Effect of surface roughness on laminar flow in closed channels

Abstract

This study explores the flow characteristics of liquid water and liquid metals in closed channels with different roughness by using a modified roughness–viscosity model (RVM). The RVM model explains the influence of surface roughness on laminar flow by incorporating roughness and viscosity. This study proposes that the local Reynolds number should be used instead of the overall Reynolds number. This modified model in the flow of liquid water with different rough enclosures is studied by numerical simulation and then verified by experiments. Moreover, the verification model is used to explore the flow of conductive liquid metal in closed channels with different roughness under a magnetic field. According to the results of the study: (1) In the radial direction of the closed channel, the larger the radius was, the greater the change in the flow rate due to surface roughness. (2) As the flow direction through a closed channel changed, the larger the relative surface roughness was, the smaller the frictional resistance. (3) In a vertical magnetic field, the effect of surface roughness first weakened and then strengthened as the strength of the magnetic field increased. As the latter increased in a horizontal magnetic field, the effect of surface roughness decreased. This verified modified RVM model provides ideas and methods for research on laminar roughness in micro-closed channels in the future.