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Post by dpottier on Aug 15, 2014 15:55:30 GMT -8
I do like your posts but can't wait for a real world trial. I am curious to learn about buoyancy, pressure, and energy with your model. P.S. Kayakers rule! Much design and test work to do before a real world test. If you live near the ocean on the East Coast of North America try a short, fiberglass, white water kayak the day after a hurricane passes. The wind has gone, the ocean smooth and the playground is open for the extremely insane. A 40 foot wave provides a drop of 80 feet to the bottom. Sort of like balancing on the edge of an 8 story building then going over the edge or just riding a few million tons of water for miles. :-) |
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Post by dpottier on Aug 15, 2014 17:05:46 GMT -8
Hey dpottier, I, for one, like your analogy of white water kayaking. Having grown up on rivers both fresh water and tidal, I remember experiencing this effect myself. I believe in the fluidity of different mediums, sharing similar flows and such. Please keep the thinking and software simulations coming... I do agree that simulation is more cost effective than multiple experimental(and costly) builds, but we must consider the efforts of all in this forum, especially peterberg, and the indispensable effort and posting they have contributed. I am certainly appreciative, and I know many more are, too. That being said, this use of software is VERY intriguing; please continue to post results and videos! I love videos as much as the next rocketeer! Thanks for sharing your work David, Eric VW Hi Eric I grew up in Canada, North East of you and as you did, with rivers and tidal playgrounds. It is the combined effort of the collective mind in this forum, and in general, that advances technology. Each idea leading to another and a "what if...?" It is a place to share and develop the collective "mind candy" of many with a common goal. One of the great joys of the communications technologies we developed in the '80's is that it has allowed the global mind to be in the same place and focused on the same problems. Let me add a twist to the technology. A few years ago I designed a DYI refrigerator unit using 2 propane bottles, one with a mini rocket stove core (post thought/creation addition). It burns cow dung as a fuel source and looks a bit like a moonshine still. One technology - two applications. I think Peter's work is brilliant, as are his contributions to the collective knowledge base and thought process. The same is true for all that have given to this forum. I try to add visuals to those ideas before Peter has to do all the hard work of building the unit. When others get involved then we can build better, more efficient units. Another twist on fuel sources. Everyone is thinking wood because they have it. I am thinking of how to build a coal burning rocket stove because where I am, at this time, there is little wood but lots of cheap coal. That fuel source has its own issues if you just think of feed and clean-out. I am in the most polluted city on earth. A place where the air in winter is orange and visibility is measured in hundreds of meters and winters are -30 to -40C and last for 8 months. Because of the pollution levels, 50 percent of pregnancies don't make term and of those that do make it, 65% of the babies have birth defects. How many lives are affected? 1.3 million David |
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Post by ericvw on Aug 15, 2014 19:58:37 GMT -8
Very sobering account, David, at the end of your post. While only 42, and a bit of a troglodyte until recently, I am seeing how technology and the like are bringing so many minds to bear on ANY given situation, with such ethereal proximity as to be sitting next to me on the couch adjacent to my blue cap wearing dog of avatar likeness... It is truly wonderful! I prodded you to build in the real but, rest assured, I think your efforts deserve the proper respect, and by your tone, I will quickly come to respect your own experiences and shared knowledge forthcoming!
That being said, as a New Yorker I say, "Canuck, eh?"
No offense, David(which is my brilliant brother's name, too); little northerner fun,yes?
Awaiting future posts,
Eric VW
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Post by Daryl on Aug 16, 2014 4:00:42 GMT -8
My first kick in my mother's womb took place at Gay Head on Martha's Vineyard. Growing up along the ocean does have a grand influence. So keep the analogies, stories, and suggestions rolling. Cheers!
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Post by dpottier on Aug 16, 2014 17:09:40 GMT -8
Very sobering account, David, at the end of your post. While only 42, and a bit of a troglodyte until recently, I am seeing how technology and the like are bringing so many minds to bear on ANY given situation, with such ethereal proximity as to be sitting next to me on the couch adjacent to my blue cap wearing dog of avatar likeness... It is truly wonderful! I prodded you to build in the real but, rest assured, I think your efforts deserve the proper respect, and by your tone, I will quickly come to respect your own experiences and shared knowledge forthcoming! That being said, as a New Yorker I say, "Canuck, eh?" No offense, David(which is my brilliant brother's name, too); little northerner fun,yes? Eric Canuck, yes, but more Bluenoser. (Google TEERS Founder) Either way, we are and always have been friends and neighbors. To draw on another analogy, Peter is from the Netherlands. Canada and Holland are like brothers and sisters. Peter and I are the same "vintage". As an FYI, here is the software that is producing the test results I post. |
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Post by dpottier on Aug 16, 2014 17:43:46 GMT -8
David, The purpose of the trip wire in the rocket heater tunnel is to introduce small eddies, just to disrupt the boundary layer and break up laminar stream along the ceiling. Any vortex will create drag as well, that's why I tried to keep it small. Larger vortices will create more drag so there's a trade off somewhere where the medication is getting worse than the defect. Peter My first design based on the swimsuit technology. All edges are 90 degrees, measurements are in inches.  Rendered  It was then tested in this configuration using 3 "flasks", then with 2 and finally a single. Drag coeffecient was 0.081 with 3 flasks, lower with the single  Vortex (in red box) noticed in the tunnel test, Test video coming soon. I just have to lace them together in a test sequence.  This is what is happening at the "flask" level  |
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Post by dpottier on Aug 19, 2014 5:59:00 GMT -8
David, The purpose of the trip wire in the rocket heater tunnel is to introduce small eddies, just to disrupt the boundary layer and break up laminar stream along the ceiling. Any vortex will create drag as well, that's why I tried to keep it small. Larger vortices will create more drag so there's a trade off somewhere where the medication is getting worse than the defect. Hi Peter Three images below are drag plots and self explanatory First, is your tripwire at 20 degrees  Next the Erlenmeyer flask idea - 3 flasks - 2 then 1 in next brick - 5mm high  Finally 3 - 10mm high flasks. drag was 0.01 below the 5mm flasks  If you want I can model your configuration at 10mm high and see what happens David This is the 3 - 5mm flasks reversed  |
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Post by peterberg on Aug 19, 2014 7:15:25 GMT -8
David,
It would be nice to see what a higher trip wire would do. I fully expect there will be a higher drag force. Goal should be the lowest drag force and drag coefficient while maintaining nice little turbulence.
