Quote from: aero on 07/19/2015 02:20 AM@Rodal.Quote the Finite Difference mesh is coarser for the smaller big diameter of the Yang model (0.201m) than the big diameter of rfmwguy's model (0.2794 m): a less precise FD mesh with less nodes in the cross-section. The actual physical distance between nodes was kept practically the same. But what matters for a numerical discretization of a partial differential equation is the number of nodes to characterize the fields in the solution to the partial differential equation. For the same natural frequency mode shape it would be best to keep the same mesh regardless of the actual physical size. ]I don't know why you say that. It is not correct. The actual Meep pixel separation is identical at 0.004 and the time step is identical at 0.002 between the Yang-Shell model and rfmwguy's NSF-1701 model. I use the same code, setting a switch to select the Yang-Shell model dimensions and antenna location. When creating the lattice, the control file is designed to use only a large enough lattice to include the model and a fixed space around the model. Because the Yang-Shell frustum has a significantly smaller big base diameter, the lattice is significantly smaller in the y and z coordinate directions, but the step size and node separation within the cavity is identical between the two models. The drive center frequency and noise bandwidth is identical between models so there are an identical number of nodes per wavelength and an identical number of time steps per period. The mesh is NOT courser. It is identical. The difference is that the Yang-Shell frustum is smaller, so the lattice surrounding the frustum is smaller.I see what you are saying that you expected perhaps to excite a lower mode with less of a field variation. That you expected perhaps to excite a 01 mode instead of a 11 mode. But one doesn't know the solution ahead of time, otherwise one would not be using a numerical solution to solve the problem. In this case the indication (the two crescent shapes characteristic of mode 11) is that mode 11 was excited, not 01. Even if you expected to excite m=0 (constant in the circumferential direction), TE01 still has n=1 requiring the same discretization in the diameter direction as TM11 for example, they both have n=1.

@Rodal.Quote the Finite Difference mesh is coarser for the smaller big diameter of the Yang model (0.201m) than the big diameter of rfmwguy's model (0.2794 m): a less precise FD mesh with less nodes in the cross-section. The actual physical distance between nodes was kept practically the same. But what matters for a numerical discretization of a partial differential equation is the number of nodes to characterize the fields in the solution to the partial differential equation. For the same natural frequency mode shape it would be best to keep the same mesh regardless of the actual physical size. ]I don't know why you say that. It is not correct. The actual Meep pixel separation is identical at 0.004 and the time step is identical at 0.002 between the Yang-Shell model and rfmwguy's NSF-1701 model. I use the same code, setting a switch to select the Yang-Shell model dimensions and antenna location. When creating the lattice, the control file is designed to use only a large enough lattice to include the model and a fixed space around the model. Because the Yang-Shell frustum has a significantly smaller big base diameter, the lattice is significantly smaller in the y and z coordinate directions, but the step size and node separation within the cavity is identical between the two models. The drive center frequency and noise bandwidth is identical between models so there are an identical number of nodes per wavelength and an identical number of time steps per period. The mesh is NOT courser. It is identical. The difference is that the Yang-Shell frustum is smaller, so the lattice surrounding the frustum is smaller.

the Finite Difference mesh is coarser for the smaller big diameter of the Yang model (0.201m) than the big diameter of rfmwguy's model (0.2794 m): a less precise FD mesh with less nodes in the cross-section. The actual physical distance between nodes was kept practically the same. But what matters for a numerical discretization of a partial differential equation is the number of nodes to characterize the fields in the solution to the partial differential equation. For the same natural frequency mode shape it would be best to keep the same mesh regardless of the actual physical size. ]

The FD mesh you used is coarser:NSF-1701 - 245x261x261 Yang-Shell - 229x196x196 245 is larger than 229261 is larger than 196261 is larger than 196Multiplying all the numbers, the mesh is 1.89 times coarser . The mesh for RFMWGUY had 1.89 times more nodes. Using the same FD operator. That's what matters.The FD mesh is the number of nodes per side. That's it.<<The actual Meep pixel separation is identical at 0.004 >><< node separation within the cavity is identical between the two models.>> yes, that's what I said. That's the physical distance between the nodes (in meters) .What matters is the discretization of the fields.A smaller EM Drive, operating at the same mode shape at higher frequency should require the same mesh discretization not the same physical distance between the nodes. If one carries this to the absurdum: if one insists on the separation between nodes in meters as being significant, you would be saying that something smaller than the distance between the nodes would require no nodes to be modeled.To model something that is nanometers long still requires a fine mesh if it has strong field variation.Partial differential equations are solved by the FD method at the FD nodes. (Keeping the same type of FD operator, for example for a central-difference operator being used in both cases) The number of nodes is what matters.

adjective, Mathematics1.of or relating to a topology on a topological space whose open sets are included among the open sets of a second specified topology on the space.Compare finer.

