CFD Online Logo CFD Online URL
Home > Forums > FLUENT

Ship Wall Roughness

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

LinkBack Thread Tools Display Modes
Old   December 21, 1999, 06:27
Default Ship Wall Roughness
Giovanni Ieria
Posts: n/a
I am a student of Calabria University (Italy), I am developing a thesis about CFD for ship. If I use Wall Functions in order to model the boundary layer, I must specify two roughness parameters which I don't know: Ks and Cks. May you help me indicating some typical values for ship hulls? Thanks in advance
  Reply With Quote

Old   December 21, 1999, 10:12
Default Re: Ship Wall Roughness
Sung-Eun Kim
Posts: n/a
When you model "hydrodynamically smooth" ship hulls, you don't need to specify the two wall roughness parameters, i.e., Ks (roughness height) and Cks (roughness constant). The defaults are 0.0 and 0.5, respectively, which is directly applicable to "hydrdynamically smmoth" walls. Scaled model ships tested in towing tanks have all "hydrodynamically smooth" surfaces, unless roughness is deliberately put on the surfaces to study the effects of roughness, which is very rare.

Roughness effects on ships' resustance can become an issue when you deal with full scales ships whose surfaces are actually "fouled" in the sea. I understand ship designers use the so-called "roughness allowance" for the roughness when estimating total resistance of full-scale ships. In the CFD modeling, what you can do in this situation is to specify your best estimate of the roughness height (e.g. of the average height of biological creatures on ship hull) for Ks and use the default value of Cks.

Please keep in mind that Cks is calibrated using roughened pipes with sand roughness and Fluent Inc. doesn't have much expertise how Cks should be varied for different roughness types.
  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
Natural convection in a closed domain STILL NEEDING help! Yr0gErG FLUENT 3 June 12, 2013 02:12
Laminar flow and wall roughness junbbung FLUENT 1 December 2, 2012 06:57
Roughness Height of a wall Vijay FLUENT 0 December 17, 2009 16:13
Errors running allwmake in OpenFOAM141dev with WM_COMPILE_OPTION%3ddebug unoder OpenFOAM Installation 11 January 30, 2008 21:30
Wall Roughness Error Ken FLUENT 1 April 23, 2007 12:59

All times are GMT -4. The time now is 11:55.