Postwar Contact with Gottingen

A number of significant changes, both organizational and personal, took place in the higher reaches of British aeronautics at the end of the war. The size of the aeronautical section at the National Physical Laboratory had grown considerably during the conflict. Starting from three or four active workers in 1909, the section had expanded to around forty by the time of the armistice.39 Predictably, the return of peace meant that the budget was now to be cut back. Lord Rayleigh had died in 1919, and the Advisory Committee he had guided for a decade was formally dissolved and reconstituted as the Aeronautical Research Committee (ARC). The new committee held its first meeting on May 11, 1920.40 Glazebrook was given the job of restructuring it and preparing it for its new peacetime role. The National Physical Laboratory and the Aero­nautical Research Committee now came under the aegis of the newly formed Department of Scientific and Industrial Research (DSIR).41 Horace Lamb had been appointed to the Aerodynamics Sub-Committee in July 1918 and later joined the full committee.42 In an attempt to avoid the old hostility between the scientists and the manufacturers, there were now to be representatives of industry on the committee. J. D. North, of Boulton Paul, was appointed to the Aerodynamics Sub-Committee to represent the Society of British Aircraft Constructors. Bairstow left the National Physical Laboratory in 1917 and took up a post with the Air Board, the precursor to the Air Ministry, though he continued to serve on the new committee.43 Bairstow then moved again and become the Zaharoff Professor of Aviation at Imperial College, London. Sir Basil Zaharoff, who financed the chair, was an international arms dealer.44 Shortly afterward Emile Mond provided the money to set up a chair in aero­nautics at Cambridge in memory of his son killed flying on the western front. This chair was taken by Melvill Jones.45 Bairstow’s post as superintendent of the Aerodynamics Department at the NPL was taken over by Southwell, who moved from Farnborough to Teddington. Lanchester, who sometimes felt that Rayleigh was the only sympathetic member of the committee, left a year after Rayleigh’s death. Lanchester had been assiduous in his duties but had al­ready resigned from the Aerodynamics Sub-Committee in December 1918.46 Now that the emergency of the war was over he felt able to cite pressure of work as a basis for leaving. In his letter to the chairman of the Aerodynamics Sub-Committee he expressed “great pleasure in having been able to serve the committee,” but the retrospective account he gave of his departure from the full committee was very different in tone. He complained that he had been sidelined, snubbed, and deliberately edged out by Glazebrook.47

At the moment that Lanchester left the Whitehall scene feeling, justi­fiably, that his ideas had been ignored, moves were under way that would eventually lead to the triumph of the circulation theory he had pioneered. Two things happened. First, on November 13, 1920, Southwell received a let­ter from Prandtl, who sent him some up-to-date papers on wing theory and material from the Technische Berichte. Prandtl explained that his action had been prompted by his meeting with William Knight. Knight had apparently told Prandtl that Southwell wanted to get hold of information about develop­ments at Gottingen. Southwell replied on November 29 with thanks and ten­tatively asked Prandtl for details about his wind tunnel and the techniques for keeping the flow steady. He also stressed that the exchange with Prandtl had to be considered personal rather than official because of the British govern­ment’s policy of restricting formal contact with German institutions. Prandtl sent Southwell the required data about the air flow and said that more in­formation would soon be published in a volume to be titled Ergebnisse der Aerodynamischen Versuchsanstalt zu Gottingen.48

The second development was that two Farnborough scientists, Robert McKinnon Wood and Hermann Glauert, both members of the Chudleigh

set, were sent to Germany to report on the situation. McKinnon Wood, a product of the Cambridge Mechanical Sciences Tripos, was deputy director of the Aerodynamics Department at Farnborough and worked on propel­lers and the experimental side of aerodynamics.49 Hermann Glauert (fig. 8.3) had studied mathematics at Trinity College, Cambridge, where his circle of friends included David Pinsent, G. P. Thomson, and Ludwig Wittgenstein.50 He graduated with distinction in the first class of part II of the Tripos in 1913 and won an Isaac Newton studentship in 1914 and the Rayleigh Prize for mathematics in 1915.51 Glauert was born in Sheffield. His mother was an Englishwoman who had been born in Germany, while his father, a cutlery manufacturer, was German but had taken British citizenship. Originally spe­cializing in astronomy, Glauert published a number of papers on astronomi­cal topics at the beginning of the war and then, through a chance meeting with W. S. Farren, he was appointed to the staff of the Royal Aircraft Factory in 1916.52

