Gotthilf Heinrich Ludwig Hagen (3 March 1797 – 3 February 1884) was a German

civil engineer A civil engineer is a person who practices civil engineering – the application of planning, designing, constructing, maintaining, and operating infrastructure while protecting the public and environmental health, as well as improving existing i ...

who made important contributions to

fluid dynamics In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in motion ...

hydraulic engineering Hydraulic engineering as a sub-discipline of civil engineering is concerned with the flow and conveyance of fluids, principally water and sewage. One feature of these systems is the extensive use of gravity as the motive force to cause the move ...

and

probability Probability is a branch of mathematics and statistics concerning events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1; the larger the probability, the more likely an e ...

theory.

Life and work

Hagen was born in

Königsberg Königsberg (; ; ; ; ; ; , ) is the historic Germany, German and Prussian name of the city now called Kaliningrad, Russia. The city was founded in 1255 on the site of the small Old Prussians, Old Prussian settlement ''Twangste'' by the Teuton ...

East Prussia East Prussia was a Provinces of Prussia, province of the Kingdom of Prussia from 1772 to 1829 and again from 1878 (with the Kingdom itself being part of the German Empire from 1871); following World War I it formed part of the Weimar Republic's ...

(

Kaliningrad Kaliningrad,. known as Königsberg; ; . until 1946, is the largest city and administrative centre of Kaliningrad Oblast, an Enclave and exclave, exclave of Russia between Lithuania and Poland ( west of the bulk of Russia), located on the Prego ...

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

) to Friedrich Ludwig Hagen and Helene Charlotte Albertine Hagen.Schroeder, Ralph, "Hagen, Gotthilf Heinrich Ludwig" in: New German Biography 7 (1966), p 472 nline version URL: http://www.deutsche-biographie.de/ppn118719874.html His father was a government official and his mother was the daughter of Christian Reccard, professor of Theology at

University of Königsberg The University of Königsberg () was the university of Königsberg in Duchy of Prussia, which was a fief of Poland. It was founded in 1544 as the world's second Protestant Reformation, Protestant academy (after the University of Marburg) by Duke A ...

, consistorial councillor and astronomer. He showed promise in

mathematics Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...

in high school and he went on to study at the University of Königsberg where his uncle, Karl Gottfried Hagen was professor of

physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

and

chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

. In 1816 Hagen began studying mathematics and

astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

with

Friedrich Wilhelm Bessel Friedrich Wilhelm Bessel (; 22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist, and geodesist. He was the first astronomer who determined reliable values for the distance from the Sun to another star by the method ...

, but in 1818 he switched to study civil engineering as he was more attracted to applied than theoretical science. Nevertheless, he remained in close contact with Bessel throughout his life.Willi Hager, Hydraulicians in Europe 1800-2000, Volume 2, CRC Press, 21 Mar 2014. In 1819 he undertook the examination for surveyors (Landvermesserprüfung) and after graduating took a job as a junior engineer (Baukondukteur) in the civil service. His main responsibility was for hydraulic engineering and water management. In 1822 he took the state examination in

Berlin Berlin ( ; ) is the Capital of Germany, capital and largest city of Germany, by both area and List of cities in Germany by population, population. With 3.7 million inhabitants, it has the List of cities in the European Union by population withi ...

to qualify as a master builder (Baumeister). He became known through his publications about various hydraulic constructions which he had visited during travels in Europe. In 1824 he was appointed director of building (Baukondukteur) by the mercantile community in Königsberg and in 1825 he became deputy governmental building officer (stellvertretender Regierungs- und Baurat) for Danzig (

Gdańsk Gdańsk is a city on the Baltic Sea, Baltic coast of northern Poland, and the capital of the Pomeranian Voivodeship. With a population of 486,492, Data for territorial unit 2261000. it is Poland's sixth-largest city and principal seaport. Gdań ...

). A year later he transferred to become harbor building inspector (Hafenbauinspektor) in

Pillau Baltiysk ( ); ; Old Prussian: ''Pillawa''; ; ; is a seaport town and the administrative center of Baltiysky District in Kaliningrad Oblast, Russia, located on the northern part of the Vistula Spit, on the shore of the Strait of Baltiysk separ ...

