Search found 155 matches

by mika
03 Feb 2020, 10:52
Forum: ElmerSolver
Topic: 2d simulation of acoustic wave propagation
Replies: 58
Views: 3458

Re: 2d simulation of acoustic wave propagation

If the normal acceleration has units L/T^2 (you however wrote 1/s^2, was a missing length just a typo or am I missing something?), in view of the equation of motion I'd define BCs for example as $ a0 = 5.6849e5 * rho0 Wave Flux 1 = Real MATC "a0*cos(-phases(0))" Wave Flux 2 = Real MATC "a0*sin(-phas...
by mika
31 Jan 2020, 17:58
Forum: ElmerSolver
Topic: 2d simulation of acoustic wave propagation
Replies: 58
Views: 3458

Re: 2d simulation of acoustic wave propagation

To have the same sources Elmer definitions should be written as BCs for the normal pressure gradient. This should be easy to do. I guess the Comsol model has PML BCs on the edges x = const. This is difficult to mimic with Elmer. The simple impedance BC of Elmer is best suited for cases where the wav...
by mika
31 Jan 2020, 15:59
Forum: ElmerSolver
Topic: 2d simulation of acoustic wave propagation
Replies: 58
Views: 3458

Re: 2d simulation of acoustic wave propagation

I altered the signs of all phase values and got the solution of the attached figure.

-- Mika
by mika
28 Jan 2020, 17:27
Forum: ElmerSolver
Topic: 2d simulation of acoustic wave propagation
Replies: 58
Views: 3458

Re: 2d simulation of acoustic wave propagation

Hi, The description the source is represented by exp(1j*k*r) is not complete, there has to be an additional time-dependent part. Well, I now try to be quite specific since this appears to be necessary in order to make progress. If each transducer is supposed to create a plane wave (that is, a wave f...
by mika
28 Jan 2020, 13:20
Forum: ElmerSolver
Topic: Simulation of the force between two magnets
Replies: 28
Views: 2453

Re: Simulation of the force between two magnets

Despite what I wrote earlier, obtaining a finite curl of the potential variable A_phi seems necessarily to imply that A_phi = 0 on the axis r = 0. Thus the homogeneous Dirichlet BC may indeed be the right BC on the axis.

-- Mika
by mika
26 Jan 2020, 18:23
Forum: ElmerSolver
Topic: 2d simulation of acoustic wave propagation
Replies: 58
Views: 3458

Re: 2d simulation of acoustic wave propagation

I made a mistake, the intention was to write "either exp(iwt) or exp(-iwt)]". So Elmer assumes the representation p(x,t) = P(x)exp(iwt) and this is the sole option.
by mika
26 Jan 2020, 15:07
Forum: ElmerSolver
Topic: 2d simulation of acoustic wave propagation
Replies: 58
Views: 3458

Re: 2d simulation of acoustic wave propagation

Another source for sign changes to be necessary in the equations could be that a different exponential ansatz [either exp(iwt) or exp(iwt)] is used in different software. Elmer employs the alternate exp(iwt).
by mika
25 Jan 2020, 16:32
Forum: ElmerSolver
Topic: 2d simulation of acoustic wave propagation
Replies: 58
Views: 3458

Re: 2d simulation of acoustic wave propagation

There has to be some inconsistency. Any chance that there could be a +/- issue between the top and bottom array BCs, which could arise for example from different conventions to define positive normal directions? Does the boundary normal direction or similar appear somehow in the phase calculation?
by mika
24 Jan 2020, 18:52
Forum: ElmerSolver
Topic: 2d simulation of acoustic wave propagation
Replies: 58
Views: 3458

Re: 2d simulation of acoustic wave propagation

Do you have some explicit mathematical formula how the values of phases are generated?
by mika
24 Jan 2020, 12:23
Forum: ElmerSolver
Topic: 2d simulation of acoustic wave propagation
Replies: 58
Views: 3458

Re: 2d simulation of acoustic wave propagation

It seems to me that some facts about the model may have been misunderstood. Since the problem relates to sound, the wave motion is longitudinal so that the field variations are in the same direction as the direction of the wave propagation. As the solution (pressure) is not a vector, no direction is...