Entrance loss from open channel to pipe

[miriza]

Hi!

I have the following equation for the entrance loss from an open channel to a pipe, but I'm not sure how it was derived:

hloss = K*(V2^2 - V1^2)/2g

I have always seen entrance losses as: K*(V^2)/2g, but why is the channel flow velocity considered in the equation above.

Thanks, Michelle

 

[rover2402]

I think it is because the velocity in the open channel (V1) is assumed to be zero, but I am not 100% sure.