Based in the Hotel Hessler in Charlottenburg, Glauert wrote on Janu­ary 21, 1921, to make contact with Prandtl and ask if was possible to arrange a

visit to Gottingen.53 The approach could not have been more different from Knight’s. Knight had sent a typed letter, in English, on elaborately headed NACA notepaper. The letter was replete with office reference numbers and subject headings and was introduced with a flourish of (questionable) diplo­matic credentials.54 Glauert penned his note in German on a modest sheet of unheaded paper. He introduced himself as a fellow of Trinity who worked at Farnborough and explained that he was very interested in the reports shown to him by his friend Herr Southwell. Could he and his friend Herr Wood, also of the Royal Aircraft Factory, come along next Monday? The visit duly took place but cannot have been an extended one because on February 2 Glauert was writing from Farnborough (again in German) to say that he and Wood were safely home after a thirty-six hour journey. All of the technical material that Prandtl had given them, he reported, had been carried over the border without difficulty. In return Glauert sent Prandtl a copy of Bairstow’s new Applied Aerodynamics.55 It was, he said, currently the best English book on aerodynamics.

Bairstow’s Applied Aerodynamics, published in 1920, offered a massive com­pilation of design data from the aerodynamic laboratories which, for Bair – stow, primarily meant from the National Physical Laboratory. It was com­prehensive and detailed but, as far as lift and drag were concerned, heavily empirical. The circulation theory of lift was placed on a par with the dis­continuity theory and rapidly dismissed. Both theories were said to be based on “special assumptions,” that is, ad hoc devices designed to get around the fatal zero-drag result. Kutta’s work, according to Bairstow, offered no more than a “somewhat complex and not very accurate empirical formula” (364). No account, he complained, was given by Kutta or Joukowsky of the critical angle of stall. Bairstow admitted that Joukowsky had found a way to avoid the infinite speeds at the leading edge of a wing profile, but he spoke of the Joukowsky transformation as if it were little more than a mathematical trick. Bairstow called it a “particular piece of analysis” and did not deem it suf­ficiently important to explain it to the reader. Prandtl must have perused Glauert’s gift with mixed feelings. He would have agreed with all of Bairstow’s facts but none of his evaluations. In particular, he would surely have dissented from Bairstow’s conclusion that it “appears to be fundamentally impossible to represent the motion of a real fluid accurately by any theory relating to an inviscid fluid” (361). Wasn’t this exactly what Prandtl and his colleagues had just done for the flow of air over a wing?

It is clear from the subsequent letters exchanged between Glauert and Prandtl that, during the visit, their conversations had been confined to tech­nical matters. Prandtl was now keen to discuss politics as well as aerodynam­ics. He was distressed by the economic and political situation, particularly the stance of the French and the severe reparations that were being demanded. Glauert expressed agreement with much that Prandtl said on these topics, for example, with the “absurd restrictions that have been placed on the develop­ment of German aviation,” but in his replies he encouraged Prandtl to see things in a less pessimistic light. Glauert explained that not everyone in Brit­ain agreed with these policies, and he thought there were strong economic reasons why, sooner or later, they would be modified. Writing now in English, he drew Prandtl’s attention to the influential arguments of the Cambridge economist John Maynard Keynes and mentioned that opposition to punitive sanctions was also part of the official policy of the Labour party.56 He even in­cluded a reassuring cutting from the correspondence columns of the Times.57 The concern was not just personal; it was also professional. Glauert was wor­ried that Prandtl would become so antagonized by allied policy that he would cease to take part in scientific exchanges. The anxiety was more than justified. The academic atmosphere in the immediate postwar years was a poisonous mixture of bitterness, intransigence, boycott, and counterboycott.58

