Ludwig Prandtl (4 February 1875 – 15 August 1953) was a German scientist. He was a pioneer in the
development of rigorous systematic mathematical analyses which he
used to underlay the science of
aerodynamics, which have come to form the basis
of the applied science of aeronautical engineering. In the 1920s he
developed the mathematical basis for the fundamental principles of
subsonic aerodynamics in particular; and in
general up to and including
transonic
velocities. His studies identified the
boundary layer, thin-airfoils, and
lifting-line theories. The
Prandtl
number was named after him.
Early years
Prandtl
was born in Freising, near
Munich, in 1875. His mother suffered from a lengthy
illness and, as a result, Ludwig spent more time with his father, a
professor of engineering. His father also encouraged him to observe
nature and think about his observations.
He entered
the Technische Hochschule Munich in 1894 and graduated with a Ph.D. in six
years. His work at Munich had been in solid mechanics, and
his first job was as an engineer designing factory equipment.
There, he entered the field of
fluid
mechanics where he had to design a suction device. After
carrying out some experiments, he came up with a new device that
worked well and used less power than the one it replaced.
Later years
In 1901 Prandtl became a professor of fluid mechanics at the
technical school in Hannover, now the Technical University
Hannover. It was here that he developed many of his most important
theories. In 1904 he delivered a groundbreaking paper,
Fluid
Flow in Very Little Friction, in which he described the
boundary layer and its importance for
drag and
streamlining. The paper also described
flow separation as a result of the boundary
layer, clearly explaining the concept of
stall for the first time. Several of his
students made attempts at closed-form solutions, but failed, and in
the end the approximation contained in his original paper remains
in widespread use.
The effect
of the paper was so great that Prandtl became director of the
Institute for Technical
Physics at the University of Göttingen later in the year. Over the next decades he
developed it into a powerhouse of aerodynamics, leading the world
until the end of
World War II.
In 1925
the university spun off his research arm to create the Kaiser Wilhelm
Institute for Flow Research (now the Max Planck Institute for Dynamics and
Self-Organization).
Following earlier leads by
Frederick Lanchester from 1902–1907,
Prandtl worked with
Albert Betz and
Max Munk on the problem of a useful
mathematical tool for examining lift from "real world" wings. The
results were published in 1918–1919, known as the
Lanchester-Prandtl wing
theory. He also made specific additions to study cambered
airfoils, like those on
World War I aircraft, and published a simplified
thin-airfoil theory for these
designs. This work led to the realization that on any wing of
finite length, wing-tip effects became very important to the
overall performance and characterization of the wing. Considerable
work was included on the nature of
induced
drag and wingtip
vortices, which had
previously been ignored. These tools enabled aircraft designers to
make meaningful theoretical studies of their aircraft before they
were built.
Ludwig Prandtl 1904 with his fluid
test channel
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.
In 1922 Prandtl, together with
Richard
von Mises, founded the
GAMM
(the International Association of Applied Mathematics and
Mechanics). and was its chairman from 1922 until 1933. Until 1945
he also worked closely with the
RLM.
Other work examined the problem of
compressibility at high subsonic speeds,
known as the
Prandtl-Glauert
correction. This became very useful during World War II as
aircraft began approaching supersonic speeds for the first time. He
also worked on
meteorology, plasticity
and
structural mechanics.
Prandtl's life was marked by overtones of naïveté. At the age of
thirty-four, he decided it was time to marry, so he went to his old
professor,
August Föppl, to ask
his daughter's hand in marriage. But Prandtl didn't say which
daughter. The professor and his wife had a hurried discussion and
wisely decided it should be the older one. That was fine. The
marriage was a long and happy one.
Death and afterwards
Prandtl
worked at Göttingen until he died on August
15, 1953. His work in fluid dynamics
is still used today in many areas of aerodynamics and chemical
engineering. He is often referred to as the father of modern
aerodynamics.
The crater
Prandtl on the
far side of the Moon is named in his honor.
The
Ludwig-Prandtl-Ring is
awarded by
Deutsche
Gesellschaft für Luft- und Raumfahrt in his honor for
outstanding contribution in the field of aerospace
engineering.
Notable Students
Books
- Paul Peter Ewald, Theodor Pöschl, Ludwig Prandtl; authorized
translation by J. Dougall and W.M. Deans The Physics of Solids
and Fluids: With Recent Developments Blackie and Son
(1930).
- Ludwig Prandtl, Essentials of Fluid Dynamics, Hafner
Publications, New York (1952).
See also
Notes
External links