EK Flow Diagram Explanation?

[ridethecliche]

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There's a diagram in EK Physics CH5 on page 87 that's describing flow and energy lines and a hydraulic gradient line and such.

Can anyone explain this. I'm staring at it crosseyed trying to figure it out but not getting anywhere.

Thanks.

 

[tttgo]

ok, I just read that page like 4 times and will try my best to explain. Basically, they're using Bernoulli's equation to explain how the fluid flows in the diagram. They got the different heads by dividing each term in Bernoulli's by the fluid's specific weight (pg (p=rho)). They made it confusing because in the picture, they didn't divide by pg, but still used the term heads. If you look at the picture, orange corresponds to elevation head (pgh), green corresponds to velocity head (1/2pv^2) and purple corresponds to pressure head (P). The Energy Line is the sum of all three.

They put 2 types of tubes to measure stuff. The static pressure tap measures from the tube to the tip of the purple arrow. The Piezo tube measure up to the tip of the green arrow.

The hydraulic gradient line (in blue) connects the tips of the static pressure taps (the tips of the purple arrow).

This is useful because if the velocity head (green) starts before the elevation head (orange) ends, there's negative gaage pressure. this is related to the pressure head (purple).

http://www.engineeringtoolbox.com/energy-hydraulic-grade-line-d_613.html