This study presents a theoretical method to find the dimensions of rectangular micro asperities, using the principles of hydrodynamics and strength of materials. The suitable value of the width of microasperities is calculated; the critical height of micro asperities is also calculated. The suitable width and the critical height are both calculated with different flow speeds. Numerical calculation is carried out using the solidworks flow simulation, the present study is realized at steady state. The simulation results illustrated the flow speed trajectory, the variation of the shear stress and the flow pressure on different faces of micro asperities. The turbulence area, due to the geometry of micro asperities, is localized. The prediction of the maximum wear area, due to the skin friction, is also localized in consideration of the shear stress variation.