hydro static pressure

8/3/2019 Hydro Static Pressure

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Hydrostatic Pressure

The pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force

of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface

because of the increasing weight of fluid exerting downward force from above.

Hydrostatic Pressure Apparatus

The Hydrostatic Pressure accessory has been designed to determine the static thrust

exerted by a fluid on a submerged surface and allow comparison of the measured magnitude

and position of this force with simple theory. Determining the centre of pressure on both a

submerged or partially submerged plane surface and comparison with the theoretical position.


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Technical description

The key component of the apparatus is the transparent measurement tank of

circular cross-section, this is filled with water for the experiments. A scale on

the tank permits the water levels to be read off with precision. The tank is suspended

on a bearing. If the tank is set to zero using a lever with appropriate

weights, the force acting at the pressure centre can be determined. This force,

generated by the hydrostatic force, is an important parameter in ship building

and maritime structures. The materials used for the experimental set-up were

carefully selected to minimise corrosion problems.

Working


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Equipment Calibration

Measure the dimensions B and D of the quadrant end-face and the distances H and L. Update

the values in your results table as necessary.

Equipment Set Up

Position the empty tank on the hydrostatic bench, and adjust the screwed feet until the built-in

circular spirit level indicates that the base is horizontal. Position the balance arm on the knife

edges. Locate the weight hangar in the groove at the end of the balance arm.

Ensure that the drain valve is closed and that a length of clear plastic pipe is attached to the

drain cock. Direct the free end of this pipe to the sink in the bench. Take the free end of the

delivery pipe which supplies water to the other apparatus on the bench and place it in the

triangular aperture on top of the plastic tank.

Move the counter-balance weight until the balance arm is horizontal.

Taking a Set of Results

Add a small mass (50g) to the weight hanger.

Add water until the hydrostatic thrust on the end-face of the quadrant causes the balance arm

to raise. Ensure that there is no water spilled on the upper surfaces of the quadrant or the

sides, above the water level.

Continue to add water until the balance arm is horizontal, measuring this by aligning the base

of the balance arm with the top or bottom of the central marking on the balance rest (either

can be used, but it must be kept consistent during the experiment). You may find it easier to

slightly over-fill the tank, and obtain the equilibrium position by opening the drain cock to allow

a small outflow.


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Read the depth of immersion from the scale on the face of the quadrant; more accurate results

can be obtained from reading with the line of sight slightly below the surface, to avoid the

effects of surface tension.

Repeat the above procedure for each load increment, produced by adding a further weight to

the weight hanger. The weights supplied allow increments of ten, twenty, and fifty grams to be

used, depending on the number of samples required. Fifty-gram intervals are suggested for an

initial set of results, which will give a total of nineteen samples.

Continue until the water level reaches the top of the upper scale on the quadrant face. Repeat

the procedure in reverse, by progressively removing the weights.

hydro static pressure

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