Skip to main content

Questions tagged [bernoulli-equation]

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.

Filter by
Sorted by
Tagged with
0 votes
1 answer
44 views

Where does the pressure go when the fluid leaved the pipe?

I have an elementary question on Bernoulli's law. Consider the pipe as depicted below. At point $1$, the pipe has the cross-section $A_1$ and the incompressible, non-viscous fluid is flowing with the ...
Igor F.'s user avatar
  • 265
3 votes
1 answer
74 views

Given the same cross-sectional area, is fluid velocity constant?

I'm currently studying a introductory section on fluids and was given this principle of continuity: $$A_1 v_1 = A_2 v_2$$ I understand the logic behind it (viz. the conservation of mass and whatnot). ...
procommania's user avatar
2 votes
2 answers
332 views

Bernoulli principle (classic form) in irrotational viscous flow (a paradox?)

We derive the Euler equation for inviscid flow. Then, for irrotational flow, we use the Euler equation to get Bernoulli equation (classic form) and show it holds in the irrotational region (still ...
Ebi's user avatar
  • 1,148
2 votes
1 answer
55 views

What is the pressure near the end of the siphon tube inside water?

Consider a standard siphon Tube as shown What is the pressure at point O in the figure? A continuous streamline is there from A to O to B to C to D (correct me if I m wrong) Applying Bernoulli’s and ...
Kampann's user avatar
  • 151
0 votes
1 answer
26 views

Can the air have to travel slower than the aeroplane for the plane to experience a forward force?

The speeds are relative to the ground. Firstly, I don't understand how the speed of the air adds onto the horizontal speed of the plane. Since, the air moves slower than the plane in the horizontal I ...
Devil's Advocate 2321's user avatar
0 votes
0 answers
37 views

Why will the Coanda effect make a piece of paper bend?

There is an answer here that explains the Coanda effect very well in my opinion. To summarize, the Coanda effect is when a stream of air flowing will ‘pull along’ the air molecules beside it, mainly ...
Wyatt's user avatar
  • 275
0 votes
0 answers
26 views

Generated pressure when two water interfaces collide

Background I'm studying a bulk cavitaion problem as described in V. J. Cushing - On the theory of bulk cavitation. In the problem an incident shock wave (from the water $z < 0$) is reflected as a ...
MOOSE's user avatar
  • 13
1 vote
0 answers
39 views

Why doesn't the Coanda effect pull fluid from the center of the streamline?

As explained nicely in this answer, the Coanda effect will pull air from the surrounding air outside of the streamline. This picture shows it nicely : So my question is what stops the low pressure ...
Wyatt's user avatar
  • 275
0 votes
0 answers
30 views

Pressure at tail end of a water pipe

I was wondering about what is the pressure at end B based on these requirements: the flow velocity through the pipe is vcon(m/s) and flow rate is q(m^3/s), no requirement for delivery pressure at B, ...
manuel martin's user avatar
5 votes
3 answers
371 views

Bottle with a hole, with straw through the lid

Consider a bottle filled with water, with an air tight lid, with a hole at height h. It's well known that the water doesn't flow out when the lid is closed. Now, if a straw is inserted through the lid,...
vishvAs vAsuki's user avatar
1 vote
7 answers
265 views

Explaining lift on a wing via forces

Consider the bottom of a wing. Air below the wing is deflected downwards by the wing. Hence by Newton's 3rd Law the wind must exert an equal and opposite force on the wing. Hence lift, and this makes ...
Quin Gardiner Bax's user avatar
0 votes
0 answers
21 views

Equation for flow out of a container through a vertical slot so the discharge area changes with water height

lets say a fish tank leaks along a vertical edge seam. What is the equation for the flow rate as the volume and discharge area changes?
kpanik's user avatar
  • 1
2 votes
3 answers
87 views

