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#820 by SeeShells on 27 Dec, 2015 21:02
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WarpDrive was doing something like this if I remember correctly. I can't access his papers right now as my system is down too. Looks like we both got a lump of coal... were you bad notsosureofit?http://arxiv.org/abs/1512.01130
@Notsosureofit. I thought you may be interested.QuoteIn this letter, we have thus shown that in “effective
mass”, a notion routinely used to describe the dispersion
of the light in planar (or cylindrical) cavities, “effective”
should be dropped. Indeed as photons are brought to a
full stop in a cavity, they indeed acquire a mass in the
usual sense of the word, both from the inertial and the
gravitational point-of-view.
Yes, that has been the viewpoint for quite some time (my computer is down at the moment) -
#821 by OnlyMe on 27 Dec, 2015 21:56
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[/b]
....
WarpDrive was doing something like this if I remember correctly. I can't access his papers right now as my system is down too. Looks like we both got a lump of coal... were you bad notsosureofit?
Now see there! If you had been sharing more pics, you might have been on the other list. -
#822 by ThereIWas3 on 27 Dec, 2015 22:18
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Getting the openSCAD images better now. This one is automatically generated from MEEP rather than by hand like the last one. I thought the cut-away rendering would be helpful to show the insides. Next is to add in the antennas.
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#823 by VAXHeadroom on 28 Dec, 2015 01:36
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New video of the same data (aero's model of SeeShells meep simulation) as last time. New animation has the following changes:
Min/Max/Frame# are now always in the same location in the video frame - this is a first step to making a scale for the animation to show min/max.
'Whiskers' show H field vectors. Whisker length only indicates field strength and direction, not how far the field 'extends' in 3 space.
Max is in 'meep units'.
Min is always zero to 3 decimal places.
Only fields whose vector length > 1e-6 are shown.
Slices are now Red/Blue - they're colored to match Red/Cyan 3D viewing glasses. By concentrating on one or the other you can 'view' one layer at time. This is in preparation for a full 3D anaglyph video
H fields are now shown as cones instead of cylinders - makes it easier to see the vector base and direction and also to see through the upper layer. Background was darkened to make the Red/Blue glasses work better
This is a first step in formulating a display to put the sum of a full wave's H fields shown on the frustum boundary.
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#824 by kitsuac on 28 Dec, 2015 04:24
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Coming from a C/C++/assembly programmer - it bothers me deeply that there isn't available to you folks a piece of open source simulation software which is capable of taking advantage of parallelism strategies including: SIMD, threading, MPI. Meep does "support" these, but in practice none provide a significant performance advantage as they not only fail to scale linearly as you add more resources, but instead performance quickly starts to decrease as the necessary coordination overwhelms the ever-diminishing parallelism gains [see: my only other posts on this forum].
But, I'd be premature to blame Meep since I don't know the physics well enough to know whether or not this sort of simulation can even theoretically be accurately modeled in a massively parallel way on even our beefiest Turing machines. I think some of you know the physics well enough to have an opinion there. Fast and accurate simulations aren't going to build us a working EMdrive, but they would sure help to light the way. But how?
On a human note, it's been inspiring to keep up with this thread even though frankly I don't understand the vast majority of technical posts. Engineers, scientists, thinkers of all sorts work in much the same way though and there's the distinct flavor of something fundamental on the tip of all of your tongues. Whether it's new science or new insight into existing science, I plan to continue following until it's all sussed out.
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#825 by TheTraveller on 28 Dec, 2015 07:25
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Simply do a small Z match hole in the side of the frustum where the waveguide is attached. They do it in microwave ovens all the time. It will keep the frustum cavity from seeing the full waveguide and in the case of a asymmetric traveling mode keep the VSWR lower in the reflected load to the waveguide antenna.
This is one of my "Fixes" to the smoking matchstick antenna in my waveguides.
Shell
Putting a choke hole or slit in the side wall of the frustum was one of Roger's bread crumbs as attached.
