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

turbulence and viscosity near Mach

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 16, 2006, 06:02
Default turbulence and viscosity near Mach
  #1
Anthony
Guest
 
Posts: n/a
Hello, I'm simulating a rotating disk in the air but my simulation doesn't correspond to the experimental measurements. I've already meshed the disk and the control volume, and the mesh quality is about 0.3 and there aren't bad cells. Within this velocity, the temperature around the disk is about 100C by experiment but during my simulation the temperature is only at 50C. The aim of this simulation is to determine the moment at the axis. Now, I try to change the fluid (air) into ideal gas and change the options for the density and viscosity.

Could someone give me some advice about really important parameter ? What is really the consequence of the turbulent viscosity option in fluent?

Disk specification: Radius 95 mm; thickness 2 mm; roughness 5 micrometer, frequency 0-500 Hz

Model: k-epsilon RNG; coupled; energy

Best regards

anthony
  Reply With Quote

Old   August 16, 2006, 20:44
Default Re: turbulence and viscosity near Mach
  #2
Raj Kiran Grandhi
Guest
 
Posts: n/a
Check the y+ value near the wall. If you are using the wall function approach, the y+ has to be above ~30. If, however you are using the enhanced wall treatement, then a y+ ~1 is desirable. Check the fluent user guide for recommendations on the grid for near wall computations.

Regarding the correspondence with experimental data, is the temperature measured in the experiment, the surface temperature of the disk, or the temperature of the air? If it the surface temperature of the disk, then you will have to predict the heat flux at the surface of the disk from your CFD simulation and then perform a heat conduction study in order the determine the surface temperature of the disk.

In any case, proper resolution of the mesh near the wall is important.

Hope that helps, Raj Kiran
  Reply With Quote

Old   August 21, 2006, 07:23
Default Re: turbulence and viscosity near Mach
  #3
David
Guest
 
Posts: n/a
Thank you,

Now we have remesh properly and we try to simulate but we still have some questions.

Is k-omega standard with shear flow correction, coupled, density (ideal gaz) and viscosity (kinetik theory) the best option?

I use the ploter under solve/monitor/moment and I choose the rotating wall to obtain the moment at axis z. Is it the best way in order to obtain the total moment on axis z?

How can I decrease the residuals (I'm near ten).

Thank you for answer, the values don't fit the measurement so we are really stuck.

  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
Discussion: Reason of Turbulence!! Wen Long Main CFD Forum 3 May 15, 2009 09:52
Turbulence viscosity ratio Haitham FLUENT 5 February 5, 2008 05:49
Turbulence viscosity limited Madhukar Rapaka FLUENT 0 June 26, 2006 03:17
Wall turbulence, viscosity, boundary layer Patrick Godon Main CFD Forum 1 November 5, 2003 16:39


All times are GMT -4. The time now is 10:36.