Ludwig Prandtl

Ludwig Prandtl (4 February 1875 – 15 August 1953) was a German fluid dynamicist, physicist and aerospace scientist. He was a pioneer in the development of rigorous systematic mathematical analyses which he used for underlying 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. under guidance of Professor August Foeppl 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, later the Technical University Hannover and now the University of Hannover. It was here that he developed many of his most important theories. On August 8th 1904, he delivered a groundbreaking paper, "Über Flüssigkeitsbewegung bei sehr kleiner Reibung" ("On the Motion of Fluids in Very Little Friction"), at the Third International Mathematics Congress in Heidelberg. In this paper, 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. Prandtl showed that an elliptical spanwise lift distribution the most efficient, giving the minimum induced drag for the given span. These tools enabled aircraft designers to make meaningful theoretical studies of their aircraft before they were built.
Prandtl later extended his theory to describe a bell-like lift distribution, obtained by washing out the wing tips until negative lift was obtained, which gave the minimum induced drag for any given aircraft weight, also suggesting that adverse yaw forces could be countered solely by wing tip aerodynamics, but this new theory was largely ignored. In the 21st century the American engineer Al Bowers has confirmed the idea, calling his experimental wing the PRANDTL-D.
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.

Orphans of the Genocide

Orphans of the Genocide (), is a 2013 television film written and directed by American-Armenian filmmaker Bared Maronian. Filmed was premiered in 2015 at the 100th anniversary of the Armenian Genocide. The heroes of the film who tell their stories are the descendants of the Genocide survivors.
Plot.
In the documentary an Armenian orphanage located at Antoura, Beirut, Lebanon was unveiled, where thousands of Armenian Genocide Orphans had lived and were forcefully "Turkified" during World War I. Interviews of software engineer and historian Maurice Kelechian, Almast Boghossian, Jack Kevorkian, British journalist Robert Fisk, Debórah Dwork are included in the film.
Author's word.
"The stories of the Armenian Genocide orphans that we highlight in the documentary are of universal proportions. Meaning, the experiences that the orphans of the Armenian Genocide went through are the same experiences (loss of family members, starvation, pain, epidemics such as typhus, social displacement) that the orphans of the Cambodian genocide, the Holocaust orphans, and the Darfur Genocide orphans went through.
Therefore, the Armenian Genocide is not only an Armenian issue. It concerns all of the civilized world. A large number of scholars agree that, had the world paid closer attention to the Armenian Genocide – the first genocide of the 20th century – the genocides that followed it would have never happened.- Bared Maronian"