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Interaction of prevailing ocean waves and wind with the platforms containing the small modular reactors (SMRs) employed in marine environments may significantly alter the flow and friction characteristics inside these reactors. The present research is focused on the numerical study of the effects of rolling motions on the turbulent flow and frictional characteristics of a three-dimensional closed loop of narrow rectangular channels using Ansys Fluent. The computational results have been corroborated with experimental data present in literature. The results illustrate that flow and friction characteristics fluctuate sinusoidally as the loop undergoes rolling motion. Strong fluctuations were observed in the flow rate and time-dependent friction coefficient with an increase in rolling amplitude or reduction in the rolling period. These variations became more pronounced at low Reynolds numbers and diminished at higher Reynolds numbers. Increasing the fluid viscosity also subsided the rolling effects. The average flow velocity in the loop was found to decrease from 0.27 to 0.15 m/s in various phases of the rolling period. The relative Reynolds number was found to be reduced by 50% under rolling motions for the range of steady-state Reynolds numbers investigated in the present study. The transient friction coefficient was also found to oscillate under rolling motion with the same period as that of excitation. The transient friction coefficient's oscillations also increased with rolling amplitude or reduction in the rolling period. However, the temporally averaged friction coefficient under rolling motions was found to be equal to the steady-state frictional coefficient in the loop. [ABSTRACT FROM AUTHOR]