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#1840
by
Rodal
on 09 Oct, 2014 21:51
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The dielectric is clearly visible as a
small flat douhgnut (a disk with a central hole) in these pictures of the Electric Field for their future truncated cone. The NASA researchers think that it is best located at the
small flat surface.
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#1841
by
RotoSequence
on 09 Oct, 2014 21:59
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The dielectric is clearly visible as a small flat douhgnut (a disk with a central hole) in these pictures of the Electric Field for their future truncated cone. The NASA researchers think that it is best located at the small flat surface.
All the more reason to try to break it and see if it breaks as anticipated.
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#1842
by
Mulletron
on 09 Oct, 2014 22:00
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The dielectric is clearly visible as a small flat douhgnut (a disk with a central hole) in these pictures of the Electric Field for their future truncated cone. The NASA researchers think that it is best located at the small flat surface.
Given what we (think) we know now. That is the
worst place to put it. I'm drawing a pic now. Using this guy's info as a ref in transverse E and the right hand rule.
http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.htmlEdit:
I don't even need to draw it. Just scroll down where you see the three TE modes. Place imaginary dielectric in the right places (max H) and with the right orientation. Then cross fingers.
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#1843
by
Rodal
on 09 Oct, 2014 22:02
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The
magnetic field in the truncated cone is in
blue Observe that the magnetic field is directed along the axis of revolution of the truncated cone, while the
electric field is in red and it circulates along two main cells of different rotational sign, clockwise and counterclockwise:
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#1844
by
Mulletron
on 09 Oct, 2014 22:06
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The magnetic field in the truncated cone is in blue Observe that the magnetic field is directed along the axis of revolution of the truncated cone, while the electric field is in red and it circulates along two main cells of different rotational sign, clockwise and counterclockwise:
Yep you got it. There's your differences in angular and linear momentum too.
Given the placement of the dielectric between Cannae and Shawyer, Cannae got it
more correct. Guess that's why they are pretty close. Shawyer had a better shape, Cannae had a better dielectric setup.
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#1845
by
Rodal
on 09 Oct, 2014 22:11
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The magnetic field in the truncated cone is in blue Observe that the magnetic field is directed along the axis of revolution of the truncated cone, while the electric field is in red and it circulates along two main cells of different rotational sign, clockwise and counterclockwise:
Yep you got it. There's your differences in angular and linear momentum too.
Observe that t
he magnetic field arrows point away from both surfaces, towards the middle of the truncated cone, but
it is stronger emanating from the larger surface, so the neutral point is closer towards the small surface
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#1846
by
Mulletron
on 09 Oct, 2014 22:14
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The magnetic field in the truncated cone is in blue Observe that the magnetic field is directed along the axis of revolution of the truncated cone, while the electric field is in red and it circulates along two main cells of different rotational sign, clockwise and counterclockwise:
Yep you got it. There's your differences in angular and linear momentum too.
Observe that the magnetic field arrows point away from both surfaces, towards the center of the truncated cone.
They are counter rotation circles in the vertical axis, meeting in the center. The magnetic flux flows like water down a drain, because the whole rf field has a rotation, and the direction of the poynting vector.
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#1847
by
Rodal
on 09 Oct, 2014 22:27
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The magnetic field in the truncated cone is in blue Observe that the magnetic field is directed along the axis of revolution of the truncated cone, while the electric field is in red and it circulates along two main cells of different rotational sign, clockwise and counterclockwise:
Yep you got it. There's your differences in angular and linear momentum too.
Observe that the magnetic field arrows point away from both surfaces, towards the center of the truncated cone.
They are counter rotation circles in the vertical axis, meeting in the center. The magnetic flux flows like water down a drain, because the whole rf field has a rotation.
but it is stronger emanating from the larger surface, so the neutral point is closer towards the small surface
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#1848
by
Mulletron
on 09 Oct, 2014 22:41
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Areas of max H flow in poynting vector. Wonder which one would be best?
A separate issue just realized is if this resolves the Q discrepancy on page 18 for the TM mode, the dielectric was probably in a magnetic null zone.
Sure hope that arxiv paper
http://arxiv-web3.library.cornell.edu/abs/1404.5990 on momentum is correct and applicable.
I still haven't gotten around to looking at how chiral PTFE is along x, y, z axis.
