Turbulent convective heat transfer with appreciable buoyancy effect on a horizontal flat plate with a step change in surface temperature is numerically analyzed by solving two equations for turbulent kinetic energy k and the rate of kinetic energy dissipation ε.
For both stable and unstable flow conditions, the mean velocity and temperature show logarithmic equilibrium profile in a certain range of the normal distance. But in this case, von Karman constants for the velocity and temperature for the logarithmic representation are found to be variables depending on the thermal stratification. Both constants κ and $κ_θ$ decrease with increasing stability. It is found that this variation depends on the Reynolds number and Richardson number.