In 1901 Prandtl became a professor of fluid mechanics at the technical school in
Hannover, later the
Technical University Hannover and then the
University of Hannover. It was here that he developed many of his most important theories. In this paper, he described the boundary layer and its importance for
drag Due to the complexity of Prandtl's boundary layer ideas in his 1904 paper, the spread of the concept was initially slow. Many people failed to adopt the idea due to lack of understanding. There was a halt on new boundary layer discoveries until 1908 when two of his students at Gottingen, Blasius and Boltze, released their dissertations on the boundary layer. Blasius' dissertation explained what happened with the boundary layer when a flat plate comes in parallel contact with a uniform stream. Boltze's research was similar to Blasius' but applied Prandtl's theory to spherical shapes instead of flat objects. Prandtl expanded upon the ideas in his student's dissertations to include a thermal boundary layer associated with heat transfer. There would be three more papers from Gottingen researchers regarding the boundary layer released by 1914. Due to similar reasons to Prandtl's 1904 paper, these first 7 papers on the boundary layer would be slow to spread outside of Gottingen. Partially due to World War I, there would be a lack of papers published regarding the boundary layer until another of Prandtl's students, Theodore Von Karman, published a paper in 1921 on the momentum integral equation across the boundary layer. However, this new lift distribution drew less interest than the elliptical distribution and was initially ignored in most practical aircraft designs. This concept has been rediscovered by other researchers and has become increasingly important (see also the
Prandtl-D experimental aircraft). Prandtl and his student
Theodor Meyer developed the first theories of
supersonic shock waves and flow in 1908. The
Prandtl–Meyer expansion fans allowed for the construction of
supersonic wind tunnels. He had little time to work on the problem further until the 1920s, when he worked with
Adolf Busemann and created a method for designing a supersonic nozzle in 1929. Today, all supersonic wind tunnels and
rocket nozzles are designed using the same method. A full development of supersonics would have to wait for the work of
Theodore von Kármán, a student of Prandtl at Göttingen. Prandtl developed the concept of "circulation" which proved to be particularly important for the
hydrodynamics of ship propellers. He did most of the experimental work at his lab in Göttingen from 1910-1918 with his assistant Albert Betz and student Max Munk. Most of his discoveries related to circulation would be kept secret from the western world until after World War I. Prior to World War I, the
Society of German Natural Scientists and Physicians (GDNÄ) was the only opportunity for applied mathematicians, physicists, and engineers in German speaking countries to discuss. In 1920, they met in
Bad Nauheim and came to the conclusion that there was a need for a new umbrella for applied sciences due to their experience during the war. This journal advertised the common goals of Prandtl,
Theodore von Kármán,
Richard von Mises, and
Hans Reissner. Following Prandtl's investigation into instabilities from 1921-1929, he then moved to exploring developed turbulence. This was also being investigated by Kármán, resulting in a race to formulate a solution for the velocity profile in developed turbulence. Around 1930, the race ended in a draw as both men concluded that the inverse square of
skin friction was related to the logarithmic value of the product of
Reynold's number and skin friction as seen below where
k and
C are constants. Prandtl and von Kármán's work on the boundary was influential and adopted by aerodynamic and hydrodynamic experts around the world after WWI. In May 1932, the International Conference on Hydromechanical Problems of Ship Propulsion was held in
Hamburg. Günther Kempf showcased a number of experiments at the conference which confirmed many of the theoretical discoveries of von Kármán and Prandtl. ==Prandtl and the Third Reich==