LANG

GERMANY (see also List of Individuals)

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.. 1855 /D - 29.8.1931 Bonn/D

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Hermann Lang graduated as a civil engineer. He was from the 1890s a Regierungs-Baumeister in Hamburg and after World War I stayed as a Geheimrat in Köln-Nippes.

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Lang was mainly known in Germany for a simple formula describing uniform pipe flow. After several equations for the hydraulic rough regime had been developed in the 19th century and both Osborne Reynolds (1842-1912) and Heinrich Blasius (1883-1970) had formulated formulas for the turbulent smooth regime, practicing engineers felt unsafe in the application of the true relation that describes a basic hydraulic phenomenon. The problem was only solved from a scientific point of view in the 1930s once the Prandtl-Nikuradse data were available, and the English Cyril Frank Colebrook (1910-1997) and Cedric Masey White (1898-1993) had presented their famous formula spanning over the entire turbulent flow regime. Lang published his formula first in the 1910 Hütte book, a still widely used engineering reference. It should include all experimental data available up to 1910 and 300 additional observations of the author. The friction coefficient in the Darcy-Weisbach pipe flow equation was expressed as the sum of a constant plus the inverse square root of the product velocity times pipe diameter. The dimensionally incorrect relation is similar to other proposals. Lang recommended his previous results with a note in 1923. He also rejected the popular formula of the Swiss Ganguillet and Kutter established in 1869. He finally in 1931 presented a still modified formula for open channels thereby obviously overlooking the developments in this field mainly from Ludwig Prandtl (1875-1953) and his collaborators at Göttingen University.

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_{Fischer, A. (1930). Graphische Rechentafel für die Lang'sche Formel zur Berechnung des Druckhöhenverlustes in Rohrleitungen. Wasserwirtschaft 25(7): 109-111.}

_{Lang, H. (1893). Durchflusskoeffizienten von Steuerschiebern hydraulischer Hebezeuge. Zeitschrift Verein Deutscher Ingenieure 37(42): 1281-1286.}

_{Lang, H. (1910). Mechanik tropfbar flüssiger Körper. Hütte - Taschenbuch für Eisenhüttenleute: 293. Ernst&Sohn: Berlin.}

_{Lang, H. (1931). Die Mängel der Ganguillet-Kutterschen Geschwindigkeitsformel für Flüsse und die Gefahren bei ihrer Anwendung auf gefüllte Rohrleitungen. Zentralblatt der Bauverwaltung 51(36): 517-521; 51(37): 530-531.}

_{Lang, H. (1931). Beitrag zur Abflussformel für Flüsse. Mitteilung 6: 5-12. Preussische Versuchsanstalt für Wasserbau und Schiffbau: Berlin.}