How to define the Reynolds Number in CFX?

ghorrocks · November 6, 2013, 05:53

The streamlines are the velocity field. If you ignore that - then why bother doing CFD?

sepidecent · April 27, 2014, 03:32

Quote:

Originally Posted by ghorrocks

I do not understand your question. Are you having problems calculating the particle Re number? Are problems implementing you drag law?

Hi There,

Yeah I want to define Re Number as an expression in CFX-pre, and then drag coefficient. In that way I can define a new drag model than a common Schiller-Naumann correlation. Thank's a lot.

Regards,
Sep

ghorrocks · April 27, 2014, 06:27

Have you done the tutorials? They show you have to implement CEL expressions.

bestniaz · September 3, 2015, 22:09

How to check material properties valve in CFX. It just show the material like air, water.etc...no material propoerties here... Plz help me how to change the material properties...
I am new here and new in CFX.
Thanks in advance

Quote:

Originally Posted by Loris88

Hi ghorrocks!

Since you have said me to read this post, I will write here my question.
I have read the questions and the relative answers but I did not find the solution for my problem.
I have a 2D problem. I created the mesh with ICEM and then I extruded it with the shrewdness of to put as depth, 1 cell like thikness.

After importing the mesh in CFX, I have put boundary condition of symmetry for to simulate the 2D problem.

I have these measures of the rectangular channel:
-Length: 3900 mm
-Heigth: 50 mm (Characteristic length L)
-Depth: 1 cell like thikness
-Re= 80000 (known input of the problem)
-Velocity along x axis= 24 m/s (u) at the inlet. The other velocities are 0 m/s. No swirl component.
-Dynamic viscosity: 1.8058e-05 kg/m*s (alpha)
-Density: 1.20438 kg/m^3 (beta)
-Kinematic viscosity: alpha/beta= 1.4993e-5 (ni)

Re= (u*L)/ni ~ 80000 [for precision 80034]

But Ansys has given me Re=9.2723E+04

How can I do for to solve this problem?
Thanks

Lance · September 4, 2015, 01:58

In CFX-pre in the tree to the left you have stuff like Simulation, Analysis Type, Solver, Coordinate Frames, and a thing called Materials. Right click, insert/material. Or from the menu in the top, click insert/material.
This is the easy part with CFD, and if you have problems with this you should at least do all the tutorials before doing anything else.

bestniaz · September 7, 2015, 00:59

Thanks dear... This forum is really great for the beginner... it help me alot....

Quote:

Originally Posted by Lance

In CFX-pre in the tree to the left you have stuff like Simulation, Analysis Type, Solver, Coordinate Frames, and a thing called Materials. Right click, insert/material. Or from the menu in the top, click insert/material.
This is the easy part with CFD, and if you have problems with this you should at least do all the tutorials before doing anything else.

BARKAT · November 23, 2018, 05:53

good morning
how to varying the number reynolds in fluent so that study the effect re on other parameters

thanks

ghorrocks · November 24, 2018, 04:20

First of all, Fluent is a dimensional solver so you need to change the velocity, size or fluid properties to give the Reynolds number you want.

Secondly, this is the CFX forum. For questions on Fluent try the Fluent forum.

November 23, 2018, 05:53	varying the number reynolds	#27
BARKAT New Member amroune Join Date: Nov 2013 Posts: 12 Rep Power: 12	good morning how to varying the number reynolds in fluent so that study the effect re on other parameters thanks

November 24, 2018, 04:20		#28
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	First of all, Fluent is a dimensional solver so you need to change the velocity, size or fluid properties to give the Reynolds number you want. Secondly, this is the CFX forum. For questions on Fluent try the Fluent forum. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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November 6, 2013, 05:53		#21
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The streamlines are the velocity field. If you ignore that - then why bother doing CFD?

April 27, 2014, 06:27		#23
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Have you done the tutorials? They show you have to implement CEL expressions.

September 4, 2015, 01:58		#25
Lance Senior Member Lance Join Date: Mar 2009 Posts: 669 Rep Power: 22	In CFX-pre in the tree to the left you have stuff like Simulation, Analysis Type, Solver, Coordinate Frames, and a thing called Materials. Right click, insert/material. Or from the menu in the top, click insert/material. This is the easy part with CFD, and if you have problems with this you should at least do all the tutorials before doing anything else.