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Da Leonardo ai Wright: Breve storia della fluidodinamica, con un occhio al cielo PAF

Da Leonardo ai Wright: Breve storia della fluidodinamica, con un occhio al cielo PAF Teresa López-Arias 21 maggio 2010. I PRECURSORI. Il RINASCIMENTO. LA SCIENZA NUOVA. LA FLUIDOSTATICA. Aristotele di Stagira (384-322 a.C.). Archimede di Siracusa (287-212 a.C.).

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Da Leonardo ai Wright: Breve storia della fluidodinamica, con un occhio al cielo PAF

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  1. Da Leonardo ai Wright: Breve storia della fluidodinamica, con un occhio al cielo PAF Teresa López-Arias 21 maggio 2010

  2. I PRECURSORI Il RINASCIMENTO LA SCIENZA NUOVA LA FLUIDOSTATICA Aristotele di Stagira (384-322 a.C.) Archimede di Siracusa (287-212 a.C.) Erone di Alessandria (II-I a.C.) S. Stevino (1548-1620) E.Torricelli (1564-1642) Galileo Galilei (1564-1642) IL PENSIERO MATEMATICO SI APPLICA ALLA FLUIDODINAMICA B. Pascal (1623-1662) Leonardo da Vinci (1452-1519) D. Bernoulli (1700-1782) L. Eulero (1707-1783) I. Newton (1643-1727) J-L. Lagrange (1736-1813) P-S. Laplace (1749-1827) J-B Le Rond D’Alembert (1717-1783)

  3. LA FLUIDODINAMICA SPERIMENTALE Edme Mariotte (1620-1684) Christian Huyghens (1629-1695) Benjamin Robins (1707-1751) La bilancia a braccio ruotante Henri Pitot (1695-1771) Pressione statica e dinamica in un flusso Frank H. Wenham (1824-1908) La prima galleria del vento "I think the paper just read is one of great interest and importance, especially as it points out the true mechanical explanation of the curious problem, as to how and why it is that birds of the most powerful flight always have the longest and narrowest wings.“ The Duke of Argyll, after Wenham’s presentation of his paper “Aerial locomotive” to the Aeronautical Society (London) in 1866

  4. Il tubo di Pitot Bilancia aerodinamica a braccio ruotante (Benjamin Robins, 1730) Henri Pitot, 1732 Galleria del vento dei fratelli Wright (riproduzione) Tubo di Pitot-Prandtl Ludwig Prandtl (1930)

  5. LE EQUAZIONI DETERMINISTICHE DEL FLUIDO REALE: EQUAZIONI DI NAVIER-STOKES “Con la sua (di Eulero) scoperta tutta la meccanica dei fluidi è stata ridotta ad una questione di sola analisi e, se le equazioni si proveranno mai integrabili, le caratteristiche del flusso, e il comportamento del fluido sotto l’azione delle forze, sarà determinato per ogni circostanza” (Lagrange, 1788) Claude Louis Marie Henri Navier (1785-1836) Sir George Gabriel Stokes (1819-1903)

  6. "When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first.“ Werner Heisenberg (1901-1976) OSBORNE REYNOLDS (1842-1912) DISTINZIONE REGIME LAMINARE (“diretto”) E TURBOLENTO (“sinuoso”) HERMANN HELMHOLTZ (1821-1894) I FLUSSI VORTICOSI

  7. L’IPOTESI DELLO STRATO LIMITE Third International Mathematics Congress, Heidelberg, 1904 L’equazioni di Navier-Stokes: irrisolvibili (analiticamente) se non in particolari condizioni La viscosità c’è ma non si sa come trattarla “When the complete mathematical problem looks hopeless, it is recommended to enquire what happens when one essential parameter of the problem reaches the limit zero” (Ludwig Prandtl, 1948) Prandtl had “the ability to see the solution of equations without going through the calculations” (Werner Heisenberg) Prandtl:“No, I strive to form in my mind a thorough picture… the equations come only later when I believe I have understood…[and are] good means of proving my conclusions in a way that others can accept.” “..his ability to establish systems of simplified equations which expressed the essential physical relations and dropped the nonessentials was unique, I believe, even when compared with his great predecessors in the field of mechanics - men like Leonhard Euler and d’Alembert” (Theodore Von Kármán, 1954, about Prandtl) Ludwig Prandtl (1874-1953)

  8. GLI UOMINI CON LE ALI “Der Vogelflug als Grundlage der Fliegekunst” (1889) (Il volo degli uccelli come base per il volo) Orville Wright(1871-1948) Wilbur Wright(1867-1912) Otto Lilienthal(1848-1896)

  9. Gli uomini di azione The “chauffeurs” (S.P. Langley) The “airman” (i fratelli Wright) Concezione dinamica dell’aeroplano Si prova e si progetta Si impara a pilotare da se I movimenti dell’aeroplano sono controllati e si possono effettuare manovre • Concezione statica dell’aeroplano • Si progetta e si prova • Si fa pilotare agli altri • Mancano il controllo e la manovrabilità

  10. “Nobodywillflyfor a thousandyears!” Wilbur Wright, 1901, in a fitofdispair

  11. “..the first in the history of the world in which a machine carrying a man had raised itself by its own power into the air in full flight, had sailed forward without reduction of speed and had finally landed at a point as high as that from which it started” Orville Wright, 1903 describing their first flight

  12. Il linguaggio della fluidodinamica • Ipotesi del continuo • La particella di fluido • Pressione totale, statica e dinamica • Sforzo di taglio • Viscosità e condizione di non-slittamento • Strato limite (ipotesi di Prandtl) • Regimi fluidodinamici: laminare e turbolento • Similitudine fluidodinamica

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