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 04-16-2012, 05:16 PM #1 Senior Member   Status: Pre-Medical Join Date: Mar 2011 Posts: 147 Bernoulli's SDN Members don't see this ad. (About Ads) Ok I know there's thousands of threads like this, but my physics prof skipped fluids, so will somebody tell me that I'm correct. Ok in a closed system only relate area w/ the velocity b/c flow rate is constant Q=av. Then I relate the velocity to the pressure w/ Bernoullis's. This is the typical thought process right? In an open system if P increased V can increase too, but in a closed system they're inversly related. Do I need to know anything else about Bernoulli's, like the v is squared? Or am I straight? Also, how do I know when to apply Poiseuille's law vs q=av? Last edited by bajoneswadup; 04-16-2012 at 05:50 PM.
 04-16-2012, 05:27 PM #2 1K Member   Status: Pre-Medical Join Date: Jan 2012 Posts: 1,479 Bernoulli, pressure straight up related to velocity bro, super impertanto --check it out
04-16-2012, 05:32 PM   #3
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Quote:
 Originally Posted by SaintJude Bernoulli, pressure straight up related to velocity bro, super impertanto --check it out
Hahaha

 04-16-2012, 05:46 PM #4 MS-0     Status: Pre-Medical MDApps: View Profile Join Date: Jan 2011 Location: CA Posts: 797 don't pressure me, bro!
 04-16-2012, 05:52 PM #5 1K Member   Status: Pre-Medical Join Date: Jan 2012 Posts: 1,479 Ok, now in all seriousness, the most important relationship from Bernoulli is that as velocity increase, pressure decreases. Also I pm'd you a good source for more info.
04-16-2012, 06:30 PM   #6
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Quote:
 Originally Posted by bajoneswadup Ok I know there's thousands of threads like this, but my physics prof skipped fluids, so will somebody tell me that I'm correct. Ok in a closed system only relate area w/ the velocity b/c flow rate is constant Q=av. Then I relate the velocity to the pressure w/ Bernoullis's. This is the typical thought process right? In an open system if P increased V can increase too, but in a closed system they're inversly related. Do I need to know anything else about Bernoulli's, like the v is squared? Or am I straight? Also, how do I know when to apply Poiseuille's law vs q=av?
I think you're ok.

Poiseuille's law and q=av are not contradictory. The former gives you the pressure difference along a pipe for a non-ideal, viscous fluid. q=av just relates the velocity and the flow at a specific cross-section of the pipe. It will be correct for any non-compressible fluid.

04-16-2012, 07:21 PM   #7
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Quote:
 Originally Posted by bajoneswadup Ok I know there's thousands of threads like this, but my physics prof skipped fluids, so will somebody tell me that I'm correct. Ok in a closed system only relate area w/ the velocity b/c flow rate is constant Q=av. Then I relate the velocity to the pressure w/ Bernoullis's. This is the typical thought process right? In an open system if P increased V can increase too, but in a closed system they're inversly related. Do I need to know anything else about Bernoulli's, like the v is squared? Or am I straight? Also, how do I know when to apply Poiseuille's law vs q=av?
Bernoulli's equation:
Where 1. Points one and two lie on a streamline, 2. The fluid has constant density, 3. The flow is steady, and 4. There is no friction

Fluid= gas or liquid

Increase in fluid speed results in decrease of internal pressure. And vice versa.

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