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Questions tagged [bernoulli-equation]

An equation governing fluid flow for an incompressible steady fluid

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What is Pressure Energy?

While deriving Bernoulli's Theorem, our teacher said that the sum of KE, PE and Pressure Energy per unit volume remains constant at any two points. $$P + \rho g h + \frac{\rho v^2}{2} = \text{...
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4answers
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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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4answers
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How much effect does the Bernoulli effect have on lift?

I understand that the Bernoulli effect is a flawed explanation for the cause of lift, and does not cause much at all, but how much? Is there any experimental data on the force caused by the ...
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1answer
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Bernoulli's equation and reference frames

So I was thinking about this while driving home the other day. I've never been quite clear on why when you drive with the windows down air rushes into your car. I thought this might be explained by ...
11
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1answer
1k views

Pipe in a flowing river problem

I'm working on a certain problem in fluid mechanics, which isn't really my strongest area. The problem is as follows: Curved pipe is partially submerged in a flowing river so that one end is pointing ...
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2answers
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Problem understanding basic sail mechanics

I am trying to understand the physics behind a single sailed boat. I have read the following questions Sailing against the wind. Is this a fair model? What exactly is the 'lift' of a ...
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9answers
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Are eductors working on the Bernoulli principle?

This is a picture of an eductor. The wikipedia article claims that it works on the Bernoulli principle. The Bernoulli principle is famous due to the misconception about how aeroplanes fly and because ...
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3answers
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Does continuity equation hold if the flow is accelerated?

I'm Studying the streamline flow, specifically the continuity equation Bernoulli's Principle. Consider the following system where a liquid flows through the pipe of a uniform area of cross section A,...
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5answers
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Why does it seem as if big vehicles “attract” mine when I drive close to them?

When I drive a car at high speed and when I am near to another big car (like a van, or transport vehicle) I feel an attraction to or something push me toward the other big car. What's the physics in ...
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5answers
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What is basically the difference between static pressure and dynamic pressure?

What is basically the difference between static pressure and dynamic pressure? While studying Bernoulli's theorem, I came before these terms. The law says: When the fluid flows through a small area,...
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3answers
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What exactly is the 'lift' of a sailboat as explained by Bernoulli principle

I have heard that when a sailboat is sailing against the wind, it operates on the principle of 'lift'. I am unable to understand the explanation, based on Bernoulli principle, completely. My question ...
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3answers
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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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3answers
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Is Torricelli's law “wrong” for big holes? - Tank draining problem

Consider a tank full of water with a constant cross-sectional area A1 placed vertically on the ground. Now someone drills a hole of an area A2 in the bottom of the tank, and the liquid starts escaping ...
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1answer
792 views

Intuitive meaning of a special case of the Bernoulli equation

In the Bernoulli equation, if $h$ equals zero, it reduces to $$P_1+\frac12\rho v_1^2 = P_2+\frac12\rho v_2^2$$ The equation does not have an intuitive meaning other than the fact that it is a bare ...
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3answers
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Bernoulli's principle on a curve ball

I've seen a few excellent answers here on the Magnus force, which explains why balls with a spin will curve. However, my intuition is still telling me that the Bernoulli's principle would push it the ...
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1answer
740 views

Question about the Bernouilli equation

There are some things I encountered, studying the Bernouilly equation, that I don't understand. I was studying in the following book: http://www.unimasr.net/ums/upload/files/2012/Sep/UniMasr....
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1answer
679 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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4answers
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Why are roofs blown away by wind?

Whenever there are high winds, such as in storms, thin metal roofs on sheds as well as concave roofs on huts are sometimes blown away. One explanation provided to me said that the higher velocity of ...
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2answers
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Static vs Dynamic pressure

According to Bernoulli's law, the narrower the tube where the fluid is flowing the lower its static pressure and the higher its dynamic pressure. Does this make any difference? If the dynamic pressure ...
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2answers
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Why can Bernoulli's equation be applied along two different streamlines for an irrotational flow?

The following is written in Physics by Halliday, Resnick and Krane (5th ed.). $$p + \frac{1}{2} \rho v^2 + \rho g y = \mathrm{constant}$$ Strictly speaking, the points to which we apply ...
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2answers
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Is Magnus effect a corollary of Bernoulli principle?

Magnus effect is commonly explained using Bernoulli principle. However, taking the lift on a rotating cylinder as an example, the velocity difference is caused by the extra work done by the rotating ...
5
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1answer
284 views

Can the continuity equation and Bernoulli contradict each other?

Please bear with me - I'm a lapsed mathematician and I'm self-studying these concepts. A question asks the following: Water flows in a pipe of diameter 5 m at a velocity of 10 m/s. It then flows ...
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1answer
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How does an atomizer work? [duplicate]

Will someone please explain how a basic pump atomizer works? I have a feeling it has something to do with pressure and the Venturi effect, but I'd really like to know precisely how they work as ...
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2answers
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Inverted U manometer

I have some doubts on inverted U manometer. In the picture there is one U inverted manometer, the space above the liquid in the manometer is filled with air which can be admitted or expelled through ...
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4answers
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Is a causal relationship implied by Newton's 2nd Law?

