Direct numerical simulations on influences of buoyancy forces on turbulent flow

Direct numerical simulations were performed for a fully developed axially rotating turbulent square duct flow with a turbulent Reynolds number of 400 and a Prandtl number of 0.71. In order to analyze the influences of buoyancy forces on fluid flow, the ensemble averaged turbulent statistical quantities including velocity field, temperature field, turbulent intensity, and Reynolds stress at different Grashof numbers were presented. The stability or instability properties of rotation and their effects on the statistical quantities were also analyzed. The results show that the centrifugal buoyancy influences the averaged velocity field and temperature field significantly and the influence is more obvious with the increase in Grashof number. The centrifugal buoyancy also affects the fluctuation quantities greatly, and the fluctuation intensity increases in the instable side and decreases in the stable side.