Quote from: Notsosureofit on 02/18/2015 07:50 pm@ RODALCan you generate a dispersion relation from the exact solution ?(Almost) anything is possible if I get the time This work done whenever I take a break from $$$ paying work It continues to snow over here
@ RODALCan you generate a dispersion relation from the exact solution ?
Quote from: Notsosureofit on 02/18/2015 07:50 pm@ RODALCan you generate a dispersion relation from the exact solution ?@NotSoSureOfItI think that the relation between the wavenumber k and the angular frequency omega is perfectly linear for a truncated cone homogeneously filled with a medium having constant, isotropic, electric permittivity and constant magnetic permeability. It follows from the homogeneous electromagnetic wave equation, which for the truncated cone is solved in spherical coordinates via spherical waves (this involves an assumption of spherical ends, instead of flat ends).Is your question what is the effective dispersion relation for a truncated cavity containing a dielectric (with constant properties) filling only a portion of the truncated cone?Or is your question what is the dispersion relation for a truncated cavity containing a dielectric with nonlinear properties? Or anisotropic properties?Or am I wrong, or missing something, ...
Quote from: Rodal on 02/18/2015 09:13 pmQuote from: Notsosureofit on 02/18/2015 07:50 pm@ RODALCan you generate a dispersion relation from the exact solution ?@NotSoSureOfItI think that the relation between the wavenumber k and the angular frequency omega is perfectly linear for a truncated cone homogeneously filled with a medium having constant, isotropic, electric permittivity and constant magnetic permeability. It follows from the homogeneous electromagnetic wave equation, which for the truncated cone is solved in spherical coordinates via spherical waves (this involves an assumption of spherical ends, instead of flat ends).Is your question what is the effective dispersion relation for a truncated cavity containing a dielectric (with constant properties) filling only a portion of the truncated cone?Or is your question what is the dispersion relation for a truncated cavity containing a dielectric with nonlinear properties? Or anisotropic properties?Or am I wrong, or missing something, ...I was just thinking of the simplest case but based on your exact solution, rather than using that of the cylindrical cavity evaluated at both ends, which is what I have been using. The radii of both ends would presumably be already present in the single (presumably quadratic ?) expression.
Mmmm...I see the problem.
Quote from: Star-Drive on 02/18/2015 12:32 pmFolks:While you all talk about various ways to accomplish the E&M simulations of these frustum cavities, I thought you might like to take a look at the COMSOL derived resonances of the Eagleworks Lab's copper frustum resonant cavity driven with a ~16mm OD loop antenna located 15% up the side wall of the frustum from the large OD end of the cavity. BTW, the EMPower amplifiers were delivered to the Lab yesterday and I'll be calibrating the power metering for one that was installed yesterday on the torque pendulum.Best, Paul M,Thank you, Paul, for posting this, the attached pdf with COMSOL plots (which I first missed, my bad, thanks to Mulletron for pointing it out to me ) is very useful for all of us (those like me working on the exact solution of the frustum, and those working with numerical methods like MEEP, COMSOL, ANSYS-multiphysics, etc.).I could not find in the pdf attached to your post, or in your post. language to indicate whether the COMSOL calculations in the attachment (http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=796287) include or do not include a dielectric inside the truncated cone (frustum). My impression is that these COMSOL calculations do not include the dielectric inside the truncated cone (this impression is based on the frequency calculated for TE012).Still a clarification for some readers like me, may be useful (to those to whom what I write below is obvious, please forgive me for taking your time):1) Clarification: the jpg image you posted are not "COMSOL derived resonances of the Eagleworks Lab's copper frustum resonant cavity", the COMSOL plots are in the pdf attached to your post (http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=796287)2) The mode shapes in the slide are for a different geometry: a circular waveguide (instead of a truncated cone/frustum like NASA's EM Drive) , that had been plotted in published journals since 1936, without using a digital computer. The actual reference's date is 1985 (instead of 1966): http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=1132998. Since COMSOL was started in 1986, Lee, Lee and Chuang did not use COMSOL: they had no need to use a finite element program, because an exact solution exists for what they plotted: the mode shapes of a circular waveguide.The circular waveguide exact solution is present in the 1943 textbook by Schelkunoff, and in papers he published in the 1930's. The mode shapes look identical to the plots that Schelkunoff published in the 1930's without the benefit of a digital computer: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1332981#msg1332981. The article by Lee, Lee and Chuang states: "The earliest plots of modal field distribution in rectangular/circular waveguides were given by Southworth (1936), Barrow (1936), Schelkunoff (1937), and Chu and Barrow (1937)"3) The solution for a truncated cone (the geometry of the NASA frustum, and the geometry analyzed by COMSOL in the attached pdf) is different from the solution for a circular waveguide in several respects: the natural frequencies are quite different, and while in a circular waveguide different mode shapes are either resonant or cutoff, in a truncated cone some mode shapes are resonant, some are evanescent and some have a transition from resonant to evanescent (a characteristic not present in circular waveguides). Also, the attenuation and focusing aspects of the truncated cone (frustum) are not present in the circular waveguide.
Folks:While you all talk about various ways to accomplish the E&M simulations of these frustum cavities, I thought you might like to take a look at the COMSOL derived resonances of the Eagleworks Lab's copper frustum resonant cavity driven with a ~16mm OD loop antenna located 15% up the side wall of the frustum from the large OD end of the cavity. BTW, the EMPower amplifiers were delivered to the Lab yesterday and I'll be calibrating the power metering for one that was installed yesterday on the torque pendulum.Best, Paul M,
Quote from: Mulletron on 02/18/2015 05:57 pmStrong H field at dielectric disc. Just like theory suggests. Wow. Those are quite remarkable papers. It seems like a very likely cause for the thrust, with previous published results availing it.I wonder why the research wasn't pursued to its logical conclusion (a thruster). Maybe the researchers didn't believe they could get usable forces?
Strong H field at dielectric disc. Just like theory suggests.
Well this is a gut check moment and there is no doubt this post will be controversial and might get me in trouble for being off topic and for the subject matter. I am being serious here. I'm no dummy. Either we didn't figure out jack or we actually did. It seems very likely that we did. If we did, we weren't the first. We all know how the world works. If a bunch of guys on an internet forum can figure out the basic principles of "q-thrusters".... someone else has already perfected them and kept them black; rightfully so. The cat is now out of the bag gentlemen. We want to explore space. I want to see human space missions to the planets. We all do. Please give what you have to the world. This isn't tin foil hat wearing nonsense. NOT UFO conspiracy theory bs. It is no different than this:http://www.aviationweek.com/technology/skunk-works-reveals-compact-fusion-reactor-detailshttp://en.wikipedia.org/wiki/Skunk_Works#giveusthegoodsSorry moderators. This won't happen again. I don't want the thread to devolve into this kind of discussion. I am pointing out the obvious. I'll delete the post if asked to do so.
FYIhttps://www.dropbox.com/s/xiw9mq7dawhp00c/other1.jpg?dl=0What I would really like to do is stack these 2 puppies on the left into a single vertical chamber and try the Cavandish type experiment under battery power w/ a solid-state oscillator. OK, couldn't get the pic to post but the link works ... so that would be my retirement plan (fat chance)
A little less fantasy;https://www.dropbox.com/s/cxfcrf822n0dpsa/IMAG0359.jpg?dl=0I'm (slowly) collecting parts for an X-band miniature version in the cans shown in the middle of the picture.Higher frequency and lower power. (we have a lot of experience w/ battery power in vacuum and/or plasma)Anybody have a short taper section from X to something smaller ?
?? can't get pics to post directly .. must be the Alzhiemers !