Guggenheim Aeronautical Laboratory Research Articles

Von Kármán's Work: The Later Years (1952 to 1963) and Legacy

In view of the earlier publication in this journal of a biography of Theodore von Kármán by Sears & Sears (1979), which referred to his years in Germany at Göttingen (1908 to 1912) and Aachen (1912 to 1930) and at the Guggenheim Aeronautical Laboratory of the California Institute of Technology (GALCIT) from 1930 to 1952, we restrict our review here to his later years (from 1952 until his death in 1963). We also comment on his scientific legacy and identify representative institutions and outstanding workers whose research continues the von Kármán style of work in the general areas of aerothermochemistry and allied fields.

Cal Tech's Program in Meteorology: 1933–1948

The California Institute of Technology (Cal Tech) established a course of study in meteorology in 1933. It was intimately tied to the upsurge of activity in commercial and military aviation that occurred in the period between the world wars. The tragic crash of the airship U.S.S. Akron provided the stimulus for including meteorology as a subprogram in the aeronautics department at Cal Tech. Theodore von Karman, head of the department and director of the school's Guggenheim Aeronautics Laboratory, masterminded the design of the program and geared it toward the solution of practical problems using the principles of dynamic meteorology. One of his doctoral students, Irving Krick, was groomed to develop the program. Robert Millikan, head of the institute, fostered an approach to science that encouraged the faculty to consult and work with industry. In this environment, Krick established links with aviation, motion picture studios, and public utilities that would set the stage for the research thrust in meteor...

Advanced Education and Academic Research in Aeronautics

The Forty-Fifth Wilbur Wright Memorial Lecture, “Advanced Education and Academic Research in Aeronautics” was given before the Society by Dr. Clark B. Millikan, Hon.F.I.A.S., F.R.Ae.S., on 13th September 1957, at the Institution of Civil Engineers, Great George St., London, before a large and distinguished audience which included H.R.H. The Prince of the Netherlands and a number of the Americans who had attended the Sixth Anglo-American Aeronautical Conference. Sir George Edwards, C.B.E., B.Sc, F.R.Ae.S., President of the Society, presided. As has now become customary the principal awards of the Society awarded by the Council for the year were presented before the lecture (see July and October 1957 Journals). This year they included Honorary Fellowship of the Society which was accepted by His Royal Highness, The Prince of the Netherlands.Introducing the Lecturer, Sir George Edwards said:–Dr. Millikan was born in Chicago in 1903, he graduated from Yale University in 1924 with the degree of Ph.B. and received a Ph.D. degree in physics and mathematics at the California Institute of Technology in 1928. In that year he was appointed Assistant Professor at the California Institute, in 1934 he became Assistant Professor, and since 1940 he has been a full Professor in the Aeronautics Department. He was a member of the Executive Committee of the Institute from 1945 to 1947 and was appointed Director of the Guggenheim Aeronautical Laboratory in 1949. He has been Director of Wind Tunnel Testing at the California Institute since 1935, and Director of the Southern California Cooperative Wind Tunnel since it began operations in 1945. He is Chairman of the C.I.T. Trustees Jet Propulsion Laboratory Committee.A Fellow of the Royal Aeronautical Society and an Honorary Fellow of the Institute of the Aeronautical Sciences, of which he was President in 1937, he is also a member of a number of other Societies. In 1948 the British Government awarded him the King's Medal for Service in the Cause of Freedom, and in 1949 he received the United States Medal for Merit.Dr. Millikan is currently serving as Chairman of the Scientific Advisory Committee to the U.S. Secretary of Defense and as Chairman of the Aircraft and Guided Missiles Panel of the U.S.A.F. Scientific Advisory Board. He is also a member of the Army's Ballistic Research Laboratories' Scientific Advisory Committee, Chairman of the Sub- Committee on Fluid Mechanics and a member of the Aerodynamics Committee of the National Advisory Committee for Aeronautics.

