Questions tagged [bernoulli-equation]

An equation governing fluid flow for an incompressible steady fluid

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1answer
193 views

Finding velocity of air using Hare apparatus (Bernoulli`s principle )

A horizontal stream of air is blown just above the open end of the hares apparatus with an initial speed "V". The density of air is 1.2 kgm-3.Then the water column rises to 6 cm in the respective limb....
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3answers
252 views

Have I understood the Bernoulli equation wrong?

I just want to solve for the speed of flow of a column of fluid of height $h$ down a vertical smooth pipe. The pressure on the fluid is $P_{atm}$ everywhere. The pressure difference due to gravity is $...
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0answers
90 views

What is the physics behind lifting a submerged bucket out of water?

When you submerge a cylindrical bucket into the water and let all the air out, trying to lift the bucket back out is particularly difficult if we keep it vertical to the surface. In order for the ...
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2answers
144 views

Necessity of increasing pressure fluid to pump up water

The volute casing in the centrifugal reduces the velocity as the fluid flows through it, there by in increasing the pressure , So my question is Why is high pressure and low velocity necessary to ...
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2answers
915 views

Calculating pressure at a point in a pipe?

How do I work out what the pressure will be at a given point in a pipe? I am working with a pipe of diameter 3.5cm at point 1 which then joins to a pipe of 1.4cm diameter at point 2. I know that the ...
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125 views

Bernoulli equation

Can we apply Bernoulli equation to a closed system the same way we apply it to an open system? In an open system increasing the speed of the fluid implies that either the pressure or GPE should ...
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1answer
344 views

Outflow from a tank

Consider a tank with an outflow a the bottom: with the unsteady Bernoulli equation:$$\int_S \frac{\partial v}{\partial t} \ dS+\frac{v^2}{2}+\frac{p}{\rho}+gz=0$$where $s$ is the path between $S_1$ ...
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1answer
47 views

z in incompressible flow equation

I'm trying to calculate the flow rate out of my water tank. On Wikipedia one can find Bernoulli's incompressible flow equation as: $$\frac{v^2}2 + gz + \frac p \rho = \mathrm{const}$$ With $p = \rho ...
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3answers
635 views

Can you power a car by using air pressure [closed]

In my fluid mechanics class, I've learned that a fluid traveling in a pipe will generate a force when the exit area is smaller then the entrance area. Suppose a pipe is attached to a car that will use ...
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0answers
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Bernoulli's principle and gases: not matching real-world experience

Bernoulli's principle is said to be applicable to compressible fluids at low mach numbers, with the pressure substituted by pressure potential, which is linear with temperature (http://www.cns.gatech....
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1answer
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Pumping speed between atmosphere and atmosphere

How to determine flow rate at which air passes through system consisting of an air pump and pipe with a nozzle? In all publications I've found it is important to know the pressure drop, but there's no ...
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Bernoulli's principle: Why an increase in the section area in a hose makes the pressure increase?

I'm having trouble understanding Bernoulli's principle, in particular, why an increase in the section area of a hose increases the pressure? All the answers I read say: " In order for the energy to ...
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1answer
441 views

Model a fountain

I try to calculate the shape of a fountain under the assumptions of an invscid, incompressible fluid, so Bernoulli is applicable. So the task is to get the evolving shape of a cylindrical waterflow ...
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1answer
132 views

Flow over an indentation

I have a question regarding classical fluid dynamics: I want to describe the shape of fluid flowing over an indentation as shown in grey the figure below. I would like to understand which result is ...
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1answer
51 views

Does air with zero viscosity has effect on the motion of a top-spin ping-pong ball?

Normally (in air with a non-zero viscosity), when I give a ping-pong ball top-spin, the air above the ball tends to decrease in velocity while the air on the downside tends to decrease, resulting in a ...
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1answer
182 views

Two reservoirs connected with tube

The question goes like this (picture included): Two large, open reservoirs A and F contain the same liquid. The liquid in A escapes the reservoir through a tube BCD, with a narrowing in C ($D_b = \...
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4answers
2k views

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 hypothosis, it states that energy is constant ...
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1answer
63 views

Why is Bernoullis Isentropic

I have trouble understanding why we classify an inviscid adiabatic incompressible flow along a streamline as isentropic Thermodynamic definition $$dS = dQ/T$$ Adiabatic Invsicid $$dQ =0= dS$$ So ...
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2answers
479 views

Bernoulli's Equation application to find velocity of a leak

I was trying to do my homework. I just want to understand how do I find a velocity of a leak when the area of a given hole should be considered. I can find it if the hole's area is omitted from by ...
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978 views

What is the value of the constant on the right hand side of Bernoulli equation?

