lets try 200khz ( as resonant freq of injector coil/capacitor as from valentin petkov experiments)
previously I calculated for 20khz which gave ( sound wave in water wavelengths)
20khz
1482/20000=0.0741m (7.41cm) 1/2=0.03705 (3.7cm)
( note: units above given in cm,
units below I've given in mm)
200khz
1482/200000=0.00741 ( 7.41mm)
So 1/2 wavelength would be
3.7mm
1/4 wavelength
1.85mm (0.07 inch)
( note: there was an error in original post dimensions, numbers above should be correct )

So now we are getting a bit closer to matching  the dimensions of the injector.


Microwave wavelengths go down to about 1mm, so although here were dealing with sound waves ( i'm still assuming sound waves play a role in stans designs), the sound waves have wavelengths similar to microwaves ( although the speeds are much much slower), but because the wavelengths are similar waveguides for radar might be relevant to understanding the injector.
The radar waveguides use rectangular shapes as the em waves are polarised, the sound waves in stans injector I dont think would be polarised so circular waveguide is suitable.
It might be fortuitous that stan had radar background and that sound waves in water have similar wavelengths to longer  wavelength microwaves)

just something of interest, for sound waves in air and water, they have 'impedence' .
from this article:
http://www.animations.physics.unsw.edu.au/jw/sound-impedance-intensity.htm
they calculate:
" Values for air and water. For air, the density is 1.2 kg.m−3 and v is 343 m.s−1, so the specific acoustic impedance for air is 420 kg.s−1.m−2  =  420 Pa.s.m−1. The values for condensed phases are usually much higher than those of gases. For (fresh) water, the density is 1000  kg.m−3 and v is 1480  m.s−1, so the specific acoustic impedance for water is 1.48 MPa.s.m−1 "

just going back to a previous calculation I did:
" for injector style wfc:
water gap = 0.01inch ( 0.254mm) water gap
using formula previous post
f=vel/wavelength
for 1/2 wavelength resonance
f=1482/2*0.254 mm
f=1482/0.00508m
f=291,732hz
f=292khz
I think might be around the value of frequency required for injector.
According to Valentin Petkov experiment about 200khz resonant frequency of injector coil, using copper windings.
Perhaps a higher frequency resonance is required, type of wire used ( stainless steel) will change inductance of coil, my guess is somewhat higher frequency is required than used with copper windings or perhaps core shape? Though copper windings is getting near to frequency required, if acoustic resonance is playing a role. And if concentric acoustic waveforms are playing a role.
Injector along length of voltage zone is 1 inch, longitudonal waves if acoustic in form,
calculations would be :
for 1/2 wavelength:
f=1482/2* 2.54mm
f=1482/5.08mm
f=1482/0.0508m
f=29173hz
f=29khz
for 1/4 wavelength
f=1482/0.1016m
f=14,587hz
f=14.6khz
Results above might suggest concentric waveforms are closer frequency to petkov results,
so that longitudonal acoustic waveforms might not be important in function.
It is certainly simpler to visualise concentric acoustic wave pattern.
Also it appears ultrasound range is being used in stans injector, which happens to cause cavitation and high acoustic pressure areas, as cavitation may occur. If caviation forced to occur near to electrode surface it might aid in efficient splitting of water?

Picture of concentric acoustic standing wave pattern in water in piezo-electric tube,
( in stans setup it could be visualised as having inner piezo electric tube not shown in pic)
Just a pic to visualise what I'm meaning by concentric waves
pic from a research article

something I hadn't known:
the water misters use cavitation to produce the water droplets,
nice animation and explanation on this page:
http://www.stulz-ats.com/products/ultrasonic-humidification/stulz-direct-room-drh-ultrasonic-humidifiers/ultrasonic-operating-principle/

here is some good info on sonoluminescence
https://www.isnare.com/encyclopedia/Sonoluminescence

for an ultrasonic humidifier/mister:
lets say 1.7mhz transducer
the wavelength it would produce in water:
wavelength = vel/freq
wavelength= 1482/1700000=8.7e-4=0.00087m
=0.87mm so a bit less than 1mm
1/2 wavelength= 0.435mm
stans water gap in voltage zone of injector = 0.01inch ( 0.254mm)
So half wavelength of 1.7mhz transducer is over almost twice the gap of injector.
What freqency transducer would match the 1/2wavelength of the gap?
freq=vel/wavelength
f=1482/(0.254*2mm)
f=1482/0.508mm
f=1482/0.000508m
f=2917322
f=2.92mhz
So if it were possible to vibrate the inner ( electrode) and/or outer ( stainless steel) of the injector with transducers, you would require 2.92mhz to match the half wavelength distance, and create maximum nodes at the metal surfaces ( for concentric wave resonance).
That might increase efficiency of water splitting in the injector?
But it  might possibly erode the electrodes prematurely.
Or putting it another way you could produce a cavitation type pressure effects on the electrode surfaces. ( thought: would it be more beneficial to have the antinodes ( min. wave pressure) on the electrode surface?) I'm guessing maxima nodes at surface. It might provide for an interesting experiment.

