22.23. Fluid flow, diffusion Flashcards
Viscosity formula
η=t/D
t : sheer stress F/A
D : velocity gradient dV/dy
Viscosity of distilled water
1mPa*s
What is dynamic pressure?
1/2rho*v²
What is hydrostatic pressure?
rhogh
Bernoulli’s law equation
[1/2rhov²]+[rhog*h]+pstat = CST
Stokes law
F = 6piηrv
F : stokes drag, frictional force
v : flow rate
Stokes coefficient
Measure of the frag of an object in a moving fluid.
F = gamma * v
Average blood viscosity
5mPa*s
What is the normal range of hematocrit
40-50%
High-molecular weight proteins in plasma
Immunoglobulins, fibrinogen
Mean free path equation
L = v * τ
v : velocity
τ : average time between collisions
Diffusion constant equation
D = (v*L)/3
Mean speed of particles
vmean = sqrt [(3kT)/m]
Equation of mobility
u = vdrift / E u = vdrift / (f/q)
Unit of diffusion coefficient?
m²/s
Unit of matter flow density (flux)
mol/(m²*s)
Unit of matter flow rate
mol/s
Flow density and flow rate relation
Jv = Iv/A
PC02 and PO2 in alveoli
PCO2 : 40 mmHg
P02 : 100 mmHG
PCO2 and P02 in cell
PCO2 : 46 mmHg
P02 : 40 mmHg
Osmotic pressure
Hydrostatic pressure which needs to be applied to a solution to prevent inwards flow of its pure solvent across a semipermeable mb
Osmotic pressure formula
pi = iMR*T
i : vanthoff factor
M : molar concentration (mol/L)
What are streamlines?
- They characterize the direction of motion
- The denser the lines, the greater the speed
What does viscosity characterize?
It characterizes the internal friction of fluids and gases
What causes viscosity?
resistance of fluid to inner interactions (gas have low interactions bw molecules)
What is sheer stress?
force tending to cause deformation of a material by slippage along a plane (parallel)
What are 4 main characteristics of an ideal fluid?
- No viscosity
- Doesn’t experience sheer stress
- Constant density
- Incompressible
What is Bernoulli’s law?
in a stationary flow of an ideal fluid, the sum of all forms of energy along a streamline is the same at all points on that streamline
What is plasma skimming?
natural separation of RBC from plasma at bifurcations - makes hematocrit of capillaries lower than that of arteries
What is shear rate?
Shear rate is the rate of change of velocity at which one layer of fluid passes over an adjacent layer (velocity gradient)
What is Newton’s law of friction?
sheer stress between adjacent fluid layers is proportional to the velocity gradient difference between the 2 layers
What are the 6 main determinants of blood viscosity?
- Hematocrit
- Plasma viscosity
- Plasticity of RBC
- Aggregation of RBC
- Flow rate, velocity gradient
- Blood vessel diameter
What is the random walk of particles?
- Path of particles is a succession of random steps
- the particle travels a R(t) net distance from its original position in t time
What are the 4 parameters used to describe transport of matter?
- Mean free path (average displacement)
- Drift speed
- Mobility
- Diffusion coefficient
What is diffusion?
change in spatial distribution of particles because of random thermal motion
On what 4 factors does heat conduction depend?
- temperature gradient
- cross section of the materials involved
- material length
- Properties of the material
What is osmosis?
molecules of SOLVENT diffusing across partially permeable membrane from a less concentrated solution to a more concentrated one
What is osmolarity?
The concentration of a solution needed to keep balance with a heterogenous solution
