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Syllabus Dot Point
fluid mechanics
– Pascal’s principle
– hydrostatic and dynamic pressure
– applications to aircraft components and instruments
What is Pascal's principle in simple terms?
Pascal's principle, also called Pascal's law, in fluid (gas or liquid) mechanics, statement that, in a fluid at rest in a closed container, a pressure change in one part is transmitted without loss to every portion of the fluid and to the walls of the container
Examples of Pascal's principle applications include hydraulic crane, hydraulic lift, hydraulic jack, and hydraulic brake system. An excavator digging a hole, a car being lifted by a hydraulic lift, and even squeezing a toothpaste tube applies Pascal's principle.
Static and Dynamic Pressure
Static and dynamic pressure are often used to determine the pressure in a closed system. So assuming that we are talking about a fluid (water, mist, etc.) in a pipe. This piece of pipe is placed horizontally and is filled with liquid.
The liquid inside this pipe is stationary and not moving, but that doesn’t mean that there is no pressure on it. The air provides pressure pushing it downwards, this is known as the static pressure when the liquid is at a state of rest. Now, imagine there is rushing water in the pipe, the pressure put placed by the water pushing out against the present liquid, this is known as dynamic pressure.
Pitot Tubes
Pitot Tubes
Pitot tubes are used on aircraft as speedometers.
Draw a diagram to represent the workings of a pitot tube.
Airspeed Indicator
This is an instrument that makes use of the aircraft’s pitot-static system to provide the pilot with a real time readout of the aircraft’s airspeed. The airspeed indicator is a pressure instrument and requires both a pitot pressure (total pressure) and a static pressure measurement to operate correctly.
Watch the first 5 minutes of this video to get a better understanding of how an airspeed indicator works.
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