Large eddy simulations of flow inside a cubical differentially heated cavity under realistic boundary conditions

A series of analytical and experimental studies have been conducted at the Paul Scherrer Institut (PSI) to investigate particulate flows inside a model containment consisting of a differentially heated cubical cavity (DHC). Lately, LES simulations were performed using the finite volume ANSYS Fluent CFD code at Rayleigh number 109. After initial confrontation of the predicted fluid field against experimental data, it was concluded that important physical phenomena had not been accounted for in the original pre-test simulations. Namely, radiation and wall conduction in the test section were not negligible and contributed to producing a fluid field that departed in significant ways from that obtained assuming idealized boundary conditions. We show hereafter that the LES predictions with realistic boundary conditions, including radiation and conduction, are in good overall agreement with the experimental mean velocity and temperature fields. In particular, we show that radiation increases turbulence, which in turn increases mixing and reduces the thermal stratification in the cavity. We also find that the velocity rms peaks near the vertical walls are well captured with the realistic boundary conditions (typically within 30%), in contrast to the previous ideal simulations which miss these peaks by a factor 3 to 4