Ludwig Prandtl

Ludwig Prandtl
” The Father of Modern Aerodynamics”

Author: Dr. Sandeep Mouvanal

Prof. Ludwig Prandtl is known as a physicist who revolutionized fluid dynamics with his notion that the effect of friction is experienced only very near an object moving through a fluid. The modern fluid dynamics and aerodynamics world is based on this great scientist’s idea. His seminal paper which he presented in 1904 at the third international mathematics congress in Heidelberg is regarded as equivalent to that of the seminal paper of Albert Einstein and deserved a Nobel Prize in classical physics.

Portrait of Ludwig Prandtl, watercolor on paper (15 x 11″, Artist: Dr.Sandeep Mouvanal)

Some Important Contributions:

  • Pioneer of modern aerodynamics
  • Identified boundary layer in fluid flow
  • The mathematical basis for subsonic and transonic aerodynamics
  • Thin aerofoils
  • Lifting line theories
  • Prandtl Number
  • Developed the first theories of supersonic shock waves along with his student, Meyer
  • Today all supersonic wind tunnels work on his and his student’s ideas/contribution
  • “Real world wing” or Lanchester- Prandtl wing theory
  • Turbulence and universal law of wall which was also parallelly independently developed by his student Von Karmann

More information:

Ludwig Prandtl (4 Feb 1875 to 15 Aug 1953) is a German fluid dynamist born in 1875 in Freising near Munich. He did his Ph.D. at the Technical University of Munich under the guidance of Professor August Foeppl in Solid Mechanics. Interestingly his first job was as a Design Engineer which helped him to bring the practical Engineering approach to his research in the later stages. He entered Fluid Mechanics for designing a suction device during his job. Later he became a professor of Fluid Mechanics at the University of Hannover.

In 1904, a 29-year-old young professor delivered a groundbreaking paper [6] which was less than 10 pages and 10 minutes long talk on the motion of fluids in very little friction at the International Mathematics Congress in Heidelberg. In this paper, he described the boundary layer and its importance for drag and streamlining. It also described flow separation as a result of the boundary layer, clearly explaining the concept of the stall for the first time ever. The impact of this paper was such that he immediately became the director of the Institute for Technical physics at the University of Göttingen. In the next two decades, he made it the world’s focal point of aerodynamics until the end of world war 2. It is believed that Prandtl should have been conferred with the Nobel prize but it never happened because of the geopolitical situation of that era. Actually, Prandtl had been nominated for the Nobel prize twice in 1928 by German colleagues, and again in 1936 by the British Nobel prize laureate William Lawrence Bragg.

Concept of the boundary layer. (Image source [3])

His notable students are Schlichting, Tollmein, VonKarmann, Timoshinke, Valcovici, and Vishnu Madhav Ghatage. All of them had a great contribution to fluid dynamics/aerodynamics and can be a separate topic for several blogs. One interesting student to be noted is Von Karmann. He later became a competitor and arch-rival of Prandtl in the field of turbulence. The first class rivalry was in fact between Göttingen and Aachen Universities in the “playing field” Congress of Applied Mechanics for the search of the Univeral law of wall for Turbulence. Both of them independently developed the idea for the Universal law of wall which is widely being used for wall-bounded flows.

Prandtl worked at Göttingen until he died on 15 August 1953. His contributions to fluid dynamics are still used today in many areas of Engineering. He is regarded as the father of modern aerodynamics. The crater on the far side of the Moon is named in his honor as crater Prandtl. The Ludwig-Prandtl-Ring is awarded by Deutsche Gesellschaft für Luft- und Raumfahrt in his honor for outstanding contribution to the field of aerospace engineering.

Ludwig-Prandtl-Ring. (Image source: http://www.fluid.tuwien.ac.at/)
Crater Prandtl (source: https://the-moon.us/wiki/Prandtl)

References:

[1] “Ludwig_Prandtl.” Wikipedia, Wikimedia Foundation, 11 Dec 2022, https://en.wikipedia.org/wiki/Ludwig_Prandtl
[2] Eckert M. Ludwig Prandtl and the growth of fluid mechanics in Germany. Comptes Rendus Mécanique. 2017 Jul 1;345(7):467-76.
[3] Anderson JD. Ludwig Prandtl’s boundary layer. Physics Today. 2005 Dec 1;58(12):42-8.
[4] Anderson Jr JD, Anderson JD. A history of aerodynamics: and its impact on flying machines. Cambridge university press; 1998.
[5] Prandtl L. Early developments of modern aerodynamics. English Translation, JAK Ackroyd, BP Axcell, and AI Ruban, Eds. 2001:77.
[6] Prandtl L. Verhandlungen des dritten internationalen Mathematiker-Kongresses. Heidelberg, Leipeizig. 1904:484-91.

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