CFD Online Logo CFD Online URL
Home > Forums > Siemens


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

LinkBack Thread Tools Display Modes
Old   January 30, 2003, 08:25
Default ABL/grid/model
Posts: n/a
Dear StarCD users,

I try to study flow around square cyninder with a commercial code (k-epsilon) ..... and i've got some problems.

This square cylinder is in atmospheric bounary layer and i found some correlations for neutal ABL :

wind speed V=u_tau/kappa*ln(z/z0) Turbulence Intensity I=1/ln(z/z0) Lenght Scale = f(z,zg,z0,zc) (Harris JWEIA 1986) Re = 4.10^4

First, I see that lot of authors use It= constant and Lenght Scale = constant on vertical profil at boundary layer. Witch modelisation is good? Correlation or constant?

Second, i see that lot of authors use power law : U=Uref(z/ref)^alpha but in the book "Boundary layer Meteorology (Stull)" log law is used to modelise wind speed profil. I know that log law is equal to power law for Re~10^5 and alpha=1/7 but witch profil is good to have got a good modelisation?

Third, Witch grid near wall???? With log law, V=0 for z=z0, i want to use a two-layer turbulence model but how can i generate mesh? Betheen z=0 and z=z0 and for z>=z0 ??? Witch k and epsilon i can take for 0<=z<=z0?

Thanks a lot for your answers ......
  Reply With Quote


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
why first grid point is at log layer in ke model student Main CFD Forum 6 May 13, 2007 12:25
Smagorinsky Sub-grid Model Craig Johansen CFX 1 October 13, 2004 03:10
ABL/grid/model Alain B. Main CFD Forum 0 January 30, 2003 07:22
Grid independence with k-eps model Mark Render Main CFD Forum 3 February 21, 2002 10:54
Grid generation for F.D. model in 2d domain Robin Sanderson Main CFD Forum 6 September 3, 2001 09:08

All times are GMT -4. The time now is 18:17.