Elmer Discussion Forum

My system definitely doesn't converge for 40kHz with ILUn, only with ILUT. And when it does, most solutions I get are completely different than the ones I get from Comsol and Matlab. So, I'm wondering if there are any mistakes in my code or I just can't deal with the fact that conditioners in Elmer ...

I'm interested in this one too. Anyone here knows how to do this?

The standard iterative solvers for the Helmholtz problem at a high wavenumber are generally known to be ineffective unless a special preconditioner is devised. Perhaps the Comsol result was based on a direct solver. You might also try the same approach and use a direct (MUMPS) solver, if installed,...

I'm aware of that. However, I want this to be fully automated with python scripts, as I did with the other steps in my pipeline: geometry and mesh is created in SALOME with a py script, and in the same way the sif file is created and is executed with a py script that opens the terminal and calls for...

Hi, I've created a simple pipeline where I create geometry and mesh in Salome, then use Elmer to simulate the pressure field, and finally visualize the field in ParaView. Then, I can take a screenshot of this field, however ParaView doesn't let you specify the exact boundaries of the area that the s...

Hi mika,

By 'pressure wave 1' and 'pressure wave 2' I mostly mean Real and Imaginary part of pressure, so then I can visualize different things like absolute value etc. So then, what does 'pressure wave' represent in the .vtu file? The absolute value of pressure?

Panos

I ran several simulations with Helmholtz equation (in 3d meshes though), with the same approach, and always got pressure wave 1 & 2. That's why it seems weird to me.

The standard iterative solvers for the Helmholtz problem at a high wavenumber are generally known to be ineffective unless a special preconditioner is devised. Perhaps the Comsol result was based on a direct solver. You might also try the same approach and use a direct (MUMPS) solver, if installed,...

It seems that my system converged in 40kHz only by using the ILUT preconditioner. Could you explain why this happened? Also, what are the differences between different ILUs and does one ILU produce a "better" result than another? (maybe that's a stupid question I don't know) EDIT: Also, I ...

The characteristic length of the domain seems to be ~ 0.2 m while the frequency is set to be f = 40 kHz. For air this gives the wavelength lambda = c/f = 343/40000 m = 8.6 mm. At least the mesh is too coarse to capture tens of waves propagating in the domain. Lowering the frequency starts to give m...