Ludwig Prandtl: the father of modern aerodynamics

Take smooth flights for granted? Siddharth Trivedi meets the man behind the mechanics

Born in Freising, Germany in 1875, Ludwig Prandtl spent a significant portion of his childhood with his father due to his mother’s long term illness. A professor in engineering, his father was probably the reason Prandtl picked up his innate ability for scientific observation. He later utilised these same skills as he earned his PhD in Munich and entered his first job in a factory where he designed a suction device as an equipment engineer.

In 1901, he became a professor in fluid mechanics at the presently named Technical University Hannover. This was the location of his first major publication: a breakthrough paper titled Fluid Flow in Very Little Friction. This breakthrough in fluid mechanics saw him becoming the Directory of Institute of Technical Physics at University of Göttingen, where he worked until his death on 15 August 1953. In the general scientific field, he is a relatively unknown character. However, in chemical and aeronautical engineering he is commonly known as the father of modern aerodynamics. But why is that?

During his 50 years in Göttingen, Prandtl became a powerhouse of fluid mechanics research. Fluid Flow in Very Little Friction described the boundary layer formation on contact between solids and fluids, leading to a better understanding of skin friction. He also detailed stalling and streamlining, he reduction of drag, of airplane wings and other bodies in motion. Using research by Frederick Lancaster, Prandtl worked with other engineers such as Albert Betz and Max Munk to develop mathematical tools to model the lift from non-ideal aircraft wings. The results are known as the Lancaster-Prandtl wing theory.

Studying World War I aircraft, he published a simplified thin-airfoil theory that showed the importance of designing wing-tips. Wing-tips became a main design criteria for the manufacturing of airplanes due to the induced drag and vortices which previously had been ignored. These mathematical models allowed designers to theoretically model their designs before building, leading to better engineering. As World War II planes approached supersonic speeds, Prandtl and Hermann Glauert coined the Prandtl-Glauert correction which became very useful in countering compressibility at high velocities.

A great number of practical contributions to the chemical and aeronautical engineering field marked Prandtl’s long career. His contributions are not well recognised to the common scientist though his name has recently been used for significant scientific pursuits. For this reason, Ludwig-Prandtl-Ring is the highest honour awarded by German Society for Aeronautics and Astronautics for outstanding contribution to aerospace engineering. In honour of Prandtl’s research, NASA has also named two research and exploration aircraft after Prandtl, one known as PRANDTL-D tailless aircraft, which has been used to prove his theories that adverse yaw forces could be countered solely by wing-tip aerodynamics.

So, Ludwig Prandtl: a German engineer that has made travel and transport possible for all and made significant contributions unknown to most. Revolutionising the aerodynamics field that has taken off and become a significant part of human life: this is why he is the father of modern aerodynamics.

From Issue 11