Flow ppt notes Flashcards
what are a matter that continuously changes shape when subjected to shear force (tangential force?
Fluids
What are not fluids as they resist shape changes, when their shape is changed they maintain that changed shape
Solid
With FLUIDS the stress is proportional to the what?? in r/t to hydrostactics
Rate of change
with SOLIDS stress is proportional to the what? in r/t hydrostatics?
change in shape
*************************************************
Are liquids and gasses both fluids?
Yes
*****************************************
what is the big difference between fluids (liq/gas) and solids?
Solids don’t change
what is perpendicular forces (normal forces)?
force applied perpendicular to surface
fluids are matter that respond in one of two ways to normal forces (perpendicular forces).
how do liquids respond?
how do gasses respons?
liquids- resistance to compression , minimal volume changes.
Gasses- compressible and easily expandable
equation for force?
F=ma
force= mass X acceleration
what are the 3 forces associated with fluids
- gravity
- pressure
- friction
pressure forces are the result of differences in pressure from one point to another. this is also called the what?
Pressure Gradient
friction is proportional to what?
viscosity
what is the physical property of a fluid that relates shear stress to rate of strain?
viscosity
what is the measure of resistance to flow?
viscosity
what is the quanity of a fluid passing a point per unit of time?
flow
*************************************
equation for flow.
give example of how flow is written
F=Q/t
F= mean flow
Q= Quanity
t= time
eg- L/min
mL/hr
etc
*********************************
what type of flow is smooth flow free of eddies or turbulance, streamlined
Laminar flow
*******************************
with laminar flow, the flow _______________ is the greatest being about twice the mean flow.
in the center
*****************************
with laminar flow the flow along the walls of the tube is near what?
zero
just to listen for a basic understanding about flow
your on a boat on the sSt. johns river and just cruising along,(lamina the tide is moving and your just cruisin along, thn you get to down town, and the river narrows (by main street bridge) the watr is jst churning little whirl pools and etc. that is now turbulent
this a picture of laminar flow notice that the flow in the center is the greatest
*************************************
laminar (streamlined) flow is described mathmatically by who’s law?
Pouiseuille’s law
*********************
what is the formula for Pouiseuille’s law
π=pie 3.14
r= radius
xP= pressure gradient
n= viscosity
l= length
*****************************
With Pouiseuille’s law, what 2 thigs are directly proportional
radius4
pressure gradient
with Pouiseuille’s law F is directly proportional to the fourth power of the radius. what does this mean in laymen terms
flow through a larger bore needle is faster than a small one
With Pouiseuille’s law F is directly proportional to the hydrostatic pressure gradient, what does this mean in laymen terms?
raising the IV pole increases hydrostatic pressure in fluid delivered to a pt by gravity, flow iincreases proportionally
****************************
with Pouiseuille’s law what 2 things are inverly proportional to flow
fluid viscosity
length
With Pouiseuille’s law give an example of how viscosity is inversly proportional to flow
polycythemic pts have higher blood viscosity, flow reduced
Anemic pt’s have low viscosity, so flow increased
With Pouiseuille’s law give an example in laymen terms how length is inversly proportional to flow
reducing the length of a needle inclreases flow from an IV bag
************************************
With Pouiseuille’s law which factor is the most sensitive to change that will effect flow the most!!!!!
and why?
this will be a test question
Radius
double the radius= increase in flow x 16
Half the radius= decrease flow t0 1/16th
ex 24=16
14= 1
with laminar flow
flow is directly proportional to what besides radius
Pressure
ex in Pouiseuille’s law the change in pressure gradient
the higher the pressure the greater the flow (raise the IV bag)
what is teh equation for resistance
R= P/Q
R= resistance
P= pressure
Q= flow
flow is _______ propartion to viscosity r/t Pouiseuille’s law
inveresly
Blood viscosity increases with what factors
Low temp
increase in age
cigarette smoking
Increased Hct
Abnormal plasma levels
********
what is the BIGGEST factor that increases blood viscosity thus decreasing flow
Increasing Hct
According to Pouiseuille’s law length is _________ proporionate to flow
Inversely
With Pouiseuille’s law and its relationship to length. decreasing the length by 1/2 results in flow that is _________ the original volume?
and thus if you double the length you ______ the flow
Twice
Half
(1/2 length u double the flow, you double the length you 1/2 the flow, yes this is a large factor but remember the largest factor that affects flow remain the radius which has a 16 fold increase if u double it)
A recap of all learned
Flow is directly proportional to ______
Flow is directly proportional to ______
Flow is inversely proportional to ______
Flow is inversely proportional to ______
Radius4
change in pressure
viscosity
length
don’t memorize just remember the formula for resistance and what effects it.
so what is the formula for resistance
R=P/F
R=resistance
P=change in pressure
F= flow
or basically
P1-P2/ flow (Q)= R
what is the equation for resistance with laminar flow?
