The influence of natural convection on a mixed convection boundary layer in a vertical channel is studied using Large-eddy simulation. A constant heat flux boundary condition is applied to one of the channel walls while the other wall is insulated. The Grashof and Reynolds numbers based on the wall heat flux and the channel width are Gr = 9.4 · 10 7 and Re = 5080. As the temperature difference between the hot wall and the inlet air is large, the governing equations are solved using two

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... approaches namely Boussinesq approximation considering constant properties and the equations with variable properties. As a consequence of hot wall high temperature, radiation is also taken into account and it is shown that about 10% of the heat is transferred via radiation. Although variable property equations yield better solutions compared to the constant property equations, there exist substantial differences between the computed and the measured profiles which might be due to the numerical scheme that has impaired the imposed turbulence at the inlet.