I love this thread and am totally addicted, can't put it down. Thanks for all the work and information! Discussions about Q, oxidation, broad / narrow spectrum and the shape of the ends have got me thinking about an alternate configuration. It has many of the same characteristics but might be slightly easier to build / find parts / work with. It is an ordinary cylinder with a cone inside. Maybe something to consider once folks are enjoying consistent thrust (lifting small objects and pets, etc... Keep up the great work!
Quote from: Ricvil on 08/08/2015 11:08 pmQuote from: WarpTech on 08/08/2015 09:58 pmQuote from: Ricvil on 08/08/2015 09:48 pmQuote from: Rodal on 08/08/2015 08:15 pmQuote from: WarpTech on 08/08/2015 07:58 pmToddI opted out of a summer end party tonight mainly because Monday is a milestone birthday. Think I will celebrate with the sense that the next generation will question everything and challenge the status quo. Here's to nonconformity...
Quote from: WarpTech on 08/08/2015 09:58 pmQuote from: Ricvil on 08/08/2015 09:48 pmQuote from: Rodal on 08/08/2015 08:15 pmQuote from: WarpTech on 08/08/2015 07:58 pmTodd
Quote from: Ricvil on 08/08/2015 09:48 pmQuote from: Rodal on 08/08/2015 08:15 pmQuote from: WarpTech on 08/08/2015 07:58 pmTodd
Quote from: Rodal on 08/08/2015 08:15 pmQuote from: WarpTech on 08/08/2015 07:58 pmTodd
Quote from: WarpTech on 08/08/2015 07:58 pmTodd
Todd
Quote from: SeeShells on 08/08/2015 10:14 pmSomething has been bothering me since last night and I couldn't help but watching the modes change and flip in meep.How can you calculate seriously any Q in a cavity that simply jumps around from one T mode decaying and building into another in such a short time? And they all do it, every simulation with varying speeds.Just something to mull over on a day away from the shop.ShellAdded: Back to lurk mode and I'll be quiet.Excellent question. I hope that you don't shy away from asking such questions because it is only this way that one can understand what is being output.My understanding (aero to confirm) is that the quality factor is calculated by aero using the routine Harminv.Please notice that Meep has this disclaimer for using Hamrinv to calculate the quality factor Q:http://ab-initio.mit.edu/wiki/index.php/Meep_Reference#HarminvQuoteImportant: normally, you should only use harminv to analyze data after the sources are off. Wrapping it in (after-sources (harminv ...)) is sufficient.Thus, the Quality factor and the frequency (also obtained by Harminv) should properly be obtained after the sources are OFF, not when they are on. This takes us back to the whole discussion about Q quality factor in experiments. The problem is not only how to best experimentally measure and report Q, but it seems not ideal to me to discuss and report a Q (as first done by Shawyer and then imitated by all other EM Drive experimenters) with the source ON.It seems to me that proper measurement of Q also in experiments should be done upon turning the source off and examining the decay (as posted by Frobnicat in a separate post).With the sources OFF, the definition of Q (inverse to damping) is well-posed.With the sources ON, the meaning of Q is tricky. It seems to me that when people are measuring Q with the sources on they are assuming a well-posed problem with "nice" properties (symmetry, etc.) that may not be fulfilled. This is particularly contradictory with TheTraveller: who rejects Finite Element solutions (using COMSOL or ANSYS) and exact solutions of the problem saying that only a solution that calculates a force can properly calculate the frequency and at the same time Shawyer "measures" Q with the RF feed ON which assumes a well posed nice solution amenable to presentation of Q as if it would be the same Q as the one calculated with the RF feed off.The way that the Q is being measured experimentally by Shawyer and others using S11 and the 3db width is similar to a common method in structural vibration analysis. Of course, this presupposes a steady-state response. In reality with the RF feed ON, the measurement may be a transient instead.?QUESTION TO aero: have you been calculating the quality factor Q with Harminv, and if so, have you been doing so with the sources ON or OFF. Have you been wrapping with (after-sources (harminv ...)) ?
Something has been bothering me since last night and I couldn't help but watching the modes change and flip in meep.How can you calculate seriously any Q in a cavity that simply jumps around from one T mode decaying and building into another in such a short time? And they all do it, every simulation with varying speeds.Just something to mull over on a day away from the shop.ShellAdded: Back to lurk mode and I'll be quiet.
Important: normally, you should only use harminv to analyze data after the sources are off. Wrapping it in (after-sources (harminv ...)) is sufficient.
