Unknown Simulation Error


#1

Hello there!

I just started using Simscale with the intent of creating Cl vs AoA graphs for the wing of a fixed-wing drone.

I’m following this tutorial: DBF Workshop Session 1 - Aerodynamic Study of Model Plane (Part 1) (more so the YouTube video) and applying it to my own project: https://www.simscale.com/projects/UBCUAS/acda_vg_analysis/

The Meshes seemed to have been successfully created, and after attempting a few simulations, it always gets an error at a specific time. The error only tells me to check the simulation log, but I’m unsure how to read it.

Here’s a snippet of the log:

Time = 477
DILUPBiCG: Solving for Ux, Initial residual = 8.1836877843e-27, Final residual = 8.1836877843e-27, No Iterations 0
[30] Signal 8 encountered
[6] Signal 8 encountered
[6] Going to reraise SIGTERM after writting
[6] Resetting old handlers (just in case)
[6] Unset SIGFPE(8) signal handler
[6] Unset SIGSEGV(11) signal handler
[6] Unset SIGQUIT(3) signal handler
[6] Writing old times:
[6] 1 times to write
[6] Write t=476 to “processor6/476”
[30] Going to reraise SIGTERM after writting
[30] Resetting old handlers (just in case)
[30] Unset SIGFPE(8) signal handler
[30] Unset SIGSEGV(11) signal handler
[30] Unset SIGQUIT(3) signal handler
[30] Writing old times:
[30] 1 times to write
[30] Write t=476 to “processor30/476”
[30] Writing current time 477
[6] Writing current time 477
[30] Printstack:
[30]
[30]
[30]
[30] Raising SIGTERM so that other processes will dump too
[30] Signal 15 encountered
[30] Resetting old handlers (just in case)
[30] Unset SIGTERM(15) signal handler
[30] Other handler dumped already. Exiting
[30] Sleeping 60 before reraising SIGTERM to allow other processes to write
[30] Reraising original signal
[25] Signal 15 encountered
[25] Resetting old handlers (just in case)
[25] Unset SIGFPE(8) signal handler
[25] Unset SIGSEGV(11) signal handler
[25] Unset SIGTERM(15) signal handler
[25] Unset SIGQUIT(3) signal handler
[25] Writing old times:
[25] 1 times to write
[25] Write t=476 to “processor25/476”
[1] Signal 15 encountered
[1] Resetting old handlers (just in case)
[1] Unset SIGFPE(8) signal handler
[1] Unset SIGSEGV(11) signal handler
[1] Unset SIGTERM(15) signal handler
[1] Unset SIGQUIT(3) signal handler
[1] Writing old times:
[1] 1 times to write
[1] Write t=476 to “processor1/476”
[2] Signal 15 encountered
[2] Resetting old handlers (just in case)
[2] Unset SIGFPE(8) signal handler
[2] Unset SIGSEGV(11) signal handler
[2] Unset SIGTERM(15) signal handler
[2] Unset SIGQUIT(3) signal handler
[2] Writing old times:
[2] 1 times to write
[2] Write t=476 to “processor2/476”
[3] Signal 15 encountered
[3] Resetting old handlers (just in case)
[3] Unset SIGFPE(8) signal handler
[3] Unset SIGSEGV(11) signal handler
[3] Unset SIGTERM(15) signal handler
[3] Unset SIGQUIT(3) signal handler
[3] Writing old times:
[3] 1 times to write
[3] Write t=476 to “processor3/476”
[4] Signal 15 encountered
[4] Resetting old handlers (just in case)
[4] Unset SIGFPE(8) signal handler
[4] Unset SIGSEGV(11) signal handler
[4] Unset SIGTERM(15) signal handler
[4] Unset SIGQUIT(3) signal handler
[4] Writing old times:
[4] 1 times to write
[4] Write t=476 to “processor4/476”
[19] Signal 15 encountered
[19] Resetting old handlers (just in case)
[19] Unset SIGFPE(8) signal handler
[19] Unset SIGSEGV(11) signal handler
[19] Unset SIGTERM(15) signal handler
[19] Unset SIGQUIT(3) signal handler
[19] Writing old times:
[19] 1 times to write
[19] Write t=476 to “processor19/476”

Can anyone kindly offer input as to why the error occurred and how I can fix it?
(I only have a limited background in fluid mechanics/aerodynamics.)

Thanks!


#2

Hi @UBCUAS,

I’ve checked your project out and here are a few of the errors that if fixed might get your simulation working.

“ATD_Left_Wing_REV08_STEP mesh 2” has over 1000 illegal faces. This will likely give very off results if not divergence during your simulation. You need to ensure that the illegal cells of this mesh are reduced. Looking through your geometry I would say remove the two holes and make a simple flat surfaces that the wing root. That should solve most of your problems on top of increasing the mesh fineness in general. However, your first mesh “ATD_Left_Wing_REV08_STEP mesh” is fine and you can continue to use that.

In your simulation you have set the outlet boundary condition as a velocity outlet. You do not want to do that as it may cause eventual instability due to the fluid being “forced” out of the computational domain and you risk running into a continuity error of sorts. The fix is simple, just set the outlet as a pressure outlet with a zero value.

Hope this helps!

Cheers.

Regards,
Barry