Air Flow Flashcards
What is the COANDA effect
When the flow of air encounters an object in its path it attaches itself to the objects surface and flows smoothly around it.
2 conditions for the COANDA effect
The object is presented to at the airflow at aa slight angle.
The objects shape is relatively thin and smooth.(streamlined).
Why does high pressure attract to low pressure
Air naturally goes from areas of high pressure to low pressure.Areas of depleted molecules need filling.
What is a pressure gradient
Differences in pressure over a distance.
What are streamlines/streamtube.
Streamlines are directions of flowing air .
A volume of air bounded by streamlines.
What are the three types of flow
Laminar flow,
Turbulent flow,
Vortex flow
What is laminar flow/streamlined flow
Laminar flow is when airflow moves from one direction to another in layered predicable flows. Smooth and predictable.
Turbulent Flow
Air flowing past unstreamlined object breaks the streamlined flow resulting in an unsteady or turbulent flow. Forms a resistant to the streamlined flow that becomes drag.
Vortex flow
Loses energy as it moves away from aircraft. Caused by aircraft itself from drag.
All 3 types of flow moving around aircraft at same time
What is an ideal fluid
Has 2 key properties.
It is incompressible (density does not change))
Has no Viscosity.
Air is known as an ideal fluid.
Equation of continuity in relation to mass flow
Mass can neither be destroyed nor created. Mass flow must remain the same (E.g when entering a streamtube)
Relationship of area and Volume in a Venturi
A1XV1=A2XV2=A3XV3
When A2 decreases V2 increases
When A3 increases V3 decreases.
Speed at which air density does not change
Upto 300knots
Venturi Tube
Mass Flow entering must remain same exiting. At the throat of a Venturi flow rate increases as cross section area decreases.
Relationship between airflow velocity and distance between streamlines
Spacing between stream lines reduces as flow velocity increases and increases when flow velocity decreases.
Law of conservation of energy
Energy can neither be destroyed nor created only change from one form to another. Bernoulli’s theorem energy in a flow must remain constant.
Bernoulli Principle
In the flow of an ideal fluid, the sum of pressure (static)and kinetic energy(dynamic pressure) must remain constant. Energy in a flow must remain constant.
Converging Airflow (Venturi)
As tube converges flows speed increases. Dynamic pressure increases and static pressure decreases by
the same proportions.
In a diverging flow the opposite occurs.
SAME TOTAL PRESSURE MIST ME MAINTAINED.
