L2 - Intro to aerodynamics (TBC) Flashcards
Introduction to Aerodynamics
What is the effect of air resistance on objects? (3 points)
o Exerts forces on objects and can reduce their speed
o Causes objects to bend through the air
o Even increase their distance travelled
Introduction to Aerodynamics
Some ways in which Atheletes can use aerodynamics? (3 points)
o Swing in cricket
o Swerve in football
o Knuckle-ball in baseball
Introduction to Aerodynamics
Why are Aerodynamics acting on people and equipment studied? (2 points)
o In order to understand the behaviour
o To gain competitive advantage
Introduction to Aerodynamics
How is Aerodynamics applied? (2 Points)
o To ball development
o To racing
(F1, cycling, skiing, speed skating, swimming, yachting)
(Football, cricket, tennis, golf, baseball, volleyball)
Studying Aerodynamics
How are the Aerodynamics of sports equipment is studied? (3 Points)
o Wind tunnel testing
o Trajectory analysis
o Computational Fluid Dynamics (CFD)
Studying Aerodynamics
• How is trajectory analysis conducted? (2 points)
(Comment on the accuracy of the method)
o High speed videos are used to capture the initial conditions and flight path of balls that are kicked, thrown or projected under test conditions
o The drag and lift coefficients are extracted by comparing trajectories to a projectile in a vacuum (using Newton’s equations of motion)
Real effects are captured; however the method is not particularly accurate.
Studying Aerodynamics
How is Computational Fluid Dynamics (CFD) used? (2 points)
o Air flow around different balls is simulated numerically
o The forces acting on them are calculated accurately
Studying Aerodynamics
What is Computational Fluid Dynamics (CFD) used for? (3 points)
• CFD is a very powerful flow visualisation tool
o Helps immensely in understanding the fundamentals of the air flow.
o CFD must always be fully validated and used in conjunction with wind tunnel tests.
Reynolds Number
Reynolds found that ……. …………… could be considered similar in different cases provided a …………….. ………. known as the ……….. ……….. …. was the same.
flow conditions
dimensionless constant
Reynolds number (Re)
Reynolds Number
Define Reynolds number as an Equation and state the meaning of the variables
Reynolds Number
What does the reynolds number represent and what are the consequences of this? (3 points)
• The Reynolds number represents the ratio of inertial to viscous forces
o At high Reynolds numbers, inertial effects dominate
o At low Reynolds numbers, viscous effects dominate
Viscosity
What is viscosity caused by?
Viscosity is caused by the shear stresses (T) that act between fluid elements as they slide past each other
Viscosity can be thought of as a fluid’s resistance to deformation
Viscosity
The ……….. of a …… is described by …, the ………… (or absolute) viscosity
viscosity
fluid
µ
dynamic
Viscosity
What is v used for relating to viscosity?
Kinematic viscosity = v = µ/p
p = density of fluid
µ = Dynamic viscosity
Velocity profile over a flat plate
What are the consequences of the no slip condition?
The flow velocity at the plate surface is zero (no-slip condition)
Flow velocity gradually increases further from the wall until it reaches the freestream value
Velocity profile over a flat plate
How do shear stresses affect fluid elements?
Velocity profile over a flat plate
Give the equation for shear stress within a fluid, define each variable (3 variables)
