In order to investigate the effects of transverse ribs, the Coriolis force, and cross-sectional aspect ratios on turbulence, the large eddy simulation was performed changing the relation number and the aspect ratio. The results reproduced the experimentally observed high heat transfer areas: in front of the rib on the rib-roughened walls and around the rib on the smooth side walls. In the rotating case, an interesting dissimilarity between the velocity and temperature fields was seen. The heat transfer enhancement caused by the rotation was larger for the higher aspect ratios because of the intensified Coriolis induced secondary flow. (C) 2000 Elsevier Science Ltd. All rights reserved.