# 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.

566 questions
Filter by
Sorted by
Tagged with
1 vote
20 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-...
20 views

### How can I make sure that my outflow rate is the same as my inflow rate? [closed]

I have a basin that is 110 mm wide, 200 mm long, and 15 mm deep. The walls are 2 mm thick. It has water being pumped into it at a rate of 0.1078 gpm from the side. In order to ensure that this pan ...
25 views

### Model for exhaling through a hose into a water tank [closed]

I am looking for a realistic model to describe exhaling through a hose into a water tank. The person is outside the tank at normal pressure and breathes through the hose into the tank against a ...
644 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 ...
6 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 ...
1 vote
32 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) ?
278 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 ...
20 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 ...
80 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 ...
26 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 ...
68 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 ...
33 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, ...
1 vote
36 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 ...
1 vote
105 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, ...
55 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 ...
26 views

### To find the speed of a beaker that is ejecting fluid, using Bernoulli's equation

I wish to mathematically model the speed of a beaker which is ejecting fluid out of a tiny orifice (area a) at the bottom, as a function of time, t. [I'll assume the surface area of the beaker to be A ...
1 vote
57 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 $\rho$. ...
1 vote
87 views

### Why are these balloons attracted when there is air blowing between them?

There are two party air balloons pending by their own weight through strings. When we blow strongly in the pipe, they move to approximate from each other as shown in the picture. It seems that the ...
30 views

### Is stagnation pressure the limit on pressure you can get out of a flow without adding more energy?

I have a complex area of a pipe system where I'm not totally sure all that's going to be going on in terms of turbulence and compressible flow, though I would still like to verify that nothing in the ...
83 views

### Why does Bernoulli's principle say higher water velocity is at a lower pressure? [duplicate]

I'm reading Khan Academy which says in this picture: That P1 > P2 since P1's positive work is greater than ...
1 vote
49 views

### In the derivation for Poiseuille’s formula for laminar flow through a cylindrical tube the speed parallel to the central axis increases. Why?

To start off with, I'm a first year undergrad and do not have much knowledge at all about fluids, and am simply working with context that has been provided to me from a lab script (of a lab I did not ...
34 views

### Bernoulli's Equation [duplicate]

I have a doubt that why does bernoulli's equation doesn't work in some cases, even after considering streamline flow, for example consider the system in image, we can apply A1v=A2v' , where A1 and A2 ...
75 views

### Why when I suck water of a tube and connect that tube to a lower tank water keeps flowing towards lower one? (syphon)

lets say I suck water of a tube then put that tube in a lower tank why does water keeps flowing even when there is a component of gravity up. my guess is that by bernullis law I add up some speed in ...
123 views

### How can I mathematically model the entrainment of air through a window?

The Problem Suppose I have an open window with an area $A$, and a uniform wind source (a fan) pointing towards the window, positioned at a distance $s$ away from the window. At the exit of the fan, ...
55 views

59 views

### Concentrated and distributed pressure drops in a pipe

In a pipe, the Bernoulli equation can be expressed as: \begin{equation} {\Delta_2^1 \left(P_\mathrm{dynamic} + P_\mathrm{static} + P_\mathrm{hydrostatic} \right) + w_\mathrm{pumps} - w_\mathrm{... 41 views

### Why does the speed of efflux depend on container pressure in rocket propulsion?

I know that the speed of efflux, $v_{efflux}$, is given by the application of Bernoulli's principle. The formula for the speed of efflux as given in my textbook, Physics—Part II, Textbook for Class XI,...
56 views

### Applying Bernoulli's Equation to siphon system giving negative value

Consider the following situation when a tube is filled with water and inserted in a beaker where : h = height of beaker y = height at which opening of tube is $\rho$ = density of water Now, I want to ...
1 vote
61 views

### Really can we exploit Bernoulli theorem to study Pitot tube?

One of the assumption in proving Bernoulli theorem is that motion is laminar, the presence of turbulence will destroy the proof. Now, I can't believe that inside a Pitot tube the aren't turbolences: ...
29 views

### Static pressure at orifice can be negative?

Because of the vena contract, the total pressure and absolute pressure drops at the orifice. I know the total pressure and absolute pressure cannot be negative, but can the static pressure be negative ...
78 views

### Bernoulli Theorem Proof Doubt

In the wikipedia page when I was reading the proof of Bernoulli Theorem, In the work done by pressure force why only work on two parts of fluid are considered? Why mass displaced are equal the mass ... 20 views

### Questions about Bernoulli Equation in moving reference frames paper

I am trying to understand this paper (PDF). I think I follow until equation (6). The authors say that after cancelling terms, you get out the standard Bernoulli equation "which thus only holds ...