Quote from: ThereIWas3 on 12/27/2015 01:32 amA further idea for faster computation is using cylindrical symmetry. Although this constrains the shapes that can be used, initial experiments suggest a 100x speedup.The geometrical axisymmetry of the frustum of the cone is presently not being exploited. However, assuming full axisymmetry would only produce fully axisymmetric electromagnetic modes. One would not be able to get the TM212 mode that NASA obtains in their experimental measurements for example.A number of modes are not fully axisymmetric but display m-fold symmetry (where "m" is the first quantum number in TEmnp or TMmnp modes). The following images shows the lowest TEmn and TMmn modes, for arbitrary "p":Only modes with m=0 are fully axisymmetric (for example TE012) . For m=1 one has to model half of the circular cross-section (and one can impose symmetry on the boundaries). For higher m>1 one has to model "smaller pie slices". So, it looks like one could at least save 50% of the mesh by exploiting axisymmetryMore problematic, it would preclude non-fully axisymmetric modes. To exploit axisymmetry one would have to determine what is the maximum number of poles around the circumference one wants to model: it would effectively set a pre-defined limit on the "m" and "n" quantum numbers that the model could model for TEmnp and TMmnp modes.This is further complicated by the fact that Meep has revealed asymmetric modes not present in cylindrical cavities. Imposing axysymmetry would get rid of such asymmetric modes. For example, an asymmetric placement of an antenna, or an asymmetric placement of a waveguide can excite asymmetric modes in a real cavity, and it is useful for the designer to know this.Actually, one of the greatest contributions of Meep analysis has been to make this asymmetric modes evident, and show how difficult it is to achieve axisymmetric resonant modes with antennas.
A further idea for faster computation is using cylindrical symmetry. Although this constrains the shapes that can be used, initial experiments suggest a 100x speedup.
Here is the link to Meep symmetries: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.
...Dr. Rodal,Love reading your posts.It's important to review the hundreds of posts on our attempts to get a TExx mode from antennas inserted into the frustum. The closest we got was a loop aero did and it created unstable traveling modes. I have no doubt that this is this is the reason that EW, Shawyer, Tajmar and (possibly) Yang have went to the waveguide insertion.Shell
JFYI, Attached are COMSOL simulations for the frustum (with coax coupling) I am going to build. It is now time for some sheet metal cutting and torch soldering... And then there will be the moment of truth....
In this letter, we have thus shown that in “effectivemass”, a notion routinely used to describe the dispersionof the light in planar (or cylindrical) cavities, “effective”should be dropped. Indeed as photons are brought to afull stop in a cavity, they indeed acquire a mass in theusual sense of the word, both from the inertial and thegravitational point-of-view.
http://arxiv.org/abs/1512.01130@Notsosureofit. I thought you may be interested. QuoteIn this letter, we have thus shown that in “effectivemass”, a notion routinely used to describe the dispersionof the light in planar (or cylindrical) cavities, “effective”should be dropped. Indeed as photons are brought to afull stop in a cavity, they indeed acquire a mass in theusual sense of the word, both from the inertial and thegravitational point-of-view.
Quote from: Mulletron on 12/27/2015 05:21 pmhttp://arxiv.org/abs/1512.01130@Notsosureofit. I thought you may be interested. QuoteIn this letter, we have thus shown that in “effectivemass”, a notion routinely used to describe the dispersionof the light in planar (or cylindrical) cavities, “effective”should be dropped. Indeed as photons are brought to afull stop in a cavity, they indeed acquire a mass in theusual sense of the word, both from the inertial and thegravitational point-of-view.Isn't that something new? Photons with rest mass?
Quote from: aero on 12/27/2015 05:40 pmQuote from: Mulletron on 12/27/2015 05:21 pmhttp://arxiv.org/abs/1512.01130@Notsosureofit. I thought you may be interested. QuoteIn this letter, we have thus shown that in “effectivemass”, a notion routinely used to describe the dispersionof the light in planar (or cylindrical) cavities, “effective”should be dropped. Indeed as photons are brought to afull stop in a cavity, they indeed acquire a mass in theusual sense of the word, both from the inertial and thegravitational point-of-view.Isn't that something new? Photons with rest mass?Has been discussed for several threads. I posted a link to a whole book on the subject several threads ago:Theory of Photon Acceleration. Taylor & Francis. 2000. Hardcoverby J.T. MENDONCA
Quote from: RFPlumber on 12/27/2015 02:58 amJFYI, Attached are COMSOL simulations for the frustum (with coax coupling) I am going to build. It is now time for some sheet metal cutting and torch soldering... And then there will be the moment of truth....Wow, your results look great!Please excuse me if I missed this, but may I ask why you've decided on a coupler inside the frustum?I was under the impression that a waveguide delivery with aperture coupling allowed for better reflection and quality.