Throughout my time learning physics I have been imbued with the notion that forces cause accelerations, period. Accelerations don't cause forces, and they aren't merely correlated phenomena. By ...
4
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1answer
784 views

Fuel tank draining [closed]

A cylindrical fuel tank is being drained from the bottom as in this picture : Conservation of flow rate : $v_A = \frac{S_B}{S_A}v_B = \alpha v_B$ Assuming that $z_B = 0$, Bernoulli's theorem states ...
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3answers
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A paradox when I was deriving Bernoulli's equation from energy equation

I am having an exercise: Deriving the Bernoulli's equation ($\space p_1+\frac{1}{2}\rho V_1^2 = p_2+\frac{1}{2}\rho V_2^2 $ ) from the energy equation: $$\rho \frac{D(e+V^2/2)}{Dt} = \nabla(pV)$$To ...
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3answers
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Why does Bernoulli's equation only apply to flow along a streamline that is in viscid, incompressible, steady, irrotational?

I am learning about hydrofoil on this website. In a later video I watched, I learned that in the process of deriving Bernoulli's equation, $$constant=P/d+gh+1/2v^2$$ has to multiplied through by ...
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2answers
279 views

Torricelli's Law and Variable Density

I wish to explore a slight modification of a well known result found in several physics texts - Torricelli's Law of Efflux. The most common problem on the above result has the following setup: The ...
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2answers
1k views

What physically happens to decrease the pressure when the velocity of a fluid increases

Neglecting any special cases and generally speaking, when the velocity of a fluid increases the pressure decreases (Bernoulli's principle). This can be observed in experiments like "air over paper" ...
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1answer
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Solve unsteady state Bernoulli equation for flow in a pipe

I am an engineer studying an unsteady-state flow through a pipe. The Pipeline has been cleanly cut into two halves, without deforming the cylindrical form of the pipe, exposing the contents to ...
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1answer
2k views

Why is the dynamic pressure not a vector quantity? [duplicate]

I understand that static pressure is a scalar quantity as it acts equally in all directions, then by the same reasoning dynamic pressure should be a vector quantity as it only can be measured by ...
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1answer
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Compressible fluid flow through a branched pipe junctions

Backdrop: Designing a dust extraction system (LEV) with a branched junction. What principles allow for the calculation of volume flow rate and pressure at the inlets if the volume flow rate and ...
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1answer
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Bernoulli's Equation for flow of gas and changing area

My task is to determine the size of piping needed in a system. In this system, hydrogen gas flows horizontally in a $\frac{3}{4}\,\mathrm{inch}$ pipe and into a vertical pipe of a larger diameter. My ...
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3answers
130k views

Relation between water flow and pressure

Is there any equation that states the relation between pressure and water flow. I.e. Let's say that in 1 hour with 8mca (water collum meters) pressure I obtain 50m3. What if (giving the same ...
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4answers
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Why does moving air have low pressure?

According to Wikipedia lift in an aircraft is due to an area of low pressure formed above the wings of an aircraft due to the fast moving air there. So why exactly is an area of low pressure created ...
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2answers
308 views

Vasodilation decreases blood pressure

Okay it should make sense intuitively, but Bernoulli's principle says that a higher cross sectional flow area means less velocity which means higher pressure! I also read in a related post that ...
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2answers
62 views

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 ...
3
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1answer
114 views

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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2answers
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How is work done in a nozzle zero

Fluid flow gets accelerated through a nozzle. As the flow is accelerating( and there is a change in momentum). According to Newton's second law we can say a net force is acting on the fluid through a ...
3
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1answer
90 views

Floating sketchpen?

This post is about an experiment of mine , which was for me, remarkably interesting! Why do I post it here? I'm interested in knowing the physics behind this. MATERIALS USED A light weight ...
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1answer
405 views

Feynman's derivation of Bernoulli (part of it)

OK, so what's up with the $\Delta M$ here? I don't get it. In fact, my textbook doesn't even put it in. I don't think it is a type-o because he continues on with the explanation. If anything I got it ...
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2answers
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Bernoulli's equation for flow between cylinders

Let's consider the situation bellow noting that the water cylinders aren't equal and there will be water flowing to the right (As indicated by the arrow) Taking Bernoulli's equation at the tip of the ...
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1answer
269 views

Deriving the expression for the height of liquid in a cylinder spinning on a turntable using Bernoulli's principle

When a liquid in a cylinder is spun on a turntable, it will experience a vortex or whirlpool effect, as shown below: I have seen and understood a proof for the value of $h$ by taking the motion of a ...
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2answers
582 views

Bernoulli equations when different fluids and volumetric flow rates are involved

I have doubts on the use of Bernoulli equation when multiple volumetric flow rates are involved. Consider for istance the device in picture. Water flows in the main tube, while in the tank below ...
3
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1answer
389 views

Is the change in cochlear potentials dependent on perilymph velocity? [closed]

context: This question may appear to be off topic because it is about the biological particulars of the human ear. Physics can solve abstract models inspired by living organisms, but it is biology ...
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1answer
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Static pressure of free air stream

One of the common misunderstandings regarding Bernoulli's principle is that, in general, "faster moving air has lower pressure". Bernoulli's principle can only be applied to asingle streamline in ...
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0answers
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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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0answers
3k views

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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2answers
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Can the lift generated by a helicopter be justified using Bernoulli theorem? [duplicate]

When the shaft of the helicopter rotates, it creates a low pressure. Because of the low pressure, the helicopter lifts. Is my understanding that this is just an application of Bernoulli's theorem?