I've never used that constant in solving problems. In the questions in my book, I just equate $P_1+\frac{1}{2}pv_1^2+pgh_1$ to $P_2+\frac{1}{2}pv_2^2+pgh_2$ to get the unknowns. But what is the value ...
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550 views

The use of Bernoulli's equation with a siphon and similar problems?

There are a variety of problems in fluid mechanics that involve the flow out off, for example, a beaker. A typical example is that of a siphon shown below: (From wikipedia, by Tomia, CC BY 2.5) ...
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1answer
325 views

channel flow with a linear velocity profile [closed]

The width of a rectangular channel with constant height $h$ perpendicular to the plane is decreaseing from $b_1$ to $b_2$. The inflow velocity is increasing linear at point 1 from $0$ to $u_1$. The ...
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1answer
189 views

Application of Bernoulli Theorem

Can we apply Bernoulli theorem to two different fluids? I tried to visualise this problem in the following way: Let's imagine a container having two fluids , one of some arbitrary density twice the ...
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1answer
4k views

Temperature Changes in a Venturi Tube

If we have a gas (like air) moving through the narrow throat of a Venturi Tube, do we get a lower temperature to go with the lower pressure at that throat? Here's what I've worked out: For Venturi ...
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2answers
662 views

Bernoulli equation, energy conservation and unsteady flow?

The Bernoulli equation for unsteady flow is given by: $$\newcommand{\p}[2]{\frac{\partial #1}{\partial #2}} \newcommand{\f}[2]{\frac{ #1}{ #2}} \newcommand{\l}[0]{\left(} \newcommand{\r}[0]{\right)} \...
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Comparision of P= F/A to Bernoulli's principle

According to $P= \frac{F}{A}$, pressure reduces as area increase. But according to Bernoulli's principle $P$ reduces as velocity increase. But in nozzle velocity at reduced area is high and ...
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1answer
248 views

Extending the Bernoulli Equation to Rotation

The standard Bernoulli Equation has three terms on each side, a kinetic energy term, a potential energy term and a pressure term. I've never seen an extension of this to also include a rotational ...
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2answers
631 views

Necessary and sufficient condition for Bernoulli's theorem

For an ideal fluid, if the vorticity is $\vec{\omega}=\nabla \times \vec{v}$, then Euler's equations can be rewritten as: $$\rho \dot{v}_i = \rho \epsilon_{ijk} v_j \omega_k - \frac{1}{2} \rho \...
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1answer
480 views

Torricelli's law generalized

Since we never faced in a deep way the dynamics of fluids, and related subjects, I was wondering about this: as a very particular case of Bernoulli's theorem, we get Torricelli's law for some fluid ...
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Deriving Bernoulli's equation from Navier-Stokes equation [closed]

I can prove the Bernoulli equation in an elementary way (that is, using the conservation of energy law). But I was asked to derive the Bernoulli equation from the Navier-Stokes equations, and I have ...
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1answer
732 views

Static Pressure in a Venturi vs a Free stream

We seem to have two conflicting measures of pressure in a Venturi siphon open to the atmosphere,$\hspace{100px}$. Bernoulli's principle says that, by energy conservation for a steady flow $Q$, the ...
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3answers
522 views

Can I apply $\rho g h$ in fluid dynamics

The pressure in a fluid at a depth $h$ below the free surface (due to liquid itself) is $\rho g h$ where $\rho$=density of the fluid. Does this apply to case when the liquid is in motion also by which ...
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1answer
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Physics and Oil pipelines

Is there a concise source or reference that details the physics that one deals with in the construction and/or operation of an oil pipeline. This is for a Project-based Learning Unit in HS Physics.
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4answers
364 views

Pressure in Bernoulli's Theorem

I am not sure about what does pressure mean in this theorem.Is it the pressure applied by the pipe when the fluid flows in it or something else?Please explain clearly.
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583 views

Torricelli's Law and the Continuity Equation: why is volume flow rate allowed to increase if we change the area of the exit hole?

