|
[Sponsors] |
May 24, 2002, 09:14 |
y+ calculations
|
#1 |
Guest
Posts: n/a
|
hi
Does any one now how to calculate the distance a near wall cell should be ,if I know the flow details, and I want to maintain the y+ between 30 and 100 as per CFX. please help. henry |
|
May 24, 2002, 09:41 |
Re: y+ calculations
|
#2 |
Guest
Posts: n/a
|
Hi,
In TASCflow and CFX-5 the yplus values at walls are stored by default in the results file. In CFX-4 you only need to add three lines in your command file to see these values under the post-processor. Regards, cfd guy |
|
May 24, 2002, 11:36 |
Re: y+ calculations
|
#3 |
Guest
Posts: n/a
|
Actually, TASCflow will only output yplus values if the BCINFO = t flag is set.
As an initial guess before you run for the first time, there are correlations for boundary layer development over a flat plate. Look up section 4.4.4 of the TASCflow doc for details, or Mathmatical Models and Solution Algorithms > Modelling Flow Near the Wall > Guidelines for Grid Generation section of the CFX-5.5 doc (see math_models.pdf). Regards, Robin |
|
May 27, 2002, 09:45 |
Re: y+ calculations
|
#4 |
Guest
Posts: n/a
|
||
May 27, 2002, 09:47 |
Re: y+ calculations
|
#5 |
Guest
Posts: n/a
|
hi Thanks for the info,
but I wanted the formula to calculate the Y+ from the flow variables like Re ,etc henry |
|
May 27, 2002, 10:01 |
Re: y+ calculations
|
#6 |
Guest
Posts: n/a
|
hi
Could some one give the formula please. joe |
|
May 28, 2002, 09:41 |
Re: y+ calculations
|
#7 |
Guest
Posts: n/a
|
y+, the dimensionless distance from the wall, can be calculated from the formula :
y+=(rho.u*.y)/mu where rho and mu are respectively the density and the dinamic viscosity of the fluid, y is the distance from the wall and u* is the shear velocity. The three regions are (may vary from different authors) : The viscous sublayer 0<y+<5 The intermediate zone : 5<y+<30 The turbulent zone : 30<y+<500 Regards. |
|
May 30, 2002, 17:43 |
Re: y+ calculations
|
#8 |
Guest
Posts: n/a
|
Have a look at the documentation, it's in there.
Robin |
|
June 3, 2002, 04:38 |
Re: y+ calculations
|
#9 |
Guest
Posts: n/a
|
hi
Patrice thanks soo much , do you know how the shear velocity is calculated. thanks again joseph |
|
June 27, 2002, 21:48 |
Re: y+ calculations
|
#10 |
Guest
Posts: n/a
|
Hello, All:
I am very interested in this topic. I am using CFD-4 now. I am trying to export y+ data from the simulation. It seems to me that one can obtain some meanfull y+ values as the wall is still (not moving). Do I still expect the correct y+ values from the simulation with a standard wall function if the wall is in moving ( bassically the wall is rotating in my study)? Min-Hua Wang |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Hardware for Cfx/openfoam calculations of 30-50 million cells | Rkeck | Hardware | 8 | July 13, 2009 13:12 |
transient calculations! | lelia | Siemens | 9 | April 14, 2008 09:33 |
Mass Flux values and calculations | Cb | Siemens | 1 | January 22, 2005 10:21 |
Difference between two calculations | Lennart | FLUENT | 7 | November 24, 2002 02:19 |
Implicit transient calculations using Fluent5 | G. Berntsen | Main CFD Forum | 4 | November 10, 1999 16:32 |