what would be the effects on the 'water jacket' (which is a possibility for the structure of stans injector) if a 2.92mhz transducer was used?
The water jacket would have 10 concentric nodes ( since it 10times the gap of the voltage zone),
if those 10 nodes could transfer their energy through the small 0.01" gap above the quenching disc and into the voltage zone, then it would be acting a bit like a resevoir of energy, which would add to the voltage zone energy ( but would create more complex wave patterns than simply concentric). But I think there is a slight chance that water jacket might add to the acoustic energy in the voltage zone.

a couple of pics for 1/2 wavelength ultrasound between plates:
first pic shows one transducer and reflection, second shows two transducers, both using 1/2 wavelength, which leads me to think 3/4 wavelength will be needed to concentrate acoustic energy at the faces of injector or tubes of stan. 1/2 wavelength will put a maximum in the centre of the tube. Still not 100% sure on this though.
Both pics from research articles.

Found something quite interesting, its from a patent for a ultrasonic device using water,
part of its structure looks  identical to stans quenching disc.
I haven't read in detail the patent as yet, but pics below to show the structure
I shall post its function once I understand it.

In the patent above it appears the function of the disc is to
"to reduce water swirling and bubble formation"
So now it makes it possible that  the  quenching disc of stan might be a disc which has another function not the function stated in his document ( would stan put a curve-ball in his documents i.e. a slight deception to mask the operation of the device?).
If the water is in bulk form in the voltage zone ( rather than atomised/droplet form which is something I have suggested previously), then the disc might actually be reducing bubble formation and swirling of the water......interesting.
In the patent the reason for reducing bubbles and swirling is
"minimize ultrasonic energy loss due to stream break up" and since ultrasonic energy might be playing a role in stans injector ( and tubes) this would make sense.
I mentioned previously the  ball valve will act as a flash back arrestor without need for quenching disc........food for thought.

Just another thought regarding the water jacket:
I had been thinking along the lines that the water jacket ( 2.54mm width, 10times the 0.254mm width of the gap above the quenching disc....going by one dimension of stans) was somehow acting as a reserve of acoustic waves which would reflect back into the voltage zone eventually.
But now I'm thinking this water jacket filled with acoustic waves might in fact cause the whole injector device to vibrate at the resonant frequency. So the acoustic energy in the water jacket is transferred to the outer/inner stainless. Part of the waves would be reflected but part will be absorbed by the stainless of the injector, if the whole injector vibrates at the resonant frequency it might add to efficiency. Just a theory!
The down side might be fatigue of the stainless or engine block ( in region of the spark plug threads) over time, resulting in cracking.

speed of sound in stainless steel is:
5760m/s ( source: http://www.engineeringtoolbox.com/sound-speed-solids-d_713.html)
speed of sound in water:
1482m/s
approx 4times faster in stainless steel. Change of speed of sound across water/stainless barrier,
refraction ( perhaps) of waves along with reflection .

seems ultrasonic waves are refracted from water into stainless steel:
http://www.ndt.net/article/v09n04/karpelson/karpelson.htm

I've watched every video I could find of stan talking about his devices, and probably read most of his patents, I've never heard or read him mention ultrasound or sound waves as playing a role in his devices. Though we know from the slots in his tube style wfc, that he might have been matching the tube acoustic resonance.
Valentin Petkov reported vibration ringing in tube style wfc experiments at a certain frequency,
which also supports acoustic energy playing a role.
Finding the patent above and since it was available at the time stan was doing his research ( the first patent goes back to 1977 for the device above) and the undeniable similarity to his "quenching disc" I cant help but think acoustic energy is a part of the devices ( probably caused by volume changes in the water molecules due to shape change of the hydrogen/water bonds due to high electric fields). If the role of the quenching disc channels is to reduce swirling and bubbles, it would suggest water is in the bulk water from in the voltage zone of the injector.
So is it simply chance that a device already used the same shape as stans quenching disc but for a completely different function? Or did stan use this device for same reason as the patent above? I'm leaning towards the later.
If the quenching disc is forcing water through the thin channels ( 0.01") to reduce bubbles and swirling, then it would probably mean there is no water gap between quenching disc, and outer stainless casing. That would mean the water jacket theory is not relevant,but it still leaves the question of why is there a 2.54mm gap inbetween the stainless jackets, and why is it there at all( including the rubber o-ring which is probably there to stop water escaping). What would be the reason for having something that is redundant in the design?
So it appears to be a bit of a problem to be solved.
( note the patent referred to above: there are two patents an earlier one and a later one, the later one includes a thin disc on the ultrasonic transducer, which allows wider range of frequency operation, but the part that resembles stans quenching disc is unchanged in design.
Unfortunately the dimensions of the slots are not given in the patent), though using the the few dimensions that are given, it appears they are very similar in size ( guesstimate)).
( note also the recent interviews with stans sister, she mentions stans surviving brother said no-one has quite figured out how it works as yet, maybe they did hold back on what info they published?)

