In this paper, a numerical study of the effect of a hot square cylinder placed on a
cooled elliptical enclosure of a laminar natural convection was carried out. This problem
is solved by using the partial differential equations, which are the stream vorticity
formulation for the flow and heat transfer in curvilinear coordinates. An elliptical
function is used, which makes the coordinate transformation from the physical domain
to the computational domain be set up by an analytical expression. About 48 tests are
performed for different ratios of the geometry such as, a /b =1.5,2.,3 , l /b = 0.25,0.5 ,
and Rayleigh number from 103 to 106, for two position of the major axis of the elliptical
enclosure, horizontal (HEE) and vertical (VEE). The results obtained in the form of
velocity vectors, streamlines, isotherms, and Nusselt number. The results show that, the
increase of the major axis of the enclosure ( a /b ratio) leads to increase the average
Nusselt number and decrease the flow strength for all Rayleigh numbers. Moreover, for
Ra≤104, there are a little difference in the results of ave Nu for all a / b and l / b ratios,
but if Ra increases, the change in the results is clear and large.