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Units and dimensions, systems of units, dimensional homogeneity |
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Click here to submit questions pertaining to this lesson to your instructor via E-mail. |
Q: How does a differential manometer work? The picture of the manometer on page 12 didn't quite make sense to me. I don't understand exactly how the pressure on the manometer fluid would have been unequal on the left and the right, since it seems like the fluid flows right through the top pipe.
A: The question that you asked about the differential manometer
is really a question about fluid flow in a pipe (which is a topic that
generally comes in the fall of the junior year in the chemical engineering
curriculum!). Basically, the reason that the pressure is lower down-stream
than it is up-stream in the pipe is because a pressure force is needed
to push the fluid through the pipe. The difference in pressure on the
up-stream side of the fluid and the down-stream side of the fluid leads
to a force that causes the fluid to flow. This force overcomes viscous
forces and friction forces that tend to slow the fluid down. For this
reason, the fluid pressure drops continuously down the length of the
pipe as the fluid flows (this is called the pressure drop, and when
you take a class in fluid flow and transport you will learn how to calculate
the pressure drop as a function of the fluid viscosity, the pipe diameter,
and the flow rate).
Alec Scranton
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