Recent Developments in Hypersonic Flow1

Our understanding of hypersonic flow over blunt-nosed bodies has progressed considerably during the last two years. Hayes showed that the lateral flow over a nearly flat-faced body is governed by a choking m e c h a n i s m at the shoulder, and recent experiments at t h e Guggenheim Aeronautical Laboratory, California Inst i tute of Technology, at Moo = 5.8 confirm the qualitative aspects of Hayes' analysis. These experiments, covering a wide range of b lunt-nose shapes, also show that the bow shock shape is determined mainly by the body geometry in t h e sonic region, while the surface pressures are influenced both by the sonic region and by the local body shape. Some of the forward integrat ion procedures that have been developed for the flow in the nose region could possibly be modified to include these essential features. At hypersonic velocity the transverse flow field produced by a b lunt nosed slender body in a fixed plane normal to the flight direction is analogous to the flow generated by an expanding blast wave. The blast wave analogy has been applied to two problems tha t exhibit flow similarity: 1. Unyawed hemisphere-cyl inder (or b lunt-nosed slab); 2. Power bodies of the form r& ^ x. Here flow s imilarity is possible only when m' < m ^ 1, where m ' = V2 for bodies of revolution, and m' — for two-dimensional bodies. Experimental results on such bodies obtained in air at MOT = 7.7 and in he l ium at M^ = 18.4 show good agreement wi th the theoretically predicted shock shapes and surface pressures. Now tha t some features of the i n viscid pressure field generated by a b lunt nose are becoming clearer, the history of the boundary layer can be properly incorporated in to the treatment of hypersonic viscous interactions downstream of the nose-dominated region. A brief discussion of the power body and the hemisphere cylinder shows that two important problems require careful a t tent ion: 1. Emergence of the boundary layer from the blanket of Mach number gas generated by the strong portion of the bow shock; 2. Effects of transverse curvature on the viscous layer in the presence of axial pressure gradients tha t may be partially selfinduced. At low Reynolds numbers the dist inction between shock layer and viscous layer in the nose region will probably have to be abandoned. B u t i t appears that sl ipflow effects are postponed to m u c h lower Reynolds numbers t h a n had been supposed at one t ime , largely because viscous interactions raise the local pressure level. This area of Reynolds number hypersonic flow is a fruitful one for future research.

Royal Society: New Foreign Members

AT a meeting of the Royal Society on May 9, the following were elected to the foreign membership of the Society: Dr. Herbert Spencer Gasser, director of the Rockefeller Institute for Medical Research in New York ; Prof. Frédéric Joliot, head of the National Centre of Scientific Research in Paris ; Prof. Theodor von Karmán (Pasadena), professor of aeronautics and director of the Guggenheim Aeronautics Laboratory at the California Institute of Technology ; Prof. Erik Andersson Stensiö, professor in the University of Uppsala and director of the Riks Museum, Stockholm.

BOOK REVIEWS

Book reviewed in this article:Birds, by Gayle Pickwell, Professor of Zoology, at San José State College, San José, California.A Laboratory Introduction to Animal Ecology and Taxonomy, by Orlando Park, Associate Professor of Zoölogy, Northwestern University; W. C. Allee, Professor of Zoölogy, University of Chicago; and V. E. Shelford, Professor of Zoölogy, University of IllinoisGrowing Plants Without Soil. The A.B.C. of Plant Chemiculture (Soilless Chemiculture, Water Culture, Hydroponics, Tank Farming, Sand Culture) Including Plant Growth Hormones and Their Use. By D. R. Matlin, M.A, Professor of Plant Chemicullure, Belmont Evening High School, Los Angeles, Calif.The Principles of Heredity, Second Edition, by Laurence H. Snyder, Sc.D., Professor of Zoology, Ohio State University, Columbus, OhioThe Photismi de Lumine of Maurolycus, Translated from the Latin into English by Henry Crew, Northwestern University.The Origin of Canyons, by Douglas Johnson, Professor of physiography, Columbia University.Modern Agricultural Mathematics, a Text Book for Students of Agriculture in High Schools, Vocational Schools and Rural Schools; and a Handy Reference Book for Farmers and Other Workers in the Various Branches of Agriculture. Containing Methods of Calculation for All Types of Agricultural Problems, by Maurice Nadler, Department of Mathematics, Agriculture Division of Newtown High School, Long Island.Mathematical Methods in Engineering, by Theodore v. Karman, Director of the Guggenheim Aeronautics Laboratory, California Institute of Technology and Maurice A. Biot, Assistant Professor of Mechanics, Columbia University; Honorary Professor, University of Louvain.Useful Mathematics Workbook, by Mary A. Potter, Supervisor of Mathematics, Racine, Wisconsin.

Contributions to the development of the radio‐meteorograph by the United States Weather Bureau

Considerable progress has been made in this country during the past two years in the development of the radio‐meteorograph. Seven independent investigations have been carried on during this period with various models of instruments. The first successful model was developed by Dr. K. O. Lange of the Blue Hill Meteorological Observatory in cooperation with the Massachusetts Institute of Technology. The Olland system of telemetering was used in this instrument and the models were constructed by the Feiber Instrument Company. Other models of the Olland type were: One developed by Dr. L. F. Curtlss of the National Bureau of Standards in cooperation with the United States Weather Bureau and manufactured by the American Instrument Company; one developed by Captain O. C. Maier of the Army, and L. E. Wood of the Guggenheim Aeronautical Laboratory of the California Institute of Technology; one developed by Dr. J. Piccard and others of the University of Minnesota; one developed by Messrs. Mears, Little, and Moon of the United States Weather Bureau; and one now under development by the Julien P. Friez Instrument Company on a United States Weather Bureau contract.

