sentences:  Theodorsen then became the Chief of Research for Republic Aviation Corporation, manufacturer of the P-47 Thunderbolt fighter plane of World War II, and the later F-84 Thunderjet and the F-105 Thunderchief, a post from which he retired in 1962 when he became an active consultant to Sikorsky Helicopter Corporation, where he specialized in ducted propeller work and helicopter rotors.A significant development was his contribution to the structure of turbulence in a paper honoring Ludwig Prandtl’s 75th birthday.The universality of turbulence from microphenomena to astrophysics is well known.