, where he was responsible for the harbor and dyke construction. Methods he developed are still relevant to current harbor management in the region. On 27 April 1827 he married his niece Auguste Hagen (1806–1884), with whom he had two daughters and five sons. His son Ludwig Hagen also became a notable civil engineer. In 1830 Hagen joined the supreme building authority (Oberbaudeputation) in Berlin and became chief government building surveyor (Oberbaurat) in 1831. From 1834 to 1849 he taught as a professor of hydraulic engineering at the

Bauakademie The Bauakademie (Building Academy, also known as the ''Schinkelsche Bauakademie'') in Berlin, Germany, was a higher education institution for the art of building to train master builders. Founded on 18 March 1799 by King Frederick William II ...

and the United Artillery and Engineering School in Berlin. Hagen was unusual in stressing the mathematical and theoretical aspects of hydraulic engineering. In particular he was interested in using probability calculus for land surveying and this interest led to his contributions to probability theory. In a letter to Bessel dated 2 August 1836 Hagen presented his hypothesis of elementary errors and deduced a Gaussian distribution for observational errors. This idea was further developed in a book published in 1837 ''Grundzüge der Wahrscheinlichkeitsrechnung mit besonderer Anwendung auf die Operationen der Feldmeßkunst'' (“Foundations of Probability Calculus with Special Application to the Operations of Land Surveying”) which applied probability theory and

least squares The method of least squares is a mathematical optimization technique that aims to determine the best fit function by minimizing the sum of the squares of the differences between the observed values and the predicted values of the model. The me ...

techniques to construction and surveying and deduced an error law that was not based on inverse probability arguments.

Hagen–Poiseuille equation

In 1839 Hagen undertook careful experiments in brass tubes that enabled him to discover the relationship between the

pressure drop Pressure drop (often abbreviated as "dP" or "ΔP") is defined as the difference in total pressure between two points of a fluid carrying network. A pressure drop occurs when frictional forces, caused by the resistance to flow, act on a fluid as i ...

and the tube

diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

under conditions of

laminar flow Laminar flow () is the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral m ...

of homogeneous

viscous Viscosity is a measure of a fluid's rate-dependent resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for example, syrup h ...

liquid Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

s. Hagen observed an empirical

power law In statistics, a power law is a Function (mathematics), functional relationship between two quantities, where a Relative change and difference, relative change in one quantity results in a relative change in the other quantity proportional to the ...

relationship between the

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

drop (ΔP) and radius (R) of a tube corresponding to ΔP ∝ 1/R^−4.12, but suggested in view of possible measurement errors that a value of 4.0 be assumed. This relationship was also discovered independently at around the same time by the French physicist and physiologist Jean Poiseuille and is therefore now known as the Hagen–Poiseuille equation or Poiseuille's law. In 1849 he was appointed as an expert adviser (Sachverständiger) to the Frankfurt National Assembly and in 1850 was appointed expert councillor (Vortragenden Rat) in the

Prussia Prussia (; ; Old Prussian: ''Prūsija'') was a Germans, German state centred on the North European Plain that originated from the 1525 secularization of the Prussia (region), Prussian part of the State of the Teutonic Order. For centuries, ...

n Ministry of Commerce. In 1852 Hagen published a notable paperG. H. L. Hagen, Bericht ̈uber die zur Bekanntmachung geeigneten Verhandlungen der Koniglich Preussischen Akademie der Wissenschaften zu Berlin. 1852: 35–42. that described and explained two fundamental aspects of

granular material A granular material is a conglomeration of discrete solid, macroscopic scale, macroscopic particles characterized by a loss of energy whenever the particles interact (the most common example would be friction when granulation, grains collide). T ...

: saturation of pressure with depth in a confined static granular system - generally known as the Janssen effect; and the dynamics of granular flow out of a container – sometimes called the Beverloo law - the foundation of the hourglass theory. Hagen played a decisive role in planning the development of numerous German rivers and harbors. The Prussian Admiralty appointed him to supervise the planning of

Wilhelmshaven Wilhelmshaven (, ''Wilhelm's Harbour''; Northern Low Saxon: ''Willemshaven'') is a coastal town in Lower Saxony, Germany. It is situated on the western side of the Jade Bight, a bay of the North Sea, and has a population of 76,089. Wilhelmsha ...

in 1855. Hagen took leave from his post in the Ministry of Trade and became chair of the Commission for the port construction in the

Jade Bight The Jade Bight (also known as ''Jade Bay''; , ) is a bight or bay on the North Sea coast of Germany. It was formerly known simply as (the) Jade or Jahde. Because of the very low input of freshwater, it is classified as a bay rather than an e ...

