A theoretical analysis about the mechanism of the effect of rolling motion on single-phase flow resistance in rectangular duct

• Mechanism of effects of rolling on flow resistance is revealed theoretically.
• Transient shear stress and frictional resistance in rolling are calculated.
• Effects of relative pressure gradient & aspect ratio on flow resistance are studied.
• Wall friction in rolling motion due to different sides is compared.
• One method calculated frictional pressure drop in rolling has been proposed.

Marine reactors are received increasing attention recently, because that the coolant flow behaviors of the offshore nuclear power plants are very complicated and important. In this paper, the mechanism of the effect of rolling motion on single-phase laminar flow resistance in rectangular duct is theoretically studied by the way of analyzing the wall shear stress. The results show that the area-averaged oscillatory velocity fluctuates periodically, with its amplitude increasing as the relative pressure gradient increases and the aspect ratio decreases. When the relative pressure gradient is very low, the flow tends to be steady. The shear stress and wall friction tend to steady flow. While for the high relative pressure gradient, the wall shear stress varies periodically, which leads to the periodical fluctuation of frictional pressure drop. A larger relative pressure gradient and a smaller aspect ratio will intensify the effect of rolling motion on the shear stress and wall friction. Despite that the influence of the rolling motion on shear stress and wall friction, the proportion of frictional resistance due to wide sides out of the total is nearly independent of rolling motion. Finally, the periodically frictional pressure drop in rolling motion is calculated by the present model which is validated by experimental data from literature.