Fluid Mechanics: Hydrostatics Flashcards

Vocabulary flashcards covering fundamental principles of hydrostatics, pressure definitions, measuring devices, hydrostatic forces, and dam classification from MECH E4 lecture notes.

Pressure

The ratio of normal force $dF$ to the small area $dA$ on which it acts ($P = \frac{dF}{dA}$), or force divided by area ($P = \frac{F}{A}$) when force is uniformly distributed.

Pascal's Law

A principle developed by French mathematician Blaise Pascal stating that the pressure on a fluid is equal in all directions and in all parts of the container.

Absolute Pressure

The true pressure measured above a perfect vacuum.

Gage Pressure

The pressure measured from the level of atmospheric pressure by most pressure recording instruments.

Atmospheric Pressure

The pressure obtained by barometric reading.

Vacuum Pressure

Pressure measured below atmospheric pressure, expressed mathematically as Atmospheric Pressure minus Absolute Pressure.

Mercury Barometer

An instrument that measures changes in atmospheric pressure by forcing mercury $760\,\text{mm}$ ($29.9\,\text{in}$) up a calibrated glass tube at sea level.

Aneroid Barometer

An instrument that measures air pressure using a partially evacuated metal drum that expands or contracts, translating top movement into pointer rotation via levers and springs.

Free Liquid Surface

A liquid surface that is subject to zero gage pressure or atmospheric pressure only.

Pressure Head

The height $h$ of a column of homogeneous liquid of unit weight $\gamma$ that produces an intensity of pressure $p$, defined as $h = \frac{p}{\gamma}$.

Manometer

A tube, usually bent in the form of a U, containing a liquid of known specific gravity whose surface moves proportionally to pressure changes; used to measure pressure.

Open Type Manometer

A manometer that has an atmospheric surface in one leg and is capable of measuring gage pressures.

Differential Type Manometer

A manometer without an atmospheric surface that is capable of measuring only differences of pressure.

Piezometer

The simplest form of open manometer consisting of a tube tapped in the wall of a container or conduit to measure fluid pressure.

Total Pressure

The force exerted by a static fluid on a plane or curved surface when it comes in contact with the surface, acting normal to the surface.

Centre of Pressure

The point of application of the total pressure force on a surface.

Gravity Dam

A concrete or masonry dam that resists water pressure by the sheer force of its own massive weight and is thick at the base.

Arch Dam

A concrete or masonry dam curved upstream into the reservoir that transfers the water force load to the canyon walls.

Buttress Dam

A dam supported by several buttresses on the downstream side, allowing for a hollow or less massive structure.