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#826 by dustinthewind on 28 Dec, 2015 07:29
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http://arxiv.org/abs/1512.01130
@Notsosureofit. I thought you may be interested.QuoteIn this letter, we have thus shown that in “effective
mass”, a notion routinely used to describe the dispersion
of the light in planar (or cylindrical) cavities, “effective”
should be dropped. Indeed as photons are brought to a
full stop in a cavity, they indeed acquire a mass in the
usual sense of the word, both from the inertial and the
gravitational point-of-view.
I am not sure why they don't think of the light falling into a black hole as having real mass also. The light falling in will stop all acceleration and freeze in time effectively forming part of the black hole. Enough light falls into a black hole and it should grow larger, energy having equivalence to mass, and light can push a solar sail. Antimatter matter reactions also make a lot of light, and atomic (or nuclear) bonding energy can increase the mass of an atom?
What I thought was interesting was this quote,
page 3 4th paragraph i think.
"However unlike in a vacuum cavity, the gravitational acceleration of the wavepacket is reduced by the medium, that acts as a kind of drag force for the wavepacket of light, as pointed out already in the context of light propagation in transparent moving media [18]."
You can think of the dielectric for free space as having a drag on the light also. This suggest that the dielectric of free space is actually moving with respect to the cavity but the dielectric in the cavity isn't moving. The light is both being dragged by the moving free space and the non-moving dielectric in the cavity.
If your not sure of what I am talking about with respect to free space as moving then I will link this to the other thread where I discuss it on the Woodward's effect thread here: http://forum.nasaspaceflight.com/index.php?topic=31037.msg1465733#msg1465733
Edit: If gravity could create traveling modes that accelerate by its drag then maybe inducing (accelerating) modes in a cavity could also drag space?
A gif of what looked like one of the traveling modes attached below and the link for the rest of the files.
Not sure any of them were accelerating.
https://drive.google.com/folderview?id=0B1XizxEfB23tRERjT0tEYWxwMXM&usp=sharing
Link above from this link here: http://forum.nasaspaceflight.com/index.php?topic=38577.msg1450764#msg1450764
Edit2: Eh? just realized this but maybe in this image you could think of it as ratcheting space time?
Glad your doing well Traveler. Life can be so fragile and at the same time it is resilient. I guess it reminds us to make the most of it with what we have. I like the Moby Dick quote.
P.S. this image is probably an incomplete filled EM cavity so it is probably energy being transmitted from the antenna to the rest of the cavity (early MEEP analysis). I would expect the modes to stand still once the cavity is filled (like a capacitor). I would imagine we would need an open end of the cavity to have permanently traveling modes.
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#827 by TheTraveller on 28 Dec, 2015 08:48
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Good news!
The furniture a friend stored in my workshop, during my battle with prostate cancer, should soon be gone. They have sold their old house and bought another.
So soon I'll get my workshop floor space back to start building my 1st rotary test rig.
Floor is fire brick on 100mm of hard compacted sand. Should be very stable. Can bolt the rotary test rig legs to the bricks if necessary to stop any "walking".
Yea OK, seems a little thing but to me is major for several reasons:
1) my prostate cancer is in "Wishful Watching State".
2) my health in 2016 will allow me to engage the several experimental pathways I have mapped out.
3) I'm 100% confident my health, electronics / microwave engineering knowledge & EmDrive operational physics knowledge will deliver the result I expect. Not to say there will not be a few suprises along the way but hey that is what makes it interesting.
As from the start my goal is to replicate Roger's experimental data. My builds will not be to blaze new territory but to follow Roger as close as I can.
Along the way will be tests to measure thrust versus mode (TM113 versus Roger's suggested TE013) versus Q versus power versus end plate rad pressure. Will probably build 6 to 10 frustums with various end plates (flat, tuneable, spherical) to test all this out.
So YES I need the furniture gone.
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#828 by frobnicat on 28 Dec, 2015 11:35
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.../...
3) During the extremely short runs of Meep up to now, the Poynting vector and stresses were increasing at an exponential rate. What does the equilibrium balance between Poynting vector field rate and stress gradient look like vs time?
.../...
