Lectures 19-20 Fluid Dynamics Flashcards
Definition of buoyancy
A solid immerses in a fluid will be buoyed up by a force that is equal to the weight of the fluid displaced
Equation for density
Density = mass/volume
Units for density
Kg/m(cubed)
Look at different density’s of water
Slide 8, lecture 19
What are some types of drag (when swimming)
Surface or skin (friction) drag
Form or pressure drag
Wave drag
Look at what different symbols mean
Slide 14, lecture 19
Different types of flows
Slide 15, lecture 19
What is the Bernoulli effect?
When flow lines in a fluid get close together, their velocity increases and the pressure drops
(Diagram on slide 4, lecture 20 explains)
Look at Magnus effect in PE book
Pages 105/106
Equation for Reynolds number (check if you have to learn this on recap recording)
Slide 14, lecture 20
What is the equation for drag?
F(drag) = 1/2 C(drag). A. (rho). v(squared)
What does F(drag) stand for in the drag equation?
Force due to drag
What does C(drag) stand for in the drag equation?
Coefficient of drag
What does A stand for in the drag equation?
Surface area
What does (rho) stand for in the drag equation?
Density (or viscosity)
What does v(squared) stand for in the drag equation?
Relative velocity
What is laminar flow?
Where there is a nice separation and return back of particles and the flow of air
When does laminar flow occur?
At very low speeds
What happens to the movement of air particles around an object when the air starts to move faster?
You have a separation of the flow but the particles do not come back together because the air flow is moving so fast
When air particles start to not rejoin each other after they pass an object, what does this cause?
A low pressure, turbulent wake behind the object
Why is having low pressure behind you a negative thing?
Because if you have low pressure behind you, it acts to drag you back
Equation for Reynolds number?
Reynolds number = density x size x viscosity x relative velocity
At greater speeds what happens to drag on a rough ball?
It (in the case of that video) has less drag than the smooth ball
What happens at lower speeds in terms of drag on a rough ball and smooth ball of equal sizes?
There is less drag on the smooth ball
Why does a golf ball, when hit very hard, have less drag than a smooth ball?
Because of the dimples on the surface
For any given force, an eccentric contraction requires less what than a concentric contraction? What is a benefit of this?
Requires less activity
Requires less o2 uptake and energy intake
Can go longer before fatigue
