Results

[Anonymous]

Hi 

I have a doubt regarding the data obtained after the simulation by testing a simple horizontal pipe of diameter 10 mm. Rehearsing with the Simulation CFD, I have noticed that the speed of the fluid is not kept constant in an incomprehensible fluid such as water. And it is something that I can not solve, because according to the results, the speed increases me from 10 mm / s to almost 18 mm / s, and should not because in a pipe of the same section must be satisfied that Q = V * A (Equation continuity). Therefore, the velocity of the fluid should be constant.

Fluid: Water (default) 

Solid: PVC

boundary conditions:

- input Velocity: 10 mm/s

- output Pressure (gage): 0 Pa

How Can I solve the problem. 

Since in a pipe of constant section the speed of the fluid must be equal, and in any case, that due to the losses of load the speed slows down.

[Anonymous]

Hi 

I have a doubt regarding the data obtained after the simulation by testing a simple horizontal pipe of diameter 10 mm. Rehearsing with the Simulation CFD, I have noticed that the speed of the fluid is not kept constant in an incomprehensible fluid such as water. And it is something that I can not solve, because according to the results, the speed increases me from 10 mm / s to almost 18 mm / s, and should not because in a pipe of the same section must be satisfied that Q = V * A (Equation continuity). Therefore, the velocity of the fluid should be constant.

Fluid: Water (default) 

Solid: PVC

boundary conditions:

- input Velocity: 10 mm/s

- output Pressure (gage): 0 Pa

How Can I solve the problem. 

Since in a pipe of constant section the speed of the fluid must be equal, and in any case, that due to the losses of load the speed slows down.

[matt.bemis · Accepted solution]

Hi @Anonymous,

Thanks for reaching out to us on the forums! The reason you are seeing a velocity higher than the inlet is because as the flow develops in the pipe, the velocity profile is no longer uniform. We know from fluid dynamics there is a "no slip" boundary condition at the wall. This means the fluid at the wall is equal to the velocity of the wall; ie 0. The zero velocity at the wall means the fluid needs to move faster than the mean inlet velocity to conserve mass. Basically, the fluid is sticking at the bottom and top walls, and therefore the fluid in the middle of the pipe is the fastest and is going faster than the mean inlet speed. 

Check out this image:

Here's a pretty good 5 min lecture from youtube. Check it out. Did I answer your question? Am I missing something?

Thanks,

[matt.bemis · Accepted solution]

Hi @Anonymous,

Thanks for reaching out to us on the forums! The reason you are seeing a velocity higher than the inlet is because as the flow develops in the pipe, the velocity profile is no longer uniform. We know from fluid dynamics there is a "no slip" boundary condition at the wall. This means the fluid at the wall is equal to the velocity of the wall; ie 0. The zero velocity at the wall means the fluid needs to move faster than the mean inlet velocity to conserve mass. Basically, the fluid is sticking at the bottom and top walls, and therefore the fluid in the middle of the pipe is the fastest and is going faster than the mean inlet speed. 

Check out this image:

Here's a pretty good 5 min lecture from youtube. Check it out. Did I answer your question? Am I missing something?

Thanks,

[Anonymous]

Thank you very much for solving the doubt and explaining it in detail. 

[Anonymous]

Thank you very much for solving the doubt and explaining it in detail. 

[matt.bemis]

@Anonymous absolutely! Feel free to reach out again on the forums if you have more questions.

Thanks,

[matt.bemis]

@Anonymous absolutely! Feel free to reach out again on the forums if you have more questions.

Thanks,