Talk:Microfluidics/Hydraulic resistance and capacity

Hello, As I have already told it during the lessons, there are some varied points that i still do not understand in the Hydraulic resistance chapter... Maybe someone will be alble to help me.. Well, I do not understand this sentence:

"Assuming a uniform pressure in the tube (which is not true in long tube where pressure decreases subtantially), we find a flow rate entering the tube to inflate to be:

$$Q=\frac{dV_{tube}}{dt}=K_{tube}V\frac{\Delta P}{dt}$$ "

How can we have a $$\Delta P$$ with a uniform pressure in the tube? I suppose that to have a $$\Delta P$$ we need at least a decrease of the pressure in the tube, the result of which is given for a linear decrease in the next paragraph and is totally different... Well as i understand it, compressibility depends on the pressure drop. I do not see how you can have a volume variation due to dilatation with no pressure drop in the tube. Maybe someone is clearer on that point and could be able to give a nice explanation :)

Anyway, good revisions to everybody !!

Marc.Drouard (talk) 19:47, 6 May 2010 (UTC)