[Belimane]

Hello,
In an annular flow where we have two pipes (or two cylinders), eccentricity results in a higher flow rate values under the same pressure gradients compared to the concentric case (whatever the fluid rheology is).
I want to know why (or how) does eccentricity increase flow rate?

[LuckyTran]

Consider delivering a volume of flow through one single large pipe versus two smaller pipes. One bigger pipe is better.

The reason has a lot to do with dynamic head being the square of velocity plus a tiny contribution due to friction factor dependence on Reynolds number.

Consider an intermediate case where there are still two pipes, but one is larger than the other. For the same dynamic head, the velocity is smaller in the smaller pipe (which can be counter-intuitive). One might think that for the same head, the velocity is higher in the smaller pipe due to Bernoulli's principle.

[Belimane]

Originally Posted by LuckyTran

Consider delivering a volume of flow through one single large pipe versus two smaller pipes. One bigger pipe is better.

The reason has a lot to do with dynamic head being the square of velocity plus a tiny contribution due to friction factor dependence on Reynolds number.

Consider an intermediate case where there are still two pipes, but one is larger than the other. For the same dynamic head, the velocity is smaller in the smaller pipe (which can be counter-intuitive). One might think that for the same head, the velocity is higher in the smaller pipe due to Bernoulli's principle.

Thanks ....
Although ... i didn't really understand your explanation.
To make my question more clear, i am adding this picture.[ATTACH]

[LuckyTran]

The eccentric pipe splits the flow into a smaller area and large area. It's like having two equally sized pipes, and then making one bigger and one smaller.