CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > ANSYS Meshing & Geometry

[ICEM] y-plus calculation & transmission into icem cfd

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 7, 2016, 06:22
Post y-plus calculation & transmission into icem cfd
  #1
New Member
 
Join Date: Mar 2016
Posts: 4
Rep Power: 8
smaru is on a distinguished road
Hello Everybody,

actually I'm trying to model a fluid flow over a pipe in icem and convert it into cfx. It's my first try to do some simulation in ansys software.

I decide to do a tetra mesh in the volume and a prism layer on the walls of the pipe. I wondered how big the cells in the prism layer has to be and found out that there is a size called y plus. I understand the theory of boundaries.
I searched a long time for the calculation and I think my calculating method is right. The simulation is an exercise for university so it would be very nice if someone could confirm my method.
At first I calculate the Reynolds number of the system:
- Re (= ~1e4 => turbulent) , and the velocity v [m/s]
- lambda [1]
- tau [N/m^2]
- y [m] for y+=5
- delta= (12.64*D)/(Re)^(3/4) [m]
- y=h0 * (q^n-1)/(q-1) = h0*7.4416 with q=1.2 and n=5
- height of the wall nearest cell: h0=y/7.4416

1.:
Now I'm not sure if I can explain (especially with my english) where my problem is. So the boundary layer theory says there are 3 layers (sublayer, bufferlayer, loglayer) and for these 3 layers there are defined y+ values (0-5, 5-30, >30). Do I have to calculate different y values with the different y+ values? But in icem I can only define the 'height' (height of the first cell, so h0) and the 'height ratio' (= q, so 1.2). Am I right?

2.:
I defined here n=5, so there are 5 layers of the prism layer. How can I find out how many layers I need?

3.:
What does the size delta mean? Theoretically it's the height of the viscous layer. It's independent of y+, but depends on the Reynolds number. So does it mean, that I have to do such a big prism layer? And then in some way to calculate how many layers I need and how big is the height h0?

I'm still not sure which turbulence model I have to choose, but I think k-omega would be good for good resolution of near-wall regions. How does the choosed turbulence model effects my calculation of y+?

It would be so great to get an answer!
I really tried to find solution for my own, but now I don't think I can find it by myself.
Thanks in advance!
greets
-smaru
smaru is offline   Reply With Quote

Old   May 9, 2016, 02:56
Default
  #2
New Member
 
Join Date: Mar 2016
Posts: 4
Rep Power: 8
smaru is on a distinguished road
Can someone help me?
smaru is offline   Reply With Quote

Reply

Tags
boundary layer, calculate, wall, yplus

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Need help icem cfd kakhtar ANSYS Meshing & Geometry 25 January 31, 2017 01:09
Transport mesh from ICEM CFD, to Fluent, to Sysnoise Wieland FLUENT 2 April 15, 2012 06:28
Can I specify boundary conditon in icem cfd Harry Main CFD Forum 4 September 23, 2010 13:28
Where do we go from here? CFD in 2001 John C. Chien Main CFD Forum 36 January 24, 2001 21:10
Which is better to develop in-house CFD code or to buy a available CFD package. Tareq Al-shaalan Main CFD Forum 10 June 12, 1999 23:27


All times are GMT -4. The time now is 10:23.