CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum


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

LinkBack Thread Tools Search this Thread Display Modes
Old   November 19, 2007, 08:38
Default CFD VS SPH
James Downing
Posts: n/a

i would like to have your ideas about how to simulate hydrodynamic losses of a ship,

i try cfx and ls dyna via sph, as i know the cfd codes are better to simulate this kind of analysis but recentrly i hear that the sph method is better,

so is there anyone that try to see that , or anyone with any idea about that?

thanks james
  Reply With Quote

Old   November 21, 2007, 13:59
Default Re: CFD VS SPH
Posts: n/a
Hi James,

I actually would like to know more about SPH too; esp. concerning the calculation time and accuracy

Greetings! Fab
  Reply With Quote

Old   November 24, 2007, 07:32
Default Re: CFD VS SPH
Posts: n/a
SPH is meshless method and simply it can be said that: its computational time is considerably higher than any mesh based method and due to irregularity of spatial stensil^1, its accuracy is also lower than mesh based methods (accuracy of boundary condition is also in question). e.g. read this paper:

it is shown that convergence rate is below first order !

Also SPH in its formal version is weakly compressible and so time step size is severly limited by courant number based on sound speed. In incompressible format you have to slove a sparse unstrcutured poisson equation with large number of non-zero which is expensive to invert.

But when you have severe splashing e.g. atomization ... (presence of sub grid scale free surface) SPH is good candidate and could be superior than mesh based methods (in terms of CPU and accuracy).

1- To compare meshless vs. meshbase: assume 2d case, to reach to 2nd order accuracy of second derivative 3 point is sufficient on unifirm cartesian grid, but if sample points do not have reqularity it is needed to write multidimensional taylor seris and then for computation of second order derivative 9-sampe point is needed (this is more in 3d) also singularity of this matrix could be issue.

  Reply With Quote


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
Where do we go from here? CFD in 2001 John C. Chien Main CFD Forum 36 January 24, 2001 22:10
ASME CFD Symposium, Atlanta, July 2001 Chris R. Kleijn Main CFD Forum 0 August 21, 2000 05:49
Since Last June John C. Chien Main CFD Forum 3 July 12, 1999 10:38
Which is better to develop in-house CFD code or to buy a available CFD package. Tareq Al-shaalan Main CFD Forum 10 June 13, 1999 00:27
CFD Symposium (Call for Papers) Chris R. Kleijn Main CFD Forum 0 October 5, 1998 11:25

All times are GMT -4. The time now is 15:42.