BR Physics Question: Ex 7.8a

[meliora27]

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Is this a typo or am I missing something here...

The question asks which of the following will decrease the chance of turbulent blood flow in a vein. The idea is to use the Reynolds Number formula and see how each situation would change the variables and ultimately effect the Reynolds number. The first choice is "Narrowing the vein" which would decrease the radius of the vessel however in the solution it says that this would widen the vein? Can someone please offer some clarification? Thanks!

 

[phEight]

Is this a typo or am I missing something here...

The question asks which of the following will decrease the chance of turbulent blood flow in a vein. The idea is to use the Reynolds Number formula and see how each situation would change the variables and ultimately effect the Reynolds number. The first choice is "Narrowing the vein" which would decrease the radius of the vessel however in the solution it says that this would widen the vein? Can someone please offer some clarification? Thanks!

Haha hey I just worked on this section today and was wondering the same thing! Funny you post it, but I do think it's a typo. Didn't make sense to me either...

 

[ChinaDoll]

Here is the thing

Nr = dvD/n (d- density, v - velocity, D- diameter, n - viscosity)

When Nr is less than 2000, it's laminar flow, when Nr is greater than 3000, it's turbulent flow.

So you want the number to be big, right? at least bigger than 3000 to create turbulent flow... then you want to widen the pipe (D increases)...

 

[phEight]

Here is the thing

Nr = dvD/n (d- density, v - velocity, D- diameter, n - viscosity)

When Nr is less than 2000, it's laminar flow, when Nr is greater than 3000, it's turbulent flow.

So you want the number to be big, right? at least bigger than 3000 to create turbulent flow... then you want to widen the pipe (D increases)...

The question asks which answer decreases the chance of turbulent flow.

It presents as one of the answer choices (answer choice A) "narrowing the vein". Then, in the answer explanation it says "...choice A widens the vein and increases Reynolds number..."

I'm not sure how that makes any sense. I guess you can have something cylindrical shaped and lay it horizontally and squash it from the top, it narrows yet becomes wider? When the answer said narrowing I immediately thought R decreases, which decreases Reynolds number, which decreases the chance of turbulence. But this was not the case. Narrowing the vein widens it.. I dunno lol

 

[ChinaDoll]

The question asks which answer decreases the chance of turbulent flow.

It presents as one of the answer choices (answer choice A) "narrowing the vein". Then, in the answer explanation it says "...choice A widens the vein and increases Reynolds number..."

I'm not sure how that makes any sense. I guess you can have something cylindrical shaped and lay it horizontally and squash it from the top, it narrows yet becomes wider? When the answer said narrowing I immediately thought R decreases, which decreases Reynolds number, which decreases the chance of turbulence. But this was not the case. Narrowing the vein widens it.. I dunno lol

...I think I need a new pair of glasses....😱

 

[phEight]

...i think i need a new pair of glasses....😱

🙂

 

[godsdoc2b]

Still wondering about this question....can anyone provide more insight?

 

[godsdoc2b]

bump

 

[Biebs]

Haha... just rad this chapter today. Does anyone have any insight? It does state that narrow paths or objects are less likely to encounter turbulence, which makes sense, but I still do not understand how they got that "Option A--narrowing the vein" (decreasing the radius) does not decrease Reynolds number (creating more laminar flow).

 

[monkeyvokes]

Haha... just rad this chapter today. Does anyone have any insight? It does state that narrow paths or objects are less likely to encounter turbulence, which makes sense, but I still do not understand how they got that "Option A--narrowing the vein" (decreasing the radius) does not decrease Reynolds number (creating more laminar flow).

have you tried applying the bieber fever principle?