Quote from: aero on 07/19/2015 02:20 AM...Regarding SeeShell's question?Was the same antenna dimensions and orientation and Io=1 amp used for Yang-Shell as for RFMWGUY NSF-1701 ? Was all you changed (regarding the antenna) the location to be near the big end?

...

What about the momentum back-reaction on the antenna feed?

I think there is miscommunication here.Is "mesh coarseness" and "mesh density" the same things?It is important to define terms before discussing them. Doesn't the MEEP manual talk about this subject? I personally couldn't find it.

Quote from: leomillert on 07/19/2015 03:51 PMI think there is miscommunication here.Is "mesh coarseness" and "mesh density" the same things?It is important to define terms before discussing them. Doesn't the MEEP manual talk about this subject? I personally couldn't find it.Yes.. isn't the 'coarser' mesh as it is because its modeled cavity is smaller, thus requiring fewer points? My understanding was that meep plants a mesh on the model plus some fixed distance around that model.Perhaps a disagreement of definitions.

Quote from: apoc2021 on 07/19/2015 04:12 PMQuote from: leomillert on 07/19/2015 03:51 PMI think there is miscommunication here.Is "mesh coarseness" and "mesh density" the same things?It is important to define terms before discussing them. Doesn't the MEEP manual talk about this subject? I personally couldn't find it.Yes.. isn't the 'coarser' mesh as it is because its modeled cavity is smaller, thus requiring fewer points? My understanding was that meep plants a mesh on the model plus some fixed distance around that model.Perhaps a disagreement of definitions.So accordingly something smaller deserves less Finite Difference nodes just on the basis of being smaller?So accordingly the Baby EM Drive could be analyzed with Meep using a Finite Difference mesh with much less nodes than the NASA EM Drive truncated cone? Of course not.This is not a disagreement about definitions. This pertains to an understanding of how the Finite Difference model solves the partial differential equations.

Quote from: deltaMass on 07/19/2015 05:11 AMYes, we cringed....dynamic characteristics such as the rate that Power is consumed to the rate of Acceleration and Velocity increase....I decided to abandon doing Static testing as I want to explore the Power to Acceleration & Velocity relationships as if there is any new physics, that is where it may show up. ...In my opinion any serious EMDrive experimenter should be doing rotary testing...

Yes, we cringed.

Seems to me that in general the value of A/B should remain approximately constant between models, whereA = # nodes per unit lengthB = some measure of dE/dx or dB/dx. In other words the number of nodes per unit length should be sufficient to capture the spatial differentials.

Quote from: deltaMass on 07/19/2015 05:44 PMSeems to me that in general the value of A/B should remain approximately constant between models, whereA = # nodes per unit lengthB = some measure of dE/dx or dB/dx. In other words the number of nodes per unit length should be sufficient to capture the spatial differentials.Yes, and the issue is that higher mode shapes have higher variation of dE/dx etc. (the lowest mode shape m=0 is constant in the azimuthal direction). The issue is that in a given bandwidth there are several mode shapes, some having significantly higher m, than others. The number of nodes thus should be based on the highest mode that can possibly be excited in a given bandwith.

Quote from: deltaMass on 07/19/2015 12:20 AMWhat about the momentum back-reaction on the antenna feed?Radiation is symmetrically emitted from the antenna. All back reactions cancel at the antenna.

