Fluctuating residuals

tichaona · February 7, 2012, 12:27

Dear collegues

I am new to fluent. I have modeled a room 8m length by 4m. The room has 2 windows and 1 door on windward side and 2 windows and 1 door on leeward. I have also modeled the atmospheric air as an enclosure of the room. The atmospheric air enclosure measures 252m (width) by 256m (length) by 105m (height). I am using polyhedra mesh. I am running steady flow simulation. The energy equation is off. The solution has converged after 77 iterations. I am having fluctuating residuals and the continuity and epslon residuals are fluctuating above 10e-3. The others are fluctuating below. What causes these fluctuations and how can I solve the problem. May you please assist with regard to the above.

Thank you in advance for any contributions.

Vitaly · February 7, 2012, 15:49

Hi,

What do you mean by "fluctuating residuals?" Are they just oscilating around a single value that is greater than 10^-3? That's normal, you might just need to relax the solution a little bit (take smaller guessing steps).

What is your criteria for convergence?

February 7, 2012, 12:27	Fluctuating residuals	#1
tichaona New Member tichaona Join Date: Dec 2011 Location: South Africa Posts: 13 Rep Power: 14	Dear collegues I am new to fluent. I have modeled a room 8m length by 4m. The room has 2 windows and 1 door on windward side and 2 windows and 1 door on leeward. I have also modeled the atmospheric air as an enclosure of the room. The atmospheric air enclosure measures 252m (width) by 256m (length) by 105m (height). I am using polyhedra mesh. I am running steady flow simulation. The energy equation is off. The solution has converged after 77 iterations. I am having fluctuating residuals and the continuity and epslon residuals are fluctuating above 10e-3. The others are fluctuating below. What causes these fluctuations and how can I solve the problem. May you please assist with regard to the above. Thank you in advance for any contributions.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
what to monitor besides residuals?	franzdrs	FLUENT	5	March 21, 2013 04:59
Fluctuating residuals in transient simulation (transientSimpleFoam)	robingilbert	OpenFOAM	1	November 17, 2011 20:36
fluctuating residuals	shilpamkar	FLUENT	0	August 2, 2011 02:57
pls help fluctuating residuals due to courant no	sagar	CFX	3	March 28, 2006 02:10
Convergence - scaled vs unscaled residuals	HS	FLUENT	1	November 7, 2005 06:45

February 7, 2012, 15:49		#2
Vitaly Member Vitaly Join Date: Jan 2012 Posts: 32 Rep Power: 14	Hi, What do you mean by "fluctuating residuals?" Are they just oscilating around a single value that is greater than 10^-3? That's normal, you might just need to relax the solution a little bit (take smaller guessing steps). What is your criteria for convergence?