# Definition of friction coefficients in a t-pipe

Hiah,

I've got a question concerning a t-pipe configuration and the corresponding friction coefficient values because there are two different friction coefficients stated in literature. Let's assume we have a simple t-pipe where the main passage is larger than the side branch. The friction coefficient for the side branch is defined as $\frac{\Delta p_{sb}}{\frac{1}{2} \rho v_{c}^{2}}$ where $v_{c}$ is the initial velocity of the main passage flow. The friciton coefficient for the straight passage is then defined as $\frac{\Delta p_{st}}{\frac{1}{2} \rho v_{c}^{2}}$ .

This would be all hunky-dory except that I have no idea how the two pressure differences $\Delta p_{sb}$ (sb stands for side branch) and $\Delta p_{st}$ are defined. Is the former, for instance, just the difference between the initial pressure in the side branch and the final pressure in the merged stream? Could anyone offer any insight on this?

Cheers.

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