MDME: MANUFACTURING, DESIGN, MECHANICAL ENGINEERING

# FLUID STATICS

Fluid statics is all about pressure. Here are the rules;
1. Pressure at any point in a fluid is the same in all directions and is transmitted through static fluids without loss (Pascal's principle)
2. From 1, the pressure at the wall of any vessel is perpendicular to the wall
3. Pressure due to depth is P = g h, and is the same at any horizontal level of connected fluid.
4. The weight of a buoyant object is equal to the weight of the displaced liquid (Archemedes)

Lecture Notes Fluid-Statics.pdf    Fluid-Statics.one

 Image Video Lesson Description and Link Duration Date Download Fluid Statics 23:04 min 20140806 Fluid Statics: Examples 26:25 min 20140806

Fluid Statics

Fluid Statics: Examples

#### Fluid Statics

1. Pressure at any point in a fluid is the same in all directions
2. Pressure at the wall of any vessel is perpendicular to the wall

Ref 1
3. Pressure is transmitted through static fluids without loss (Pascal's principle)

Ref 1
4. Pressure due to depth is P = g h, and is the same at any horizontal level of connected fluid.

Ref 1

Pressure at the deepest part of the ocean: Trieste

On January 23, 1960, Trieste reached the deepest part of the ocean - the Mariana Trench 10,911m. It carried Jacques Piccard and Lieutenant Don Walsh, USN and was the first (and only) time a manned vessel has got down there.

To make the record dive, the Trieste was fitted with a 2.16 m pressure sphere, with walls 127 mm thick. The sphere weighed 13 tonnes in air and 8 tonnes in water. It was too heavy to float because a sphere large enough to hold a person and strong enough to withstand the water pressure, was heavier than water.

For buoyancy, no air tank could survive, nor wood or foam since the air would be crushed, so gasoline (petrol) was chosen as the float fluid because it is less dense than water, yet relatively incompressible even at extreme pressure, thus retaining its buoyant properties. The buoyancy tank of the Trieste was over 15 m long and the ballast tanks 4m in diameter. The majority of this was a series of floats filled with 85,000 liters of gasoline. There was also a releasable iron ballast in two conical hoppers along the bottom, fore and aft of the crew sphere, which helped the Trieste come back up.

The average depth of the ocean is about 4200 m.

A normal submarine can go to a depth of a few hundred meters.

## Manometers

Pressure proportional to height difference.  P = g h.

Ref 1

A vacuum (barometer).
The vacuum does not "pull", the atmosphere "pushes". Fluids never pull (except for very weak surface tension).

Ref 1

## Pressure on Submerged Surfaces

Acts through centre of pressure, which is at the centoid of the area.

Ref 1

Ref 1

See Textbook: Example 10.7: P226

## Buoyancy

Turning moment between the centre of gravity G of vessel and centre of buoyancy B (the center of gravity of the displaced water)

Ref 1

Hydrostatic buoyancy simulator. (Tim Lovett 2004)
hydrostatic_roll.exe (88kB)
Explained here: http://www.worldwideflood.com/ark/stability/roll_stability_calculator.htm

Ref 2

Ref 2

Ref 1: Illustrations from http://www.scribd.com/doc/10988770/Pressure-Fluid-Statics
Ref 2: Illustrations from http://www.worldwideflood.com/ark/stability/roll_stability_calculator.htm

## Questions:

Homework Assignment: Kinksy new edition
Do all questions; Chapter 10: Fluid Statics
10.1 to 10.30 (page 229-234)

Do all questions.