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Paranoid (IV) Inmate

From: Beyond that line...
Insane since: Apr 2004

posted posted 03-08-2005 15:52

That's true! I don't know of any Physics forums or I'd post there, my Physics sir is too busy these days and rarely gets the time to get into class. This has been bothering me for quite some time now and with my exams looming over the horizon I am desperate!

Can someone please explain to me Bernoulli's Equation, the Equation of Continuity, Tercolli's Theorm and Venturi Relation with respect to Fluid Dynamics!!

Where each is equal to the following:

I really need help here I can't figure head to tail of them and there are millions more questions still in me head! If no one can explain it maybe someone might know of some useful Physics resources??

Paranoid (IV) Inmate

From: Dublin, Ireland
Insane since: Jul 2000

posted posted 03-08-2005 16:43

Christ on a bike, I wouldn't want to be in that lecture.

The Equation of Continuity looks like a simple proving of conservation. Are the V and A, Volume and Area/Mass? It looks like its just showing that A and V are in direct relation. (Probably if the density stays consistent, or could well be equal to the density)

Never heard of any of those people.

Good luck with that, did a quick google search for one or two of em couldn't see anything meaningful/helpful.

Found this page on Bernoulli's when I searched for Continuity so it may help you.

Paranoid (IV) Inmate

From: Madison, Indiana, USA
Insane since: Aug 2000

posted posted 03-08-2005 16:57

Help me out here. It has been a very long time since I looked at these. You tell me what each of the letters in each equation stands for. This will help you to get acquainted with the equations. Once you have said what each variable stands for we can probably work out the meaning of the equations.

For example, Looking at the Equation of Continuity. I think A1 and A2 are the areas of two different diameter pipes and v1 and v2 are the corresponding velocities of fluid flowing through the pipes.

If my assumptions are correct then that equation says that the area of a pipe times the velocity of a fluid flowing through the pipe is proportional to a different area times the velocity of the same fluid at that point.

In other words, Lets say I have a pipe with an area of 100 square cm and water flowing through it at 1 meter per minute. If I place a coupling in the pipe and attach another pipe to it that has an area of 50 square cm the velocity of the water in the smaller pipe must increase to 2 meters per minute to keep the law of continuity.

If you'll explain the variables in the other equations, I think I can help you to understand the other equations.

Just make a list like

  • A1 = area of pipe 1
  • v1 = velocity of fluid through the pipe at A1
  • A2 = area of pipe 2
  • v2 = velocity of the fluid at A2.


-- not necessarily stoned... just beautiful.

Paranoid (IV) Inmate

From: Swansea, Wales, UK
Insane since: Aug 2001

posted posted 03-08-2005 18:37

**Mummyyyyyyyy, theres a nasty man at the door..............**

No Sig ?

Maniac (V) Inmate

From: Cell 53, East Wing
Insane since: Jul 2001

posted posted 03-08-2005 21:26

Oooooooooo its been a while since I did fluid mechamics and thermodynamics.

Bernoulli's Equation/Theorem essentially means that the faster something moves through a pipe the lower the pressure is.

I always think of it like a train going through a tunnel (Freud would have a field day!!) - if you are in a subway/underground and the train whistles past the platform where you are standing you actually feel sucked towards the moving train. If it glides into the stop it is much less noticeable.

I think you best bet is to find information on the varius theorems and if you can understand what they are desrcibing ithe equations make more sense. Its trickier working back from the equations.

I'll have a nose aorund and see if anything good jumps out at me.

[edit: Also they rely on a variety of assumptions so if you can grasp these then you are in a better position.]

[edit2: The Wikipedia has a good page on this:

see also: ]


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if I went 'round saying I was an Emperor just because some moistened bint had lobbed a scimitar at me, they'd put me away!

(Edited by Emperor on 03-08-2005 21:31)

Paranoid (IV) Inmate

From: France
Insane since: Jun 2002

posted posted 03-08-2005 21:54

I wish I attended such lecture.
Thermodynamic sounds cool and could lead to some interresting apps/scripts.

Maniac (V) Mad Scientist

Insane since: Aug 2000

posted posted 03-08-2005 23:44

Bernoulli's principle is one of those things that got hammered into our heads. As we said it, as a fluids velocity increases, it's internal pressure decreases.
That's why a wing's top has more curve, or surface area, than the bottom. I think...
Also why your ears might pop in a very strong wind.

Can't say I've ever worked with that equation, though.

(Edited by warjournal on 03-08-2005 23:46)

Bipolar (III) Inmate

From: New England
Insane since: Sep 2000

posted posted 03-09-2005 05:33

So, templar, you're looking for us to give you an entire lecture (or lectures) here because you felt that you didn't need to pay attention in class? Or did you not go to class at all? And you think all of us inmates on all of these little black pills, can sit here all night typing out explanations of these equations? I think you'd better just check yourself in and get your quota of pills and slip into a corner for a while.

Paranoid (IV) Inmate

From: Beyond that line...
Insane since: Apr 2004

posted posted 03-09-2005 06:52

Hugh: Thanks that info really helps alot!

hyperbole: Bernoulli's Equation is defined as (in simple terms) the lower the pressure the higher the speed. You're right for the Equation of Continuity, for Torricelli's Theroem:

  • v2: the velocity of water at the small orifice created near the end of the tub
  • g: the value of gravitational acceleration i.e. 9.8m/s2
  • (h1-h2): the difference in height between the two orifice's created in the tub.

For Bernoulli's Equation:

  • v1 and v2: the velocities of water at the tow ends of the pipe
  • h1 and h2: the height's of the pipe i.e. one end is higher than the other where h1 is higher
  • roh: the density of the liquid that's inside the pipe
  • P1 and P2: the pressures exterted in the pipe by the flow of the liquid

Same goes for Venturi Relation.

Emperor: I never actually knew the wikipedia had all that there!

warjournal: Your example is right it's in my Physics book. That and why a tennis ball has an unusual swing to it when it's hit really really hard... not very unusual now!

briggl: I missed many Physics lectures not that I didn't pay attention or didn't like the subject I was among the only five students who actually asked questions or gave answers! It's my stupid Computer sir who's to blame the Fish-Head (dude looks like a fish) would make me along with a few more dudes late for our Physics class (which was next by the way) he'd keep us there for internship and helping out in the lab... even being good at studies pays! The idiot would make us around a half hour late for class. We had a break in between around an hour and he'd keep us there. Oh well atleast it was a good way to meet babes

(Edited by templar654 on 03-09-2005 06:54)

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