Investigation on effects of rolling on single-phase flow frictional resistance in narrow channel

Effects of rolling motion on frictional resistance characteristics of single-phase water flow in narrow rectangular channel are investigated experimentally. The results show that the frictional pressure drops under rolling condition fluctuates periodically, and its amplitude decreases as Reynolds number increases and increases as the rolling amplitude increases, but doesn't vary evidently with rolling period. Rolling motion has insignificant influence on time-averaged frictional resistance of single-phase flow. Rolling motion influences the fluctuation amplitude of frictional pressure drop in two aspects: on the one hand, periodical pulsing flow reduced by rolling leads to the fluctuation of the frictional pressure drop; on the other hand, additional force acting on fluid near the wall due to the rolling motion makes local frictional resistance oscillate periodically. A new correlation applied to calculate instantaneous frictional coefficient under rolling condition in laminar flow region is obtained by fitting experimental data.