NUMERICAL STUDY OF 3-DIMENSIONAL INCOMPRESSIBLE THERMAL-FLOWS IN COMPLEX GEOMETRIES .2. COMPUTATIONAL STUDIES

In part I of this study, a three-dimensional finite difference iterati ve solver capable of handling the coupled Navier-Stokes and energy equ ations for incompressible viscous flows was described and validated wi th two-and three-dimensional benchmarks. Part II describes the results of the computational study of two distinct complex geometries: 1) two -dimensional and three-dimensional natural convection in cavity whose surface is cooled while two internal blocks are heated; 2) two-dimensi onal and three-dimensional natural convection in the region defined by two interconnected cavities of different sizes which are differential ly heated. All computations have been performed for a Prandtl number o f 1.0, and different values of the Rayleigh number ranging between 10( 3) and 10(6) depending on the problem. In the first problem, three-dim ensional effects in the top region of the cavity trap fluid in vortice s near the top of the heated blocks adversely affecting heat transfer in the region while enhancing it in the region between the two heated blocks. In the second problem, the sudden expansion of fluid as it lea ves the top cavity and enters the bottom one generates three-dimension al wakes in the bottom cavity that enhance the convective heat transfe r across the system walls near them. These studies tend to suggest tha t three-dimensional effects play a very important role in the enhancem ent of convective heat transfer in complex geometries, especially at h igher Rayleigh numbers.