CONCEPUAL FLUIDS tbr

[pizza1994]

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hi guys:

so using the poiseuille's principle can someone explain why a) why it takes longer to pour syrup than it takes to pour water and b) why a wider straw is much more efficent for obtaining a chilled, carbontaed beverage from a glass than a thinner straw?

Thanks

 

[quicheduty]

Poiseuille's deals with viscosity and flow, so conceptually, liquids we call "thicker" (syrup, honey, tar) are harder to pour than water, right? Sometimes you find yourself turning the whole bottle vertically just to get that last bit of honey out for your tea. For the wider straw it might be a little harder intuitively, but if you just think about sheer volume of liquid obtained, the wider straw gives you much more volume at a time. Might not be the most kosher example but say you are allowed to breathe only through a straw. Which straw would you prefer, the wider or thinner? Wider, because you wouldn't be able to get enough air with the thinner straw unless you hyperventilated.

In terms of equation:
R = 8nL/πr^4, where R = resistance to flow

a) if viscosity is higher (e.g. syrup) then n for syrup > n for water and R for syrup > R for water
b) if radius is higher (e.g. wider straw), then r^4 for wider straw >> r^4 for thinner and R for wider < R for thinner

 

[pizza1994]

Poiseuille's deals with viscosity and flow, so conceptually, liquids we call "thicker" (syrup, honey, tar) are harder to pour than water, right? Sometimes you find yourself turning the whole bottle vertically just to get that last bit of honey out for your tea. For the wider straw it might be a little harder intuitively, but if you just think about sheer volume of liquid obtained, the wider straw gives you much more volume at a time. Might not be the most kosher example but say you are allowed to breathe only through a straw. Which straw would you prefer, the wider or thinner? Wider, because you wouldn't be able to get enough air with the thinner straw unless you hyperventilated.

In terms of equation:
R = 8nL/πr^4, where R = resistance to flow

a) if viscosity is higher (e.g. syrup) then n for syrup > n for water and R for syrup > R for water
b) if radius is higher (e.g. wider straw), then r^4 for wider straw >> r^4 for thinner and R for wider < R for thinner

ahh perfect thanks and so a high radius means high flow rate and thats why we use wider straws?