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Andy F January 4, 2006 13:29

Transient analysis
Im running a transient analysis and am using the CFX code for working averaged navier stokes for an aeracoustic analysis.


| Action required : Increase the character stack memory size.

Thats the error i keep getting, i have increased it in the solver parameters to 1.2, then 1.5 but still the same error coming up. I am using Sun system machines (blade 2500), is it my analysis is too big (24,000 timesteps) or am i doing something else wrong? I have just started it again with the memory stack parameter set at 2.5. Posting this now as each one of these runs is taking about a week.

longbow January 4, 2006 14:17

Re: Transient analysis
Do you run your job in serial or parallel? If in parallel, how many nodes have you put on each partition? What are the CPU and OS on your machine?

Andy January 4, 2006 18:20

Re: Transient analysis
It is in serial, unfortunately we do not have parallel licences. The CPU is 1.6GHz with 2Gig Dimm memory on a solaris 9 unix work system. I am using ANSYS CFX 10

Kiddo January 4, 2006 18:53

Re: Transient analysis
I suggest just increas the <font color=red>character</font> stack memory size, instead of total . you should expand the detail items, and set<font color=red> 1.5x</font> (or other factor)for column character only.

Andy January 4, 2006 19:20

Re: Transient analysis
i have already reduced it, i should hae said 2x and 4x in my post, sorry. It was originally crashing at about 4000 iterations, i increased the stack size to 2x and it went to 8000, and i am waiting for the results from a size of 4x.

longbow January 4, 2006 22:55

Re: Transient analysis
The fact that you have to adjust memory size indicates that your job is too big to run efficiently in serial on the machine you are using now. Adjusting memory size is a short term solution. You probably want to consider either increasing physical memory on your machine or getting parallel license. CFX 10 has very good parallel performance, which can significantly reduce running time.

TB January 5, 2006 05:40

Re: Transient analysis
Try running your problem in smaller lots. e.g. from step 1 to 2000, 2000 to 4000 etc.

Andy January 5, 2006 12:35

Re: Transient analysis
thankyou, i will continue to hassle my uni to get the parallel licences

Andy F January 6, 2006 10:55

Re: Transient analysis
Tried your suggestion TB, and i have managed to get it up to 9000 timesteps using two batches, memeory stack of 3.5 and only 5 coeff loops.Thankyou

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