pparaska Posted June 25, 2001 Share Posted June 25, 2001 O.k. So I was reading the tech column in the back of the recent Road and Track, and came across a short bit on the Coanda effect, and was wondering what was in a recent SAE paper about it. I was intrigued by the picture about how a lip spoiler on the rear of the car can unpset the flow attachment, etc. maybe in a different context than had been explained to me previously (static vortex set up, and the flow separates above it). So I started up the Google.com engine and started reading. Henri Coanda did this stuff back in the 1910-30 time frame. But there's some interesting stuff going on - even a Electro Hydro Dynamic Coanda effect - for building flying saucers . Check out a search and start reading, if you're interested. Anyway, one site : http://www.jefraskin.com/forjef2/jefweb-compiled/published/coanda_effect.html starts going one about how people seem to get different theories about lift, physicists, soccer players, etc. Pretty wild, I thought this was all nailed down 50 years ago or more! Even Einstein goofed using only Bernoulli's equation to design an airfoil! Anyway, the Z content here is that the spoiler may have a larger effect than thought possible on separating the flow early to reduce lift. Michael (Ol), and other aero types, I'd love to hear some comments. I'm just dabbling here again. Pretty wild stuff! I also wonder how else this applies to the Z body. Anybody else intrigued? Quote Link to comment Share on other sites More sharing options...
jeromio Posted June 25, 2001 Share Posted June 25, 2001 Great link. Thanks... Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 25, 2001 Share Posted June 25, 2001 Uhhhh, so what do I put a soccer player or flying saucer on the back of the car? Regards, Lone [ June 25, 2001: Message edited by: lonehdrider ] Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 25, 2001 Share Posted June 25, 2001 soccer player...that way, if your car is parked near a basketball hoop, or a soccer field, he can intercept all the stray balls that are attracted to the z... Quote Link to comment Share on other sites More sharing options...
johnc Posted June 27, 2001 Share Posted June 27, 2001 Funny... I did a search of NACA, NASA, Dryden, Edwards AFB, Langley, and Marshall technical report servers and only found 6 references to Coanda in all of the published flight research from 1920 through today. These mostly had to do with vectored jet thrust research. I'm not disputing the article, it just seems that little basic research has been done on this effect. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 27, 2001 Share Posted June 27, 2001 Hmmm..okay. So the Bre type spoiler on the rear of my Z works to spoil the lift produced by the Bernoulli effect? At the same time it creates a significant amount of drag. According to the article it seems that a much better way to reduce lift would be to increase the angle of attack by lowering the front of the car more than the rear. Less drag would be produced. Except then the angle of the windsheild becomes flatter increasing wind resistance slightly? If a very large wing type spoiler were used at an improper angle it would also seem possible that the angle of attack could be increased. The rear goes down, the front goes up and catches air...liftoff!? It seems to me that my rear spoiler just makes the airflow leaving the car more turbulent. Okay Pete, you started this, what are your ideas? I feel quite talented being able to talk out of my a$$. Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 27, 2001 Author Share Posted June 27, 2001 I'm pretty good at talking out of that part of my anatomy also . I think the BRE and Z432 and the 3 piece "70s Camaro" spoiler all do two things: 1) possibly create a stagnant ciculation of air over the aft end of the hatch, allowing the flow to separate from the roof/hatch farther up the hatch than without it, reducing lift. I thank Michael Ol for explaining this to my aero-feeble mind. 2) Possibly, the Coanda effect creates a negative lift on the aft end of the car. The upward-curved (concave) spoiler entrains (these guys word for the "attached" flow - a tough concept for me te buy off on easily) the airflow to move upwards, and a force downward results (negative lift). The back edge of the spoiler moves away from the airflow too abruptly and no longer can follow the spoiler's downward slope. O.K., you real aero guys can at me up now . Quote Link to comment Share on other sites More sharing options...
johnc Posted June 27, 2001 Share Posted June 27, 2001 I think what we need is a row of spoons taped to our rear spoilers! Quote Link to comment Share on other sites More sharing options...
blueovalz Posted June 29, 2001 Share Posted June 29, 2001 The nearly horizontal spoilers take advantage of the low pressure behind the car, rather than create a high pressure situation over the top of it. I even remember a team using this in F1 with a real low rear wing. FIA out-lawed it and made a minimum height for the rear wing. Quote Link to comment Share on other sites More sharing options...
DavyZ Posted June 29, 2001 Share Posted June 29, 2001 quote: Originally posted by pparaska: I think the BRE and Z432 and the 3 piece "70s Camaro" spoiler all do two things: 1) possibly create a stagnant ciculation of air over the aft end of the hatch, allowing the flow to separate from the roof/hatch farther up the hatch than without it, reducing lift...2) Possibly, the Coanda effect creates a negative lift on the aft end of the car. The upward-curved (concave) spoiler entrains the airflow to move upwards, and a force downward results (negative lift). The back edge of the spoiler moves away from the airflow too abruptly and no longer can follow the spoiler's downward slope. Pete, perhaps we can solve this by increasing the length of the rear spoiler (riceboys here we come ) or by decreasing the angle of the "Camaro" 3-piece spoiler? It almost looked like Scottie's rear spoiler was not as angled upward as the typical rear spoiler, but I could be wrong. If you notice, a lot of 1/4 mile drag cars have large, almost horizontal sheetmetal wings. I don't think it takes much of an angle to keep the back end down. Davy Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted July 3, 2001 Share Posted July 3, 2001 I happened upon that article also Pete, while at the book store, thumbing thru it; I also had the same thought, "Wow, all this aero stuff being nailed down in the early 1900's?" I havent read your ref.sight yet but will look it over; aerodynamics also intrigues me. A book I found rather informing was "Competition Car Downforce" by Simon McBeath. The author was a competitor in the UK and is a writer for car mag's & owns/operates his own business designing and mfg'g composite wings for racing cars. The book is a hardbound book w/lots of pictures, even more theory than pictures & well explained for the aerodynamic impaired-such as I. How I understand the aerodynamics is that the chin splitters & front air dams ect, ect, push the front end down and keep the air rushing underneath the car to a minimum-this causes the air on top of the car to create a "Higher Pressure".....lower pressure underneath/higher pressure above-tada [Negative Lift]. Now if you did nothing more than that then the rear end would be unstable from air trying to get underneath from the side of the car-this would cause the rear of the car to lift & this is where we get our unstable rear end feeling; so the body effect kits solve that; while the rear wings help create drag-to not only push the rear end down but also to slow down the air on top of the car so that it merges w/the lower pressure of the underneath air....in other words-a little drag is good while too much drag robs too much power from the car's engine. I'm still learning myself-but from what I've read thus far; the aerodynamics is a balancing act-we want negative lift (drag) but not so much we are loosing excessive power from the engine & are wearing tires prematurely! Definately interesting stuff! BTW: the book I mentioned above-is about 210 pages & has a glossary of about 100 aerodynamic terms. The book is also chock full of formulas for the beginner/established auto enthusiest that is contemplating the aerodynamic approach. Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
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