Flow ppt notes Flashcards by Josh Newby

what are a matter that continuously changes shape when subjected to shear force (tangential force?

Fluids

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What are not fluids as they resist shape changes, when their shape is changed they maintain that changed shape

Solid

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With FLUIDS the stress is proportional to the what?? in r/t to hydrostactics

Rate of change

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with SOLIDS stress is proportional to the what? in r/t hydrostatics?

change in shape

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Are liquids and gasses both fluids?

Yes

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what is the big difference between fluids (liq/gas) and solids?

Solids don’t change

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what is perpendicular forces (normal forces)?

force applied perpendicular to surface

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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

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equation for force?

F=ma

force= mass X acceleration

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what are the 3 forces associated with fluids

gravity
pressure
friction

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pressure forces are the result of differences in pressure from one point to another. this is also called the what?

Pressure Gradient

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friction is proportional to what?

viscosity

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what is the physical property of a fluid that relates shear stress to rate of strain?

viscosity

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what is the measure of resistance to flow?

viscosity

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what is the quanity of a fluid passing a point per unit of time?

flow

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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

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what type of flow is smooth flow free of eddies or turbulance, streamlined

Laminar flow

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with laminar flow, the flow _______________ is the greatest being about twice the mean flow.

in the center

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with laminar flow the flow along the walls of the tube is near what?

zero

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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

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this a picture of laminar flow notice that the flow in the center is the greatest

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laminar (streamlined) flow is described mathmatically by who’s law?

Pouiseuille’s law

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what is the formula for Pouiseuille’s law

π=pie 3.14

r= radius

xP= pressure gradient

n= viscosity

l= length

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With Pouiseuille’s law, what 2 thigs are directly proportional

radius⁴

pressure gradient

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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)