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

Which factors can suppress the amplitude of a wave?

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

LinkBack Thread Tools Display Modes
Old   July 6, 2009, 00:52
Default Which factors can suppress the amplitude of a wave?
Join Date: Mar 2009
Posts: 40
Rep Power: 8
hadesmajesty is on a distinguished road
I give a small time-dependent disturbance to a steady flow field (boundary layer) to generate a wave (TS wave). However, I find that the wave’s amplitude is smaller than what it should be at high Reynolds number region. Is there anybody who knows the reason?

The numerical model I use is 2nd order back difference in time (fully implicit) and 2nd order centered difference in space. Is it possible that the amplitude of the wave is suppressed by the numerical dissipation of the 2nd order back difference?
hadesmajesty is offline   Reply With Quote

Old   July 6, 2009, 17:32
Senior Member
sbaffini's Avatar
Paolo Lampitella
Join Date: Mar 2009
Location: Italy
Posts: 538
Blog Entries: 14
Rep Power: 17
sbaffini will become famous soon enough
In my experience the 2nd order backward difference in time is highly dissipative for courant numbers higher than 1-2 (see Hirsch), actually the whole frequency spectrum will be highly damped (except for a narrow band in the highest resolved frequency region). So this could be the cause of your problem.

Usually, for time dependent problems, the convective part is treated explicitly because of this (also because big courant numbers are not physical for the unsteady convection). If you're using fluent than you have to use a time step such that an optimal value of 0.1-0.5 for the courant number is reached.
sbaffini 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
how to find wave amplitude chandrasekhar Main CFD Forum 2 March 13, 2010 08:17
About probe result of Wave simulation shiw FLOW-3D 3 March 13, 2009 10:15
Wave simulation Navin Fogla FLUENT 0 March 6, 2008 10:50
DPM model w/ Wave model - errors in documentation HS FLUENT 0 April 12, 2006 04:37
Question about the shock wave in CFX software nucharin Main CFD Forum 1 January 25, 2005 09:26

All times are GMT -4. The time now is 13:25.