By "exponential rate" do you mean exp(-t/tau) as a first order charge at constant power against leaking power proportional to stored energy, asymptotically reaching a plateau (would make sense), or exp(t/tau) as ever increasing (at increasing rates) values, i.e. diverging (would not make sense, but your phrasing leaves ambiguity). Sorry for the nitpicking.
At hollidays with limited connectivity, happy celebrations everyone.
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#829 by rfmwguy on 28 Dec, 2015 13:14
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Good news!
Best of luck to you in 2016 Phil...health first, experiments second.
The furniture a friend stored in my workshop, during my battle with prostate cancer, should soon be gone. They have sold their old house and bought another.
So soon I'll get my workshop floor space back to start building my 1st rotary test rig.
Floor is fire brick on 100mm of hard compacted sand. Should be very stable. Can bolt the rotary test rig legs to the bricks if necessary to stop any "walking".
Yea OK, seems a little thing but to me is major for several reasons:
1) my prostate cancer is in "Wishful Watching State".
2) my health in 2016 will allow me to engage the several experimental pathways I have mapped out.
3) I'm 100% confident my health, electronics / microwave engineering knowledge & EmDrive operational physics knowledge will deliver the result I expect. Not to say there will not be a few suprises along the way but hey that is what makes it interesting.
As from the start my goal is to replicate Roger's experimental data. My builds will not be to blaze new territory but to follow Roger as close as I can.
Along the way will be tests to measure thrust versus mode (TM113 versus Roger's suggested TE013) versus Q versus power versus end plate rad pressure. Will probably build 6 to 10 frustums with various end plates (flat, tuneable, spherical) to test all this out.
So YES I need the furniture gone. -
#830 by SeeShells on 28 Dec, 2015 14:08
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Simply do a small Z match hole in the side of the frustum where the waveguide is attached. They do it in microwave ovens all the time. It will keep the frustum cavity from seeing the full waveguide and in the case of a asymmetric traveling mode keep the VSWR lower in the reflected load to the waveguide antenna.
This is one of my "Fixes" to the smoking matchstick antenna in my waveguides.
Shell
Putting a choke hole or slit in the side wall of the frustum was one of Roger's bread crumbs as attached.
I saw it first in the microwave oven!
I saw it in a proposal by Paul March with one of their designs before Shawyer's bread crumbs. Doesn't matter where, it's a very viable way to match.
Shell
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#831 by Rodal on 28 Dec, 2015 14:47
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I showed this over multiple posts, using Mathematica to post-process the Meep data output by Aero (*). See for example http://forum.nasaspaceflight.com/index.php?topic=37642.msg1406309#msg1406309.../...
3) During the extremely short runs of Meep up to now, the Poynting vector and stresses were increasing at an exponential rate. What does the equilibrium balance between Poynting vector field rate and stress gradient look like vs time?
.../...
By "exponential rate" do you mean exp(-t/tau) as a first order charge at constant power against leaking power proportional to stored energy, asymptotically reaching a plateau (would make sense), or exp(t/tau) as ever increasing (at increasing rates) values, i.e. diverging (would not make sense, but your phrasing leaves ambiguity). Sorry for the nitpicking.
At hollidays with limited connectivity, happy celebrations everyone.
that shows an excellent fit of the net force (on the flat ends) data (from which the force has been computed and shown during the last two cycles ending at 0.013 microseconds from the time at which the Microwave feed was turned on) using the following fit:
A t +B (exp(t/tau) Sin [C t + D] + E
where the circles represent the data points output by Meep and the solid line represents the fitted model (with excellent R^2 = 0.999353)
I also wrote:Quotethe present Finite Difference model (from which the force has been computed at the last two cycles ending at 0.013 microseconds from the time at which the Microwave feed was turned on), would have to be marched forward for 1,000 times longer, to a total of 10 microseconds, for the force to be magnified by the calculated exponential growth to a value of 10 microNewtons (for an inputPower of 43 watts). Given the fact that the present Meep model takes an hour to run on a good PC modern computer, 1,000 hours of computer time represents over 41 days of computing time. Thus running the Meep model to steady state is impractical. Rather than using a supercomputer to perform such a computation, I suggest to use an implicit (unconditionally stable) Finite Difference model in time (rather than the explicit time difference model presently used that is subject to stability problems that limit the maximum finite difference time step). Such implicit finite difference models are well known (I developed a version of them in my PhD thesis 35 years ago) and can be run much faster than explicit FD models. There are also numerous alternative numerical schemes that are more accurate than Finite Differences.