Aero and you deserve tons of praise for persevering with Meep and finally modeling waveguide insertion. Several thread ago it was believed that it was straightforward to make the truncated cone of the EM Drive resonate in any mode wanted, whether transverse electric (TE) or transverse magnetic (TM). It was thanks to aero that this was shown to be incorrect: that it is very difficult to excite certain modes, particularly TE modes, and that the truncated cone does not always behave as a different kind of cylindrical cavity, as there are other modes that are not found in cylindrical cavities. Reality, our Universe is once again found to be so much more interesting and fascinating than our imagination !And thanks to you for insisting on looking at waveguide insertion and realizing that the way to eliminate asymmetry and rotation was to have dual symmetric waveguides ! You thought of that early on, and pioneered the way much further than shown by Shawyer, Yang and Tajmar (who to my my recollection only used one-sided waveguide insertion, with Tajmar measuring experimentally very asymmetric side forces ! )
Quote from: aero on 12/27/2015 04:10 amHere is the link to Meep symmetries: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 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.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
Quote from: SeeShells on 12/27/2015 01:35 pmQuote from: aero on 12/27/2015 04:10 amHere is the link to Meep symmetries: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 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.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.ShellPlease 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?Back to getting my system up again. I'm going to meed a new bare bone system. sigh.Shell
Quote from: zellerium on 12/27/2015 04:44 pmQuote from: RFPlumber on 12/27/2015 02:58 amJFYI, Attached are COMSOL simulations for the frustum (with coax coupling) I am going to build. It is now time for some sheet metal cutting and torch soldering... And then there will be the moment of truth....Wow, your results look great!Please excuse me if I missed this, but may I ask why you've decided on a coupler inside the frustum?I was under the impression that a waveguide delivery with aperture coupling allowed for better reflection and quality. I think the modified loop (for TE01p) is as good as every other coupling if it's done right. A large coupling window in the sidewall could leads to more asymmetry. As long as we don't know exactly what causes the (possible, measured) thrust keep the experiment as simple as possible. The cavity without a hole in the sidewall is complicated enough. The additional copper of the waveguide leads to more ohmic losses and it could reduce the total Q_0 of the resonator caused by the wall currents in this section (compared with the cavity without waveguide coupler). So the modified loop looks like a good choice.
Quote from: SeeShells on 12/27/2015 08:17 pmQuote from: SeeShells on 12/27/2015 01:35 pmQuote from: aero on 12/27/2015 04:10 amHere is the link to Meep symmetries: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 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.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.ShellPlease 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?Back to getting my system up again. I'm going to meed a new bare bone system. sigh.ShellYes, there is a huge difference, as Meep solves Maxwells' differential equations (in a central difference scheme at each node). The limitation with Meep's finite difference scheme is the coarseness of the 3-D mesh of nodes. It imposes a three dimensional mesh, where Maxwell's equations are solved only at the nodes of the mesh. Hence it is not looking or solving at cylinders, but a number of nodes in 3-D. Think of the boundary as a staircase boundary, rather than as a collection of cylinders, because there are no cylinders connecting the stairs in the finite difference scheme, instead you have a number of nodes, and the difference equations are being solved at each node, and there are many, many nodes separating the staircase boundaries. Each node is connected to the surrounding nodes in 3-D, so as you go from a node from the left boundary to a node at the right boundary there are many finite difference paths that connects the boundaries: not just straight paths like in a cylinder, but you can imagine other paths, zig-zags that describe many other connections.It involves the simultaneous solution of all these coupled equations that connect all the nodes.
Quote from: Rodal on 12/27/2015 08:25 pmQuote from: SeeShells on 12/27/2015 08:17 pmQuote from: SeeShells on 12/27/2015 01:35 pmQuote from: aero on 12/27/2015 04:10 amHere is the link to Meep symmetries: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 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.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.ShellPlease 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?Back to getting my system up again. I'm going to meed a new bare bone system. sigh.ShellYes, there is a huge difference, as Meep solves Maxwells' differential equations (in a central difference scheme at each node). The limitation with Meep's finite difference scheme is the coarseness of the 3-D mesh of nodes. It imposes a three dimensional mesh, where Maxwell's equations are solved only at the nodes of the mesh. Hence it is not looking or solving at cylinders, but a number of nodes in 3-D. Think of the boundary as a staircase boundary, rather than as a collection of cylinders, because there are no cylinders connecting the stairs in the finite difference scheme, instead you have a number of nodes, and the difference equations are being solved at each node, and there are many, many nodes separating the staircase boundaries. Each node is connected to the surrounding nodes in 3-D, so as you go from a node from the left boundary to a node at the right boundary there are many finite difference paths that connects the boundaries: not just straight paths like in a cylinder, but you can imagine other paths, zig-zags that describe many other connections.It involves the simultaneous solution of all these coupled equations that connect all the nodes.http://static.planetminecraft.com/files/resource_media/screenshot/1126/20110701_011218_134841.jpgSo meep solves small meep units that are little blocks? I see what your saying Dr. Rodal but it will take me sometime to get the image out of my head.Thanks...Shell