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Re: ScanTesla V7.61 - V7.62 ;-)
Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
Hi.
At 08:22 AM 6/7/2006, you wrote:
At 11:11 PM 6/6/2006, Tesla list wrote:
Original poster: "dest" <dest@xxxxxxxxxxx>
Re: ScanTesla V7.61>Original poster: Vardan vardan01@xxxxxxxxxxxxxxxxxxxxxxx
>Most of the streamer "model" is based on Bazelyan and Raizer's "Spark
>Discharge" book.
so now Marco can don`t bother anymore with his model, right? and you have
succesfully implemented positive and negative dicharges in your model too,
and it can predict sparks lenght with +- couple of inches of accuracy, etc?
i think you can call Bazelyan then and inform him about this too, not only
tesla listies % )
There's a bit of difference between an algorithm which predicts
behavior of a system to within a few percent and an actual model of
what's going on. A trivial example would be that one can very
accurately represent the gravitational force between two objects
with the equation:
F= k*m1*m2/d^2
However accurate that equation is, it doesn't say much about how or
why the force occurs.
In the case of tesla coil modeling (with sparks), we're somewhere in
between. We have equations that are "physics derived" in that they
have a basis in the physics underlying what's going on (i.e. omega =
1/sqrt(LC)), and we have others that are essentially empirical
models of observed behavior: 220K resistors in series with wires.
Of course, "my" little model is only a "tiny" step. I suppose one
day there will be a giant 3D E-field model that will take into
account all of Paul's work, Bart's work, and other people's work who
might not even be born yet, and model streamers at the sub-atomic
level. I might be at the "sub-terrainian" level when that happens ;-))
But "right now", there is the model of "1pF/foot+220K" and the
dynamic (the "first" dynamic) model, at least for coiler's... If
anyone has any better one, I have been waiting for a "year" to hear
about it :D ScanTesla was designed for new dynamic leader models and
how they effect the system and streamer length. "Not having" a model
became sort of a problem... So "I" made one ;o)) Like it, or
not... If anyone has a better one.....
As is widely acknowledged, the actual modeling of sparks, in
physical terms, is poorly understood.
They are actually very well understood!!! But with Tesla coils, we
have this oscillation thing on the drive, BPS, linear decrement of
the voltage source, top load dimensions, previous streamer
paths...... OK, all of those added details "breaks" the known
stuff... So we try and take what is known and adapt it... It sort
of works ok... But much to be improved for sure!!!
That doesn't stop us from using an approximation that is based on
observed behavior and which allows better prediction of actual coil
behavior. The fact that the model resembles current thinking on
what's actually happening with the spark is just a manifestation
that such a model is computationally or conceptually efficient.
It is "better" than the "old one", vastly far from "perfect" ;-)
>The streamer part of the program really is not based much on
>circuit theory.
of coz not, but the power calculation is based on simplified lumped model,
and
lenght calculation too. if all is so simple - why do the "russians" say,
that there is NO
any accurate models at all? and many of their formulas are suitable only for
"order of
magnitude" calcs?
In many cases, order of magnitude calcs are better than what we have
today!! The models are lumped and pretty "simple". Please make
better ones(!!), I had never programmed in C before I started doing
it for Tesla coils... Sarah fixed E-Tesla for me ;-)) I mostly copy
her stuff :o))
A lumped order of magnitude model for a spark/streamer is a heck of
a lot better than NO model, or modeling it as a fixed R and fixed
C. A time varying model that matches observed behavior for actual
sparks is a logical next step.
I am sort of amazed at how long and successful "1pF/foot+220K" lasted
and still rules today (five years...)!!! You will not find any
DRSSTC calculations or any modern "models" that don't use
it!! Obnoxiously, it seems to still work well... I forget the post
where I spent 30 minutes "making it up"... I am not sure "dynamic"
modeling makes a giant difference, but it is a step forward.
While it would be nice to have an actual model of actual behavior,
we're a ways from that.
Consider just making a "static" 3D E-field model of a coil with a
streamer. Time goes up about 800X in E-Tesla. If we use the
"dynamic" time frame of ScanTesla it is 10,000X more... But that
would all "depend" on a "dynamic leader model" :o))) Without "that
model", a Giga-Giga-Giga-Hz CPU of computer power is no more use than
a space heater...
The next step is to use the model to predict some measurements (for
systems that aren't the ones you built the model from), go make the
measurements, and see if it matches. If the model is built from
some understanding or theory of the physics, so much the better.
My model does NOT take into account BPS! Karl's coil show that is a
problem ;-)) But we like problems!! Every time we solve one, we get
ten more :o)))
But in the over all picture, or spark lengths have not been going "down" :-)))
Cheers,
Terry