4.4 Fluid Dynamics Flashcards
What is a dynamic fluid force?
Movement of liquid and gases, e.g. drag and lift
What is drag?
Drag is a resistant force, acting in opposition to the direction of motion and has a negative effect on velocity. Drag is caused by a body travelling through a fluid.
Drag is a combination of……….
Air resistance and friction.
What are the two types of drag?
-Surface
-Form
What is surface drag?
Surface drag is friction between surface of an object and the fluid environment.
What is form drag?
Form drag is the impact of the fluid environment of an object…..Forces affecting the leading edge of an object increases form drag……Forces affecting the trailing edge of an object reduces form drag.
What is streamlining?
Shaping a body so it can move through fluid effectively and quickly.
What are the characteristics of streamlining?
-Incorporate a ‘gradual taper’
-Enables air flow smoothly
-Reduces fluid drag
What is turbulent flow?
Flow in which the fluid undergoes irregular fluctuations, or mixing, constantly undergoing changes in magnitude and direction.
It increases fluid drag + friction and decreases velocity
What is laminar flow?
When layers of fluid flow slide smoothly over on another.
They undertake smooth paths, or layers and are less resistant to movement.
What are the 3 factors that reduce/increase drag?
1) Velocity of the moving body.
2) The cross-sectional area of the moving body.
3) The shape/surface of the moving body.
How does the velocity of the moving body effect drag?
The greater the velocity of a body through a fluid, the greater the drag force.
How does the cross-sectional area of the moving body effect drag.
A large cross-sectional area will increase drag. While a small cross-sectional area will decrease drag.
How does the shape and surface characteristics effect drag?
A more streamlined, aerodynamic shape reduces drag.
What does Bernoulli’s theory suggest?
An increase in the speed of a fluid occurs as a result of a decrease in pressure.