The need to march forward the analysis to the order of tens of microseconds (instead of the extremely small time of 0.013 microseconds in the present Meep analysis) to ascertain what is going on agrees with a recent estimate by TheTraveller (where he proposed 30something microseconds was needed).
__________
(*) I have not seen anyone else similarly analyzing the Meep data in these threads, as they usually just output the electric or magnetic field values at one point in (extremely early) time (usually around 0.01 microseconds
-many times the Meep electric or magnetic field output are shown without indicating at what time, or without showing the audience that the output is increasing with time -), without analysis of the stresses or analysis of the time variation of the Meep model. Also, I have not seen the Meep model validated by checking it against the experimental results and COMSOL FEA analysis for TM 212 of NASA. -
#832 by Vesc on 28 Dec, 2015 15:19
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After watching the linked video, YouTube suggested another which I watched. I HIGHLY suggest those who are only passingly familiar(like me!) with waveguides and resonances watch this FANTASTIC lecture by Dr Walter Lewin from MIT (a genius lecturer!). (you old veterans might want to watch it too ) ESPECIALLY the last 10 minutes - the demonstration of resonance convergence and decay is pretty fascinating. I really need to watch all of that semester (8.03)
[link elided, see OP
Running commentary I'm only at 28:43 in this video so far.
1) At first I was going to question why cos(wt) at end of equation should be removed as per comment at 12:21 but his head was blocking the traveling wave component of the equation which already incorporated cos(wt) as the traveling wave component! Thus all variables in E(x,z,t) are used! So yep makes sense.
2) Uncorrected notation error at 17:42 Phase velocity in the z direction is > c not > 0. Love this super-luminal stuff! And I love how he establishes the relationship of the the solutions from both aspects of electrical propagation & geometry.
Boy does this bring back the memories for this old EE and his (then) shiny new TI SR-50.... which replaced the Versalog.... ;-) -
#833 by rfmwguy on 28 Dec, 2015 15:27
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Pardon my intrusion modelers...have a really basic question: What theory is being researched with the meep & other models? IOW, other than resonance, is the end result of the models trying to propose a theory for the emdrive effect?
My guess is poynting vectors, but has anyone established an energy flux density to kinetic energy formulae or hypothesis?
If there is an old post regarding this, I could not find it. Perhaps someone can post a link to it.
Thanks - Dave
p.s. What I'm looking for is a directional newton (F) formula.
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#834 by ThereIWas3 on 28 Dec, 2015 15:34
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My view is that MEEP can show what is happening inside the frustrum in ways that are difficult or impossible to detect with hardware experiments. What modes are you getting really? What is the pattern of current induction in the sidewalls?
You can make a change to a MEEP model in minutes that would take weeks with hardware. For example, what is the sensitivity to frustrum half-angle? What does changing the half-angle in 1 degree increments reveal? You couldn't do that with hardware, unless you have a lot of copper lying about. With MEEP you could write a script that automates that, let it run overnight for a few days, and end up with hundreds of images of resonance patterns, from which you might gain some insight into what is going on.
MEEP can do more than find resonance. It can generate movies of how the waves move, and can measure forces generated.
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#835 by Rodal on 28 Dec, 2015 15:36
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Pardon my intrusion modelers...have a really basic question: What theory is being researched with the meep & other models? IOW, other than resonance, is the end result of the models trying to propose a theory for the emdrive effect?
My guess is poynting vectors, but has anyone established an energy flux density to kinetic energy formulae or hypothesis?
If there is an old post regarding this, I could not find it. Perhaps someone can post a link to it.
Thanks - Dave
1) There is no "new physics" in Meep (out of the box, as run up to now). (*) Out-of-the-box Meep is old physics: standard classical physics. No "new theory" is being researched or "can be researched" by only running Meep, since Meep's theory is well known: Meep is just solving Maxwell's equations, all you are going to get is a solution to Maxwell's equations. And you are only going to get a valid solution to the real actual problem if the data input input is correct, as per the known principle of "Garbage-In Garbage-Out".
