# Leybenzon, Leonid Samuilovich

# Leybenzon, Leonid Samuilovich

(*b*, Kharkov, Russia, 26 June 1879; *d.* Moscow, U.S.S.R., 15, March 1951),

*mechanical engineering, geophysics.*

The son of a physician, Leybenzon graduated in 1897 form the Tula classical Gymnasium. He then entered the physics and mathematics section of Moscow University. In 1901 he graduated from the university and in 1906 form the Moscow higher technical School. While still a student, he went, on the recommendation of his teacher Zhukovsky, as a mechanical engineer to the Aerodynamics Institute in Kuchino (1904). Here he helped to build the first wind tunnel in Russia and a machine for testing propellers. He also constructed two-component aerodynamic scales, built models, and worked out the first methods of aerodynamic and structural design of the airplane, following Zhukovsky’s instructions.

In 1915 he defended his dissertation for a master’s degree in applied mathematics at Moscow University, “K teorii bezbaloehnykh pokryty” (“Toward a Theory of Ribless Covering”), and in 1916 was made professor of mechanics at Yurev University, In 1917 Leybenzon presented his dissertation for a doctorate in applied mathematics, “O prilozhenii metoda garmonicheskikh funktsy Tomsona K boprosu obvstoychivosti szhatyth sfericheskoy i tsilindricheskoy uprugikh obolochek” (“On the Application of the Method of Harmonic Functions of Thomson to the Question of the Stability of Compressed Spherical and Cylindrical Elastic Membranes”). From 1919 to 1929 Leybenzon was professor of applied mechanics at Tbilisi Polytechnical Institute and University.

In 1921 Leybenzon became professor at the Polytechnical Institute in Baku. At that time he began his remarkable activity in the science and technology of petroleum. In 1922 he returned to Moscow and was made head of the Department of Applied Mechanics at Moscow University. In 1933 Leybenzon was elected corresponding member of the Academy of Sciences of the U.S.S.R. and in 1943 active member.

The range of Leybenzon’s scientific interests was extraordinarily wide. He did extensive research in aerodynamics, elasticity theory, hydraulics, and geophysics. In the theoretical section of the Central Aerohydrodynamic Institute from 1933 to 1936, Leybenzon was concerned with airplane design, with the theory of the border layer, and gas dynamics. His works on the theory of hydrodynamic lubrications and the theory of evaporation of liquid drops in a gas current are of great significance. The important transformation given by Leybenzon for the basic equations of gas dynamics of Chaplygin should also be noted.

Leybenzon contributed to elasticity theory and resistance of materials. He gave a method of determining the position of the center of a curve and presented an interesting theorem on the circulation of tangent stress on a curve. He also demonstrated a general method for softening or relaxing border conditions. He deserves credit for the development of methods of approximating the determination of the turning moment into the theory of torsion and the setting of upper and lower limits to its size.

Leybenzon’s scientific research and his many years of teaching the theory of elasticity (culminated in notable monographs and textbooks. Among them are *Kairs teorii uprugosti* (“Course in the Theory of Elasticity”; 1942), *Elementy matematicheskoy teorii plastichnosti* (“Elements of the Mathematical Theory of Plasticity”; 1943), and *Variatsionnye melody resheniya zadach teorii uprugosti* (“Variational Methods of Solving Problems in the Theory of Elasticity”; 1943).

Leybenzon’s work on the production of petroleum was also of great significance. In 1932 he published a fundamental investigation, “Priblizhennaya dinamicheskaya teoria glubokogo nasosa” (“An Approximating Dynamic Theory of the Deep Pump”). His “Podzemnaya gidravlika vody, nefti i gaza” (“Underground Hydraulics of Water, Petroleum and Gas”; 1934) provided a scientific basis for the rational development of petroleum and gas deposits. His works laid the foundation for the development of the theory of filtration of aerated liquids. Leybenzon had a direct role in the planning and building of the first Soviet pipelines from Baku to Batumi and from Groznyy to Tuapse. A large part of his work was in geophysics, particularly the application of the elasticity theory to the study of the structure of the earth.

## BIBLIOGRAPHY

I. Original Works. For Leybenzon’s works, see *Sobranie trudov* (“Collected Works”), 4 vols. (Moscow 1951-1955); I. *Teoria uprugosti* (“Theory of Elasticity”; 1951); II, *Podzemnayagidrogazodmamika* (“Underground Gas Dynamics”; 1953); III. *Neftepromyslovaya mektmnika* (“Mechanics of the Petroleum Industry”; 1955); and IV. *Gidrodinamika, Geofizika* (“Hydrodynamics. Geophysics”; 1955).

II. Secondary Literature. For information on Leybenzon’s life, see L. I. Sedov, “Osnovnye daty zhizni i deyatelnosti L, S. Lcybenzona” (“Basic Facts in the Life and Work of L, S. Leybenzon”), In *Vspekhi matematicheskikh nauk*, **7** (1952), 127-134; and B. N. Yurev, “Leonid Samuilovtch Leybenzon,” in *hvestiya Akademii nauk SSSR. Otdelenie tekhnicheskikh nauk* (1949), no. 8, 1138-1142.

A. T. Grigorian

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