Kinetic energy of fluid + collision

In summary, the conversation discusses the concept of kinetic power in fluid dynamics, specifically when a fluid collides with a solid object. The question posed is whether all molecules in the mass flow rate ρAV collide with the solid or if it is more similar to a collision between two solid objects. The conversation also touches on the relationship between velocity, surface area, and mass flow rate.
  • #1
tonyjk
227
3
Hello,

When a fluid is flowing, it has of course a kinetic energy and thus we can define kinetic power equal to ρAv v is the velocity and A is the surface of a solid for example. I have a question (maybe it is a strange one) : When fluid collides with a solid, do all the molecules collide with the solid or some of them or we cannot know?

Thanks
 
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  • #2
When you put a penny in a river, does ever molecule of water collide with the penny?
 
  • #3
Vanadium 50 said:
When you put a penny in a river, does ever molecule of water collide with the penny?
I am talking about the quantity ρAv
 
  • #4
tonyjk said:
I am talking about the quantity ρAv

Which is not a volume.
 
  • #5
Vanadium 50 said:
Which is not a volume.
how it is the mass of the volume Av
 
  • #6
tonyjk said:
how it is the mass of the volume Av

I don't understand that. It is not a sentence, and Av is neither a mass nor a volume.
 
  • #7
Vanadium 50 said:
I don't understand that. It is not a sentence, and Av is neither a mass nor a volume.
Velocity multiply by surface you will get m3/s so it is a volumetric flow rate. If you multiply by ρ(rho) we will get mass flow rate.
 
  • #8
We're not getting anywhere. Why not pose your question again, as quantitatively as you can: using expressions for as many terms as you want to compare as possible. Keep in mind that quantities that you want to compare need to have the same dimensions.
 
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Likes tonyjk
  • #9
When we say that a fluid has a kinetic energy equal to 1/2 M V2 colliding with a solid, usually we talk about the power of the fluid that is equal to 1/2ρAV3 where V is the velocity of the fluid and A is the surface of the solid. My question is: in the quantity ρAV (mass flow rate), all the molecules in this mass flow is colliding with the solid or it is just like a collision between two solids?
 

1. What is kinetic energy of fluid?

Kinetic energy of fluid is the energy that a fluid possesses due to its motion. It is the energy that is required to accelerate a fluid from rest to a certain velocity.

2. How is kinetic energy of fluid calculated?

The kinetic energy of a fluid can be calculated by using the formula KE = 1/2 * mv^2, where m is the mass of the fluid and v is the velocity.

3. How does the velocity of a fluid affect its kinetic energy?

The kinetic energy of a fluid is directly proportional to the square of its velocity. This means that as the velocity of the fluid increases, its kinetic energy also increases.

4. What is the relationship between kinetic energy of fluid and collisions?

In a collision between two fluids, the kinetic energy of the fluids is transferred from one to the other. The total kinetic energy of the system remains constant before and after the collision.

5. How does the density of a fluid affect its kinetic energy during a collision?

The density of a fluid does not directly affect its kinetic energy during a collision. However, a more dense fluid may cause a greater change in the velocity of the other fluid, resulting in a larger transfer of kinetic energy.

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