Different types of pressure and their sources

I’m an engineering student. So far, I’ve learned about 3 types of pressure: Static fluid pressure ($P=\frac{F}{A}$). This wouldn't exist without gravity. I’ve solved problems related to the force ...
Rikas's user avatar
  • 23
0 votes
0 answers
69 views

Name of Equation $Q = \Delta P / R$

A very fundamental equation in understanding fluid flow is $Q = \Delta P / R$. When the flow is through a cylindrical pipe of constant radius, $R=8\eta L/\pi r^4$ can be substituted to give Poiseuille'...
E Tam's user avatar
  • 145
1 vote
2 answers
90 views

Using Bernoullie theorem to find efflux velocity

During the derivation of velocity of efflux Bernoulli's principle is used, $$P_A + \rho gH + \frac{1}{2}\rho V_A^2 = P_B + \rho gh+ \frac{1}{2}\rho V_B^2$$ My question is why $P_A=P_B=P_0$ = ...
SHINU_MADE's user avatar
0 votes
1 answer
37 views

Does pressure at a point in a fluid flow change with respect to different frames?

Let there be a cylindrical pipe through which a fluid is flowing. Between 2 points at the same height: $$p_1+\frac12\rho(v_1)^2 = p_2+\frac12\rho(v_2)^2$$ Thus, $$p_1 - p_2 = \frac12\rho[(v_2)^2 - (...
Shubham Goel's user avatar
0 votes
1 answer
31 views

How can Ventury tube measure velocity in a pipe when it is is zero at the wall?

In the Venturi tube the sum of static and dynamic pressure is kept constant along a streamline. A reduced cross section leads to a reduced static pressure. $$p_1+\rho v_1^2/2 = p_2 + \rho v_2^2/2$$ ...
MichaelW's user avatar
  • 1,299
0 votes
0 answers
18 views

Bernoulli's theorem be applied to Laminar flow? But Laminar flow can be non-viscious as well right?

I find this contradictory. In my high school Physics book it says that Bernoulli's theorem applies to incompressible, non-viscious fluid having streamline and irrotational flow. Then it says that ...
Syed Aabis Akhtar's user avatar
2 votes
1 answer
70 views

Bernoulli's Equation - Doubt [closed]

Ok so we have this question: Now when I take these two points: Applying bernoulli's equation to these points: taking Pressure at point 1(inside the beaker) to be $P_o$ + $\rho gd$ , and second ...
Adhway's user avatar
  • 374
3 votes
1 answer
46 views

Venturimeter - Doubt

I was reading about venturimeters , and this is what I found on net: Now my question is , where do we exactly "select" the two points required to put the bernoulli's equation? For example I ...
Adhway's user avatar
  • 374
0 votes
0 answers
51 views

How to calculate equilibrium time for a communicating vessel with height difference?

The scenario is that a communicating vessel or a U tube without lids is filled with water. There is a height difference between the two pipes of this tube. Then there will be hydraulic pressure and ...
ooo's user avatar
  • 1
1 vote
1 answer
50 views

Use of Bernouli's equation in Water Rocket calculations

In calculating the exit velocity of the water in a water rocket, all the sites I have found use Bernoulli's equation in the rockets frame of reference. I know that that is correct if the rocket was an ...
Alan Johnstone's user avatar
0 votes
2 answers
45 views

Bernoulli Principle Confusion

Sorry, beginner's question, but this counter-intuition is boggling my mind. Say I have a hose of a certain diameter. If I squeeze the hose at a certain point, then the pressure applied on that point ...
Satamanster's user avatar
4 votes
1 answer
144 views

Buckingham's Pi Theorem: Why does $G(\pi)=0$ imply $\pi$ must be a constant?

I'm learning Buckingham's Pi Theorem and there are some conclusions that I just can't wrap my head around. What I Understand Given a unit-free equation F($v_1$, ..., $v_n$)=0 where vi are physical ...
William's user avatar
  • 143
0 votes
3 answers
177 views

What is the term $P$ in bernoulli's equation defined as?