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#1849
by
Rodal
on 09 Oct, 2014 22:42
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#1850
by
Mulletron
on 09 Oct, 2014 23:27
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This is important:
Please fact check me on this but of the three TM modes on this
http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html page; the one
closest resembling TM211 would be
this one right? At least good enough for a rough model? I think so. Not exactly but close enough because what I'm really interested in are the position of transverse H with respect to Z. The view is of the Z axis running vertically so the blue magnetic X, and Y are just dots and crosses.
I can see how
highly frequency dependent and sensitive this mode is, which accounts for the big difference in Q and thrust with just a small change in frequency. Given the small size of the dielectric slug in the vertical axis at the small end, the resonant mode would very easily dip into and out of the dielectric with very small freq changes. Hence the loss of thrust. A COMSOL plot is needed for 1932.6 and 1936.7 to see this. I need to see if the magnetic field lines were in the dielectric more or less with both freqs.
At 1932.6, Q was down but thrust was up. Very telling indeed.
If I'm right, then eureka!
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#1851
by
Rodal
on 09 Oct, 2014 23:43
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This is important:
Please fact check me on this but of the three TM modes on this http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html page; the one closest resembling TM211 would be this one right? At least good enough for a rough model? I think so. Not exactly but close enough because what I'm really interested in are the position of transverse H with respect to Z. The view is of the Z axis running vertically so the blue magnetic X, and Y are just dots and crosses.
I can see how highly frequency dependent and sensitive this mode is, which accounts for the big difference in Q and thrust with just a small change in frequency. Given the small size of the dielectric slug in the vertical axis at the small end, the resonant mode would very easily dip into and out of the dielectric with very small freq changes. Hence the loss of thrust. A COSMOL plot is needed for 1932.6 and 1936.7 to see this. I need to see if the magnetic field lines were in the dielectric more or less with both freqs.
At 1932.6, Q was down but thrust was up. Very telling indeed.
If I'm right, then eureka!
Answer:
none of the modes calculated in the closed-form solution by Greg Egan here:
http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html 
agree with the modes calculated by COMSOL Finite Element analysis as presented by Brady et.al. (shown with red arrows in the attachment below).
The first Transverse Electric mode shown by Egan has a single cell along the cone's axis of revolution.
The mode calculated by COMSOL Brady et.al. has two cells along the cone's axis of revolution.
The second Transverse Electric mode shown by Egan has two cells, but they are distributed in a completely different fashion: the smaller cell is closest to the large transverse surface while the mode calculated by COMSOL shows the smaller cell closest to the smaller transverse surface.
It is not clear why this is so. It could be because of the boundary conditions.
I have a strong suspicion that the reason is due to the cylinder inside the truncated cone shown in pink red here:
When I have time I may model it with
Mathematica and see what's going on but I don't have free time to do that during the next couple of weeks.
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#1852
by
DIYFAN
on 09 Oct, 2014 23:50
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#1853
by
Mulletron
on 09 Oct, 2014 23:51
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Yeah Egan's modes are being used as generic representations. I only care about the last number here. TM211, TMXYZ. I only care about Z because X and Y follow Z. Do you see how increasing and decreasing the frequency fills the void of the cavity more or less? That's what I'm getting at. The cells get smaller with higher frequency and change shape. At a critical point when increasing frequency, you get a brand new mode by adding a cell. This is pretty intuitive. Mostly because I know radars really well. You can't see it exactly without a plot.
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#1854
by
Notsosureofit
on 09 Oct, 2014 23:55
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This is important:
Please fact check me on this but of the three TM modes on this http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html page; the one closest resembling TM211 would be this one right? At least good enough for a rough model? I think so. Not exactly but close enough because what I'm really interested in are the position of transverse H with respect to Z. The view is of the Z axis running vertically so the blue magnetic X, and Y are just dots and crosses.
I can see how highly frequency dependent and sensitive this mode is, which accounts for the big difference in Q and thrust with just a small change in frequency. Given the small size of the dielectric slug in the vertical axis at the small end, the resonant mode would very easily dip into and out of the dielectric with very small freq changes. Hence the loss of thrust. A COSMOL plot is needed for 1932.6 and 1936.7 to see this. I need to see if the magnetic field lines were in the dielectric more or less with both freqs.
At 1932.6, Q was down but thrust was up. Very telling indeed.
If I'm right, then eureka!
Answer: none of the modes calculated in the closed-form solution by Greg Egan here: http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html
agree with the modes calculated by COMSOL Finite Element analysis as presented by Brady et.al. (shown with red arrows in the attachment below).
The first Transverse Electric mode shown by Egan has a single cell along the cone's axis of revolution.
