Elmer Discussion Forum

I am using an acoustic solver (Linearized Navier-Stokes equations in the frequency domain), but the following error occurs for the 2nd order mesh. ERROR:: ComplexLUDecomp: Matrix is singular. ERROR:: ComplexInvertMatrix: inversion needs successfull LU-decomposition For linear meshes, the results com...

I am trying to do acoustic analysis in box-shaped air with Linearized NavierStokes equation. I want to create a plane wave at the x=0 boundary and apply a far-field condition on the other side at x=0.1 to ensure there are no reflected waves. The far-field conditions were set appropriately thanks to ...

Suitable BCs are explained in Section 13.2.2 of the documentation https://www.nic.funet.fi/pub/sci/physics/elmer/doc/ElmerModelsManual.pdf as "For example, outgoing waves may be approximated by setting Z = −rho_0 c and ZT = −iω/c on the outflow boundary". That is, one has to give also an i...

I am trying to do acoustic analysis in box-shaped air. A pressure sine wave was excited on one side, and the impedance was set to ρ * c (density * propagation speed) on the other side to create a far-field boundary condition. I created the boundary conditions as below in the Helmholtz solver and got...

FEA target http://www.elmerfem.org/forum/download/file.php?mode=view&id=7880&sid=b76374f36b7934deef49e80d6eb9d7e8 I'm trying to calculate the reflection coefficient using pressure in an air box like the image above. A 1000Hz sound is generated at the x = 0 position, and an acoustic impedanc...