
[Sponsors] 
[ICEM] yplus calculation & transmission into icem cfd 

LinkBack  Thread Tools  Search this Thread  Display Modes 
May 7, 2016, 06:22 
yplus calculation & transmission into icem cfd

#1 
New Member
Join Date: Mar 2016
Posts: 4
Rep Power: 8 
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^n1)/(q1) = 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 (05, 530, >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 komega would be good for good resolution of nearwall 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 

May 9, 2016, 02:56 

#2 
New Member
Join Date: Mar 2016
Posts: 4
Rep Power: 8 
Can someone help me?


Tags 
boundary layer, calculate, wall, yplus 
Thread Tools  Search this Thread 
Display Modes  


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 inhouse CFD code or to buy a available CFD package.  Tareq Alshaalan  Main CFD Forum  10  June 12, 1999 23:27 