CFD Online Logo CFD Online URL
Home > Forums > STAR-CCM+

Hydrodynamic forces on bridge structures

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

LinkBack Thread Tools Display Modes
Old   January 29, 2012, 05:38
Default Hydrodynamic forces on bridge structures
New Member
Join Date: Apr 2009
Posts: 11
Rep Power: 8
mbn1454 is on a distinguished road
I am trying to calculate hydrodynamic forces on a bridge structure subject to waves.
My results are ok for bigger waves but for small waves I am over predicting significantly (the vertical force). I can see that air gets trapped under the bridge.
I am using mesh size in vicinity of bridge and free surface of order of 2cm and time step size of order of dt=0.004s. The simulation under predicts big wave forces and grossly over predicts small wave forces. It also shows a lot of oscillation. I am using number of internal iteration up to 200. I have modeled air as compressible. Can you please let me know what I can do to improve results specially for small wave amplitudes?
mbn1454 is offline   Reply With Quote

Old   January 31, 2012, 19:24
Senior Member
Joshua Counsil
Join Date: Jul 2009
Location: Halifax, Nova Scotia, Canada
Posts: 366
Rep Power: 9
Josh is on a distinguished road
We need WAY more details of your problem. Your mesh and timestep size mean nothing without a domain size.
Josh is offline   Reply With Quote

Old   February 13, 2012, 03:30
Senior Member
Join Date: Mar 2009
Posts: 223
Rep Power: 9
ping is on a distinguished road
cant see any reason to not use constant density for both fluids.
would expect that 10-20 inner iterations are enough, but keep an eye on a range of monitors eg forces at a few locations plotted version iteration rather than timestep - force convergence dependent on timestep and inner iterations - more of one means less of the other in simplistic terms.
would get it going using timesteps of around 0.01s, then test smaller ones.
need about 20 cells vertically to capture a wave and about 40 per wave length.
sometimes need second order time to retain wave height.
ping is offline   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
hydrodynamic forces using fluent nims FLUENT 5 February 6, 2012 00:30
Hydrodynamic forces on offshore structures Mike Main CFD Forum 2 June 19, 2008 14:19
Hydrodynamic forces Tim Pugh FLUENT 0 July 27, 2004 03:05
Valve Forces in CFdesign Mike Clapp Main CFD Forum 3 March 8, 2001 15:09
Hydrodynamic forces and moments on submarines Peo Hedin Main CFD Forum 2 July 20, 1999 02:53

All times are GMT -4. The time now is 20:33.