What is pressure energy in Bernoulli's theorem?

[Frigus]

In Bernoulli's theorem I understood the gravitational potential and kinetic energy but I can't understand what is pressure energy.

 

[Delta2]

Static pressure or pressure energy is the term associated with the microscopic kinetic energy of the fluid due to its thermal motion. Dynamic pressure (the term $\frac{1}{2}\rho v^2$ ) is the term associated with the macroscopic kinetic energy of the fluid.
You can read more on this insight it contains two entries on the static pressure.
https://www.physicsforums.com/insights/demystifying-the-often-misunderstood-bernoullis-equation/

 

[jartsa]

Let's say a million liter water tank is pressurized by a "water tower" that consists of an one liter water bottle that is lifted to 100 meters height.

Now every liter in the big tank has pressure energy 1000 Joules. Right?

If we let any of those water liters out, its kinetic energy will be 1000 Joules.

After that one liter of water is let out, the rest of the water has no pressure energy.

Incompressible liquid's pressure energy is its pressure times its volume. The actual energy is not in the liquid, but somewhere else. If the amount of energy somewhere else is small, we may quite easily notice that the liquid does not have as much energy as it's pressure energy suggests, like in that example with the tiny water tower.

If the amount of actual energy somewhere else is large enough, we may get an impression that the liquid actually contains an amount of energy that is the same as its pressure energy. For example if the aforementioned water tower was large enough, then letting those million liters out of the tank would release energy: million * 1000 Joules.

 

[Frigus]

Let's say a million liter water tank is pressurized by a "water tower" that consists of an one liter water bottle that is lifted to a 100 m height.

Now every liter in the big tank has pressure energy 1000 Joules. Right?

If we let any of those water liters out, its kinetic energy will be 1000 Joules.

After that one liter of water is let out, the rest of the water has no pressure energy.

Incompressible liquid's pressure energy is its pressure times its volume. The actual energy is not in the liquid, but somewhere else. If the amount of energy somewhere else is small, we may quite easily notice that the liquid does not have as much energy as it's pressure energy suggests.

If the amount of actual energy somewhere else is large enough, we may get an impression that the liquid actually contains an amount of energy that is the same as its pressure energy. For example if the aforementioned water tower was large enough, then letting those million liters out of the tank would release energy: million * 1000 Joules.

Sir can you elaborate more,I can't understand what you want to say and please can you also tell me why pressure is more in water flowing through larger cross section area as compared to water flowing through smaller cross section area when horizontal height is same of pipe,please tell verbally like the explanation above not with use of mathematics(an request).

 

[jartsa]

Sir can you elaborate more,I can't understand what you want to say and please can you also tell me why pressure is more in water flowing through larger cross section area as compared to water flowing through smaller cross section area when horizontal height is same of pipe

Let's say there is a horizontal narrow pipe in which water is flowing at high speed. That water has lot of kinetic energy. At one point the pipe turns upwards and starts becoming wider. The water starts losing speed and kinetic energy and gaining gravitational potential energy. The pressure of the water does not increase, the water just freefalls upwards. But the water can pressurize something after it has reached a high position. I mean like water in a water tower.When water slows down, its kinetic energy must become some other type of energy, pressure energy it can not become, because pressure energy is not energy in the same way as kinetic energy. The kinetic energy of the water may push a piston, or push a tall water column upwards, or something like that. Note the word "push" there, if liquid is pushing hard on something, then we say that the pressure of the liquid is large, right?

 

[rcgldr]

It may be easier to understand the equation, since all of the terms are potentials, gravitational potential energy per unit mass, kinetic energy per unit mass, pressure energy per unit volume / density = pressure energy per unit mass.

 

[jartsa]

Sir can you elaborate more,I can't understand what you want to say

Let's see what I was saying ... I guess I was saying that pressure energy is an impression ... an impression that fluid has energy: pressure * volume.Maybe a better answer to the question "what is pressure energy in Bernoulli's law" would be just: "it's pressure * volume"

The first answer is maybe more an answer to the question "what is pressure energy really".