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

Why are my momentum residuals so low?

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

LinkBack Thread Tools Search this Thread Display Modes
Old   June 24, 2022, 14:06
Smile Why are my momentum residuals so low?
New Member
Join Date: Jun 2022
Posts: 11
Rep Power: 3
sensitiveLook is on a distinguished road
I am running a simulation with ansys for flow in an aircraft intake. The flow is transient and when I setup FLUENT for getting the solution, the momentum residuals are very low like the x-velocity starts at 1e-10. And the same goes for y-velocity and z-velocity. Then they drop down to 1e-18, and restart from 1e-10 at the beginning of the time-step.
Can anyone tell me why mymomentum residuals so low?
As for settings:
Model: Detached Eddy simulation (RANS model SST k-omega with shielding function as IDDES)
Solver: PISO, 2nd order solvers for all variables,
Transient formulation: bounded second order implicit
Time-step size: 1e-04
Max no. of iteration/time steps=30
I have attached a picture of my residuals for reference
Attached Images
File Type: png residuals.png (26.1 KB, 17 views)
sensitiveLook is offline   Reply With Quote

Old   June 24, 2022, 14:49
Senior Member
sbaffini's Avatar
Paolo Lampitella
Join Date: Mar 2009
Location: Italy
Posts: 2,124
Blog Entries: 29
Rep Power: 38
sbaffini will become famous soon enoughsbaffini will become famous soon enough
Send a message via Skype™ to sbaffini
We would need a crystall ball to tell. Could you share your velocity initialization and current field, cfl, etc.?

In general, the residual you see at the beginning of the subiterations, if I recall correctly, is still normalized with respect to the max res in the first 5 subiterations of the first time step. If your solution is changing very slowly, it might indeed happen that the following time steps all behave better than the first. But this is just speculation
sbaffini is offline   Reply With Quote


ansys, cfd simulation, fluent, residuals, transient analysis

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
Table bounds warnings at: END OF TIME STEP CFXer CFX 4 July 17, 2020 00:44
Momentum and displacement thickness: du/dy calculation Josh CFX 13 October 27, 2013 15:38
motorBike Residuals for SST k-omega... and mine JR22 OpenFOAM Running, Solving & CFD 6 August 1, 2013 10:08
convergence at 0.5 momentum residuals hugocis Main CFD Forum 3 April 7, 2010 04:37
Derivation of Momentum Equation in Integral Form Demonwolf Main CFD Forum 2 October 29, 2009 20:53

All times are GMT -4. The time now is 17:48.