CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

i need the best setup and setting for compressible flow test

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree2Likes
  • 1 Post By taxalian
  • 1 Post By beer

Reply
 
LinkBack Thread Tools Display Modes
Old   March 13, 2013, 16:13
Default i need the best setup and setting for compressible flow test
  #1
New Member
 
musab
Join Date: Nov 2012
Posts: 11
Rep Power: 4
bluAero is on a distinguished road
بِسمِ اللهِ الرَّحمَنِ الرَّحِيم

أهلا شباب ...
.Note : all figures in this problem are inside this picture



I'm trying to calculate the Lift coefficinet of naca64012 ( with chord = 10 ) at different angels of attack and at difference speed (0.25 mach (incomp), and 0.7 mach (comp) 0
I used Structured mesh as shown in the figure A .

At 0.25 mach (incompressible flow ) test , i obtained Reasonable results of lift
coefficients at different .angles as shown in figure 2
Then i try to calculate at M=0.7 ( compressible flow ) by using the same mash
that used in the incompressible flow test ,
and the i put setup as that :
solver : figure 2
Viscous model : i select to ( K omega ) < figure 3
Materials : figure 4
But when i try that , i obtained results until angel of attack around 8 ,
they are nearly like that :
angle 0 CL 0
angle 2 CL 0.3
angle 4 CL 0.65
angle 6 CL 0.75
angle 8 CL

and i didnot obtained results at angles that more than , and there are comments appeared in The fluent console ( as shown in figure 5 )0

and the CL VS iterations divergence by high ratio as shown in this pic


i want to know what are the problems ???
and what is the most suitable setup and setting for compressible flow test ?
bluAero is offline   Reply With Quote

Old   March 17, 2013, 10:57
Thumbs up
  #2
Senior Member
 
Join Date: Nov 2010
Posts: 128
Rep Power: 6
taxalian is on a distinguished road
Hi Blueaero,
I think you need to correct the initial spacing of your mesh to have an appropriate yplus value because you want to use the same mesh for different Mach numbers? (What about the Reynolds number, it will remain the same too?)

I think you also need to use the pressure-farfield boundary condition for the compressible flow.

You should also provide the proper reference area to calculate your lift and drag via Report Reference values.

As in your case its 2D, you use reference area= 10 x 1 = 10m^2.

My advice would be to start first with the Spalart-Allmaras turbulence model this should also give good result and this is also more robust due to its ease in implementation resulting in economical resources (this is just a comment for your information). Anyways their is no proper rule to choose specific turbulence model.

Best of luck and regards.
bluAero likes this.
taxalian is offline   Reply With Quote

Old   March 20, 2013, 14:22
Default
  #3
New Member
 
musab
Join Date: Nov 2012
Posts: 11
Rep Power: 4
bluAero is on a distinguished road
How i can correct the initial spacing of the mesh ???
is it bt using GAMBIT ???

( The Reynolds number remains same ^_^ )

Last edited by bluAero; March 20, 2013 at 15:12.
bluAero is offline   Reply With Quote

Old   March 20, 2013, 15:26
Default
  #4
New Member
 
musab
Join Date: Nov 2012
Posts: 11
Rep Power: 4
bluAero is on a distinguished road
If i can change it in Fluent , tell me how ? ^_^

Last edited by bluAero; March 20, 2013 at 15:58.
bluAero is offline   Reply With Quote

Old   March 20, 2013, 18:19
Default
  #5
Member
 
Join Date: Dec 2012
Posts: 78
Rep Power: 4
beer is on a distinguished road
Hi
is there a reason why you use the density-based solver? I always prefere the pressure-based one. You need a stable setup before you think about the turbulenz (btw. I recommend the k-w-SST). So my recommendation is: Pressure-based, coupled pv-coupling, maximum second order upwind advection, last squares cell based gradient, SST-model. I did calculations with this setup which worked perfektly on transsonic flows.
Oh one last thing: Fluent is a bad solver on meshes with an aspect ratio bigger than round about 100. If you want a finer layer-region, use CFX .
Greetings
bluAero likes this.
beer is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[ICEM] Hexa mesh, curve mesh setup, bunching law Anorky ANSYS Meshing & Geometry 4 November 12, 2014 01:27
Flow around ship hull, multiphase setup!! alibul FLUENT 11 September 25, 2013 03:50
I need help in setting up grid for cylinder thethirdfarial Main CFD Forum 2 November 28, 2011 05:57
OpenFOAM case setup and work flow - what are you using? Arnoldinho OpenFOAM Pre-Processing 4 July 18, 2010 09:16
CFD problem setup for flow through porous media Paresh Jain CFX 5 June 30, 2003 03:50


All times are GMT -4. The time now is 10:00.