How to apply bernoulli's equation to viscous fluids?

thebillsfan

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I know you can't mathematically, but how do you do it qualitatively?

sv3

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I know you can't mathematically, but how do you do it qualitatively?
you've actualy seen a question ask you this?

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thebillsfan

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you've actualy seen a question ask you this?
in a way...not directly. it really has to do with blood. I know blood is viscous, so nonideal, and i'm wondering how bernoulli's equation does and does not apply. I think if i can understand the relationship between bernoulli's and viscous fluids, then i'll better understand the two concepts separately.

sv3

10+ Year Member
in a way...not directly. it really has to do with blood. I know blood is viscous, so nonideal, and i'm wondering how bernoulli's equation does and does not apply. I think if i can understand the relationship between bernoulli's and viscous fluids, then i'll better understand the two concepts separately.
bernoulli's only applies to ideal. So you cant apply it to non ideal like blood.

wanderer

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I know you can't mathematically, but how do you do it qualitatively?
Bernoulli's Law is based on the conservation energy. In non-ideal fluids the friction is significant so that you can't use Bernoulli's Law (especially if the fluid is very viscous or if the diameter of the vessel is very narrow).

On the other hand Bernoulli's Law can be used qualitatively but not really quantitatively when you are asked about compressible fluids (gases).

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thebillsfan

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On the other hand Bernoulli's Law can be used qualitatively but not really quantitatively when you are asked about compressible fluids (gases).
How? I thought bernoulli's only applied to noncompressible fluids

wanderer

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How? I thought bernoulli's only applied to noncompressible fluids
It applies (since energy is conserved) but the math would be overly tedious because the density is not constant at different points, just know there is an inverse relationship between pressure and velocity.