Internal-force-driven flows in which the force acting on channel cross sections have a perfect uniform distribution create a fully developed velocity field even the axial distribution of these forces is non-uniform. In this situation, firstly the driving force with non-uniform axial distribution can be removed temporarily and then one can use an equivalent axial uniform body forcealternatively throughout the channel. In this case, although the distribution and the driving force change but the resulting velocity profiles remain unchanged. The main advantage of thisreplacement is thatthe solution of the equations in the 3-D geometries canbe converted to a 2-D solution using Poisson equationin the channel cross section. After determining the velocity distribution in the cross section, one caninverselycalculate the actual pressure distribution easily. This will be done by resuming the real axial force. One of the applications of this simplification is that the simulation of MHD channel flows can be carried out easily.Good agreement between the results of the new solution method and the results ofthe perfect solutions shows that the present method with enough accuracy can be used for prediction of velocity and pressure fields in microfluidic networks.Consequently the heavy costs of 3-D analysis are reduced considerably.