INVESTIGATION ON THE INFLUENCE OF SURFACE ROUGHNESS OF ROTATING MICROCHANNEL ON FLOW CONDITIONS

This paper presents numerical and experimental investigations of the flow in a rotating microchannel whose walls' roughness covers a substantial part of the channel height. The roughness can intensify the momentum and heat transfer but also increase the drag force. An intentionally designed roughness may contribute to the improvement in the effectiveness of different processes, especially in turbomachinery, where additional effects that accompany the rotation are of great importance. The methods of assessing the roughness impact in the rotating microchannels constitute a scientific gap and are discussed in this research. The experimental part was carried out on the Tesla turbine, whose rotor consists of multiple disks spaced by a sub-millimetre distance. The investigations were performed for two sets of disks. In the first case, the surfaces of the disks were polished to obtain a hydraulically smooth flow regime, and in the second case, they were roughened with the use of a tracing wheel. In the numerical part of the study, the impact of the roughness on the momentum transfer was modelled with the use of the turbulence boundary conditions imposed on the surfaces of the disks. The numerical and experimental results were compared and the validity of the method was assessed.