# Questions tagged [bernoulli-equation]

An equation governing fluid flow for an incompressible steady fluid

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### 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 ...
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### Bernoulli's law for turbulent flow

Is Bernoulli's law valid for turbulent flow for a non-viscous, non-compressible, non-rotating fluid with isoentropic flow? An ideal fluid has coeffieicent of viscosity=0,which implies that it's ...
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I'm studying fluid dynamics and I came up with an example that I find profoundly counterintuitive. I'd like someone more used to this kind of problems to confirm my guess. We have two identical tanks ...
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### Why do proofs of Bernoulli's equation assume that forces on opposite ends point in different directions?

I've read 4 different books and yet nobody explains why forces $F_1$ ($=p_1A_1$) and $F_2$ ($=p_2A_2$) point in different directions. Shouldn't $F_2$ point in the same direction as $v_2$? Since we'...
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### How do I calculate the pressure $p_0$ on top of the water reservoir?

Can anyone help me with this question, I can't get the right answer :-) A water reservoir with depth D=200m, which is placed H=500m above on a mountain. A pipe is placed from the bottom of the ...
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### Why moving train's windows slam shut when another train passes slowly in the same direction?

My question is related to this one but distinct as this case is trains travelling in the same direction. We're familiar with this scenario. You're sitting in train A and another passes at high speed ...
28 views

### Does the pressure inside a rigid container change with velocity?

Say you take a parcel of air and place it inside a rigid container, like a glass bottle. Then put that bottle on a rocket sled and accelerate it to very high speed. Since the air inside the bottle now ...
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### Clarification on Bernoulli's Principle

I need a clarification about Bernoulli's principle. The standard way in which this principle is taught is related to a picture like this one where usually the two sections have different areas and ...
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### What is the lift coefficient of human body?

Assuming we can change angle of attack by changing our hands orientation what is the maximum aerodynamic lift coefficient of human body?
409 views

### Can Bernoulli's theorem be applied to laminar flow?

Since in streamline flow the velocity of a particle at any point is same, Bernoulli's theorem can be applied to streamline flow, but could it be applied to laminar flow?
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### Do viscous and inviscid flow have opposite effects on pressure?

Consider flow through the converging and diverging portions of a tube with varying radius: In inviscid flow, Bernoulli's equation states that velocity at the throat will be the highest, so this area ...
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### Please explain airflows above and below aerofoils for a layman

I have read about the lift of airfoils a lot recently and just want a few things cleared up. When incoming airflow hits a typical cambered airfoil and diverges into “top” and “bottom” air flows, why ...
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### Bernoulli's equation in system of coupled tanks

Problem statement. Consider a system of two coupled tanks as the one shown below Several authors such as Bistak and Huba, 2014, Sim et al, 2017, Khalid and Kadri, 2012, Essahafi, 2014 claim that ...
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### Flow equation for system of coupled tanks

Consider the following system of interconnected tanks: The two tanks have cross-section areas $A_1$ and $A_2$ respectively and the levels of the liquid are denoted by $h_1$ and $h_2$ respectively. ...
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### Is Bernoulli's equation the correct explanation of a curved soccer ball? [duplicate]

I saw a lot of materials supposing that the Bernoulli's equation explains the curvature of a soccer ball: since the ball is spinning, two sides of the ball would experience different velocities, and ...
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### Stagnation pressure on an accelerating surface

The usual stagnation pressure $P_0$ on an object (e.g., a sphere) moving at velocity $U$ is simply $$P_0 = P_\infty + \frac{\rho}{2}U^2$$ where $P_\infty$ is the pressure of the free stream. If ...
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### Velocity of fluid dividing to two different paths [closed]

Fluid of density $\rho$ is flowing through a pipe with area $A$ with velocity of $V$. The pipe divides into two different pipes of area $\frac{1}{2}A$ and $\frac{3}{2}A$ with the right end opened. All ...
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### Can you explain the perfume bottle with the Bernoulli effect?

Someone explained the perfume bottle with the Bernoulli effect: squeezing the bulb over the fluid creates a low pressure area due to the higher speed of the air, which subsequently draws the fluid up. ...
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### Differential pressure sensor applications

I have two differential sensors and in my experiment I wish to measure the air pressure from below and on top of the ball that is levitated by air. These are my 3 possible setups. Considering the 3 ...
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### Is it correct to use Bernoulli's theorem to explain that a disk floats in the air? Should the correct explanation be based on Boyle's law?

