Prediction of Turbulent Flow and Heat Transfer in a Radially Rotating Square Duct

The present study deals with the numerical prediction of turbulent flow and heat transfer in a rotating duct of square cross section. The axis of rotation is normal to the axis of the duct, and the flow is radially outward. The duct is smooth, of finite length, and the walls are isothermal at a temperature greater than the temperature of the incoming fluid. Both the Coriolis and the centrifugal-buoyancy effects are considered; the problem is three dimensional and fully elliptic. The predicted flow field is found to be quite complex, consisting of secondary cross-stream flows due to the Coriolis effects. Centrifugal buoyancy increases the radial velocity of the cooler fluid near the trailing face and decreases the radial velocity of the warmer fluid near the leading face; indeed, when the buoyancy effects are sufficiently strong, reverse radial flow may occur over the leading face. Rotation is found to increase the heat transfer over the trailing face, while, over the leading face, the heat transfer decreases near the inlet but increases further downstream. This finding agrees with the experimental observations. The quantitative agreement with the data is also satisfactory. The predictions are found to be quite sensitive to the inlet conditions, in particular, to the presence of rotational effects in the incoming stream. The effect of exit boundary conditions is examined by comparing the predictions for a single passage with those for a double-leg passage.