Big Sparks question.....

Beau Schwabe · 2013-10-13 14:03

Does anybody have an explanation or theory for what appears to be an underlying "flow" that you often see within big sparks? .... I'm not sure exactly how to describe it, but not the spark itself, but the slow flowing almost fluid movement of the spark. Some of it can be chalked up as heat, but some of the flow doesn't quite follow what I would think to be heat (upwards), but instead for example in this video the "flow" seems to be from left to right. Perhaps the wind blowing is the cause, but I'm not convinced that the speed is quite the same... <-- (notice the smoke trail from the fires created by the sparks)

I'm just curious, this has always mesmerized me as an artifact of big sustained sparks.

http://www.youtube.com/watch?v=UWYlRyp03M8

doggiedoc · 2013-10-13 14:26

I don't know but that video you posted is INSANE!

ElectricAye · 2013-10-13 14:38

I'm certainly not an expert, but my vote is for wind + convection effects. For example, do you see any flow from right to left, against the wind?

Also, check out this demo of a plasma globe.

Duane C. Johnson · 2013-10-13 14:44

Hi Beau;

The example in that video of sparks slowly moving to the right is due mainly to the air moving to the right.
Evidence for the speed of movement is shown by the smoke from the fire at about the same speed.

The arcs form ionization in some of the air molecules which move right along with the bulk of the air.
A similar effect is shown in a Jacobs ladder. The rung of the ladder rises due to the hot ionized rising.

You may be asking about the movement of arcs caused by the Lorentz forces caused by DC current flow as used in Railguns and DC relays.

Unfortunately, a Tesla coil generates high frequency AC currents. The AC current effectively cancels the Lorentz force as the current reverses direction.

Duane J

Peter KG6LSE · 2013-10-13 16:40

Ahh yes the tesla coil ...I wish I had mine here ........ 10 kW of sparkyness is fun !

Beau Schwabe · 2013-10-13 17:50

I presumed it's airflow, but still weird. Creepy even. ...but I still think that their might be something else that's not so obvious. The analogy is like watching a TV where the lips are slightly off from the sound. In this case there is something else (I feel) that makes the 'flow' not quite match up to the ambient airflow.

ElectricAye · 2013-10-13 18:05

Beau Schwabe (Parallax) wrote: »

I presumed it's airflow, but still weird. Creepy even. ....

Sounds like a good science fair project. Find a kid with a big tesla coil and somebody with a compressed air supply and try it out. What might be cool is a way to sculpt the electrical glow - maybe get a vortex sparking away.

Peter KG6LSE · 2013-10-13 19:42

ElectricAye wrote: »

Sounds like a good science fair project. Find a kid with a big tesla coil and somebody with a compressed air supply and try it out. What might be cool is a way to sculpt the electrical glow - maybe get a vortex sparking away.

I tried air along with a 7 foot discharge and no joy but argon does and BTW my mentors at KVA effects have a argon cannon.. Its really cool !

Peter..

W9GFO · 2013-10-13 21:28

I think it is the wind also. The speed of the flow exactly matches the speed of the drifting smoke.

erco · 2013-10-13 21:35

Duane C. Johnson wrote: »

The arcs form ionization in some of the air molecules which move right along with the bulk of the air.
A similar effect is shown in a Jacobs ladder. The rung of the ladder rises due to the hot ionized rising.

+1. I have a Jacob's Ladder I use at Halloween, made from a small 20 kV neon transformer. The heated, ionized air rises to allow the spark to travel up the angled electrodes. Any wind blows the ionized, easy-breakdown air away from the electrodes and the sparks jumps back down to the bottom, where the gap is smallest. You need calm air (no wind) to get the biggest sparks.

Duane Degn · 2013-10-13 22:04

I it looks like the arcs resist the wind movement a bit. The force of the wind has to push against the lowest potential path of the arc.

Tim-M · 2013-10-13 22:59

I believe that the ionized air has much less resistance than ambient air also...

So, in the case of a Jacob's Ladder:

1. The arc strikes and starts where the resistance is lowest, at the smallest air gap.
2. The arc ionizes and also heats the air.
3. The heated, ionized air naturally rises.
4. The arc continues to follow the path of least resistance, which happens to be the rising ionized air, even though the gap is getting wider.
5. The arc will continue to rise in the ionized path until either the ionized air is dispersed or until the gap and resistance become too great.
6. The process repeats...

This is a good example too: http://www.youtube.com/watch?v=vMpGcDWPfvc

I know this doesn't directly address Beau's question, but it may be a contributing factor.

Tim

Edit: @Erco - Sorry I missed your post about this, didn't mean to repeat what you had already said!

Peter KG6LSE · 2013-10-14 00:52

Tim-M wrote: »

This is a good example too: http://www.youtube.com/watch?v=vMpGcDWPfvc

Dear Santa !
OK now That is a arc .
All I need now is a DeLorean and a huge cap..

Mark_T · 2013-10-14 02:58

Mmmm, if only I knew where to get funding for "research into effects of shock-waves on electrical discharge arcs"

There's likely to be an igNobel prize for that!

mindrobots · 2013-10-14 05:47

Mark_T wrote: »

Mmmm, if only I knew where to get funding for "research into effects of shock-waves on electrical discharge arcs"
There's likely to be an igNobel prize for that!

If you're not careful, maybe even a Darwin Award!!

ctwardell · 2013-10-14 06:53

Tim-M wrote: »

This is a good example too: http://www.youtube.com/watch?v=vMpGcDWPfvc

The reaction from the guy on the lower right at the end is priceless!

Plus it sounds like Bacon in the frying pan, so that's worth bonus points...

C.W.

Big Sparks question.....

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