Unsteady fluid flow and temperature fields in a horizontal enclosure with an adiabatic body

A two-dimensional solution for unsteady natural convection in an enclosure with an adiabatic square body is obtained using an accurate and efficient Chevyshev spectral collocation method. A spectral multi-domain methodology is used to handle an adiabatic body located at the center of computational domain. The physical model considered here is that an adiabatic body is located at the center between the bottom hot and top cold walls. In order to see the effects of the presence of an adiabatic body on time-dependent natural convection between the hot and cold walls, we investigated the detail structure of fluid flow and heat transfer as a function of time for different Rayleigh numbers varying in the range of 10 3 to 10 6 . When Ra =10 3 , streamlines and isotherms reach the steady state without any oscillatory transients, and the flow and temperature distribution around the body in the enclosure shows a four-fold symmetrical pattern. At Ra =4×10 3 , 10 4 , and 10 5 , streamlines and isotherms reach the steady state after starting oscillatory transients, and the flow and temperature fields change their shape from the symmetrical pattern to the nonsymmetrical one as time goes by. When Ra =10 6 , streamlines and isotherms become time-dependent, and the fluid flow and temperature fields also change their shape in a regularly periodic fashion as a function of time.