Saul Kaplun

After Kaplun's untimely death, his published papers and much of his unpublished work were edited by his former PhD advisor, Lagerstrom, and by Louis Norberg Howard of MIT and Ching-shi Liu of Caltech and were published in 1967 in book form under the title Fluid Mechanics and Singular Perturbation, a Collection of Papers by Saul Kaplun.

Morris Kaplun's philanthropy included funding of the Saul Kaplun Institute of Applied Mathematics and Space Physics at Tel Aviv University, Israel, consecrated in February 1966, which was attended by Prof. Paco Lagerstrom and others; and of the Saul Kaplun Building for Applied Mathematics and Theoretical Physics at the Hebrew University of Jerusalem, Israel dedicated a month later in the presence of the university president, Eliahu Eilat.

Dr. Millikan stated at the 1964 Caltech ceremony, "Few publications bear his name as author… however, in very many publications by others the author expresses his thanks to Saul Kaplun for having contributed some fundamental ideas to the work, or states that he has used methods due to Kaplun. By now his work has won world-wide recognition among specialists."

Sunil Datta wrote, "Singular perturbation method… It was left to the genius of Saul Kaplun (1957) to recognize the analogy between the theory of flow at small Reynolds number and boundary layer theory and to apply to it the singular perturbation method."

Saul Kaplun received his PhD in 1954 under the advisorship of Paco Lagerstrom at the California Institute of Technology with his thesis dissertation The role of coordinate systems in boundary layer theory. Kaplun and Lagerstrom later collaborated on and published an article together and Lagerstrom edited Kaplun's papers for publication as a monograph after the latter's death.

Kaplun spent his entire academic career, a total of 20 years, at Caltech and received four degrees there. He became a research fellow in aeronautics upon completing his PhD in 1954 and was a senior research fellow in aeronautics on the Caltech faculty from 1957 until his death.

Kaplun's work has been cited and extolled by colleagues and authors in the field. Robert Edmund O'Malley wrote, "The work of Kaplun and Lagerstrom at Caltech in the 1950s was especially important to the development of matched expansions and its applications to fluid mechanics."

Saul Kaplun (July 3, 1924 Lwów, Poland now Lviv, Ukraine – February 13, 1964, Pasadena, California, U.S.A.) was a Polish-American aerodynamicist at the California Institute of Technology (Caltech).

The father wrote a short book about his son: My Son Saul: Saul Kaplun, July 3, 1924 – February 13, 1964, in Memoriam, published in 1965.

Kaplun was the only child of Jewish immigrants from Poland, Morris J. Kaplun (February 12, 1888 Kamenetz-Podolsk, Ukraine – ?), a textile businessman and industrialist and a prominent Zionist philanthropist beginning in the 1930s, and Betty (Bettina) Kaplun (? – 1963). Saul and his parents, who were refugees from Nazi persecution, lived in Lwów until 1939, when they fled Poland; they immigrated to New York shortly before World War II. He became a naturalized American citizen in 1944 and served in the United States Navy from 1944 to 1946.