A Theoretical Investigation of the Maximum-lift Coefficient

The problem of the maximum lift of airfoils has concerned the authors greatly since there were first discovered in the spring of 1932 serious discrepancies in this characteristic between results obtained in the wind tunnel of the Guggenheim Aeronautics Laboratory at the California Institute of Technology (GALCIT) and those reported from certain other wind tunnels. An elaborate experimental investigation by the junior author and A. L. Klein indicated that the value of CLmax for a given airfoil was strongly affected both by Reynolds number and by the degree of turbulence in the tunnel wind stream.

Some Books Received

This monograph is the second of the series on the general subject of Aerodynamic Theory which is being prepared by recognised authorities under a grant from the Guggenheim Fund for the Promotion of Aeronautics, the first volume of which was reviewed in AIRCRAFT ENGINEERING, Vol. VI, September, 1934, p. 249. The preparation of the present volume is the joint work of Dr. Th. von Kármán, Director of the Guggenheim Aeronautics Laboratory, California Institute of Technology, Pasadena, and Dr. J. M. Burgers, Professor of Aero‐ and Hydrodynamics at the Technische Hoogeschool, Delft.

The Use of the Wind Tunnel in Connection With Aircraft-Design Problems

Abstract The paper is divided into two parts, the first of which deals with the general problem of extrapolating wind-tunnel results to full-scale free-flight conditions in connection with the initial prediction of overall performance characteristics of airplanes. Using the notation of Oswald, it is found that the three parameters about which the designer would like information from the wind tunnel are: the “airplane efficiency factor” giving the variation in parasite drag with lift coefficient, the “equivalent parasite area” giving essentially the minimum parasite drag, and the maximum lift coefficient. If the tests are made at Reynolds’ numbers of the order of 1,500,000 or larger and on models of modern “clean” airplanes, the extrapolation of the first parameter to full scale is felt to be trustworthy for gliding flight. The need for further data on the influence of the change to power-on flight is mentioned. For the second parameter the effect of the change in Reynolds’ number involved in the extrapolation is shown to be important, and a method for carrying out the extrapolation is described. This method is based on the modern hydrodynamical theory of skin friction, and has already met with some success as developed and used at the Guggenheim Aeronautics Laboratory of the California Institute of Technology. In connection with the third parameter, it is shown that the influence of Reynolds’ number and turbulence on the value of the maximum-lift coefficient is very large. The importance and confusion attending this phenomenon led some time ago to its intensive investigation at the laboratory. The more important results of an experimental and a theoretical approach to the problem are discussed. The experimental researches involved the testing of a 6-ft-span N.A.C.A. 2412 airfoil at a series of Reynolds’ numbers and with various degrees of turbulence produced artificially in the wind tunnel through the introduction of grids or screens upstream from the model. The results furnish quantitative evidence of the considerable dependence of CLmax on Reynolds’ number and turbulence, and in particular demonstrate the fact that, even at fairly large Reynolds’ numbers, the value of CLmax may be increased by as much as 30 per cent by introducing artificial turbulence into a normally very smooth wind-tunnel flow. The theoretical investigation involves an analysis of the boundary-layer flow around an N.A.C.A. 2412 airfoil, and is particularly concerned with the transition from the laminar to the turbulent regime and with the separation of the laminar boundary layer from the upper surface of the airfoil. The second part of the paper gives illustrations of the diverse nature of the special aircraft-design problems for which the wind tunnel may give valuable information. The examples discussed are all chosen from investigations initially undertaken at our laboratory at the request of aircraft manufacturers and at their expense. Many of the problems so begun developed an independent scientific interest, so that the tests were subsequently amplified by the staff to a degree not at all contemplated when the work was started. A series of six distinct types of investigations is included in the samples considered.

The Effect of Turbulence

THE extensive series of investigations to be discussed in the present paper has its origin in an attempt to clarify the reason for certain discrepancies, which have long plagued aerodynamicists, between the results of tests on similar aerofoils carried out in different wind tunnels. It has been well known for many years that the Reynolds number has an important influence on aerofoil characteristics. It is therefore highly desirable that aerofoil tests, to be useful for full‐scale predictions, be made at as large a value of the Reynolds number as possible. For several years the variable density wind tunnel of the National Advisory Committee for Aeronautics has been able to employ Reynolds numbers considerably higher than were attainable in any other wind tunnel. Its results have, therefore, very properly been generally accepted as furnishing the standard aerofoil data for aeroplane designers in the United States, and to some extent also in Europe. It appears from the present investigation that another factor, turbulence, may be of the same order of importance as the Reynolds number in determining certain aerofoil characteristics. In discussing the possible effects of this factor, it is desirable that as wide variations in its magnitude as can be obtained should be considered. The turbulence characteristics of the N.A.C.A. variable density tunnel and of the wind tunnel at the Guggenheim Aeronautics Laboratory at the California Institute of Technology (referred to in the figures as Galcit) are as different as those of any two large contemporary wind tunnels. It is for this reason that in the following discussion results obtained in these two tunnels are compared.