He was known for work in applying the method of asymptotic expansion to fluid mechanics problems.
[3] Several of his works have become classics, including "Matched Asymptotic Expansions: Ideas And Techniques".
[1] He then came to America as a graduate student at Princeton University, earning a PhD in 1942 in mathematics under Salomon Bochner[2] with a dissertation entitled "Measure and Integral in Partially Ordered Spaces".
[5] While he had already published significant results in pure mathematics,[6][7] he was, by this time, firmly interested in its applications to fluid dynamic and aerodynamic problems.
In 1946, Lagerstrom was recruited by Hans Liepmann to the Guggenheim Aeronautical Laboratory at Caltech.