Shear Rate

[unrealfighter]

Hey guys. I'm studying for my medical exams and I'm doing the properties of blood and I've stumbled upon viscosity. Viscosity is shear stress divided by shear rate. I don't really know what shear rate is....the book says it is the slope of the parabolic profile. Why is shear rate highest at the vessel wall, and does shear rate change with changes in diameter? The book also says that shear rate and flow are proportional to each other. Can anyone explain this to me? Maybe some people who did fluids and stuff at A level or university? Much appreciated.

[hex4]

dude

this is gamesroom, not wikipedia or google... :|

wtf is that nway :D:D:

[unrealfighter]

dude

this is gamesroom, not wikipedia or google... :|

wtf is that nway :D:D:

I googled and went on wikipedia...the information they give is quite complex. I just need a simple explanation because that is what the examiner expects...he's a hematologist not a physicist heh. And I posted in the education section didn't I? So pls, if you can't help just don't bother posting.

[filthy hippie]

why not email one of the lectures at JC via the contact form on the UNI site,

[GeneralOneBall]

i think the best guy to ask would be an architect to tlak about fluids i could be wrong

[filthy hippie]

what has an architect and fluids got to do with each other?
chemistry related you need

[metallic]

For the simple shear case, it is just a gradient of velocity in a flowing material.

From Wiki. I think you need that parabola graph.

[Polter]

a level ma ghamilnihix fuq dan laffarijiet u chapter fuq blood diga lesti.

filkaz saqsi fuq answers.yahoo.com u xihadd jajdlek nahseb

[unrealfighter]

Thanks

[PeR0XiDe]

I think shear rate is highest at the vessel wall because of eddy currents at the vessel walls, which cause turbulence (and eventually damaging the vessel walls, which can lead to arteriosclerosis).

Though I'm not really sure what shear rate is lol.

[D_SINNER]

shear rate is the the principle tempo used in queen's shear heart attack album.

[Avaloner]

Shear rate is the rate of flow - how fast the liquid is sliding past at a molecular level. Shear stress is the resistance to flow. They affect each other in that an increase in shear rate (flow) brings about an increase in shear stress (resistance). I guess a good analogy would be a car - if it is going slow (low shear rate) less air particles are hitting it so it will feel less resistance (low shear stress)... but the faster it goes (high shear rate) the more air particles hit it therefore increasing resistance it will encounter (high shear stress).

40% of the blood is made up of red blood cells while the remaining 60% is plasma. Red blood cells are relatively big, have a particular shape and are deformable, giving blood its increased viscosity (in relation to water for example). Shear rate (flow) at the vessel wall is slower because red blood cells bump into the wall and lose momentum, thus reducing the flow. I would assume that thinner blood vessels would have a lower shear rate since the chance of hitting the vessel wall is higher.

I would still ask your lecturer to explain it further.

[GeneralOneBall]

what has an architect and fluids got to do with each other?
chemistry related you need


ghandom suggett shih jismu fluids for your info

[filthy hippie]

ghandom suggett shih jismu fluids for your info

well skyuzzze me

[johnmaclane]

i was going to post that shear is the lateral force (or tangential) exerted on a fixed structure obviously it appears it has a different meaning in medicine.

actually i think its relevant.
check the bottom of this article

http://en.wikipedia.org/wiki/Shear_force

[filthy hippie]

i was going to post that shear is the lateral force (or tangential) exerted on a fixed structure obviously it appears it has a different meaning in medicine.

actually i think its relevant.
check the bottom of this article

http://en.wikipedia.org/wiki/Shear_force

no, what you provided is used in muscles, or some form of it.

[johnmaclane]

no, what you provided is used in muscles, or some form of it.

it shows you didnt read it

[Baegun]

not directly relevant to this shear rate issue, but a very important physical property that relates directly to cardiology is that:

with an obstruction within the vessel wall of up to 75% the lumen diameter, there is no reduction in flow.

obviously this concept is very important in atherosclerosis.

[unrealfighter]

Shear rate is the rate of flow - how fast the liquid is sliding past at a molecular level. Shear stress is the resistance to flow. They affect each other in that an increase in shear rate (flow) brings about an increase in shear stress (resistance). I guess a good analogy would be a car - if it is going slow (low shear rate) less air particles are hitting it so it will feel less resistance (low shear stress)... but the faster it goes (high shear rate) the more air particles hit it therefore increasing resistance it will encounter (high shear stress).

40% of the blood is made up of red blood cells while the remaining 60% is plasma. Red blood cells are relatively big, have a particular shape and are deformable, giving blood its increased viscosity (in relation to water for example). Shear rate (flow) at the vessel wall is slower because red blood cells bump into the wall and lose momentum, thus reducing the flow. I would assume that thinner blood vessels would have a lower shear rate since the chance of hitting the vessel wall is higher.

I would still ask your lecturer to explain it further.

Very helpful :) Thanks

[filthy hippie]

it shows you didnt read it

look at the picture on the right in wiki, and you can very VERY roughly apply that to muscles.
iggugiljah my frend

[johnmaclane]

look at the picture on the right in wiki, and you can very VERY roughly apply that to muscles.
iggugiljah my frend


your telling me muscle = steel bolt?

Come on

[KrI]

your telling me muscle = steel bolt?

Come on

iron man ^^

[Avaloner]

Very helpful :) Thanks

Just for the record... I did not study these things and do not know them as fact. I just made a bit of research on the subject and told you what I understood.

[filthy hippie]

your telling me muscle = steel bolt?

Come on

stopping being stupid, google it before you open your very very large mouth

[KrI]

stopping being stupid, google it before you open your very very large mouth
*stop :P

[johnmaclane]

stopping being stupid, google it before you open your very very large mouth

google your face.

Steel bolt is no muscle, tigix bin nejk

muscle

http://www.ucl.ac.uk/~sjjgsca/MuscleStriated.gif




Any similarities? NO.

[filthy hippie]

http://www.google.com/search?hl=en&safe=off&q=shear+forces+muscle+exercising&btnG=Search
feel free.
remember that i said VERY VERY ROUGHLY not its a carboncopy!

[yancho]

discuss the topic and not the persons posting .. next stupid comment means I clsoe the thread

[Avaloner]

.. next stupid comment means I clsoe the thread

Something which would only serve to annoy the OP

[cabb.]

this thread is pretty much like the turkey thread :P

[johnmaclane]

http://www.google.com/search?hl=en&safe=off&q=shear+forces+muscle+exercising&btnG=Search
feel free.
remember that i said VERY VERY ROUGHLY not its a carboncopy!

il **** rough, i could say shear force is like kicking a pole.

[unrealfighter]

ahjar nistudjaw lahwa lol fuck muscles and fuck steel....