Blasius-Biography - Experiments in Fluids 34(2003 566571...

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Blasius: A life in research and education W.H. Hager Abstract The Blasius boundary layer solution is a basic feature of Fuid mechanics, and the ±rst application of Prandtl’s boundary layer concept as a signi±cant issue in engineering. This work highlights the contributions of Blasius to hydrodynamics over a period of only six years, which marked the initiation of boundary layer theory. His main papers relating to aerodynamics and smooth tur- bulent pipe Fow are also reviewed, and a biography puts his career into the general environment of Germany over the period of two World Wars. A complete bibliography of Blasius is provided. 1 Introduction Nineteenth-century advances in hydrodynamics were directed mainly towards the understanding of ideal Fuid Fow. Accordingly, successful research was directed to- wards wave hydrodynamics. William ²roude (1810–1879) introduced a criterion named after him, according to which scale models involving free surface waves follow his similarity law. Shortly afterwards, Osborne Reynolds (1842–1912) formulated a law for viscous Fuid Fow. After Leonhard Euler had presented equations for ideal Fuid Fow in differential form, Navier, Saint-Venant and Stokes generalized his equations by accounting for viscosity. Mathematically, these relations are highly involved, how- ever, and only special solutions such as for laminar pipe Fow were amenable. In order to advance knowledge, therefore, appropriate simpli±cations had to be intro- duced. Ludwig Prandtl (1875–1953) presented his benchmark paper on boundary layers in 1904 (Prandtl 1904), postu- lating that Fow around a smooth body could be subdi- vided into two regions: (1) Close to the boundaries, Fuid viscosity governs Fow, for which the Navier–Stokes equations simplify to what we currently refer to as the boundary layer equations; and (2) away from the bound- aries, viscosity has a small effect and the Fow is inFuenced mainly by Euler’s potential Fow theory. The solutions pertaining to these two domains are suitably matched at the interface, and this approach was the key to advancing the questions of turbulence. While Prandtl at that time presented no direct appli- cation of his approach, his ±rst Ph.D. student Heinrich Blasius was able to outline the signi±cance of the novel formulation. The boundary layer solution for the Fat plate at once demonstrated the power of Prandtl’s concept. The solution was subsequently tested in a variety of Fow con±gurations, such as in naval engineering and in aero- dynamics, and substantial agreement was noted. Blasius then considered problems of potential Fow theory, in a way a step back from what he did earlier. However, his solutions were another addition to hydrodynamics, in- volving free surface Fow and the improvement of the Pitot tube. Another noteworthy contribution was published in 1912 (Blasius 1912a), relating to the Blasius friction coef- ±cient for turbulent smooth pipe Fow. As the present author was able to ±nd the daughter of Blasius, a biogra- phy is also presented. This note, therefore, would like to
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Blasius-Biography - Experiments in Fluids 34(2003 566571...

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