TURBULENT NATURAL CONVECTION IN NON-PARTITIONED AND PARTITIONED CAVITIES: CFD PREDICTIONS WITH DIFFERENT TWO-EQUATION MODELS

Two dimensional turbulent natural convection in non-partitioned and partitioned cavities with differentially heated vertical walls and conducting horizontal walls has been simulated numerically using three different two equation models: the SST-k-omega of Menter (1993), the low Reynolds number model of Launder and Sharma (1974) and the k-epsilon Standard (Launder and Spalding, 1974) associated to a wall function correction. Comparisons with experimental benchmark values show that the different versions of the model give satisfactory predictions in the simple geometry while in the partitioned cavity significant differences are noted, especially in the bottom zone of the cavity. All models accurately predict the flow in the simple cavity with a slight over-estimation by the Standard k-epsilon due to the use of wall functions. When radiation is taken into account, a clear improvement of temperature profiles is obtained, especially near the horizontal walls. However, the quantitative improvement of radiation is not expected to be the same for all turbulence models. The success of models under consideration in the case of the simple cavity does not imply that they can predict accurately the flow in the partitioned one, even though in both cases we deal with confined natural convection. In the partitioned cavity, all models predict a bottom zone colder than the experiment data indicates. The corresponding vertical velocity in the top region of the cavity is the only quantity which is satisfactorily predicted. The horizontal velocity which is not negligible compared to the vertical one is qualitatively predicted only in the top zone of the cavity. Temperature profiles are satisfactorily predicted only at the two top levels (the partitioned cavity contains six levels where data is available). Radiation allows improved predictions in the top zone of the cavity but not in the bottom one, especially at the level of the second partition.