Earlier, I asked this question: Bernoulli's equation + Torricelli's law: does the speed of the fluid change if we change the area of the hole but not the height? I now understand: in summary,...
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2answers
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Bernoulli's equation + Torricelli's law: does the speed of the fluid change if we change the area of the hole but not the height?

Let's say we have a Torricelli's Law apparatus, where, in the picture below, we are concerned about the velocity v coming out of the bottom-most spigot that is a height h below the top of the water. ...
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1answer
756 views

Why is velocity inversely related to pressure in a flow?

I've seen the equations that give this relationship, and I understand the math and have seen it worked out in problems. But I don't have a qualitative, conceptual grasp on the relationship. Is the ...
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2answers
467 views

How to consider the pressure and the potential energy when use Bernoulli principle?

Suppose a situation where we are going to apply Bernoulli principle to find the velocity of a water stream leaving at the bottom of a large lake. When we apply the Bernoulli theory, we consider a ...
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1answer
257 views

Problem in understanding the derivation of Bernoulli's principle

I am trying to understand the derivation of Bernoulli's principle by using the conservation of energy. This is the sketch I will be referring to. I am stuck in understanding a seemingly basic step in ...
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305 views

Mass Flow with Stagnation Pressure/Temperature

I saw in many papers and books that when a compressible gas flows through an orifice, the mass flow is calculated using the stagnation pressure and temperature. That is, $\dot{m} = \frac{P_o \cdot A \...
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2answers
383 views

Shape of tank for which water level falls at constant velocity [duplicate]

Greeting, I am working on a problem that involves optimizing the shape of a tank so that the level drops at a constant rate. Problem and my attempt Working on the problem, here is what I know. There ...
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2answers
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Bernoulli equation assumptions (laminar and irrotational flow)

In some books I find that, among the assumptions for proving bernoulli equation using work-energy theorem there are: stationary flow perfect fluid ($\rho=$constant, $\eta=0$) laminar flow But if ...
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1answer
54 views

How to explain rise of the disk?

The situation is as shown above. Now, to explain why the bottom disk rises, I applied Bernoulli's Equation at a point just below and just above the disk.The pressure difference hence obtained should ...
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3answers
395 views

Centrifugal Pump Head

What is pump head? and how is it different from the difference in elevation between the suction and delivery reservoir? Also why must the kinetic energy of the fluid leaving the pump must be least? I ...
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57 views

If a gas in a pipe is travelling from a large cross sectional area to a smaller cross sectional area, will it cool down?

So in a problem like the one in the link below: https://www.youtube.com/watch?v=5W2JgWKiYoU Velocity increases, so pressure must decrease, thus the pressure at the small part of the pipe will be ...
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1answer
704 views

Bernoulli equation in leaked pipe

I'm currently trying to figure out how to apply Bernoulli equation into a leaked pipe, especially to find the change of pressure before and after a leak appeared. From what I found know, Bernoulli ...
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1answer
951 views

Time to empty conical tank to half of its original height

A hollow cone of height $h$ and diameter $d$ at the base is held with its axis vertical downwards and is filled with water. A small circular hole whose diameter is $1/n$ th that of the diameter of the ...
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1answer
389 views

Does increase in dynamic pressure influence temperature growth?

Please imagine a situation where we stir cool water. As far as I remember, this process should increase temperature of the water (faster than heat exchange with air around would do). In essence, by ...
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1answer
2k views

How to calculate pressure loss in a water pipe with a leak?

I'm currently writing a paper on designing a system which can detects if there's a leakage between two certain point of water pipe. I'm using MPX5100 differential pressure sensor as the measurement ...
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45 views

how does it come that atmospheric pressure does not cut off blood flow in blood vessels? [duplicate]

We know that atmospheric pressure is 760mmHg, whereas blood pressure in blood vessels is somewhere between 80 to 120 mmHg. As outer pressure is higher than inner so shouldn't it cut off the blood flow?...