The immediate result of the Glauert-Wood visit to Germany was the production of two confidential reports. In February 1921 McKinnon Wood produced Technical Report T. 1556, “The Aerodynamics Laboratory at Gottingen.”59 He argued (contrary to government policy) that Gottingen should be included in any future international trials that were envisaged to clarify the discrepancies that existed between the results of different labo­ratories.60 When the results of the British and Germans were compared, McKinnon Wood noted that the Gottingen channel gave the same lift and drag, but always for an angle of incidence smaller by about one degree. He also studied and reported on the complicated “three-moment” balance mechanism used to measure the aerodynamic forces. A blueprint of the bal­ance was included in the report. He judged that the Gottingen balances were “very inferior” in sensitivity to the British but then conceded that “our bal­ances and manometers are unnecessarily sensitive for most of the work for which they are required” (14). McKinnon Wood concluded by saying that “Mr. Glauert discussed Prandtl’s aerofoil theories with him and obtained some further papers. A discussion of these will be embodied in a separate paper (T. 1563) which Mr. Glauert is writing” (21). The “discussion” to which McKinnon Wood alluded turned out to be a piece of brilliant advocacy that was undoubtedly a major factor in undermining resistance to the circulation theory in Britain. Glauert had a gift for clear exposition and for seizing the essentials of the subject. Once he had accepted that Prandtl’s theory repre­sented the path to follow, Glauert produced a notable series of papers and reports explaining, testing, and developing the achievements of the Gottin­gen school. He corrected inadequate formulations and produced important extensions of the theory, as well as confronting the skeptics.

What made Glauert special? Why did he, with his impeccable Tripos background, strike out in a direction that had hitherto been unattractive to experts who shared with Glauert the intellectual culture of the “Cambridge school”? The “practical men” had always been divided over Lanchester’s the­ory of lift, but the “mathematicians” had been unanimous in their skepti­cism. Why did Glauert break ranks? No definitive answer can be given to this question, though one fact stands out and invites speculation. The Ger­man name, the German father, the command of the German language may have generated some affinity with the body of German work that was under consideration. These facts distinguished Glauert from British experts such as Bairstow who did not have the command of German that would have enabled them to read the literature or converse with Prandtl.61 (At that time Prandtl had little knowledge of English.) Of course, given the bitterness of the war, personal links to Germany might have had quite a different effect. Such links could be sources of difficulty, and there is evidence that they caused prob­lems, and some inner turmoil, for Glauert. Referring to the outbreak of war in 1914, Farren and Tizard said of Glauert: “His German descent was an em­barrassment to him, and he wisely decided to stay where such trivial matters did not assume the importance that they did elsewhere, and where he could work in peaceful surroundings, though not with a peaceful mind. His friends were far afield, and as time went on he became more and more restless and concerned with the difficulty of his position.”62

Some people in Glauert’s position would have kept their distance from all things German, and even shed their German name.63 One might specu­late that, in Glauert’s case, the balance in favor of the circulation theory was tipped by the opportunity to meet members of the Gottingen group. His visit to Germany enabled him to explore the mathematics of the circulation theory with Prandtl face-to-face. Others had visited Gottingen before the war, but British experts did not have a great deal of direct contact with their Ger­man counterparts.64 Even here it is necessary to be cautious about the im­pact of personal contact. Glauert was impressed by the circulation theory before he went to Germany. Doubts and qualifications dropped away after the visit to Gottingen and his advocacy became more confident, but he had begun to explore the theory through what he read in Southwell’s copies of the Technische Berichte. Farren and Tizard suggest that exposure to engineer’s shoptalk in the Chudleigh mess at Farnborough during the war made Glauert sympathetic to the needs of engineers and hence (one may suppose) to the theoretical approaches adopted by the engineers. Beyond this, little can be ventured in terms of explanation. It must simply be accepted that, equipped with the recent papers, Glauert made it his business to explore the Gottingen theory in great detail. He became committed to it, even when this led him to diverge from such authorities as Leonard Bairstow, Horace Lamb, R. V. Southwell, and G. I. Taylor.65