Irmgard Flügge-Lotz
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Irmgard Flügge-Lotz, née Lotz (16 July 1903 – 22 May 1974) was a
German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...
-American
mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...
and
aerospace engineer Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is s ...
. She was a pioneer in the development of the theory of discontinuous automatic control, which has found wide application in hysteresis control systems; such applications include
guidance system A guidance system is a virtual or physical device, or a group of devices implementing a controlling the movement of a ship, aircraft, missile, rocket, satellite, or any other moving object. Guidance is the process of calculating the changes in pos ...
s,
electronics Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other Electric charge, electrically charged particles. It is a subfield ...
,
fire-control system A fire-control system (FCS) is a number of components working together, usually a gun data computer, a director and radar, which is designed to assist a ranged weapon system to target, track, and hit a target. It performs the same task as a hum ...
s, and
temperature regulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
. She became the first female engineering professor at
Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...
in 1961 and the first female engineer elected a Fellow of the
American Institute of Aeronautics and Astronautics The American Institute of Aeronautics and Astronautics (AIAA) is a professional society for the field of aerospace engineering Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecra ...
.


Early life and education

Lotz was born in
Hamelin Hameln ( ; ) is a town on the river Weser in Lower Saxony, Germany. It is the capital of the district of Hameln-Pyrmont and has a population of roughly 57,000. Hamelin is best known for the tale of the Pied Piper of Hamelin. History Hameln ...
,
Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
on 16 July 1903. She was encouraged at an early age to pursue technical subjects by her mother, whose family had been involved in construction for several generations. She often visited construction sites with her uncle and attended half-price matinee shows for technical films. After her father, Osark, a travelling journalist, was drafted for military service in
World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
, the young Irmgard helped the family by becoming a math tutor while studying at a girls' Gymnasium in Hanover. Several years later, when Osark returned to Hanover he was in poor health and Irmgard continued to work to bring in extra money for the family. She graduated from the Gymnasium in 1923 and entered the
Leibniz University Hannover Leibniz University Hannover (), also known as the University of Hannover, is a public university, public research university located in Hanover, Germany. Founded on 2 May 1831 as Higher Vocational School, the university has undergone six period ...
to study mathematics and engineering. Later in life, she explained why she decided to study engineering: In college she studied applied mathematics and
fluid dynamics In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in motion ...
and was often the only woman in her classes. In 1927, she received her Diplom-Ingenieur and remained in Hanover for her doctorate. In 1929 she earned her doctorate in engineering, publishing her thesis on the mathematical theory of circular cylinders and heat conduction. Lotz went to work for the Aerodynamische Versuchsanstalt (AVA) in
Göttingen Göttingen (, ; ; ) is a college town, university city in Lower Saxony, central Germany, the Capital (political), capital of Göttingen (district), the eponymous district. The River Leine runs through it. According to the 2022 German census, t ...
, one of the most prominent aeronautical research institutions in Europe. She joined as a junior research engineer and worked closely with
Ludwig Prandtl Ludwig Prandtl (4 February 1875 – 15 August 1953) was a German Fluid mechanics, fluid dynamicist, physicist and aerospace scientist. He was a pioneer in the development of rigorous systematic mathematical analyses which he used for underlyin ...
and Albert Betz, two of the leading German aerodynamicists of the time. Prior to her arrival at the AVA, Prandtl had been unsuccessfully working on solving a differential equation for his
lifting-line theory The Lanchester–Prandtl lifting-line theoryAnderson, John D. (2001), ''Fundamentals of Aerodynamics'', p. 360. McGraw-Hill, Boston. . is a mathematical model in aerodynamics that predicts lift distribution over a three-dimensional wing from ...
for the spanwise lift distribution of an airplane wing. Lotz was able to overcome his difficulties and solve the equation, and additionally developed a relatively simple method for practical use. She published what is now known as the "Lotz method" in 1931 for calculating the lift on a three-dimensional wing, and it became a standard technique used internationally. Following this achievement, she was promoted to team leader and built the theoretical department at the AVA by establishing her own research program and assisting other research groups. In 1932, she met
Wilhelm Flügge Gottfried Wilhelm Flügge (March 18, 1904 – March 19, 1990) was a German engineer, and Professor of Applied Mechanics at Stanford University.J.J. O'Connor and E.F. Robertson.Gottfried Wilhelm Flügge" at ''history.mcs.st-and.ac.uk.'' School of M ...
, who was a civil engineer and
privatdozent ''Privatdozent'' (for men) or ''Privatdozentin'' (for women), abbreviated PD, P.D. or Priv.-Doz., is an academic title conferred at some European universities, especially in German-speaking countries, to someone who holds certain formal qualifi ...
at the
University of Göttingen The University of Göttingen, officially the Georg August University of Göttingen (, commonly referred to as Georgia Augusta), is a Public university, public research university in the city of Göttingen, Lower Saxony, Germany. Founded in 1734 ...
. As they prepared to marry, Lotz's career progressed well and by the time they married in 1938 she had been appointed Head of the Department of Theoretical Aerodynamics. However, Flügge was branded "politically unreliable" and denied promotion at Göttingen for his anti-
Nazi Nazism (), formally named National Socialism (NS; , ), is the far-right politics, far-right Totalitarianism, totalitarian socio-political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) in Germany. During H ...
views. Flügge later recalled that while he was denied because of his political views, Lotz was "blocked from any possibility of ever getting into a university career, just because of being a woman". The escalation and increasing influence of
Nazi policies Nazism (), formally named National Socialism (NS; , ), is the far-right totalitarian socio-political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) in Germany. During Hitler's rise to power, it was frequen ...
on academia led to their departure from the AVA and they moved to the Deutsche Versuchsanstalt für Luftfahrt (DVL) in Berlin where Flügge-Lotz (her married name) was a consultant in aerodynamics and flight dynamics and Flügge was appointed Chief of Structures Research. Although banned from academic positions due to Nazi policies, they were permitted to continue their research activities under the protection of
Hermann Göring Hermann Wilhelm Göring (or Goering; ; 12 January 1893 – 15 October 1946) was a German Nazism, Nazi politician, aviator, military leader, and convicted war criminal. He was one of the most powerful figures in the Nazi Party, which gov ...
, who was more concerned with technical expertise than ideological purity. At DVL Flügge-Lotz began her career in
automatic control Automation describes a wide range of technologies that reduce human intervention in processes, mainly by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machine ...
theory and pioneered the theory of discontinuous control systems. These control systems, also known as "on-off" and "bang-bang" systems, have only two or three input settings and are simple to manufacture and very reliable in practical application. She was mainly interested in the implications these systems had for the development of simple automatic flight control equipment. However, the theory describing their performance needed to be developed before they could be reliably implemented in physical systems. Flügge-Lotz began developing the theory while at DVL, but wartime priorities limited her time for heavily theoretical projects so she focused mainly on aerodynamics during this time.


