Fluid Dynamics is a subject that is well over 2,000 years old. Archimedes, da Vinci, Galileo and Newton are all classical forerunners of modern fluid dynamics researchers such as Bernoulli and Euler (Anderson 42). However, until the early 19th century, this subject was not well quantified; instead, textbooks were comprised of endless tables and figures demonstrating phenomena. When Daniel Bernoulli, Claude Navier and George Stokes introduced mathematics to the realm of fluid flow, new research was possible, but this work was highly theoretical and required extensive use of differential equations (Eckert 15). Ludwig Prandtl was the man who quantified many fluid flow principles and created his own theories about boundary separation and airfoil dynamics.
Ludwig Prandtl was born in Freising, Bavaria on February 4, 1875. An only child, Prandtl often followed closely to his father due to his mother’s “protracted illness” (Anderson 46). His father was an engineering professor and was said to have continually motivated Ludwig to look beyond observations to discover the natural principles at work. Regardless of his motivation, Prandtl attended the Technische Hochschule in Munich, Germany, and he eventually graduated with a Ph.D. from the University of Munich under adviser August Foppl (Anderson 46). After a few years in industry and three years as a professor of mechanics at the technical school in Hanover, Prandtl accepted a position at the University of Göttingen in 1904. By 1898, both of his parents had died, and in 1909, he married Gertrude Foppl, the daughter of his academic adviser (Anderson 47).
The event which launched Prandtl into the limelight of fluid dynamics was the delivery of his paper “Ueber Flussigkeitsbewegung Bei Sehr Kleiner Reibung” (Fluid Flow in Very Little Friction) to the Third International Mathematics Congress in Heidelberg, Germany in 1904 (Anderson 43, Eckert 33). This paper described his theory of the boundary layer that he had formalized during his first years of teaching in Hanover. He had conducted research on flow separation, and even built a water canal to visually demonstrate this principle (Eckert 35). Prandtl “theorized that an effect of friction was to cause the fluid immediately adjacent to the surface to stick to the surface…and that frictional effects were experienced only in a boundary layer” (Anderson 43).
The two main points from Prandtl’s first major publication are still standards in today’s fluid dynamics classes. The boundary layer existence leads to the important principle of shear stresses existing along the boundaries of flow. Because the velocity gradient is very large over a small distance (from the no-slip boundary to the distance δ in Fig. 3.3), the shear stress can be very large across the skin that is exposed to flow. This principle was largely ignored by many earlier researchers, but Prandtl’s work proved that these forces must be considered (Anderson 43). The second point...