Quote from: Rodal on 07/19/2015 04:46 PMQuote from: apoc2021 on 07/19/2015 04:12 PMQuote from: leomillert on 07/19/2015 03:51 PMI think there is miscommunication here.Is "mesh coarseness" and "mesh density" the same things?It is important to define terms before discussing them. Doesn't the MEEP manual talk about this subject? I personally couldn't find it.Yes.. isn't the 'coarser' mesh as it is because its modeled cavity is smaller, thus requiring fewer points? My understanding was that meep plants a mesh on the model plus some fixed distance around that model.Perhaps a disagreement of definitions.So accordingly something smaller deserves less Finite Difference nodes just on the basis of being smaller?So accordingly the Baby EM Drive could be analyzed with Meep using a Finite Difference mesh with much less nodes than the NASA EM Drive truncated cone? Of course not.This is not a disagreement about definitions. This pertains to an understanding of how the Finite Difference model solves the partial differential equations.Have to agree with Rodal here, smaller objects don't have fewer grid points. The number of grid points shouldn't scale by size.Mesh coarseness and mesh density are the inverse of one another, in that a coarse mesh has a low density and a "fine" mesh a high density. In my experience, I always used and heard people use mesh coarseness over mesh density.

... Rodal's example of the Baby EM drive is a red herring. ...

Quote from: aero on 07/19/2015 03:36 PMQuote from: deltaMass on 07/19/2015 12:20 AMWhat about the momentum back-reaction on the antenna feed?Radiation is symmetrically emitted from the antenna. All back reactions cancel at the antenna.I don't know that I would assume all back reactions cancel at the antenna if dissipation is going on inside the frustum. A phase array antenna which can steer projected radiation with out any moving parts uses simple antennas. Though they emit symmetrically, as a whole they do not and a resulting force is experienced.

Quote from: dustinthewind on 07/19/2015 06:17 PMQuote from: aero on 07/19/2015 03:36 PMQuote from: deltaMass on 07/19/2015 12:20 AMWhat about the momentum back-reaction on the antenna feed?Radiation is symmetrically emitted from the antenna. All back reactions cancel at the antenna.I don't know that I would assume all back reactions cancel at the antenna if dissipation is going on inside the frustum. A phase array antenna which can steer projected radiation with out any moving parts uses simple antennas. Though they emit symmetrically, as a whole they do not and a resulting force is experienced. Some of your initial posts had to do with phase shift between the small base and the big base. Have you had a chance to see the phase shift in the force between the big base and the small base for the Meep/Wolfram Mathematica model for rfmwguy?

Quote from: Rodal on 07/19/2015 06:21 PMQuote from: dustinthewind on 07/19/2015 06:17 PMQuote from: aero on 07/19/2015 03:36 PMQuote from: deltaMass on 07/19/2015 12:20 AMWhat about the momentum back-reaction on the antenna feed?Radiation is symmetrically emitted from the antenna. All back reactions cancel at the antenna.I don't know that I would assume all back reactions cancel at the antenna if dissipation is going on inside the frustum. A phase array antenna which can steer projected radiation with out any moving parts uses simple antennas. Though they emit symmetrically, as a whole they do not and a resulting force is experienced. Some of your initial posts had to do with phase shift between the small base and the big base. Have you had a chance to see the phase shift in the force between the big base and the small base for the Meep/Wolfram Mathematica model for rfmwguy?I think i saw your post. I thought it interesting that there was a phase shift between the forces and a net force on the two bases in a single direction. It appears it is still open as to the net force on the side walls and the antenna. I think in the diagram I was using of interacting currents [block diagram], even though there was a phase shift in current, the force given was not phase shifted. I think what matters is if there is a net-force in a single direction. The diagram I used didn't take into account charge separation (in a wire) which fights against the magnetic interaction (for propulsion) but still, the static field appears to lose out in the case of a phase array antenna, leaving the weak photon propulsion. The reason I drew the model of the two cavities out of phase was to minimize the distance between plates with currents out of phase so as to maximize their interaction. My idea was to eliminate the charge separation and so I suggested the two cylindrical cavities in a TE mode so that current circulates around the axis of the circular plates in a way that eliminates charge separation. It would appear then energy alternates between the currents in the plates and the light stored in the cavity. The phase relationship between the cavities when brought close should have near field interaction and one cavity should lose radiation to the other and possibly allow radiation not only to tunnel from one to the other but possibly to tunnel out of both cavities in one direction. At least that is what I am imagining in my head for all the good that does me. If only magnetic interaction between the plates doesn't provide the propulsion Edit:(then) the other alternative would be transverse magnetic where charge separation does occur and then we have both magnetic and static electric field interaction between the cavities. My suspicion is that one of these would provide more propulsion than the other.