2) (If the input to Meep is consistently correct and a good model of reality, and if the mesh is fine enough to be reasonably close to a converged solution, and if the finite difference time step is small enough so as not to result in numerical instability and if the round-off error is controlled so as not to result in numerical inaccuracy and if the Meep results are post-processed as needed to properly understand the problem) Meep can serve to show solutions to Maxwell's equations that are non-intuitive and hence help in experiments as well as help clarify minds on what is going on in an electromagnetic cavity according to well-accepted standard physics. Shawyer and Yang claim that all that is required to understand the EM Drive is Maxwell's equations (and for Shawyer, also special relativity). Meep can be used to show that several statements by these authors are incorrect.
3) Strictly speaking no "steady-state resonance" can be researched with the present Meep models of time-marching solutions for only ~0.01 microseconds total run, as resonance at a natural frequency is a steady state resonance, with standing waves, and as previously discussed the present Meep models only model an extremely small time (usually 0.01 microseconds) which falls way short of the time at which steady state resonance occurs. Hence the present Meep analysis is one of very early transient response, and not one of steady state resonance.
4) Concerning <<, is the end result of the models trying to propose a theory for the emdrive effect?...My guess is poynting vectors, but has anyone established an energy flux density to kinetic energy formulae or hypothesis?>> no such hypothesis is needed, concerning how to interpret the Meep results. Since the relationship between Poynting vector field, stress and body force are well known experimentally and theoretically for over a hundred years: as per conservation of energy and momentum balance laws, as per Maxwell's theory used in Meep. So, in that regard, it is only a question of post-processing the Meep data, as the theory behind Meep is known to satisfy the conservation of momentum and conservation of energy equations.
__________
(*) Meep is an open program, and this constitutes its main strength. Many students at MIT instead of using Meep "out of the box" have written their own programs to modify it (usually in thesis or in papers). For example, one could explore new constitutive equations not present in Meep by re-writing the Meep program to accommodate different constitutive laws.
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#836 by rfmwguy on 28 Dec, 2015 15:45
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Thanks for the summary. So no one has linked EM wave flux density to a directional micro or piconewton force?
The sims are extremely interesting and useful for builders for sure, just was hoping a hypothesis lurked in the background somewhere, that's all. -
#837 by Rodal on 28 Dec, 2015 16:05
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Thanks for the summary. So no one has linked EM wave flux density to a directional micro or piconewton force?
The sims are extremely interesting and useful for builders for sure, just was hoping a hypothesis lurked in the background somewhere, that's all.
Concerning <<So no one has linked EM wave flux density to a directional micro or piconewton force?>> are you referring to my previous post (http://forum.nasaspaceflight.com/index.php?topic=39004.msg1466298#msg1466298 ) linking to stress calculations (and net forces on the end plates) obtained from post-processing Meep data?
In other words, do you have further questions regarding that post or the linked posts? -
#838 by lmbfan on 28 Dec, 2015 16:21
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Please excuse the very crude drawing in PCPaint. If I take aero's meep cell size model and slice it across where the cells are it looks much like a series of cylinders. The question is still there, is there a difference in how meep calculates this vs a series of stacked cylinders?Here is the link to Meep symmetries:
What is the difference in creating a large cell size which shows up in a very pixelated image and using short circular sections? A 2D slice to me looks the same. I mean if I take your pixelated image and fill it in making a visual 3D image it looks like multiple short cylinders.
http://ab-initio.mit.edu/wiki/index.php/Exploiting_symmetry_in_Meep
My difficulty is understanding the source phasing, and how to do it. To make it work I have resorted to running lower resolution in full 3D, saving the images, then using the good old cut and try technique until the fields calculated with symmetry look the same as the 3D images. Then I feel somewhat confident in my higher resolution symmetric runs. It only works with the source on the z axis though, or maybe mirror symmetry with the source in either the x,z or y,z plane.
