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fluid mechanics Flashcards

fuckery

1
Q

Fluid flow

A

the natural science of fluids in motion

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2
Q

Fluid forces effect

A

In some cases fluids have little effect on an objects motion eg shot-put and in some cases fluid forces have significant effect eg swimming and cycling

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3
Q

3 major fluid forces

A

Drag (works horizontally)
Lift (works vertically)
Buoyancy (works vertically)

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4
Q

Air resistance

A

Increased air resistance- kicking into the wind will decrease the time in the air and decrease the distance a ball can travel

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5
Q

Air resistance and surface area

A

The greater the surface area the greater the air resistance

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6
Q

Boundary Layer

A

Thin layer of surrounding or attached to the ball- determines how much drag is produced

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7
Q

Boundary later separation

A

Where boundary layer breaks away from the ball, the earlier the the separation the greater the pressure gradient between front and back of the ball leading to increased drag

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8
Q

Laminar flow

A

A type of fluid flow in which fluid moves smoothly in individual layers or streams

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9
Q

Turbulent flow

A

Flow in which the velocity at any point varies erratically

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10
Q

Inverse velocity and pressure relationship

A

When a fluid is flowing at low velocity, it will have high pressure and vice versa

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11
Q

3 Factors affecting boundary layer separation

A

Velocity
Surface Roughness
Shape

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12
Q

Rough surface

A

Causes the boundary separation to take place later, this causes a smaller pressure differential between front and back of the ball as their is only a small pocket of turbulent wake at the back of the ball

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13
Q

Smooth Surface

A

Causes the boundary separation to take place earlier, this causes a large pressure differential between the front and back of the ball as their is now a large pocket of turbulent wake at the back of the ball

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14
Q

Low Velocity

A

A low velocity causes the boundary separation to take place later, this causes a smaller pressure differential between front and back of the ball as their is only a small pocket of turbulent wake at the back

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15
Q

At high velocity

A

At high velocity causes the boundary layer separation to take place earlier, this causes a larger pressure differential between front and back of the ball as their is a large pocket of turbulent wake at the back

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16
Q

Oval Ball

A

An oval ball causes boundary separation to take place later, this causes a large pressure differential between front and back of the ball as their is only a small pocket of turbulent air at the rear of the ball

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17
Q

Round Ball

A

A round ball causes boundary layer separation to take place earlier, this causes a large pressure differential between from and back of the ball as their is a large pocket of turbulent wake at the rear

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18
Q

The greater the pressure gradient

A

the greater the drag

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19
Q

What is a low pressure differential

A

Pressure is high at the back and front of the ball and velocity is low at the front of the ball

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20
Q

How do objects move

A

Always from high to low pressure areas- an object experiencing high pressure above it will move downwards

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21
Q

What is form drag

A

resistance to forward motion as a result of a pressure differential between the front and back of an object

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22
Q

Magnus effect

A

When a ball is struck by an eccentric force the rotating ball interacts with oncoming air and the resulting curve is known as the Magnus effect

23
Q

How does Magnus effect take place

A

Air flowing in the same direction as the boundary layer will flow at a higher velocity, therefore lower pressure. Air flowing in the opposite direction will flow at a lower velocity and higher pressure. This pressure exerts force on the ball causing a flight path deviation

24
Q

3 types of spin

A

side, top and back

25
Q

Top Spin

A

used in tennis. A high pressure on top of the ball and low pressure on the bottom of a ball causes it to dip

26
Q

Backspin

A

A high pressure on the bottom of the ball and a low pressure on the top of a ball causes it to hang- golf

27
Q

Sidespin

A

A high pressure on one side of the ball and a low pressure on the other side cause it to curve eg free kick in soccer

28
Q

What does spin affect

A

Both the flight path of a ball and the way it bounces

29
Q

Fluid resistance

A

As an object moves through a fluid it disturbs it. The greater the disturbance to the fluid, the greater the transfer of energy from object to fluid

30
Q

2 factors affecting fluid resistance

A

Density (air)

Viscosity (liquid)

31
Q

Density

A

The more dense the fluid the more disturbed the fluid becomes and hence the greater resistance

32
Q

eg of density

A

Humid conditions create more dense conditions so a ball ill encounter greater levels of resistance

33
Q

Viscosity

A

The more the viscous the fluid the more disturbed the fluid becomes hence greater resistance

34
Q

eg of viscosity

A

Water is more viscous than air and a swimmer will experience greater resistance than a runner

35
Q

Buoyancy

A

Refers to the upward force that keeps things afloat and is used to counteract the effect of gravity

36
Q

Explain buoyancy

A

when the forces of the object are equal to or less than those of buoyancy the object will float

37
Q

Centre of Buoyancy

A

Is the COG of water displaced by the body

38
Q

COG AND COB

A

When the body parts and cog fall outside the cob, the body will rotate in the water in try and bring them into alignment

39
Q

Positive/negative Buoyancy

A

Displaces a volume of fluid greater than its weight and will float

40
Q

Bernoulli’s principle

A

Is based on pressure differences. Objects can be designed to to create low pressure above them and high pressure below them because of their shape- creating lift

41
Q

How can lift act and eg

A

Upwards eg aeroplane wing or downwards eg racing car

42
Q

Lift

A

Occurs because objects are forced to move from areas of high pressure towards low pressure

43
Q

When does lift occur

A

When objects are spinning

44
Q

Downward pressure racing car

A

A high pressure zone above the car and low pressure zone below the car ensures there is downward presto helping the car stick to the ground

45
Q

Drag

A

Is a force pulling an object backwards due to a low-pressure air pocket created behind the object

46
Q

Total Drag

A

Is a combination of form, wave and surface

47
Q

Surface drag

A

It is the friction produced between fluid and the surface of a moving object

48
Q

3 factors affecting surface drag

A

Surface area of object
Smoothness of object
Velocity of moving object

49
Q

Effect of form drag

A

When the area of high/low pressure meet a turbulent pocket of fluid is create resulting in a function like effect slowing the body down

50
Q

3 factors affecting form

A

Shape of object round vs oval
Velocity of object
Surface roughness

51
Q

Wave drag

A

Is the resistance formed by creation of waves at the point where air and water interact

52
Q

3 factors affecting wave drag

A

Velocity of the wave
Technique- streamlined
Open water vs closed conditions

53
Q

4 environmental factors affecting drag

A

Air density
Temperature
Atmospheric pressure
Humidity

Ligma (19 decks)

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