Flashcards
Lecture 8 - Fluid Mechanics
Cards in this deck (40)
- 1Define a fluida substance consisting of particles that move freely among themselves and yield
to the slightest pressure; moving or changing readily; not solid or rigid or stable - 2Define flotationthe ability of a body to maintain a
stationary position at the surface of
the water - 3Define buoyancya force in water that lifts upward
and fights against gravity - 4Archimedes' principlea body that is partially or totally
immersed in a fluid will experience an
upward buoyant force equal to the weight of the volume of fluid displaced by that body - 5Specific gravitya measure of the density of an object
(therefore the ability to float) - 6To be Neutrally buoyant body density needs to be _______ water densityequal to
- 7To be Positively buoyant body density needs to be _______ water densityless than
- 8To be Negatively buoyant body density needs to be _______ water densitygreater than
- 9Identify the buoyancyA = Neutrally buoyant
B = Positively buoyant
C = Negatively buoyant - 10What type of floater am I? float when inspire, sink when exhaleConditional floater
- 11What type of floater am I? floats no matter inspirationTrue floater
- 12What type of floater am I? sinks no matter inspirationTrue sinker
- 13Define centre of buoyancythe centre of buoyancy of a body
can be defined as the centre of
the volume of the body displacing
the water, the rotational axis in water - 14When is torque eliminated?when the centre of buoyancy and centre of gravity align vertically
- 15Define relative motionthe direction and speed of fluid
flowing past a moving object are
determined by the velocity of the
object and the motion of the
surrounding fluid - 16Define drag forcecomponent of force exerted by a
fluid against a body that reduces
the body’s speed - 17What is surface drag/skin friction?caused by the fluid tending to rub
along the surface of the body - 18What is surface drag/skin friction dependant on?- velocity of flow relative to that body
- surface area of the body
- smoothness of the surface
- the fluid involved - 19How can you reduce surface drag?reduce flow velocity
reduce surface area
reduce viscosity of fluid
increase surface smoothness - 20What is profile/form drag?caused by turbulent flow conditions
created behind an object moving
through a fluid - 21What is profile/form drag dependant on?cross-sectional area of the body
perpendicular to the flow and the shape of the body - 22How can you reduce profile/form drag?reduce the cross-sectional area of the body perpendicular to the flow
increase streamline of the body - 23Identify the classification of the following streamlinesA = non-streamlined
B = streamlined
C = semi-streamlined
- 24What is wave drag?a resistance force created by the
body moving at the interface
between two fluids, water and air,
that causes waves - 25What is wave drag dependant on?The speed of the swimmer and the vertical movements
- 26How can you reduce wave drag?reduce the speed of the swimmer
reduce vertical body movements - 27At low velocities what is the order of importance of drags?1 = Surface drag/skin friction
2 = Profile/form drag
3 = wave drag
N.B. as a reaction force, at faster
speeds, wave drag may be the most
important resistance - 28Define reynolds numbercharacterises fluid flow around an
object and is used to determine
whether flow is laminar or turbulent - 29What type of flow am I? at slowest speeds, lamina flow, skin friction/surface drag occuring onlyType 1
- 30What type of flow am I? at fast speed, low pressure zone apparent, profile drag and surface drag occur, non-streamlinedType 2
- 31Identify the following flowsA = Laminar (type 1)
B = Partially turbulent (type 2)
C = fully turbulent (type 3)
- 32What is the reynolds number dependant on?- velocity of flow
- diameter of the sphere
- physical properties of the fluid
(density and viscosity) - 33Define fluid lift forcecomponent of force acting at right
angles to drag; directed
perpendicular to the oncoming flow - 34Bernoulli's Principle“Where the flow velocity is fast, the
pressure is low; where the flow
velocity is slow, the pressure is high”
creates a pressure differential to
force directed from high to low
pressure zones, lift-to-drag ratio - 35Define angle of attackthe angle between the main plane
of the object and the flow direction
Main plane fo the object (orientation)
- 36Define angle of release/projectionthe angle the centre of gravity’s
instantaneous velocity vector makes
at release, measured from horizontal
CoG of the object and horizontal
- 37Define angle of attitudethe angle formed between the
main plane of the object and the
horizontal ground
The one you can see - 38Define centre of pressurethe point at which the resultant (lift
and drag) air forces act on the
projectile - 39—Diagram Steps
1. draw ball and flight path
2. add direction arrows, flow and spin
3. include velocity and pressure
4. put in Magnus force arrow (H to L pressure)
5. Identify Magnus Effect = MF direction (J.S Hand rule)
- 40Magnus force depends on what 5 components?1. ratio of surface rotation speed (SRS)
to forward (linear) speed of the ball
SRS = rotation rate x radius of sphere
2. air density
3. mass of sphere
4. surface smoothness
5. amount of spin
Information
- Description
- MEDI222 - Biomechanics (Lecture Notes) Flashcards on Lecture 8 - Fluid Mechanics, created by Nicole Chadwick on 06/06/2018.
- Created by
- Nicole Chadwick
- Views
- 0
- Rating
More on Buoyancy and Archimedes' Principle