Time-step clarification

raghulvr · October 23, 2015, 05:18

Hi,
I am currently working ln CFD simulation of combustion.I am doing combustion simulation of kirloskar TAF1 with sector type.
The problem is i want to simulate combustion from crank angle 570 to 833.Fluent is taking 1428 time steps for solving the problem.By default,the max iterations/per step is set to 50
If 50 iterations are run per time step in the scale of crank angle 570.25,570.5 ,570.75,571upto 833.
The total time taken for solving would be incredibly high
My question is can i reduce the number of max. iterations per time step and get the optimal results for combustion simulation
Can you recommend to which value should i set the max. Iterations per time step
Thanks in advance!!!

LuckyTran · October 24, 2015, 15:35

Yes but just check to make sure your simulation is converged at the end of each time step. I generally try to aim for 20 iterations per time step but many people go as low as 8-10.

raghulvr · October 25, 2015, 04:53

Thank you very much for the information mate.But is there any way to reduce computational time bcoz
my simulation takes 1268 time steps for solving.this would take nearly 3 days to get solution.!!

LuckyTran · October 25, 2015, 22:51

Run a bigger time-step, larger crank angle steps. Run on more cores. Using a coarser mesh helps tremendously.

3 days is not very long, it's fairly reasonable for a detailed time-accurate problem. I've left a simulation alone to run for 9 months before.

raghulvr · October 26, 2015, 04:28

Thanks a lot for your valuable inputs mate.Obviously, this is my first year in masters degree in CFD.I thought that it would run in a short time.

pradeep6890 · November 19, 2015, 02:00

The time-displacement UDF could not be given to define the mesh motion of Kirloskar TAF1..Kindly help in moving the mesh. Thanks in Advance.!

October 23, 2015, 05:18	Time-step clarification	#1
raghulvr Member Rahul Join Date: Sep 2015 Posts: 39 Rep Power: 11	Hi, I am currently working ln CFD simulation of combustion.I am doing combustion simulation of kirloskar TAF1 with sector type. The problem is i want to simulate combustion from crank angle 570 to 833.Fluent is taking 1428 time steps for solving the problem.By default,the max iterations/per step is set to 50 If 50 iterations are run per time step in the scale of crank angle 570.25,570.5 ,570.75,571upto 833. The total time taken for solving would be incredibly high My question is can i reduce the number of max. iterations per time step and get the optimal results for combustion simulation Can you recommend to which value should i set the max. Iterations per time step Thanks in advance!!!

November 19, 2015, 02:00	Problem uploading UDF	#6
pradeep6890 Member Pradeep Join Date: Nov 2014 Posts: 45 Rep Power: 12	The time-displacement UDF could not be given to define the mesh motion of Kirloskar TAF1..Kindly help in moving the mesh. Thanks in Advance.!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
High Courant Number @ icoFoam	Artex85	OpenFOAM Running, Solving & CFD	11	February 16, 2017 14:40
Extrusion with OpenFoam problem No. Iterations 0	Lord Kelvin	OpenFOAM Running, Solving & CFD	8	March 28, 2016 12:08
Floating point exception error	lpz_michele	OpenFOAM Running, Solving & CFD	53	October 19, 2015 03:50
Star cd es-ice solver error	ernarasimman	STAR-CD	2	September 12, 2014 01:01
calculation diverge after continue to run	zhajingjing	OpenFOAM	0	April 28, 2010 05:35

October 24, 2015, 15:35		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,762 Rep Power: 66	Yes but just check to make sure your simulation is converged at the end of each time step. I generally try to aim for 20 iterations per time step but many people go as low as 8-10.

October 25, 2015, 04:53		#3
raghulvr Member Rahul Join Date: Sep 2015 Posts: 39 Rep Power: 11	Thank you very much for the information mate.But is there any way to reduce computational time bcoz my simulation takes 1268 time steps for solving.this would take nearly 3 days to get solution.!!

October 25, 2015, 22:51		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,762 Rep Power: 66	Run a bigger time-step, larger crank angle steps. Run on more cores. Using a coarser mesh helps tremendously. 3 days is not very long, it's fairly reasonable for a detailed time-accurate problem. I've left a simulation alone to run for 9 months before.

October 26, 2015, 04:28		#5
raghulvr Member Rahul Join Date: Sep 2015 Posts: 39 Rep Power: 11	Thanks a lot for your valuable inputs mate.Obviously, this is my first year in masters degree in CFD.I thought that it would run in a short time.