U-Shaped Tubes & Fluids
Fluid Pressure
U-Shaped Tubes (Manometers) are used to calculate the pressure of different liquids
based on density and Height. Using the principle of pressure at equal depths in a liquid:
For two points, A and B, present at the same depth inside a liquid, the two points experience the same pressure.
To calculate the pressure done by a liquid on a point at a certain depth:
Gauge Pressure = Density * Gravitational Potential (g) * Depth (h)
Note that this formula neglects the already existing Atmospheric pressure, thus is called Gauge Pressure,
which is the pressure done by the liquid only, to calculate the real pressure on the point at a certain depth,
the Atmospheric pressure must be added to the formula:
Absolute Pressure = Atmospheric Pressure + Gauge Pressure
Pressure Measuring units are:
Bar, Pascal, and atm.
1 atm = 1.013 Bar
1 Bar = 100 Kilo-Pascal
When two points are in the same depth inside a liquid container that isn't isolated from the atmosphere,
they experience the same pressure regarding of the fluid, so the absolute pressure is equal at both points.
Absolute Pressure at A = Absolute Pressure at B
When one or the two points at a certain depth are isolated from the atmosphere,
the Atmospheric Pressure will not affect the point, so only the Gauge pressure of the isolated
point is applied:
Case 1: Point A is Isolated:
Gauge Pressure at A = Absolute Pressure at B
Case 2: Point B is Isolated:
Absolute Pressure at A = Gauge Pressure at B
Case 3: Both points are Isolated:
Gauge Pressure at A = Gauge Pressure at B
This Principle is applied to use in many applications, one of which is the Manometer,
used to measure pressure of a fluid.