Pressure plot doesn't converge

GabeN · September 13, 2023, 10:32

Hi everyone!

I've been using Star-CCM for muffler transmission loss simulations since last year or so. There is also an official tutorial made by CD-adapco, and that has worked well, but since this year january or so, these simulations started acting funny and no longer give accurate results.

So basically, you take a muffler cavity model and you send through a white noise at the inlet, and we are interested in the outlet sound (outlet pressure plot). Then that is converted into the frequency domain with FFT.

The problem is, the pressure plots doesn't converge to 0 pascals but rather to -0.1 something. It also does not really want to converge within time-step (there are 6 right now). With this issue, the Fast-Fourier transforms also look like crap.

The problem also remains when you take a correct simulation file and rerun it without changing anything, you no longer get back the once correct results. A finer mesh also doesn't solve this issue.

The issue remains with older/newer versions of Star-CCM (I mainly use 15.06.007 single-precision) but double-precision does not help either

f-w · September 13, 2023, 20:18

Sounds like memory (RAM) corruption. Run MemTest86.

GabeN · September 14, 2023, 01:01

I will, but I forgot to mention that the computer doesn’t matter either, the problem is the same everywhere else

September 13, 2023, 10:32	Pressure plot doesn't converge	#1
GabeN New Member Adam Join Date: Sep 2023 Posts: 2 Rep Power: 0	Hi everyone! I've been using Star-CCM for muffler transmission loss simulations since last year or so. There is also an official tutorial made by CD-adapco, and that has worked well, but since this year january or so, these simulations started acting funny and no longer give accurate results. So basically, you take a muffler cavity model and you send through a white noise at the inlet, and we are interested in the outlet sound (outlet pressure plot). Then that is converted into the frequency domain with FFT. The problem is, the pressure plots doesn't converge to 0 pascals but rather to -0.1 something. It also does not really want to converge within time-step (there are 6 right now). With this issue, the Fast-Fourier transforms also look like crap. The problem also remains when you take a correct simulation file and rerun it without changing anything, you no longer get back the once correct results. A finer mesh also doesn't solve this issue. The issue remains with older/newer versions of Star-CCM (I mainly use 15.06.007 single-precision) but double-precision does not help either

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September 13, 2023, 20:18		#2
f-w Senior Member Join Date: Apr 2009 Posts: 154 Rep Power: 17	Sounds like memory (RAM) corruption. Run MemTest86.

September 14, 2023, 01:01		#3
GabeN New Member Adam Join Date: Sep 2023 Posts: 2 Rep Power: 0	I will, but I forgot to mention that the computer doesn’t matter either, the problem is the same everywhere else