Flow regimes in various channels can introduce different responses that interact with inside of channel walls. Hence both flow characteristic and its effect on wall surfaces should be investigated, especially for a new channel design or usage of a new fluid. In this work, flow characteristics of a nanofluid flow and wall stress concentration locations are investigated numerically in a 3D channel with including sharp edge rectangular ribs. The ribs are arranged with periodic order and transverse positions at inside of upper and below surfaces of channel. The nanofluid flow consists of Al2O3-water solution with %8 particle volume concentrations. The used Reynolds number (Re) changes from 75 to 2000. Furthermore, commonly used two different fluids are investigated for detecting differences of flow characteristics of nanofluid. Tresca yield criterion is used with considering channel's ductile material properties in stress analysis. Interactions between ribs and flow are observed in detail. Flow separation and vortex formations effectively depend on Reynolds number. Values of wall stress concentrations depend on Reynolds number and pressure effects with respect to sharp edge rectangular ribs. Stress values of upper surfaces are less than along path of below surfaces on channel wall surfaces.