# Questions tagged [bernoulli-equation]

An equation governing fluid flow for an incompressible steady fluid

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### 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 ...
1answer
30 views

### Magnus effect without windspeed

Canagnus effect take place if windspeed is 0 ? Lets assume that our frame of reference a place an earth (e.g. soccer pitch) .We measure the windspeed and we find it zero.But if we make a knuckleshoot ...
0answers
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### Bernoulli principle and relativity [duplicate]

Bernoulli principle has many applications like airplanes take off etc. But when we apply Bernoulli's principle we dont refer the reference frame in which we measure the velocity of air for example. ...
2answers
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### Applying Bernoulli's equation in fully developed viscous pipe flow

Can we apply the inviscid Bernoulli equation $$\frac{P}{\rho} + \frac{1}{2}V^2 + gz = constant$$ along the center line of a fully developed pipe flow? I think we can since the shear stress along ...
0answers
60 views

### Do the height of the water columns decrease when we push pistons with constant speeds in this venturi pipe?

Let say when the pistons are kept stationary the height of the water columns are h. And we start exerting extra force on the left piston in figure, and the pistons are moving with constant speeds. ...
0answers
54 views

### Proof that pressure rises in a fixed control volume

I am looking for a proof using Bernoulli's equation that that for $Q=(Area)(Velocity)$, $Q_{in}>Q_{out} \Rightarrow P_{inside}>P_{outside}$. I read that for a computer, if the case fans blow a ...
1answer
96 views

### Principle of Lifting of an Aircraft [duplicate]

While using the Bernoulli's equation to deduce the upthrust on an aircraft , a statement is always made that The air particles going above th wing have to cover a greater distance in same time than ...
1answer
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### Increase Air Speed at outlet

I have a set up that inflates a rubber jacket in order release the metallic rings from underneath it. I am currently having issues with not having enough pressure (force) at the outlet to inflate the ...
1answer
65 views

### How to use General Energy Equation in parallel pipes?

My question comes from exercises with parallel pipes such as this. I know that to analyse internal flow, we use general energy equation which origins from the 1st law so each time we apply it we are ...
1answer
51 views

### Limitations of converting pressure into kinetic energy

Bernoulli's principle states that an increase in the kinetic energy of a fluid occurs simultaneously with a decrease in pressure for isentropic processes. What then limits us from converting all of ...
3answers
186 views

### Pressure in speed of efflux

While describing speed of efflux, using Bernoulli equation, we use value of $P$ at both openings as atmospheric pressure. Why don't we use $P_\text{atmosphere}+\rho gh$ for $P$ at bottom opening?
2answers
209 views

### What does the term $P$ represent in Bernoulli’s equation?

$$P+\rho gh+\frac{\rho v^2}{2} = C$$ Does the $P$ here stand for the hydrostatic pressure exerted by the fluid on its surroundings or the pressure that’s exerted on a given portion of the fluid? I ...
0answers
76 views

### Bernoulli's principle for a liquid with non uniform density

Consider a cylindrical container (section $S$, height $H$) which contains a liquid with non uniform density. Let $z$ be the axis along the height of the container ($z = 0$ indicates the top of ...
2answers
145 views

### Pressure distribution around an aerofoil

Some notes that I'm reading right now show a picture of the distribution of pressure around an aerofoil with zero angle of attack. The notes say that the pressure is identical at the top/bottom ...
1answer
74 views

### Flow through a hole in a sphere

I have a sphere of diameter $D$ (radius $R$) with a small hole of diameter $d$ (radius $a$) in it, with air flowing through the axis of the hole: I am trying to estimate the drag force due to ...
1answer
28 views

### Deriving relationship about water not falling down from a hole under a fast flowing stream [closed]

A gutter is tilted from an angle of $\theta$ with respect to earth. There is a hole on the gutter from a distance of $l$ (m) from the top of a gutter. What is the speed of the water that should flow ...
2answers
279 views

### Relationship between blood pressure and cross sectional area of blood vessel

What is the reason why blood pressure and a larger cross sectional area of blood vessel cause a lower blood pressure and vice versa? This question is related to another question I found here. The ...
0answers
61 views

### Why water doesn't drop down from a hole when a stream of water travels fast over it?

why water doesn't fall down from hole on the roof when its raining heavily (water moves fast on the roof) ? Can I know the theory behind this and the factors affecting?
2answers
249 views

### Modeling water flow between two tanks

To familiarize myself with concepts from my system modeling class, I have posed myself the following problem, which I have been struggling with for a good while now. I am an absolute physics beginner, ...
1answer
45 views

### Effect of pressure when drying wet clothes in a windy environment

When we hang wet clothes outside, they dry faster if it is windy. The wind causes forced convection and removes the air saturated with vapor, and the rate of evaporation does not decrease much in ...
0answers
63 views

### When exactly can the concept of stagnation pressure be applied?

Although I've attached a homework problem here, I'm only using it for reference for a conceptual question on stagnation pressure. From my understanding, in the photo attached above, the pressure at ...
1answer
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### Why that Bernoulli function contains many streamlines and vortex lines but not only singular streamlines?

