Yes, I know that in the design none of the geometry variables are independent. That is, they are all interdependent. What I was showing is the effect of measurement error from the photographs. Those errors can be considered to be more or less independent of each other. Measurement errors are mostly dependent on where we estimate the corners of the 2-d view of the cavity to be, then errors in the reference length be it from the image (Brady) or literature (Shawyer).
Quote from: aero on 10/24/2014 10:38 pm...I hope your records are better than mine because I don't have lengths recorded, (or the other dimensions, for that matter.)The "search" function of this thread is really awful. Too bad that this thread does not use Google as a search engine
...I hope your records are better than mine because I don't have lengths recorded, (or the other dimensions, for that matter.)
If this is the only way air inside cavity can be heated then yes.
Seems to me we'd be further along here if the researchers had posted the dimensions of these devices in the first place. As it is, we are taking a 'best guess' approach.
Quote from: frobnicat on 10/24/2014 10:51 pmIf this is the only way air inside cavity can be heated then yes.I can vouch for the phenomena that M/W air gets filled with warm water vapor, from hitting the 'potato' button the other day. The air in the M/W was warm and moist, due to potato water that had been evaporated by the influx of M/W energy. The moist air dispersed with the opening of the M/W door.
Quote from: JohnFornaro on 10/25/2014 02:05 amQuote from: frobnicat on 10/24/2014 10:51 pmIf this is the only way air inside cavity can be heated then yes.I ... [hit] the 'potato' button the other day. ...Do you think that the NASA experimenters left some moist potatoes or something similar inside these cavities by accident?You give me the material...I work with it ...
Quote from: frobnicat on 10/24/2014 10:51 pmIf this is the only way air inside cavity can be heated then yes.I ... [hit] the 'potato' button the other day. ...
...could this be the culprit behind the EM Drive?...
Needed hypothesis : air inside cavity is volumetrically heated at Pow=4W (that is, air gets around 25% of microwave power input). There are hole(s) or crevice(s) between cavity and exterior of device, in the direction of thrust (air jetting...) for a total area of A=1.6 mm².
Quote from: frobnicat on 10/25/2014 02:24 pmNeeded hypothesis : air inside cavity is volumetrically heated at Pow=4W (that is, air gets around 25% of microwave power input). There are hole(s) or crevice(s) between cavity and exterior of device, in the direction of thrust (air jetting...) for a total area of A=1.6 mm². I would say that the perimeter of the big end leaks. Not sure how you'd model that leaky connection of the PCB to the copper frustrum flange.At any rate (rate? get it?) the are coming out radially at right angles to the thrust axis of the thingy.[Hint from the inappropriate humor department: Listener maximizes humor by familiarity with Brian Eno's album cover art. Linked artwork is not true color, but that's immaterial.]
Quote from: JohnFornaro on 10/25/2014 02:40 pmQuote from: frobnicat on 10/25/2014 02:24 pmNeeded hypothesis : air inside cavity is volumetrically heated at Pow=4W (that is, air gets around 25% of microwave power input). There are hole(s) or crevice(s) between cavity and exterior of device, in the direction of thrust (air jetting...) for a total area of A=1.6 mm². I would say that the perimeter of the big end leaks. Not sure how you'd model that leaky connection of the PCB to the copper frustrum flange.At any rate (rate? get it?) the are coming out radially at right angles to the thrust axis of the thingy.[Hint from the inappropriate humor department: Listener maximizes humor by familiarity with Brian Eno's album cover art. Linked artwork is not true color, but that's immaterial.]<< are coming out radially at right angles to the thrust axis of the thingy.>>A=1.6 mm² leaking could be axial due to the gap between the bolts and the boltholes1.6 mm² is only 0.0025 square inches or a square having 0.05 inches per sideLook deeply, look at all those bolts. I count 24 bolts, so this would be a gap of only 0.0001 square inches per bolt
It is incorrect to state that only DC fields can produced ionic winds. I don't know whether such misunderstanding comes from getting information from Wikipedia.AC fields can also produce ionic wind in a variety of ways. For example, the point electrode and ring electrode system is capable of generating electric winds (with velocities of few m/s) for both DC and AC applied voltages. In the AC regime, ions generated within the corona move in the field and migrate a distance before recombining; the net flow of ions away from the corona creates a time-averaged force that drives the steady flows. AC coronas can sustain wind velocities of over 1m/s independent of electrode separation in marked contrast to DC coronas.Another arrangement in which AC fields can produce ionic wind is dielectric barrier discharge actuators. AC applied across the electrodes through the dielectric produces a variety of electric breakdown phenomena (e.g., corona, streamers, and plasma). Spark breakdown is prevented by the dielectric barrier. The dielectric material needs to be in contact with electrodes such that the electrodes contact each surface of the dielectric.Transient migration of charged species within AC fields also gives rise to steady electric winds.In contrast to winds driven by DC fields, AC fields (as in the point electrode and ring electrode system ) generate wind velocities comparable with (or better than) the strongest DC winds for any value of the electrode separation. In the high-frequency AC regime (>1 KHz), the electric force is localized within a region near the tip of the point electrode. From a fundamental perspective, any type of electric wind (DC or AC) derives from the same basic mechanism whereby a steady flux of ions transfers momentum to the surrounding fluid to drive steady gas flows.
I recall that Paul March wrote that the EMDrives tested at NASA Eagleworks had a temperature that never rose more than 1 deg (F ? or C?) above room temperature.Anybody recall that statement? Is the temperature measurement in the NASA Eagleworks report? Using search I cannot find it in the text. Is it in the pictures?I also recall AcesHigh reporting on information elsewhere reporting March's statement he made on this thread regarding temperature. Was that at nextbigfuture? Does anybody still have a link for that?
Quote from: Rodal on 10/23/2014 01:31 pmIt is incorrect to state that only DC fields can produced ionic winds. I don't know whether such misunderstanding comes from getting information from Wikipedia.AC fields can also produce ionic wind in a variety of ways. For example, the point electrode and ring electrode system is capable of generating electric winds (with velocities of few m/s) for both DC and AC applied voltages. In the AC regime, ions generated within the corona move in the field and migrate a distance before recombining; the net flow of ions away from the corona creates a time-averaged force that drives the steady flows. AC coronas can sustain wind velocities of over 1m/s independent of electrode separation in marked contrast to DC coronas.Another arrangement in which AC fields can produce ionic wind is dielectric barrier discharge actuators. AC applied across the electrodes through the dielectric produces a variety of electric breakdown phenomena (e.g., corona, streamers, and plasma). Spark breakdown is prevented by the dielectric barrier. The dielectric material needs to be in contact with electrodes such that the electrodes contact each surface of the dielectric.Transient migration of charged species within AC fields also gives rise to steady electric winds.In contrast to winds driven by DC fields, AC fields (as in the point electrode and ring electrode system ) generate wind velocities comparable with (or better than) the strongest DC winds for any value of the electrode separation. In the high-frequency AC regime (>1 KHz), the electric force is localized within a region near the tip of the point electrode. From a fundamental perspective, any type of electric wind (DC or AC) derives from the same basic mechanism whereby a steady flux of ions transfers momentum to the surrounding fluid to drive steady gas flows......If one were to use an AC high voltage power supply, there wouldn't be an ion wind, just an ion wind oscillation.
...I don't know whether such misunderstanding comes from getting information from Wikipedia. ...
No it isn't because I'm some (as you're [alluding] to) unsophisticated Wikipedia scholar.