The Laws of Prandtl and the Laws of Nature

Prandtl was not vastly outstanding in any one field, but he was eminent in so many fields. He understood mathematics better than many mathematicians do.

max munk, “My Early Aerodynamic Research” (1981)1

After Glauert and McKinnon Wood had presented the reports on their Got­tingen visit, discussions continued in the Aeronautical Research Committee as the British experts sought to mobilize a collective response to the Ger­man wartime achievements. These (sometimes sharp) exchanges took place in the monthly meetings of the committee and its subcommittees that were held in London. The Cambridge contingent made the journey to London together by train and engaged in lively aeronautical debate en route. “I fear we must have been a pest to our fellow travellers,” recalled one.2 The upshot of the committee meetings are recorded not only in the minutes of their dis­cussions but also in the confidential technical reports circulated among the participants. The content of the technical reports sometimes surfaced in the published Reports and Memoranda issued by the committee and sometimes, in the case of especially important results, in leading scientific journals. A number of the main experiments done in this period appeared in the Philo­sophical Transactions of the Royal Society and in the Proceedings of the Royal Society. There were some significant and perplexing changes in the analysis of the experimental material as the data made the journey from the private to the public realm.

I have described how Taylor, in his 1914 Adams Prize essay, had dismissed Lanchester’s idea that the flow of air over a wing was describable in terms of a perfect fluid in irrotational motion with circulation. If Prandtl was right, then Taylor had been wrong. Led by Glauert, the postwar argument in the Aero­nautical Research Committee seemed to be going in Prandtl’s direction. The circulation theory was gaining ground. By 1923 Glauert felt able to write to Prandtl to tell him that his “aerofoil theory has certainly aroused much inter­est here and it would not be an exaggeration to say that it has revolutionised

many of our ideas.”3 But Taylor (see fig. 9.1) was not to be easily convinced that his earlier reservations had been misplaced. In the postwar discussions, he made it his job to scrutinize Glauert’s reasoning and to oppose it whenever he detected a logical gap or a questionable premise.

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