# Fluids Pressure Question

If i have a syringe used to pump blood through a set of tubing that becomes smaller and smaller, the pressure will obviously increase until it gets to the smallest diameter of the tubing. However, if I create a piece that expands when the blood flows through it, will this decrease the pressure?

The idea is that the blood displaces the walls of the tubing, thus reducing pressure. Is this idea physically possible?

russ_watters
Mentor
Welcome to PF!

Actually, if the flow is slow enough that there isn't much loss due to friction, pressure is constant throughout the tubing. If there is loss, the pressure will decrease the further along in the tubing it gets. And that's even without adding in the additional decrease in static pressure (conversion to velocity pressure) due to the speeding up of the fluid and Bernoulli's principle.

You may want to look into Bernoulli's principle actually -- it explains a lot about your question: http://en.wikipedia.org/wiki/Bernoulli's_principle

However, if I create a piece that expands when the blood flows through it, will this decrease the pressure?
That sounds a lot like how a regulator works. There's more to it than that, though: http://en.wikipedia.org/wiki/Pressure_regulator