Thermofluids Flashcards
What is the maximum pressure a heart can produce?
16 KN/m^2
What is the vital capacity of the lungs?
4.8 L/breath
What is the tidal volume?
0.5 L/breath
What is the residual volume?
1.2 L/breath
What is the total lung capacity?
6 L
What is the power required to pump a pressure head of P N/m^2 at a flow rate of Q m^3/s.
W=PQ
What are the similarities between mass and heat transfer?
Both are governed by diffusion (conduction) and convection.
What is the main difference between mass and heat transfer?
Mass transfer requires a permeable membrane to be able to pass through whereas heat transfer does not.
How wide are the arteries and veins?
Close to the heart = 30-40mm
Far from the heart = fractions of a mm
What is the conversion between pressure in mmHg and Pa.
1 mmHg = 133.3 Pa
What are the different types of muscle contraction?
Concentric contraction - Shortening contraction required to produce mechanical work
Isometric contraction - Force generation with no net work
Eccentric contraction - Lengthening contraction to absorb mechanical work
What type of fibre orientation is fast?
Parallel fibres
What type of fibre orientation is strong?
Pinnate fibres
Name a non-invasive technique for measuring muscle activation and what does it do?
Surface EMG
- Measures the electrical stimulation of a muscle
- Can reveal which muscle is used for which activity
- Ok for surface muscles but can suffer from noise for deeper muscles
Name an invasive technique for measuring muscle activation and what does it do?
Indwelling EMG
- For deep muscles
- Needs precise placement
Name a non-invasive technique for measuring muscle force and what does it do?
Inverse dynamics
- Involves placing markers on external surface of subject and tracking using video processing software
- Affected by skin movement which can lead to large errors
- Can’t distinguish between muscles in a group
Name an invasive technique for measuring muscle force and what does it do?
Tendon buckle force transducers.
- Small force transducers that attach to tendon
- Can damage tendon of the subject.
Name a non-invasive technique for measuring muscle length and what does it do?
Ultrasound
- Measure fasicle and tendon length changes
- Only surface muscles
- Image processing is difficult
- Skin movement can be a problem
Name an invasive technique for measuring muscle length and what does it do?
Sonomicrometry
- Calculates distance using time taken between emission and receiving and a known speed of sound.
- Can measure length changes of a single fasicle
Why would animals be dynamically similar during locomotion?
- They are optimising the same quantity.
- A single form or function gave the greatest amount of optimisation by a significant amount.
What is the Froude number?
Non-dimensionalised speed,
Fr=V/(gl)^0.5
Maintenance power
The rate at which energy is consumed at rest.
Total metabolic power
The rate at which energy is consumed during locomotion.
Net-metabolic power
Total metabolic power - Maintenance power.
Net cost of transport
The derivative of net metabolic power w.r.t. speed. This yields the energy required to move per unit distance.
Douglass bag technique (metabolic power)
Breath into bag, compare amount of CO2 in bag air to sample from atmosphere. Known amount of CO2 means amount of ATP used can be calculated, from this metabolic power is known.
Advanatges - Cheap, simple
Disadvantages - Bag becomes large quickly, resistance to breathing is provided, only allows an average power over test to be calculated.
Open flow system (metabolic power)
A mask connected to a long straight pipe is used to create laminar flow from which a sensitive gas analayser can calculate the percentage of O2 and CO2 expelled. Advantages - Doesn’t require a tight fitting mask, no resistance to breathing and little time averaging.
Breath by breath open flow (metabolic power)
A sensitive gas analyser is integrated into the mask and calculates the co2 and O2 per breath for real time metabolic power calculation.
Advantages - Real time results
Disadvantages - Expensive and difficult to miniturise
Relationship between metabolic power and speed
Metabolic power increases linearly with speed up to the aerobic limit.
Relationship between net cost of transport and speed.
Net cost is independent of speed.
What is the difference between internal and external energy of an animal.
Internal is the energy required to move the limbs relative to the centre of mass, external is the energy required to move the COM relative to the ground.
What is the conversion between Calories and KJ
1 Cal = 4.2 KJ
What are the two types of separation in the kidneys?
Ultra-filtration: Filtration is achieved by application of a pressure gradient. The large protein molecules cannot pass through. Salts, water and metabolites are filtered out and become the filtrate.
Dialysis: Ordinary diffusion through a membrane. The correct balance of water and salts rejoins the filtered blood and any excess along with the metabolites pass into the urine to be removed from the body.
What are 2 size related observations when considering scaling?
- Form and function lie within a limited size range
- Some aspects of form and function are common across a large range.
- Some aspects of form and function change systematically with size.
What quantity is scaled for geometric, temporal and inertial similarity?
Geometric - Length, [L]
Temporal - Time [T]
Inertial - [M]
What quantities are scaled for kinematic similarity?
[L] and [T]
What quantities are scaled for dynamic similarity?
[L], [T] and [M]
What must change to allow a system to increase in size?
- The strength density of the material must increase.
- The relative load must be decreased.
- The dimensions of the load bearing elements must increase disproportionately.
- The design must change.
Why are bones more likely to fail in bending than compression?
- Bones are not perfectly straight along their length.
- Loads are not exactly aligned with the long axis of the bone.
- Cylinders are stronger under compression than bending.
How do L and T scale with M.
As g is independent of body mass we can show that SFt^2=SFl^2.
As density is independent of body mass we can show that SFm=SFl^3 and therefore SFm = SFt^6.
How would you calculate the total energy of an animal.
- Divide the animal into lumped mass segments, split up at the joints of the animal.
- Obtain the mass and second moments of area of these segments from morphometric data.
- Total energy = Σmgh + 0.5ΣIw^2 + 0.5Σmv^2
What is the stroke length and forced produced by a single myosin molecule?
5nm producing about 5pN of force.
Describe the cross-bridge cycle.
1) An ATP molecule has just been split, releasing energy. and the myosin head binds to the actin filament.
2) The myosin cranks pulling the actin filament along relative to itself (the power stroke). ADP and P are released.
3) This allows an ATP molecule to bind at which point the myosin separates from the actin filament.
4) ATP is split into ADP and P causing the myosin molecule to flatten out again ready for another power stroke.
Draw the energy vs temp map
file:///C:/Users/hazze/Downloads/MENGM6051_Solutions_2015.pdf
What is region III of the energy vs temp map known as ?
The ‘comfort zone’.
What is region IV of the energy vs temp map known as ?
The thermo-neutral zone.
What occurs when the temperature is below the cold limit for an animal?
Hypothermia
What occurs when the temperature is above the hot limit?
Hyperthermia
explain what the terms in the following equation are and what are their units? rho*dM/dt=I-epsillon(M-M0)
and what is weight equal to?
rho - energy content of stored fats (KJ/kg)
M - current weight of body fats (kg)
I - Energy intake rate
epsillon - rate of energy loss per unit body mass
Weight - M + M0
How can one show dynamic similarity experimentally
By showing that animals running at the same Froude number has the same RSL, RPF and DF.
Why does calculating efficiency of locomotion from mechanical work and metabolic work lead to overestimation of efficiency.
As they ignore the contribution made by stored elastic strain energy of the tendon.
What is the equation for thermally significant blood vessels?
Change in temp as blood travels down vessels = heat loss from vessel
upir^2rhoCpdT/dz=2PirU(Tt-Tb)
dT/dz=1/ze(Tt-Tb)