This tag is for questions relating to Bernoulli equation [named after its discoverer, the Swiss scientist Daniel Bernoulli (1700–1782)], an equation governing fluid flow for an incompressible steady fluid. It gives great insight into the balance between pressure, velocity and elevation. Bernoulli’s equation is a form of the conservation of energy principle.
Questions tagged [bernoulli-equation]
647 questions
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What is Pressure Energy?
While deriving Bernoulli's Theorem, our teacher said that the sum of KE, PE and Pressure Energy per unit volume remains constant at any two points.
$$P + \rho g h + \frac{\rho v^2}{2} = \text{Constant}$$
In this, he stated that the first term is…
Max Payne
- 639
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Bernoulli's equation and reference frames
So I was thinking about this while driving home the other day.
I've never been quite clear on why when you drive with the windows down air rushes into your car. I thought this might be explained by Bernoulli's equation for incompressible flow, but I…
PatEugene
- 391
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8 answers
How much effect does the Bernoulli effect have on lift?
I understand that the Bernoulli effect is a flawed explanation for the cause of lift, and does not cause much at all, but how much?
Is there any experimental data on the force caused by the Bernoulli effect? Maybe implicitly through data of the…
Meow
- 1,596
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votes
5 answers
Water Bottle Rocket Thrust - two calculation methods not matching
I have been launching water bottle rockets with my kids and we are in the process of creating a simulation of the launch using numerical methods. I am a mechanical engineer, but fluid dynamics is not my strong suit.
Can you give me an intuitive…
James
- 1,951
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What is the mechanism that transforms pressure into velocity?
I know it's a common question but I can't find an explanation that can clearly show how it happens. If we take Bernoulli's equation, being aware of its hypothesis, it states that energy is constant between 2 given points. So if pressure drops,…
XcodeX
- 181
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6 answers
Why does fluid pressure decrease as fluid velocity increases according to Bernoulli's principle?
I’m studying aerodynamics. I understand Bernoulli’s principle very well, I just can't wrap my head around why pressure decreases as velocity increases. Like the garden hose example: if you cover the hose with your finger, water flows out of the hose…
Richard Mancini
- 161
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4 answers
What force accelerates a liquid moving in a narrowing pipe?
Say there is a liquid which behaves like an incompressible fluid and is flowing steadily through a pipe which is moving from a cross section of area $A_1$ to the cross section of area $A_2$, where $A_2$ is less than $A_1$. As per the continuity…
Meripadhai
- 383
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What is the cause and what is the effect in the Bernoulli effect?
There is widespread confusion (among learners) about the Bernoulli effect, and I think
a large part of this confusion is owing to muddling up cause and effect. So
I am providing this question and answer to see if others find it helpful.
Let's…
Andrew Steane
- 65,285
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What causes acceleration of particles in the expansion section of a De Laval nozzle?
A De Laval nozzle has a compression section, where the propellant is compressed (and thereby accelerated) as it moves towards a narrow section (the throat). After the throat, the nozzle widens out again. Here's a reference image.
According to…
JDub
- 141
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4 answers
Is Magnus effect a corollary of Bernoulli principle?
Magnus effect is commonly explained using Bernoulli principle. However, taking the lift on a rotating cylinder as an example, the velocity difference is caused by the extra work done by the rotating cylinder but not by the pressure difference, the…
Shadumu
- 1,251
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Is the saying "fluid always flows from high pressure to low pressure" wrong?
I'm studying human physiology. And there is a often repeated notion that blood flows "from areas of high pressure to lower pressure". I was wondering why that is so. However there is no real explanation for it. I understand that in a gradient the…
saltytoad
- 121
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votes
1 answer
Pipe in a flowing river problem
I'm working on a certain problem in fluid mechanics, which isn't really my strongest area.
The problem is as follows: Curved pipe is partially submerged in a flowing river so that one end is pointing in the same direction as the velocity of river.…
user36875
- 111
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5 answers
Intuition behind Bernoulli's equation
If water is flowing from a larger subsection $A_1$ of a pipe into a smaller subsection $A_2$ (say, the radius halves), then Bernoulli's principle says that the pressure $P_{A_1} > P_{A_2}$, and $v_{A_1} < v_{A_2}$.
I understand why the velocity…
ahzired
- 115
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11 answers
Why does moving air have low pressure?
According to Wikipedia lift in an aircraft is due to an area of low pressure formed above the wings of an aircraft due to the fast moving air there. So why exactly is an area of low pressure created due to fast moving air?
A.R.K
- 1,433
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What is basically the difference between static pressure and dynamic pressure?
What is basically the difference between static pressure and dynamic pressure?
While studying Bernoulli's theorem, I came before these terms. The law says:
When the fluid flows through a small area, its pressure energy decreases & kinetic energy…
user36790