Dear Steve,
thanks for your long e-mail.
Ad 2. Now I can see that your simulation will not be overwhelmingly
big; if you set size to 320,000 microns and resolution to 0.01, the
pixels would be 100 microns and you would get 3200x3200 pixels
simulation, which may be acceptable if you have a powerful computer.
It could give sound results. Still it is inefficient in the sense that
you are using relatively high resolution for a very simple and smooth
structure. I wonder whether the 99 % of empty simulation volume could
not be replaced by some analytical model...
But, if it is so, why not get along completely without the 1e6
scaling and use the SI units instead? I suggest to define the size to
0.32 meter, so setting the resolution to 0.01*1e6 = 10,000) should
give you the same result, but in better readable units.
This also touches the problem of simulation time: if you use 1 meter
as size unit, and define MEEP to run for 9 internal time units, it is
quite clear the physical run time would be 9/c = 3.002-08 seconds =
30.02 nanoseconds. If the prescaling of 1e6 is applied, then it goes
more complicated and I tend to make errors in estimations in such
cases.
Ad 3. If a sheet of 50 micrometers is to be simulated, the resolution
has either to be increased at least 60 times, or some informed
approximation has to be applied. As I wrote, thin metallic sheets can
sometimes be well approximated by a thicker resistive metal slab, but
I do not have any clue as to what extent this can be applied to
Casimir force simulations.
Ad 4. I can recall I got big problems with symmetries that also
applied to my sources; as a result, I could never excite a plane wave
in such cases. But maybe it is only related to Python meep or maybe I
just did something wrong. I had to try everything from scratch as I
found no example of symmetries in Python-meep anywhere.
Filip
2014-11-24 20:57 GMT+01:00, Steve russell7...@roadrunner.com:
Dear Filip,
Thank you for your response.
Item 1. I am using 2.3 because I didn't have anything else to use. I am
happy to know that it is the right value to use. I am working a highly
visible problem so my mistakes will be scrutinized. Of course I only
expect to break the ice to encourage someone to use available funding
and skills to work the problem in detail, but I also want my answers to
be good enough to do that.
Another aspect is that I know of an experimental effort to build and
test this device with variations but as I wrote in an earlier message,
there is no working theory which explains previous experimental results
so all efforts to date have been cut and try type methods. (Of course
there are rudiments of theory which are being used, 5 different ones
publicly known, at last count.)
Item 2. I will need to read your read on your web site to understand
this. This is what I have done.
I set lattice size to 32 x 32 and scaling 1:1e6 and used copper
normalized to 1e-6 as my material. Then I set resolution to 1e-2. My
idea was that my wavelength is about 0.15 meters (frequency ~2 GHz) so I
need a minimum of 10 samples per cycle to characterize the driving
frequency. Anyway, 320,000 x 1e-6 gives 0.32 meters which is a little
larger than my geometry. Then with my resolution of 0.01, I am sampling
the lattice at only 3200 points. That should be more than enough, maybe
100 times more than enough, but it runs. Slowly but it runs and for very
short runs h5topng produces usable PNG files. I expect that to maintain
for longer runs. I started a run last night which should finish about
noon tomorrow. Simulating 9 seconds real time so run time is 9/1e-6 =
9,000,000. That is confusing and I don't know why Meep was made to use
Meep time as run time, but I guess that using simulated time would also
be confusing as well as hiding Meep's operation under another layer of
conversion.
Item 3. Well, 50 um is the dimension of the material used and that I
have coded into my geometry. If I can avoid approximations I want to do
so for reasons I wrote about in Item 1. above. I will need to look into
this in more detail but if the simulation currently running produces a
viable resonate field image then that will be a consideration.
Item 4. I really could benefit from symmetry. The ability cut a 36 hour
run time by 3/4 or even 1/2 is significant, and even more so when doing
what amounts to test runs. I wonder if it is simply a coding error that
mismatches the coordinates between the lattice and the geometry. After
my run completes tomorrow I will change the axis on my geometry to see
if symmetry can be maintained that way. It is pretty easy to see the
mismatch of the field phases. I may need to play with that, too.
Item 5. Cylindrical coordinates - maybe an answer will come from the
discussion group.
Filip - If my current run is successful I want to calculate forces
around the outside of the modeled resonate cavity. I am hopeful that
Meep can detect forces