Move to France

As
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
progressed, Berlin was increasingly subject to bombing raids by the Allies. In the spring of 1944, the destruction of Berlin had progressed so far that Flügge-Lotz and Flügge moved with their departments to the small town Saulgau in the hills of southern Germany. After the end of the war, Saulgau was in the French zone of
Allied-occupied Germany The entirety of Germany was occupied and administered by the Allies of World War II, from the Berlin Declaration on 5 June 1945 to the establishment of West Germany on 23 May 1949. Unlike occupied Japan, Nazi Germany was stripped of its sov ...
. The French relaunched their aeronautical research activity and were eager to hire German scientists, so in 1947 Flügge-Lotz and Flügge moved with many of their colleagues to Paris to join the
Office National d'Etudes et de Recherches Aerospatiales The Office National d'Études et de Recherches Aérospatiales ( English: National office for aerospace studies and research) or ONERA, dubbed ''The French Aerospace Lab'' in English, is the French national aerospace research center. Originally f ...
(ONERA). Flügge-Lotz served as Chief of a research group in aerodynamics until 1948 and published papers in both automatic control theory and aerodynamics, in which she discussed the problems arising from the increased speed of aircraft.


Career at Stanford University

Although Flügge-Lotz and her husband were happy living in Paris, the positions they held there provided limited opportunity for advancement. They wrote to Stephen Timoshenko at
Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...
casually asking about working in the United States and in 1948, and both received offers to teach there. However, at the time Stanford held a university policy that husband and wife could not hold professional rank in the same department, and despite Flügge-Lotz's reputation in research, she had to accept the relatively minor position of "lecturer" as her husband became professor. Despite lacking of a professorial title, she immediately began accepting students for PhD dissertation research in aerodynamic theory, and in the spring of 1949, taught her first Stanford course in boundary layer theory. At Stanford, Flügge-Lotz conducted research in
numerical methods Numerical analysis is the study of algorithms that use numerical approximation (as opposed to symbolic manipulations) for the problems of mathematical analysis (as distinguished from discrete mathematics). It is the study of numerical methods t ...
to solve boundary layer problems in fluid dynamics, making pioneering contributions with finite difference methods and the use of computers. In 1951 she set up a weekly
fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics of fluids (liquids, gases, and plasma (physics), plasmas) and the forces on them. Originally applied to water (hydromechanics), it found applications in a wide range of discipl ...
seminar for first-year graduate students to provide a forum for discussing the latest ideas and developments.


