Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 Issue 5 (Special Issue) 2021 07 23 Numerical analysis of distinction boundary of surface roughness and wall blocks in laminar pressure-driven flow within the rugged microchannels Numerical analysis of distinction boundary of surface roughness and wall blocks in laminar pressure-driven flow within the rugged microchannels 3241 3256 4155 10.22060/mej.2020.18235.6775 FA Mohammad Mahdi Fakhari Department of Mechanical Engineering (Energy Conversion), Faculty of Engineering, University of Birjand, Birjand, Iran. Seyed Ali Mirbozorgi Department of Mechanical Engineering (Energy Conversion), Faculty of Engineering, University of Birjand, Birjand, Iran. Journal Article 2020 04 09 In the present study, a laminar pressure-driven flow within a microchannel consisting of two parallel flat plates with rugged walls has been simulated. The walls’ surface ruggednesses have sinusoidal profiles with relative heights of 0≤<em>h/H</em>≤0.15. The governing equations in a two-dimensional general coordinate are solved using the finite-volume method in a non-uniform grid with the maximum orthogonality of the grid lines adjacent to the rugged boundaries. In the first step, the surface ruggednesses of the wall are divided into two categories: surface roughness and wall blocks. Then, the boundary of surface roughness from wall blocks is determined by defining and applying two qualitative and quantitative criteria. According to the qualitative criterion, when the surface ruggedness is of the order of surface roughness, the pressure distribution at the centerline remains as linear as a perfectly smooth microchannel. But when the surface ruggednesses are of the order of wall blocks, however, the pressure distribution at the centerline is oscillating. Also, on the quantitative criterion, the average shear and normal forces just adjacent to the rugged surfaces are accurately calculated and compared. According to the results, in laminar flow within the rugged planar microchannels,  is 0.042 which is independent of Δ<em>p</em>. In the present study, a laminar pressure-driven flow within a microchannel consisting of two parallel flat plates with rugged walls has been simulated. The walls’ surface ruggednesses have sinusoidal profiles with relative heights of 0≤<em>h/H</em>≤0.15. The governing equations in a two-dimensional general coordinate are solved using the finite-volume method in a non-uniform grid with the maximum orthogonality of the grid lines adjacent to the rugged boundaries. In the first step, the surface ruggednesses of the wall are divided into two categories: surface roughness and wall blocks. Then, the boundary of surface roughness from wall blocks is determined by defining and applying two qualitative and quantitative criteria. According to the qualitative criterion, when the surface ruggedness is of the order of surface roughness, the pressure distribution at the centerline remains as linear as a perfectly smooth microchannel. But when the surface ruggednesses are of the order of wall blocks, however, the pressure distribution at the centerline is oscillating. Also, on the quantitative criterion, the average shear and normal forces just adjacent to the rugged surfaces are accurately calculated and compared. According to the results, in laminar flow within the rugged planar microchannels,  is 0.042 which is independent of Δ<em>p</em>. https://mej.aut.ac.ir/article_4155_c793c7e05699ab77eefabee4963a5284.pdf