A Systematic Approach to Wall Roughness Effects in Laminar Channel Flows: Experiments and Modelling

In this study, the influence of wall roughness on laminar gas flow in small channels is investigated experimentally, comparing results to CFD solutions including the calculation of entropy production. In the experimental set-up, air flows between two parallel disks that create a channel of continuously adjustable height, ranging from macro to micro size. The roughness is created by a processed silicon wafer with homogeneous surface elements. The experimental results after a careful error analysis are compared to numerical models in order to validate these models. In rough micro channels, a crucial problem is the actual location of the wall. This location strongly influences the corresponding theoretically determined pressure drop of the flow. This influence, as well as entropy production considerations are discussed. The effects found in the experiments are in good agreement with the corresponding CFD-models and hence strongly indicate an influence of wall roughness on laminar flow.