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Post by dpottier on Aug 20, 2014 0:52:54 GMT -8
David, It would be nice to see what a higher trip wire would do. I fully expect there will be a higher drag force. Goal should be the lowest drag force and drag coefficient while maintaining nice little turbulence. Peter Funny you should ask. I was probably doing it as you were posting. I also have videos of the tests tripwire -10mm rise, 20 degree angle - rear facing  Drag coefficient - 0.59  This is interesting. Notice the two pressure ridges close to the point. I think this area will degrade (be eaten away) more quickly. Dipping, or brushing if already installed, the tripwire brick in a thin ceramic slurry might solve the erosion issue over time as it would be harder than the brick. Not sure if you have observed this erosion in your working stove or not. I will have to model the tripwire in an arc to see the effect. While it is easy to model I think not as easy to cut an arc in brick,  Second test was using this forward pointing 10mm tripwire   Drag coefficient of 0.63  I hope these parallel your real world results in some way and possibly give you more ideas for me to model. I have has some interesting results with both the flask idea and this morning got a nice surprise with 10mm radius half spheres. I tried 5mm a few days ago and they were a failure. David |
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Post by dpottier on Aug 20, 2014 1:27:33 GMT -8
Goal should be the lowest drag force and drag coefficient while maintaining nice little turbulence. Peter Images of the 20mm diameter half sphere idea  Notice the width of the turbulent area and fairly even pressure pattern. After the 5mm radius spheres failed I was expecting similar results with 10mm and got a pleasant surprise from the increase pressure. I assume this is because the laminar layer has been evenly disturbed  Drag coefficient 0.73  With your 4" chamber you would only need 5 spheres David |
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Post by dpottier on Aug 20, 2014 18:54:22 GMT -8
Peter and group
Has anyone measured the air velocity in the feed tube? Not start up velocity but a stabilized air velocity.
David
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Post by peterberg on Aug 21, 2014 1:15:21 GMT -8
Has anyone measured the air velocity in the feed tube? Not start up velocity but a stabilized air velocity. Not that I know of, my own equipment can't measure velocity. The pressure points at the corners of the 10 mm trip wire are interesting. Although I can't find any wear at that points in my experimental model which is still operational. It's a supprise to see the same drag force as the 5 mm version with an even lower coefficient. Those spheres are interesting as well but not easy to make, even in a cast version I wonder, would the stream be different when you implemented the sides of the tunnel as well? |
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Post by dpottier on Aug 21, 2014 6:35:49 GMT -8
Not that I know of, my own equipment can't measure velocity. The pressure points at the corners of the 10 mm trip wire are interesting. Although I can't find any wear at that points in my experimental model which is still operational. It's a supprise to see the same drag force as the 5 mm version with an even lower coefficient. Those spheres are interesting as well but not easy to make, even in a cast version I wonder, would the stream be different when you implemented the sides of the tunnel as well? I am using an air speed of 2 meters per second, for those using mph, that's 11 miles per hour. I have run a few more tests on the spheres and will post with video and pics. In your experimental model are you using the 5mm tripwire or a 10mm? Funny you should ask again as I added bricks to the sides to get a better view of the 4" tunnel picture. I created them as clear glass bricks and I used the 10mm tripwire and got another big surprise from the 10mm tripwire. Let me run the same test but using the 5mm tripwire so we can compare the two results. I have some ideas on a way to add the spheres and will post along with the test results tomorrow. David |
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Post by peterberg on Aug 21, 2014 13:04:11 GMT -8
I am using the 5 mm wire, probably 6 or 7 mm. Due to the mold being carved out of a block of polystyrene, not very precise.
Curious what the surprise might be.
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Post by dpottier on Aug 21, 2014 19:07:09 GMT -8
I am using the 5 mm wire, probably 6 or 7 mm. Due to the mold being carved out of a block of polystyrene, not very precise. Curious what the surprise might be. I can model 6, 7 mm as well. I only have to change one measurement and the entire drawing and model will update. Then I take the new output to Flow Design and wait for the tunnel to stabilize after the object is placed in the path and the parameters for the test are set. The surprise from the 10mm test was a ramp effect. The air went to the floor of the burn chamber and had no effect on the laminar layer at the top. Air flow as seen through the glass brick sides I added to the burn chamber.  Here is the test results video |
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