I have seen that term get defined as pressure energy (potential energy per volume). But how does that make sense? because work is $F \cdot d$ so there must be a change of volume of the fluid that the ...
John greg's user avatar
  • 103
1 vote
0 answers
38 views

Does the free surface of an ideal fluid in a cylindrical container rotating about its own axis for a paraboloid? [duplicate]

Does the free surface of an ideal fluid in a cylindrical container rotating about its own axis for a paraboloid? It is just as the question asks. I've seen proofs that the above setup will create a ...
K-01359's user avatar
  • 11
1 vote
1 answer
160 views

Why water rises up in a straw when we blow over it?

Suppose I am holding a straw in a cup filled with water and I blow over the straw, the water rises up. The explanation I have seen anywhere on the internet is "Bernoulli's principle" i.e the ...
Shyam's user avatar
  • 39
0 votes
0 answers
18 views

In which cases should one use the Navier-Stokes equations for modelling of incompresible fluid dynamics?

I have been doing some exercises in incompressible fluid dynamics, particularly with Navier-Stokes equations, and realized there was an exercise that involved a tubular pipe, that could use ...
Eduardo Kuri's user avatar
0 votes
1 answer
59 views

Bernoulli theorem on surface of rotating liquid

I have a problem in which I have to find the max height of liquid column: This problem can be done by other ways but by trying the Bernoulli theorem I having a problem. At point z and h the pressure ...
Mr. Explorer explorer's user avatar
0 votes
1 answer
30 views

Pressure difference inside a moving flowing fluid

In a moving fluid how does velocity difference cause pressure difference?
Harry potter 's user avatar
0 votes
0 answers
24 views

Why don't boundary layers have a transverse pressure gradient due to the Bernoulli effect?

This is something I always thought about but never truly understood. A boundary layer has a velocity gradient, $\partial u/ \partial y$. The Bernoulli principle states that pressure and velocity are ...
raymysterioso's user avatar
3 votes
0 answers
37 views

Why is windspeed proportional to inflated area in windsock?

I have come across this image on Twitter on how to measure wind speed with a windsocket. I noticed that the rings look equally long in the photograph (and others) and measure a speed increase of 3 ...
McLawrence's user avatar
0 votes
0 answers
59 views

Pressure difference between one moving fluid and a stationary fluid

I'm trying to understand how exactly we can show that the pressure of a fluid $x$ is lower or greater than the pressure of a fluid $y$. One good example I found is the following image. Using ...
epselonzero's user avatar
1 vote
1 answer
43 views

Unexpected result: flux using Poiseuille greater than using Bernoulli

I have a simple, easy to solve, Poiseuille type of problem, to which I added a second question, in which viscosity is zero, so I can solve it using Bernoulli. I am arriving a greater flux using ...
everything.is.fine's user avatar
1 vote
0 answers
122 views

Bernoulli's equation in a conical pipe

Question A stream is rushing from a boiler through a conical pipe, the diameter of ends of which are $D$ and $d$; if $V$ and $v$ are the corresponding velocities of the stream and if the Bernoulli's ...
P. Patil's user avatar
0 votes
2 answers
42 views

Different Bernoulli equation from $F=dp/dt$ [closed]

If any part of the question needs clarifying, there might be explanation in the post-script and of course ask if needed. I understand how the Bernoulli equation is derived for incompressible fluid in ...
elscan's user avatar
  • 138
1 vote
0 answers
86 views

What does a dynamic-pressure loss coefficient of more than 1 mean (for eg air going through bend)?