I was watching a video from the 1950s on youtube about ultrasonics ( in its infancy then),

https://www.youtube.com/watch?v=LDp8O_S5E2U
 it had a demonstration of a transducer in a large fishtank structure filled with water starting at the 8min mark. The frequency was 1mhz and using just a light source and a translucent cloth they measured the wavelength which was 0.72mm between standing waves nodes ( the waves were reflected to create the standing waves) so I think that represents one wavelength ( though it might be one half wavelength since the waves are reflected?). I'm not sure if it would be possible to use a similar method to see if there are acoustic standing waves between electrodes as the hho bubbles will make it difficult to see standing acoustic waves. But there might be some way to use a similar very simple setup to determine if acoustic waves are present
in stans devices.
Interestingly in the video he also shows a water fountain from the acoustic waves, looks like he discovered the water misters!

new vid from valentin petkov
"  https://www.youtube.com/watch?v=BcgbWcNTWa0  "
showing how 8xa works with circuit schematic

so do acoustic  waves play a role in stans wfc?
how to test?
I think it would be possible to use schlieren imaging to test for acoustic ( pressure) waves,
a transparent still water tank, light source, concave mirror and razor blade and camera is the equipment required ( of course a replication of stans circuit also).
The difficulty will be the noise caused by the h and o bubbles.......how to get around that problem?

not exactly what I was looking for, but here is schlieren imaging video of hho exploding, very interesting video

https://www.youtube.com/watch?v=Fi94vL52kVI

This research paper
http://www.nature.com/articles/srep15063
( I think i've referred to this paper before)
Shows that electrodes in water at 1000v very short duration pulses, do  produce acoustic waves in water.
Fig 5 is a schleiren image of the waves produced.
They also found that "below an electric field of 2.7 kV/cm or a pulse width of 30 ns" acoustic waves were not produced" so its still not clear to me if stans wfc will produce acoustic waves or not. So if stans wfc has an electric field intensity above 2.7kv/cm then acoustic waves may play be playing a role, the paper also goes into how they determined the voltage/cm values.

just reading over the above article in a bit more detail, I note it is not pure water being used, it is a buffer solution ( water based), but contains a number of salts and glucose. So although the results are determining acoustic waves from high voltage probes, the numbers will be not be representative of pure water. So it does show that acoustic waves can be produced ( they recorded waves of around 2.5mhz) in a water based solution. I would need to find a research paper which carries out a very similar experiment but in pure water to have data that could be directly applied to stans wfc. I think there is a very good chance that acoustic waves will be playing a role in stans wfc systems.
It appears there is very little research on this topic, and the authors of the paper above suggest there is a mechanism occuring that is not understood as yet, as to how short duration voltage bursts induce acoustic waves in water. They give a number of suggestions, including temperature effects  and water bond angle stretching and relaxation. I think its worth pursuing in more detail, but finding research on this specific area is a bit hard to come by.
They also show that near and far field effects are very different i.e. close to the electrodes there is a different process occuring than further away from the electrodes. Near to the electrodes its not clear what is happening, but whatever is happening is creating organised acoustic waves further away from the electrodes.

spectra of a 6kv 700amp discharge in water, not relevent just interesting.

here is an interesting research paper, it uses schleiren imaging to show shock waves ( acoustic travelling at speed of sound) using very short pulse of 12kv in pure water.
http://arxiv.org/ftp/arxiv/papers/1302/1302.0169.pdf

The researches were studying streamer discharges in water and plasma in water, without bubble formation due to very fast pulse times ( 10ns), in this paper they were looking at what happened with no breakdown of water ( i.e. spark discharge), I think they achieved this by the very short pulse time ( there is not enough time for bubbles to develop).
It may be releveant for stans wfc injector.

just looking into what temperature is required to split water into h and o,
turns out 2,700 deg celcius ( 3000k) is required to completely split it.
So heres a coincidence:
tungsten filaments in light globes reach that same temperature!
( although they are in an inert gas, not in air)
Why is this of interest?
E-cigarettes are now very cheap and a very efficient way to vaporise substances, they run at
much lower temperatures ( 250-300 C ), but could you pass water through them, using a tungsten
filament and get some hho? Its now very easy to get a high efficiency reliable vaporiser for very low cost.

anyone got any results yet for the meyer style injectors? anyone out there trying to get one working can comment?

http://www.chavascience.com/index.php/en/hydrogen/langmuir-excess-energy-from-hydrogen

very interesting article on langmuirs work, quite relevant to water splitting with tungsten wire