Basically, I'm designing a simple method in which a small reservoir of water is connected to a narrow pipe and the rate of flow of water changes with changing height of the reservoir. Now, the water coming out of the narrow pipe is fed into a microchannel. The resistance is given, by the makers as R (resistance) = 3x10^11 kg/m4s. 1. First of all, what exactly is this quantity (i.e R), since I've never seen the units 'kg/m4s' 2.After that, I obtained the formulae for head loss at entrance of pipe, at the bends etc using formulae given on http://books.google.co.in/books?id=...frontcover&source=gbs_atb#v=onepage&q&f=false Chapter 9....all in terms of outlet velocity.....so now how do I combine all these things to calculate how the flow through the narrow pipe depends upon the elevation of the reservoir, taking into consideration all these losses?