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#51
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Uzytkownik "Erich Adler" napisal w wiadomosci
m... I see that no civil discussion can take place here despite the fact that you "adults" claim to cherish military aviation. So why all the fuss about German aircraft, jets or otherwise? I live in America now but don't like the blatant arrogance I see whenever history is talked about in regards to military aircraft. Every American I have had discussions with usually end up in disaster because the ignorant American can't get it through his thick skull that they owe practically everything to Germany in the field of modern military aviation. We could discuss Allied centrifugal jets that lost out in the long run. German engineers told them that in 1945. We could discuss the US reliance on German wind tunnel data to build a large variety of postwar military aircraft and research aircraft. I don't want to answer all this crap 'Germans invented ALL this decades (or centuries...) ago', but wind-tunnel testing was my business. I used to do researches in transonic region - the same which aviation technology dealt with for the first time in the end of WWII and into fifties. Unfortunately, Germans HAD NO POSSIBILITY to do any wind-tunnel tests close to M=1. There was no technology and apparatus to do such tests in that time. Germans had lots of data up to approx. M=0.7 and above approx. M=1.15 and BIG STINKING HOLE in between! They had subsonic and supersonic wind-tunnels but none transonic. My first job after I finished high school was testing of three airfoils intended for helicopter use up to M=0.95. The airfoils we NACA 0012 (reference model) NACA 23012 and some modification of the later. It was during Cold War and long before Internet. I needed some literature so I dug old NACA and NASA reports which I could find. A friend of mine found a photocopy of original wartime report of AVA Göttingen upon wind-tunnel test of NACA 23012 up to M=0.9. These results were totally unreliable above M=0.7; they even shoved negative (!) lift-curve slope at zero-lift AoA at M=0.9! It could not be otherwise because the tests were made in closed test section with SOLID WALLS of circular shape using conventional finite aspect ratio wing with endplates on external mechanical balance. For those unfamiliar with testing technology: 1. However SOLID WALLS are good for subsonic and supersonic tests, they are inadequate for any transonic tests. Every wind-tunnel with solid walls has some terminal Mach number (for a given model) above which it is impossible to increase effective Mach number in the test section. A shock wave emerges in the throat (usually at model's max. cross section) between the model and the walls. Nowadays every transonic wind-tunnel has ventilated test section (slotted, perforated or mix of them). Ventilation works as a mass-flow nozzle preventing the buildup of said shock wave and thus achieve Mach numbers up to approx. 1.2 without need of any convergent-divergent nozzle. I don't remember when ventilated test section was used for the first time, but this technology was ABSENT in Germany A.D. 1945. 2. Circular cross section of the test section is not good for two-dimensional tests. Better is square test section and the best is rectangular cross-section with H/B1 (H/B=2-3 is widely used) and the model placed wall-to-wall between side walls. The configuration used in cited AVA Göttingen tests is tipical for low-speed tests (as presented in NACA Report 824 for example). 3. Both external balance (with pushrods and strings) and end plates produce additional forces which have to be tested separatelly and deducted from model's test results. This technology is proven in low speeds but in high subsonic speeds those corrections could be higher than netto force, so the tests become unreliable. 4. As for negative lift-curve slope - this is visible sign of shock wave between the model and the walls for me. Another argument about unreliability of German transonic tests. It would be all from me about these 'superior wind-tunnel data' which US rely on postwar until today. [snip rest of the crap] Peace, OK! You should RIP, too. Erich Adler JasiekS Warsaw, Poland PS. What a coincidence! Please compare these two headers (hint - NNTP-Posting-Host): ----------- Header 1 From: (Erich Adler) Newsgroups: rec.aviation.military Subject: Hey, Germany Invented It... Face It Date: 17 Feb 2004 09:54:06 -0800 Organization: http://groups.google.com Lines: 57 Message-ID: NNTP-Posting-Host: 198.81.26.44 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1077040446 4858 127.0.0.1 (17 Feb 2004 17:54:06 GMT) X-Complaints-To: NNTP-Posting-Date: Tue, 17 Feb 2004 17:54:06 +0000 (UTC) ----------- Header 2 From: (robert arndt) Newsgroups: rec.aviation.military Subject: Hey, Germany Invented It... Face It Date: 18 Feb 2004 07:16:05 -0800 Organization: http://groups.google.com Lines: 31 Message-ID: References: NNTP-Posting-Host: 198.81.26.44 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1077117365 25946 127.0.0.1 (18 Feb 2004 15:16:05 GMT) X-Complaints-To: NNTP-Posting-Date: Wed, 18 Feb 2004 15:16:05 +0000 (UTC) |
#52
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PS. What a coincidence! Please compare these two headers (hint - NNTP-Posting-Host): Teuton = Adler Clutch the pearls, Jasiek, you don't think..??? (I lot of us agree its more than a minor possibility...) v/r Gordon ====(A+C==== USN SAR Donate your memories - write a note on the back and send your old photos to a reputable museum, don't take them with you when you're gone. |
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