Air flow (eg in a duct) has a dynamic pressure, and when the air flow goes through e.g. a 90°-bend the bend has a dynamic-loss-coefficient. The dynamic-loss-coefficient is used to calculate the total-...
user84635's user avatar
3 votes
2 answers
727 views

Bernoulli's principle at molecular level

I've seen many questions and answers about this topic, which keep saying that pressure decrease is the cause of acceleration of flow, and don't explain where that pressure drop comes from in the first ...
John greg's user avatar
  • 103
0 votes
0 answers
9 views

Assumed pressure at tank outlet to derive Torriceli's law

In the derivation of Torriceli's law it is assumed that the pressure at the tank hole is equal to atmospheric pressure. I believe this is true when the water starts flowing through the hole but I do ...
yolegu's user avatar
  • 81
0 votes
0 answers
40 views

Bernoulli theorem using quantum and statistical mechanics

Can someone derive Bernoulli theorem( behavior of fluids) using quantum mechanics and statistical mechanics ( behaviour of atoms and molecules of fluids) ?
user avatar
2 votes
7 answers
427 views

Why does the water go from left to right in this question?

In this problem stated by Brilliant course in "Flow in pipes", the water flows from left to right without explaining anything: My doubt is if I'm supposed to assume there is some greater ...
Alysid's user avatar
  • 45
0 votes
0 answers
68 views

Bernoulli's Principle Versus Reynold Transport Theorem - Flow Hitting Flat Plate

I have been running into an issue regarding the analysis of the forces involved when a vertical flow is hitting a fixed horizontal flat plate. Consider the below scenarios: Scenario 1: Consider a ...
magic865's user avatar
0 votes
1 answer
360 views

Questions about compressible and incompressible Bernoulli's equation

The Bernoulli's equation is usually thought to be applied to an incompressible fluid (without potential energy change) as $$\frac12 v_1^2 + \rho P_1 = \frac12 v_2^2 + \rho P_2 $$ Where, v is ...
GRANZER's user avatar
  • 649
0 votes
0 answers
30 views

Bernoulli equation and the ideal gas law for air flow in a streamtube or pipe [duplicate]

For incompressible, inviscid, steady flow of an ideal gas in a tube, Bernoulli's principle holds: $$ \frac{1}{2}\rho v^2 + \rho g z + p = \text{constant} $$ This equation could be interpreted as ...
nwsteg's user avatar
  • 260
0 votes
1 answer
538 views

How does the compressible Bernoulli's theorem reduce to the incompressible Bernoulli's theorem?

For incompressible steady flow, such as in water, Bernoulli's theorem states that $$\frac12 \rho v^2 + P = \text{constant}. \tag{1} $$ There's also an analogue of Bernoulli's theorem for compressible ...
knzhou's user avatar
  • 103k
0 votes
0 answers
39 views

Can Bernoulli's Principle be applied to subatomic particles or virtual particles or "the quantum foam"?

If we create a pair of rotary wings like those on a helicopter, and spin them in a vacuum, would it be possible for a virtual particle and anti particle pair to spawn, be split by an approaching wing, ...
Ahkilleux's user avatar
1 vote
0 answers
40 views

Fluid dynamics and venturi

A coworker and I were discussing this issue related to fluids dynamics, Venturi and Bernoulli. We are both a bit rusty with our knowledge, so we know something is wrong in our reasoning, but I need ...
drvx's user avatar
  • 11
1 vote
2 answers
280 views

Bernoulli equation and wind

Bernoulli equation is often used to explain how rooftops are blown off during tornados: the usual explanation is that the high speed of the wind il related to a lower pressure outside the house, ...
Dario's user avatar
  • 172
0 votes
2 answers
122 views

Why does a pitot tube lose its static pressure term?

This is what I mean by a pitot tube: except, the bent tube should be closed, so there is no velocity in the pitot. But why is there no height? It's reflected in the Bernoulli equation that the small ...
SirMrpirateroberts's user avatar
1 vote
0 answers
437 views

Derivation of the exit velocity of water through a hole by force analysis at hole [closed]

As it is the setup with Torricelli's law, consider a hole (of negligible height difference) of area A at a height of h from the top of a cylinder filled with a non-viscous liquid of density $\rho$. ...
Faiyaz's user avatar
  • 35

1
2 3 4 5
12