The mode calculated by COMSOL Brady et.al. has two cells along the cone's axis of revolution.
The second Transverse Electric mode shown by Egan has two cells, but they are distributed in a completely different fashion: the smaller cell is closest to the large transverse surface while the mode calculated by COMSOL shows the smaller cell closest to the smaller transverse surface.
It is not clear why this is so. It could be because of the boundary conditions. I have a strong suspicion that the reason is due to the cylinder inside the truncated cone shown in pink red here:
When I have time I may model it with Mathematica and see what's going on but I don't have free time to do that during the next couple of weeks.
If the small end is filled w/ dielectric that would make the difference, the optical length is greater for the same physical length. Teflon n ~ 2
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#1855
by
Rodal
on 09 Oct, 2014 23:55
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Yeah Egan's modes are being used as generic representations. I only care about the last number here. Do you see how increasing and decreasing the frequency fills the void of the cavity more or less? That's what I'm getting at. The cells get smaller with higher frequency and change shape. You can't see it exactly without a plot.
Sorry, to me they are completely different mode shapes, as I wrote above. Again, I think that the Egan solution is inapplicable mainly because of the pink-red cylinder inside the truncated cone and to a much lesser extent because of the flat surfaces.
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#1856
by
Rodal
on 09 Oct, 2014 23:57
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This is important:
Please fact check me on this but of the three TM modes on this http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html page; the one closest resembling TM211 would be this one right? At least good enough for a rough model? I think so. Not exactly but close enough because what I'm really interested in are the position of transverse H with respect to Z. The view is of the Z axis running vertically so the blue magnetic X, and Y are just dots and crosses.
I can see how highly frequency dependent and sensitive this mode is, which accounts for the big difference in Q and thrust with just a small change in frequency. Given the small size of the dielectric slug in the vertical axis at the small end, the resonant mode would very easily dip into and out of the dielectric with very small freq changes. Hence the loss of thrust. A COSMOL plot is needed for 1932.6 and 1936.7 to see this. I need to see if the magnetic field lines were in the dielectric more or less with both freqs.
At 1932.6, Q was down but thrust was up. Very telling indeed.
If I'm right, then eureka!
Answer: none of the modes calculated in the closed-form solution by Greg Egan here: http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html
agree with the modes calculated by COMSOL Finite Element analysis as presented by Brady et.al. (shown with red arrows in the attachment below).
The first Transverse Electric mode shown by Egan has a single cell along the cone's axis of revolution.
The mode calculated by COMSOL Brady et.al. has two cells along the cone's axis of revolution.
The second Transverse Electric mode shown by Egan has two cells, but they are distributed in a completely different fashion: the smaller cell is closest to the large transverse surface while the mode calculated by COMSOL shows the smaller cell closest to the smaller transverse surface.
It is not clear why this is so. It could be because of the boundary conditions. I have a strong suspicion that the reason is due to the cylinder inside the truncated cone shown in pink red here:
When I have time I may model it with Mathematica and see what's going on but I don't have free time to do that during the next couple of weeks.
If the smll end is filled w/ dielectric that would make the difference, the optical length is greater for the same physical length
No, I don't think that it is the dielectric. The mode shapes are due to the geometrical boundary conditions, and the boundary condition inside is of a
cylinder
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#1857
by
Rodal
on 09 Oct, 2014 23:58
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It is incorrect to think that it is a truncated cone on the inside. Everything shows that it is a cylinder on one end joined to a truncated cone on the other end. The mode shapes for such a geometric body are different than the mode shapes for a truncated cone as modeled by Egan.
And I don't think that the cylinder is there by accident. Somebody thought this through.
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#1858
by
aero
on 10 Oct, 2014 00:00
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I made up an illustration showing the general character of dark matter thrust resulting from the varying inertia within the cavity. I need to have some data before putting numbers to the thrust, maybe someone else is curious enough to do that. I'm happy that the thrust points in the right direction. See the text on my drawing for my explanation.
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#1859
by
Mulletron
on 10 Oct, 2014 00:04
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It is incorrect to think that it is a truncated cone on the inside. Everything shows that it is a cylinder on one end joined to a truncated cone on the other end. The mode shapes for such a geometric body are different than the mode shapes for a truncated cone as modeled by Egan.
And I don't think that the cylinder is there by accident. Somebody thought this through.
Yeah it looks like they put a can inside the cone for some reason. Good eye. Still I wanna see those modes.
