# Pressure at a bend in a pipe

This is a question from a study guide for a military officer exam:

I have fluid flowing through an elbow in a pipe (the elbow is in the shape of an upside down and backwards "J") and the flow goes from south to north to east. If holes are drilled at the upper left outside part of the bend and the lower right inside part of the bend, at which point will pressure be lower? Please see attached image for a picture of the question.

When I have thought about this problem, I keep coming back to pressure being transmitted equally to all parts of a fluid, so I don't understand how the pressure can be different at one of the holes. The book gives the answer as the inside bend which I can force myself to accept since I can picture the fluid attempting to go straight to the outside bend hole and thus hitting that part harder, but I don't really understand it.

• Would this have anything to do with centripetal acceleration? Commented Aug 12, 2014 at 16:47
• Actually I take back my earlier comment. After some Googling it appears the pressure is dominated by inertial terms. It's higher on the outside of the bend because that's where the liquid is being forced inwards. See this article and this paper. Note that in figure 2 the inside of the pipe is to the right. Commented Aug 12, 2014 at 17:00
• For the close voters, this question seems to me to be as close to a conceptual question as we can get and still be borderline homework. I'd prefer that we leave it open. Commented Aug 12, 2014 at 18:08
• A way to think about it is a water slide having curves. Obviously the water will rise up on the outside of each curve (as will the child enjoying the ride). Another thought: isn't this the way those infamous gas centrifuges work? Commented Aug 12, 2014 at 18:50
• You have all been very helpful. Thank you all for your inputs. Commented Aug 16, 2014 at 14:28