
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