Discontinuous automatic control theory

In addition to fluid mechanics, Flügge-Lotz returned to her work on automatic control theory initially started at DVL. She developed new courses and began advising student theses on the subject. She published the first textbook on discontinuous automatic control in 1953. A reviewer of her textbook wrote that: Since automatic control devices often found application in
electronics Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other Electric charge, electrically charged particles. It is a subfield ...
, she also began collaborating with faculty and students in the Department of Electrical Engineering. Over time, her primary research efforts went increasingly into control theory, and in 1968, the year of her retirement, she published her second book, ''Discontinuous and Optimal Control''.


Tenure

By the mid-1950s, it became evident that Flügge-Lotz was performing all the duties of a full Professor but without official recognition. In fact, it was hard for students to understand why she was a Lecturer rather than a Professor, or even what the difference meant. The disparity of her status as a Lecturer became more apparent when she was the only female delegate from the United States at the first Congress of the
International Federation of Automatic Control The International Federation of Automatic Control (IFAC), founded in September 1957 in France, is a multinational federation of 49 national member organizations (NMO), each one representing the engineering and scientific societies concerned with a ...
in Moscow. To address the issue before school opened for the fall quarter, she was appointed a full Professor in both Engineering Mechanics and in Aeronautics and Astronautics in 1961.


Legacy

Flügge-Lotz retired in 1968 at age 65, but continued to conduct research on
satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...
control systems, heat transfer, and high-speed vehicle drag. During her lifetime, she received many honors for her work. In 1970, she was elected a Fellow of the
American Institute of Aeronautics and Astronautics The American Institute of Aeronautics and Astronautics (AIAA) is a professional society for the field of aerospace engineering Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecra ...
(AIAA) and chosen to give the von Kármán lecture to the AIAA in 1971. She received the Achievement Award by the
Society of Women Engineers The Society of Women Engineers (SWE) is an international not-for-profit educational and service organization. Founded in 1950 and headquartered in the United States, the Society of Women Engineers is a major advocate for women in engineering and ...
in 1970, and received an honorary doctorate from the
University of Maryland The University of Maryland, College Park (University of Maryland, UMD, or simply Maryland) is a public land-grant research university in College Park, Maryland, United States. Founded in 1856, UMD is the flagship institution of the Univ ...
in 1973. The citation for her honorary degree stated: She was also a senior member of the
Institute of Electrical and Electronics Engineers The Institute of Electrical and Electronics Engineers (IEEE) is an American 501(c)(3) public charity professional organization for electrical engineering, electronics engineering, and other related disciplines. The IEEE has a corporate office ...
(IEEE), a member of
Sigma Xi Sigma Xi, The Scientific Research Honor Society () is an international non-profit honor society for scientists and engineers. Sigma Xi was founded at Cornell University by a faculty member and graduate students in 1886 and is one of the oldest ...
, and a member of the advisory boards of several scientific journals. In honor of her contributions, the “Wilhelm Flügge and Irmgard Flügge-Lotz Memorial Award" was established by the Applied Mechanics Division at
Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...
for outstanding graduate students.


Death

Flügge-Lotz's health deteriorated after her retirement and she suffered increasingly severe pain from
arthritis Arthritis is a general medical term used to describe a disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, Joint effusion, swelling, and decreased range of motion of ...
that spread over her body. On May 22, 1974, Flügge-Lotz died in Stanford Hospital after a long illness.


Works

* ''Die Erwärmung des Stempels beim Stauchvorgang'', Dissertation TH Hannover 1929 * ''Discontinuous Automatic Control'', Princeton University Press 1953 * ''Discontinuous and Optimal Control'', McGraw Hill 1968


Bibliography

* J. R. Spreiter & W. Flügge, ''Irmgard Flügge-Lotz'' in p. 33-40


See also

* German inventors and discoverers * List of people in systems and control


References


External links


"Imrgard Flugge-Lotz", Biographies of Women Mathematicians
Agnes Scott College Agnes Scott College is a Private university, private Women's Colleges in the Southern United States, women's Liberal arts colleges in the United States, liberal arts college in Decatur, Georgia. The college enrolls approximately 1,000 undergra ...

Biography of Flugge-Lotz from IEEE
{{DEFAULTSORT:Flugge-Lotz, Irmgard 1903 births 1974 deaths People from Hamelin 20th-century German mathematicians German women mathematicians Stanford University School of Engineering faculty German aerospace engineers Control theorists Fellows of the American Institute of Aeronautics and Astronautics Aerodynamicists German fluid dynamicists 20th-century German inventors American women inventors Leibniz University Hannover alumni Immigrants to France Immigrants to the United States 20th-century American women mathematicians 20th-century American mathematicians 20th-century American inventors Engineers from Lower Saxony 20th-century German women