In this video, a device is introduced from 1 minute to 18 seconds. After entering the air, the disc at the bottom of the device will be suspended in the air. The video explains that this is because of ...
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### Bernoulli Principle at a Microscopic Level

I'm trying to understand the microscopic mechanisms that justify the Bernoulli principle. I found an interesting discussion on the site of NASA that tries to describe, in a general way, the mechanism ...
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### Height of Fluid in circular motion

I have a question regarding the the height of a fluid spinning due to a drain in a sink. We are following Feynmans Lecture of physics. It should be "easy to see" that, that the height is something ...
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### Pressure Difference in a Rotating Fluid Coloumn [closed]

This question has intriqued me because two methods are generally employed to derive the shape of the surface(paraboloid) . Both methods give equal numerical answer but differ in which of them P or Q (...
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### Why did this table tennis ball rise to the sky? [duplicate]

The nozzle makes the water flow through the upper part of the table tennis ball. If the angle and velocity of the water jet are well controlled, the table tennis ball will rise to the sky. The string ...
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### Why can water be sprayed farther when the pipe outlet is narrowed?

Someone told me: This is because the flow rate remains unchanged, so the flow rate of small diameter pipelines is faster. I don't think this explanation is right: the diameter of the pipe outlet is ...
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### Can Bernoulli Equation be applied across two fluids?

There is a beaker with two liquids placed above another. The beaker has a hole at bottom. So can I use Bernoulli equation across the interface of liquids.
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### Bernoulli equation: how should one imagine $\frac{p}{\rho}$?

The Bernoulli equation states the following $$\frac{1}{2}u^2 + \frac{p}{\rho}+ gz = \text{constant along a streamline}$$ where: $u$ is the fluid flow speed at a point on a streamline, $g$ is ...
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### Is it true that we can speak, sing, and play wind instruments due to the Bernoulli effect? [closed]

Is it true that we can speak, sing and play wind (brass) musical instruments due to the existence of the Bernoulli's Principle ?
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### Outflow velocity from a funnel over time for water without the simplifications made in Torricelli's law

I am trying to calculate the outflow velocity $v_2(t)$ from the orifice of a funnel for water. I am aware of Torricelli's law derived from the Bernoulli equation assuming $v_1(t)\approx 0$ resulting ...
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### Measure static pressure with measuring tubes of different diameter

Assume you have a horizontally placed cylindrical pipe with constant diameter. There is a flow of water, through this pipe. You want to measure the static pressure inside the tube, which should be the ...
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### Feeling low pressure fluid with high velocity

In Bernoulli theorem physics we say that pressure is low when velocity is high but we feel pressure when fluid hits us why?
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### Does the pressure caused by the force exerted on an ideal fluid in a Bernoulli tube decrease over an increasing distance? [closed]

Does the pressure caused by the force exerted on an ideal fluid in a Bernoulli tube decrease over an increasing distance? For example, someone pushes the water with a force from the left in this setup....
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### How pressure and velocity is related? And its effect in cavitation

As per my knowledge I think when velocity increases and discharge is constant,the fluid(liquid) molecules get away from each other in the region where velocity is high and that's why they get ...
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### Bernoulli Experiment- why is the pressure on the left greater? [closed]

Is the Pressure $P_2$ caused by a reaction force to the fluid-fluid collision, or is it the result of the collisions of the water molecules with the walls at the neck of this experiment. The part ...
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### Bernoulli's equation basics

While deriving the Bernoulli's equation, we write the change gravitational potential energy as $mg(h' - h)$ , say where $m$ is the mass and $h'$ and $h$ are the two heights. Why we don't consider the ...
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### Pressure in a moving fluid

I’m having some quite large conceptual difficulties which I hope can be resolved by considering this example. When considering the pressure in the sheet very far away from the impact zone the ...
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### Bernouli equation on streamline

I made my first point at the free surface of the water and my datum to be the very bottom. Part (b) of the question asked to find the velocity of the water in the pipe. I set my second point to be at ...
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### Material Derivative in Fluid Dynamics and Bernoulli Flow

If a fluid flow, such as water, is incompressible then the convective derivative term in the material derivative is equal to zero. How then, in a Bernoulli flow where there is an increase in velocity ...
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In the bernoulli experiment, the pressure on one side is greater than the other, thus the fluid flows faster through the thinner nozzle.In the image, is the pressure created shown correctly? Since ...
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### Question derived from Bernoulli's book “ Hydrodynamica” and his contribution to atomic Theory

Here is the extract from the book Now the weight $π$ is sought which can compress the air $ECDF$ into the space $eCDJ$, the velocities of the particles in either air (the natural and the ...
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### Why does a ping pong ball on a string move toward a running stream of water?

We keep a ping pong ball on a string near a faucet but not directly under it. When we run the water, the ball moves to the stream and sticks there. I'm only interested in the moving part not the ...
### Calculating value of $g$ from Torricelli's law
For my Physics project, I decided to do an experiment with fluids. I'm using the Torricelli's law to verify that the value of acceleration due to gravity on earth is $9.81m/s^2$. I am using the ...