# 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.

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### 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 ...
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### 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). ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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1 vote
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### 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 ...
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### 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, ...
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### 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,...
1 vote
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### 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 ...
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### 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?
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### 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 ...
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### 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'...
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### 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 $P_A=P_B=P_0$ = ...
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### 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
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### 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 ...
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### 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, ...
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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 $\rho$. ...