R= (8nL) / (πr4)
so
R=resistance
8n= viscosity
L=length
π= 3.14
r= radius4
***********************
so what effects resistance
resistance is Inversly proportional to ____
And directly proportional to __________ and _______
Inversely-r4 ( basically the greater the radius, the smaller the resistance)
Directly- viscosity (greater blood viscosity, greater resistance)
Directly- Length (longer the tubem the greater the resistance)
***basiclly the oposite of flow, b/c resistance is what opposes flow
R= (8nL) / (πr4)
What type of flow contains irregular swirls or eddies?
turbulent
*****************************
what measures the propensity for turbulent flow
Reynolds number
how is reynolds number calculated
(v p d) / n l
V= velocity
p= density
d= diameter
n= viscosity
l= length
********************************
what reynolds number = turbulent flow?
what #= laminar flow?
turbulent > 2000
laminar < 2000
what is the critical velocity r/t reynolds number
is the velocity of a gas at which Re= 2000 and laminar flow converts to turbulent
with pouiseuille’s law at low flows ________ predominates
and at high flows _______ predominates
viscosity
density
ex. a decrease in DENSITY will result in an increase in FLOW
Water is more dense than air, greater the water content of the air the more ______ the air is
Viscous
iin the smaller bronchials flow is slowed and becomes or is maintained as what type of flow?
laminar
what is the flow like in the upper larger bronchus of the airway
turbulent
flow becomes turbulent if what occurs (in a clinical presentation)
velocity of flow is high
tube wall is narrow
kinks, bends, narrowing, branches of tube
fluids flow through and orfice
****************************
what is Bernoulli’s principle
with flow through a constricted tube, the velocity of flow increases and the lateral pressure on the walls of the tube decreases
ok so basically when something gets smaller speed increases and pressure is aimed at the end of the tube more than on the walls.. not as hard as he states to understand.
to have an example if u let water gtt out of a hose it is wide spread and flows slow, if i place my finger on the end the speed (velocity) increases and the flow is more forward and straight than spread out.
**************************************
know the difference b/t venturi effect and Bernoulli’s principle
the Bernoulli’s principle explains the verterni effect
********
when fluid flows through a constricted region of a tube (venturi tube) the velocity of flow increases, and the lateral pressure on the walls decrease. is what principle?
Bernoulli’s principle aka the bernoulli effect
***********************
what is the venturi effect
with flow though a constricted tube that has an opening at the constriction air entrainment will occur owing to the decreased pressure at the constriction (as descriped by the bernoulli’s effect)
basically b/c if the bernoulli’s principle is u place a hole there a venturi effect will occur (which is simply the allowing of air in due to the increased velocity and decreased wall pressure)
What is another effect r/t Bernoulli’s principle that causes a stream of flow to be held along one side of a tubes wall at a bifurcation of wider bore than the preceding constriction
Coanda effect
The coanda effect may explain what 2 things in the body
- how gas is misdistributed at the alveolar level
- how some MI occur dispite lack of total occlusion of the vessel
what is the fluid logic utilizing the Coanda effect?
it’s the creation of a valve mechanism consisting of tubes for flow administration at the site of the constriction’s outlet, so that the flow can reach the other branch
(this is being used in smaller portable ventilators as bellows or not required***for knowledge)
Which liter NS IV bag would flow faster?
one infusing through a 20 cm (8 inch) #16g central line or a PIV #20g 1 inch angiocath (assuming the 16g is twice the diameter of a #20)
do the math out
the 16g central line
dispite the 7 inches of length difference
the doubled radius is more important than the length
which liter of NS IV bag would flow faster, one infusing through a 40cm 16inch #16G PA cath or a periphreal #20G 0.5 inch angiocath (assuming a 16g is twice the diameter)
the 20g wins
although the radius is doubled the length is such a differnce that the 20g will give better flow
give examples of the venturi effect in clinical situations
- with the bellow they are pnuematic driven and as the compress the venturi effect allows air to enter so that not only O2 is being used
- TTJV- pushing the air in causes air to enter the oropharynx as well
with Pouiseuille’s law what are the 3 variable parts of the equation, all others are constants
R
change is pressure
length
(side note n is constant per fluid type)
