FDTD + Mur : Known Stability issues (Please Help People!!!)

Hello everyone,

Since my last post was viewed by 24 people and no one bothered to help in anyway I'll try to clarify my problem.

I am making a 3D FDTD code with Mur ABCs.

When I only use the pure FDTD formulas everythin works fine but when I enable the mur formulas on the boundaries then after a while of normal behavior an abnormal increase takes place

Here is a snapshot :

This is a 3D golden waveguide with two opening on the y axis. I have only enforced Mur at y=0 to make the difference between the Mur and its absence clear.

The boundaries at y=0 is 50 cells away from the wave guide meaning 3wavelengths away at 8GHz which is a great frequency for this waveguide.

Does anyone ANYONE AT ALL know what may have gone wrong? Has anyone seen anything similar .

Concerning the standard FDTD stability issues meaning the D (cell size) and Dt (time step) there are both covered by the standard equation by Allen tavlove. D is 15 times smaller than the wavelength and Dt is produced by D/(sqrt(3)*C).

Please someone help. If someone bothers to help me then I could help someone else with this method and its various shortcomings and problems.

Thanks in advance,
Adam

somada141@yahoo.gr

Actually the Mur ABC is one of the easiest ABC, you should program it in such a way that:

// Abc at the beginning of the simulation domain
ex[0] = ex_low_m2;
ex_low_m2 = ex_low_m1;
ex_low_m1 = ex[1];

// Abc at the ending of the simulation domain
ex[nxsize-1] = ex_low_m2;
ex_low_m2 = ex_low_m1;
ex_low_m1 = ex[nxsize-2];

Hope, this helps you !

Regards

Actually I found the mistake I was making. It was something of a stupid mistake.

I only posting this in case someone finds it useful:

While updating the inner field components for E with FDTD so that you update the outer field components with MUR you calculate the inner fileds only on the directions where you enforce MUR.

For example for Ex:

We update with FDTD in:

for x in (0,end)
for y in (1,end-1)
for z in (1,end-1)
FDTD

what I did was calculate x for 1,end-1...Hence the instability caused.

Hope this helps someone out there

hi

is there more discussion about this subject

no, from the beginning there was practically no interest in this topic from other user. However I have solved my problem so if you have any similar problems or if you have any other questions concerning FDTD & Mur please ask...

hi

i'm working also with FDTDsince 2003 but my interset is focalised to study biomedicals antenna. Sincerly i have usually some FDTD problems.

cordially

what sort of problems are you facing with FDTD?

THIS MATTER HAS BEEN RESOLVED.CHECK OUT THIS :

https://www.edaboard.com/viewtopic.p...023&highlight=