I found these old videos on youtube and started putting together a playlist "Flow Visualization".
The concepts of laminar flow, flow stall, reverse flow, pressure vs velocity etc. are demonstrated. While this is done in a liquid medium and we are generally interested in gas, the concepts are presented clearly. I enjoyed watching these so much, I just had to share.
The segment below immediately made me think of the P-Channel, and so potentially adding to the theory of why it works. Where gas of higher density is added into the flow at the top of a lower density gas.
Fresh air entering the burn tunnel through the P-Channel is presumably cooler than the air (flames) already in the burn tunnel. This causes instability which provides for turbulent mixing, as shown below. Although, in our situation we may want the air to be preheated in order to prevent excessive cooling of the burn and aid in efficient combustion, it won't ever be preheated to equal temperature as the combustion itself. Thus the effect still has potential, in theory. Whether or not this actually has a significant effect, I don't know.
I figure this concept in combination with Peter's idea of the volatile gasses tending to flow at the top of the burn tunnel makes for efficient mixing and a nice clean burn.
I've embedded the video set to start at 23:05, where the example I reference is demonstrated-
Last Edit: Nov 15, 2014 3:03:38 GMT -8 by PNW Dave
For fuck sake mate! Whay haven't you dug that before!
Well, the sound seems to be a little wonky!
Thanks a lot anyway!
HA! I've only recently found these myself! But physics and conceptual understanding is one of my favorite late night pastimes. For anyone with similar interest, I highly recommend Richard A. Muller's course "Physics for Future Presidents" from Berkley, CA. (though not rocket stove related at all). All lectures from the course are available to view for free. I've seen every one since the 2006 semester at LEAST once, so long as it is Muller or Bob Jacobsen... I didn't care for the more recent lecturers. Here is a playlist on YouTube- Physics for Future Presidents
Yes, who ever did the video conversions did not compensate for differing video and audio rates, so the video progressively lags more and more behind the audio. In some places you'll hear the narrator describe something that won't be on screen for a few seconds. So it is good to keep that in mind while watching.
Getting grumpy with people who don't understand fluid mechanics. I had to research few other videos, here they are.
Despite the funnel end, this can well illustrate what the exhaust of the heat riser does.
This one is even better,
If you immagine what happens in, a T, the two blue regions are increased, even more turbulent, and the gases crashing on a flat surface instead of a sharp point, create even more turbulence. Mixing with the stalling blue adds more and more drag on the gases.
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deadstarsstillburn: The people over there recommended either a 6" batchbox or an 8" J-tube. I don't know what those are but am going to try to figure that out. What I need is a blueprint that I can scale to fit the need for my house. I have something likne 5000 square feet
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deadstarsstillburn: but I do not need to heat all of it by any means. probably only need to heat half of that, maybe less.
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deadstarsstillburn: moreover, the house has 3 storeys (large attic) so I assume if I get very efficient heating on the ground floor, that will go a long way toward heating the upstairs as well, no?
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