I know that for a stream line inside the gradient part equal to a constant. But when we consider the fluid is rotational which the velocity cross product vorticity not equal to zero. So how can we ...
2answers
83 views

### Water Height of a centered-hole tank [closed]

Here's the problem. A large tank is filled with water for a height $H$. In the center of the tank a circular hole with a radius $R_1 = 10$ cm is made from which the water flows vertically. We can ...
1answer
61 views

### What is the physical meaning of static and velocity pressure?

According to Bernouli's equation, the static pressure inside a pipe with streamline and steady flow decreases with fluid's velocity. One explanation to rationalise this phenomenon is because velocity ...
0answers
44 views

### Computing the velocity of fluid along the length of a cylinder

I am modelling the flow of fluid through a cylinder of length L.The cylinder is divided into three segments(each segment of length L/3), there are four nodes(i=0,1,2,3). I'm trying to compute the ...
1answer
69 views

### Carburetor, throttle, airflow

It is said that the less we open the throttle the speed in a Venturi tube inside the carburetor is slower, thus less reduction in pressure and less fuel is being sucked from float chamber, however, ...
0answers
55 views

### Venturi effect on molecular level

Is there a good explanation why the pressure becomes lower on the narrow part of the venturi pipe? I'm not interested in the newton explanation or pressure differences explanation. I want to ...
2answers
194 views

### Bernoulli's Effect on Blood Pressure [closed]

What is the impact of height, let's say being on top of a 4,000 m high mountain, on blood pressure / flow velocity given Bernoulli's Equation?
0answers
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### Bernoulli principle

I've been trying to deduce the Bernoulli's theorem but i have a few problems Why is it restricted to a streamline? Thank you very much
4answers
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### Bernoulli's equation and negative pressure

Here is Bernoulli's equation: $$P_{{1}}+1/2\,{\rho v_{{1}}}^{2}+\rho {\it gy}_{{1}}=P_{2}+1/2\,{\rho v _{{2}}}^{2}+\rho {\it gy}_{{2}}$$ A friend of mine was looking at some lecture notes today and ...
1answer
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### Does venturi effect violate pascal's law?

If we use Bernouill's law to compare pressure between point 1 and point 2, we find that P(2)gdH=0, we conclute P(2)=P(1). I must have made a mistake but where is?
2answers
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### Is it possible to create circulation of water in bypass pipe without water pump?

There is a pipe of 32mm in diameter. Water flows from left to right. There are two branches in that pipe. To one of them connected input of water heat exchanger, to another - output of water heat ...
1answer
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### How to find velocity of water flow and $Q$ if I know static pressure at the end of the pipe of known diameter?

I have a pipe. At its end I have mounted pressure meter. Of course there is no circulation. Water pressure meter is a kind of stopper for water. I know diameter of the pipe, and I know its pressure in ...
2answers
161 views

### What do I need for a good flow of water from a faucet: velocity of water or pressure?

I can't understand one thing. A good flow of water from bath faucet requires a good velocity of water or a good pressure? For example, I have a crane that has a pipe diameter of 1 inch. The better the ...
2answers
233 views

### Is equation of continuity valid even against gravity?

Consider a tube having variable cross section and is placed vertically. The upper part it has a cross section of $4\ \mathrm{mm^2}$ and the lower part has a cross section of $2\ \mathrm{mm^2}$. If ...
1answer
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### For a fluid travelling in a tube, if the pressure is decreased at a constant temperature, how does it affect the velocity and fluid density?

I am interested in understanding the relationship between pressure and velocity, as well as pressure and fluid density. I know that the principle of Bernoulli states that there exists a relationship ...
2answers
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### Work-energy theorem and Conservation of energy formula

We have $$W_{net}=\Delta K \quad(work-energy\; theorem)\tag{1}$$ And also $$W_{net}=\Delta K +\Delta U \quad(Conservation\;of \;energy \;formula)\tag{2}$$ How's that happening? In proof for bernoulli'...
0answers
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### Eulerian approach to control volume and energy conservation equations

After refreshing/researching the Eulerian approach to conservation equations for mass, energy, momentum I am struggling with understanding the partial derivative term that I believe represents ...
1answer
446 views

### Energy loss in Fluid flow

In a constant diameter, ground level pipe of substantial length to reflect a pressure drop of dP, how would the loss of energy be accounted for? The assumption would be that kinetic and potential ...
2answers
302 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 ...
1answer
300 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 ...
0answers
49 views

### What is the maximal velocity of air blown through a straw?

If an adult can buildup a pressure of 9kPa when blowing air through a straw then the pressure drop will be 0.5*1.25*v^2. But if I want to compute the air volocity in the straw how can I know the ...
1answer
313 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 ...
3answers
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### Where is the limitation within the assumptions leading to Bernoulli's law?

Lets say there is a horizontal pipe $P_1$ of diameter $d_1$, connected to another horizontal pipe $P_2$ with diameter $D_2$. The fluid inside shall be considered as "ideal" without viscosity and ...
1answer
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### Doubt in derivation of Velocity of efflux (Torricelli's theorem)

To find the velocity of efflux of fluid from a hole in a simple cylindrical container we use the Bernoulli's equation. $$P + ρv^2/2 + ρgh= constant$$ For our specific case we take the pressure at ...
3answers
369 views

### How does the lift force of an airplane work? [duplicate]

At first I thought that the lift force of an airplane wing came from the buoyant force of the air. Thus we can calculate it's lift force using $$F_b={\rho}gV$$ However, that does not seem to be ...
1answer
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### Is there something similar to Bernoulli effect with electricity?

There are many parallels between fluid dynamics and electricity. Is there a thing similar to a Bernoulli effect with electricity? For example, would you see a decrease in voltage as the conductor ...