Fluid Motion

Question 1

Fluid

Answer 1

A substance that flows when subjected to a shear stress

Question 2

Primary fluids that affect human movement

Answer 2

• Air

- Water

Question 3

Relative Velocity

Answer 3

Velocity of a body with respect to the velocity of something else, such as the surrounding fluid

Question 4

Laminar Flow

Answer 4

Flow characterized by smooth, parallel layers of fluid

Question 5

Turbulent Flow

Answer 5

Flow characterized by mixing of adjacent fluid layers

Question 6

Fluid Properties

Answer 6

• Density

- Specific weight

Question 7

Buoyancy

Answer 7

• A fluid force that always acts vertically upward
• F(b) = V(d)γ
• F(b) = buoyant force
• V(d) = displaced volume
• γ = fluid’s specific weight

Question 8

Archimedes Principle

Answer 8

The buoyant force acting on a body is equal to the weight of the fluid displaced by the body

Question 9

Center of Volume

Answer 9

• Point around which a body’s volume is equally distributed

- Point at which the buoyant force acts

Question 10

Drag Force

Answer 10

• A force caused by the dynamic action of a fluid that acts in the direction of the fluid flow
• F(D) = ½ C(D) ρ A(p) v²

Question 11

F(D)

Answer 11

Drag force

Question 12

C(D)

Answer 12

Coefficient of drag

Question 13

Coefficient of Drag

Answer 13

Unitless number that is an index of a body’s ability to generate fluid resistance

Question 14

ρ

Answer 14

Fluid density

Question 15

A(p)

Answer 15

Surface area of the body oriented perpendicular to the fluid flow

Question 16

v

Answer 16

velocity of the body relative to the fluid

Question 17

Skin Friction

Answer 17

• Resistance derived from friction between adjacent layers of fluid near a body moving through the fluid
• AKA surface drag or viscous drag

Question 18

Form Drag

Answer 18

• Resistance created by a pressure differential between the lead and rear sides of a body moving trough a fluid
• AKA profile drag or pressure drag

Question 19

Wave Drag

Answer 19

Resistance created by the generation of waves at the interface between 2 different fluids, such as air and water

Question 20

Lift Force

Answer 20

• Force acting on a body in a fluid in a direction perpendicular to the fluid flow
• F(L) = ½C(L)ρA(p)v²

Question 21

F(L)

Answer 21

Lift force

Question 22

C(L)

Answer 22

Coefficient of lift

Question 23

Coefficient of Lift

Answer 23

Unitless number that is an index of a body’s ability to generate lift

Question 24

ρ

Answer 24

Fluid density

Question 25

A(p)

Answer 25

Surface area of the body against which lift is generated

Question 26

v

Answer 26

Velocity of the body relative to the fluid

Question 27

Foil

Answer 27

Shape capable of generating lift in the presence of a fluid flow

Question 28

Bernoulli Principle

Answer 28

• An expression of the inverse relationship between relative velocity and relative pressure
• High-velocity areas = low pressure areas
• Low-velocity areas = high pressure areas

Question 29

Semifoil Shape

Answer 29

Certain projectiles can experience some lift force, but others cannot due to their spherical shape

Question 30

Angle of Attack

Answer 30

Angle between the longitudinal axis of a body and the direction of the fluid flow

Question 31

Magnus Force

Answer 31

Lift force created by spin

Question 32

Magnus Effect

Answer 32

• Deviation in the trajectory of a spinning object toward te direction of spin, resulting from the Magnus force
• Lift force created by spin

Question 33

Propulsive Drag

Answer 33

Force acting in the direction of a body’s motion

Question 34

Propulsive Drag Theory

Answer 34

Theory attributing propulsion in swimming to propulsive drag on the swimmer

Question 35

Propulsive Lift Theory

Answer 35

Theory attributing propulsion in swimming at least partially to lift actin on the swimmer

Question 36

Stroke Technique

Answer 36

• Swimming speed is the product of stroke length (SL) and stroke rate (SR)
• Focus on increasing force applied to increase SL