As for cylindrical symmetry, as far as I know that only works when the source is axially symmetric, that is, a point source or a dipole lying on the z axis. That is to big a constraint for our problems.
Of course, if cylindrical or spherical coordinates are useful for post processing, the csv file Cartesian coordinates can be transformed mathematically to whatever coordinate system is desired. Transforming the full .h5 file might be a way to identify the boundary of the conic section for those evaluations that need to know the boundary location. With the availability of meep on a virtual machine, (see the em drive wiki, meep section) it is almost trivial to generate your own set of .h5 files, ask VAXHeadRoom about the relative difficulty compared to post processing.
@VAXHeadRoom - I hope that's all right. If not, spank me.
What am I not seeing here? Is it what the software sees?
You'll have to excuse me some as my main system took a massive crash yesterday and this is the little lab laptop. Thank goodness I have backed up it all but still a ton of work to pull off the data from the old drive.
Shell
Back to getting my system up again. I'm going to meed a new bare bone system. sigh.
Shell
Meep's output differs from your picture in that meep uses a form of anti-aliasing (in meep documentation it is called "subpixel averaging") to "smooth" the jagged edges.
I believe this can be toggled via the "eps-averaging?" input variable. -
#839 by aero on 28 Dec, 2015 16:24
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Pardon my intrusion modelers...have a really basic question: What theory is being researched with the meep & other models? IOW, other than resonance, is the end result of the models trying to propose a theory for the emdrive effect?
My guess is poynting vectors, but has anyone established an energy flux density to kinetic energy formulae or hypothesis?
If there is an old post regarding this, I could not find it. Perhaps someone can post a link to it.
Thanks - Dave
1) There is no "new physics" in Meep. Meep is old physics: standard classical physics. No "new theory" is being researched or "can be researched" by only running Meep, since Meep's theory is well known: Meep is just solving Maxwell's equations, all you are going to get is a solution to Maxwell's equations. And you are only going to get a valid solution to the real actual problem if the data input input is correct, as per the known principle of "Garbage-In Garbage-Out". No, the end result of such a model can never be <<trying to propose a theory for the emdrive effect?>> since the Meep model theory is already known: old Maxwell's equations.
2) (If the input to Meep is consistently correct and a good model of reality, and if the mesh is fine enough to be reasonably close to a converged solution, and if the finite difference time step is small enough so as not to result in numerical instability and if the round-off error is controlled so as not to result in numerical inaccuracy and if the Meep results are post-processed as needed to properly understand the problem) Meep can serve to show solutions to Maxwell's equations that are non-intuitive and hence help in experiments as well as help clarify minds on what is going on in an electromagnetic cavity according to well-accepted standard physics.
3) Strictly speaking no "steady-state resonance" can be researched with the present Meep models, as resonance at a natural frequency is a steady state resonance, and as previously discussed the present Meep models only model an extremely small time (usually 0.01 microseconds) which falls way short of the time at which steady state resonance occurs. Hence the present Meep analysis is one of very early transient response, and not one of steady state resonance.
4) Concerning <<, is the end result of the models trying to propose a theory for the emdrive effect?...My guess is poynting vectors, but has anyone established an energy flux density to kinetic energy formulae or hypothesis?>> no such hypothesis is needed, concerning how to interpret the Meep results. Since the relationship between Poynting vector field, stress and body force are well known experimentally and theoretically for over a hundred years: as per conservation of energy and momentum balance laws, as per Maxwell's theory used in Meep.
@Dr. Rodal,
https://drive.google.com/folderview?id=0B1XizxEfB23tRm41bVFtM1pVYlU&usp=sharing
Are you finished with this data set containing 14 sets of csv files for 7 increasingly longer runs, ending with a 1 microsecond run? Runs are for the Yang-Shell 6 degree cavity model with antenna at the big end and at the small end for each run length. That is the same model that you have already post processed data for. If you are finished, or have otherwise secured the data, I would like to remove it so as to recover the Google drive space occupied by the folder. It is a significant percentage of the 15 GB of space available.
Note that the shorter run data sets should be duplicates of data that you have already post processed.
aero