...I feel there is much more going on that meep cannot show because of some of the inherent limitations. What I'd like to see is a round tube ends capped off as a resonate chamber with a RF input, measure the Q in meep. Would you look at the CSV files from aero and do a simple compare of the Q and stress values between the two? ...Shell
Quote from: SeeShells on 08/08/2015 10:14 pmSomething has been bothering me since last night and I couldn't help but watching the modes change and flip in meep.How can you calculate seriously any Q in a cavity that simply jumps around from one T mode decaying and building into another in such a short time? And they all do it, every simulation with varying speeds.Just something to mull over on a day away from the shop.ShellAdded: Back to lurk mode and I'll be quiet.Excellent question. I hope that you don't shy away from asking such questions because it is only this way that one can understand what is being output.My understanding (aero to confirm) is that the quality factor is calculated by aero using the routine Harminv.Please notice that Meep has this disclaimer for using Hamrinv to calculate the quality factor Q:http://ab-initio.mit.edu/wiki/index.php/Meep_Reference#HarminvQuoteImportant: normally, you should only use harminv to analyze data after the sources are off. Wrapping it in (after-sources (harminv ...)) is sufficient.Thus, the Quality factor and the frequency (also obtained by Harminv) should properly be obtained after the sources are OFF, not when they are on. This takes us back to the whole discussion about Q quality factor in experiments. The problem is not only how to best experimentally measure and report Q, but it seems not ideal to me to discuss and report a Q (as first done by Shawyer and then imitated by all other EM Drive experimenters) with the source ON.It seems to me that proper measurement of Q also in experiments should be done upon turning the source off and examining the decay (as posted by Frobnicat in a separate post).With the sources OFF, the definition of Q (inverse to damping) is well-posed.With the sources ON, the meaning of Q is tricky. It seems to me that when people are measuring Q with the sources on they are assuming a well-posed problem with "nice" properties (symmetry, etc.) that may not be fulfilled. This is particularly contradictory with TheTraveller: who rejects Finite Element solutions (using COMSOL or ANSYS) and exact solutions of the problem saying that only a solution that calculates a force can properly calculate the frequency and at the same time Shawyer "measures" Q with the RF feed ON which assumes a well posed nice solution amenable to presentation of Q as if it would be the same Q as the one calculated with the RF feed off.The way that the Q is being measured experimentally by Shawyer and others using S11 and the 3db width is similar to a common method in structural vibration analysis. Of course, this presupposes a steady-state response. In reality with the RF feed ON, the measurement may be a transient instead._______________________________________________________QUESTION TO aero: have you been calculating the quality factor Q with Harminv, and if so, have you been doing so with the sources ON or OFF. Have you been wrapping with (after-sources (harminv ...)) ?
Yes, analyse away: Data table is to wide to format nicely here, so a spread sheet is attached.
Quote from: aero on 08/09/2015 05:18 amYes, analyse away: Data table is to wide to format nicely here, so a spread sheet is attached.So what are we seeing? Do you need for me to dig into it?
I have a real concern with TheTraveller's Excel spreadsheet. The values I get from the first basic dimensions are inconsistent. I'm talking of the file EMDriveCalc20150617b.xls available from emdrive.wiki as well as TT's Gdrive.Let's take know values, for example Eagleworks' frustum:Db = 0.2794 mDs = 0.15875 mFrustum length = 0.2286 mcone half-angle = 14.78°Input the first three values, and the spreadsheet returns a cone half-angle of 24.5° Calculate the hypotenuse or draw the plan in a CAD software with the know values, you will easily get the frustum side length at 0.2364256 m. But the spreadsheet returns 0.2584848 m!The formula for the cone half-angle (cell D8) in the spreadsheet is :=DEGREES(ATAN((D3÷2)÷((D5×(D4÷2))+((D3÷2)−(D4÷2))+D5)))Whereas it could use arccosine, frustum centre length (diameter center to diameter center) and frustum side length:=DEGREES(ACOS(D5/D9)Talking about the frustum side length (cell D9), its formula is wrong:= SQRT(D5^2+(D3−D4)^2)The correct formula should use end radii squared instead of end diameters squared:= SQRT(D5^2+((D3−D4)÷2)^2)How is the rest right or wrong? I can't even get Df right with the available spreadsheet. When inputing the Baby EmDrive data for example, Df becomes negative which is impossible (it should be comprised between 0 and 1) EDIT: my mistake, 24 GHz instead of 2.4 GHz resolved this issue.Whatever, I don't get the same Df as TheTraveller for the same untouched spreadsheet and same input values. See fourth attachement below. Those differences are quite small, but everything else following in the spreadsheet gets very different values from those discrepancies.@TheTraveller: can you please double-check those basic values in the spreadsheet, and upload a corrected version to the emdrive.wiki? This would be much appreciated by the EmDrive community Below, I show two hypothesis for TT's EmDrive Mark 2, according to how the "Frustum centre length" is defined in the spreadsheet. - The first with Frustum centre length = 208.71 mm has a cone half-angle (corrected formula) of 30°- The second with Frustum centre length = 240.7 mm has a cone half-angle (corrected formula) of 26.6° (instead of 27.7° with the wrong angle formula).What is important to note is that "Frustum centre length" as defined in the spreadsheet is the length between the centers of the two end diameters, and not the length defined by TheTraveller in his drawing where it is the apex r2-r1 length. All the misunderstanding comes from the difference in that drawing (attached in third position below).
The Eggcelerator
Stranger things have happened. I looked at that "inverted cone" drawing and it sort of instantly generalised itself to an ovoid
If you really want to dive deep, look at Orbital Angular Momentum of circular radiation:http://arxiv.org/ftp/arxiv/papers/0905/0905.0190.pdf