. After rejecting the designs of two internationally known experts, he proposed his own design to the Prussian Admiralty on 29 May 1856. This port design met the requirements of the Prussian Admiralty but also allowed for later expansions and additions. The design was approved by cabinet order on 25 June 1856. After completion of the planning, he returned to the Prussian Ministry of Trade on 12 August 1856. The implementation of the plan was carried out in the following decade, and despite many changes, still determines the current layout of the town center. In 1863 Hagen published his encyclopaedic manual on

. This represented the state of the art for coastal protection and served for decades as the guideline for

coastal engineering Coastal engineering is a branch of civil engineering concerned with the specific demands posed by constructing at or near the coast, as well as the development of the coast itself. The fluid dynamics, hydrodynamic impact of especially wind wave, ...

in Germany. In 1866 Hagen was promoted to chief director (Oberbaudirektor) in the Department of Hydraulic Engineering and chair (Vorsitzenden) of the section of public works in the Ministry of Trade (Baudeputation). In 1869 he was made senior national building director (Oberlandesbaudirektor). This role involved responsibility for large water and harbor works in Prussia and other German States. He held this post until his retirement in 1875. In 1872 suffered an accident on a business trip and was unable to walk in the subsequent period. Hagen died in 1884, his tomb is located on the Invalidenfriedhof Berlin, Scharnhorststraße near the main railway station.

Honours and awards

On 7 April 1842 Hagen was elected as a member of the Royal Prussian Academy of Sciences, Berlin on the recommendation of

Alexander von Humboldt Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 1769 – 6 May 1859) was a German polymath, geographer, natural history, naturalist, List of explorers, explorer, and proponent of Romanticism, Romantic philosophy and Romanticism ...

. In 1843 Hagen received an honorary doctorate from the

University of Bonn The University of Bonn, officially the Rhenish Friedrich Wilhelm University of Bonn (), is a public research university in Bonn, North Rhine-Westphalia, Germany. It was founded in its present form as the () on 18 October 1818 by Frederick Willi ...

. In 1881 he was made a Freeman of Pillau On 2 May 1883 he was awarded a gold medal for extraordinary services to the construction industry.

Monuments and memorials

After his death a monument to Hagen was built in

. The monument is currently in

Baltijsk Baltiysk ( ); ; Old Prussian language, Old Prussian: ''Pillawa''; ; ; is a seaport types of inhabited localities in Russia, town and the administrative center of Baltiysky District, Kaliningrad Oblast, Baltiysky District in Kaliningrad Oblast, R ...

and is now maintained by the Russian Navy. Gotthilf Hagen square was inaugurated in

in 2007. A sculpture in honor of Gotthilf Hagen was placed in the square. It was created by the artist Hartmut Wiesner. In 1959 a pilot station ship, the "Gotthilf Hagen" was named after him

Publications

* Beschreibung neuerer Wasserbauwerke in Deutschland, Frankreich, den Niederlanden und der Schweiz 1826 * Untersuchungen über den Druck und die Reibung des Sandes 1833 * Grundzüge der Wahrscheinlichkeitsrechnung (published in 3 Editions) 1837 * Über die Bewegung des Wassers in engen zylindrischen Röhren 1839 * Handbuch der Wasserbaukunst (3 Parts) 1841-1863 * Über die Oberfläche der Flüssigkeiten 1845 * Über den Einfluß der Temperatur auf die Bewegung des Wassers in Röhren 1854 * Über Flut und Ebbe in der Ostsee 1857 * Zur Theorie der Meereswellen 1859 * Die neueren Theorien der Bewegung des strömenden Wassers. Über die Bewegung des Wassers in Strömen 1868 * Über den Seitendruck der Erde 1871 * Geschwindigkeit des strömenden Wassers in verschiedenen Tiefen 1883

References

{{DEFAULTSORT:Hagen, Gotthilf Heinrich Ludwig 1797 births 1884 deaths 19th-century German engineers Hydraulic engineers 19th-century German physicists German statisticians German fluid dynamicists Members of the Prussian Academy of Sciences Scientists from Königsberg University of Königsberg alumni Burials at the Invalids' Cemetery Engineers from the Kingdom of Prussia Scientists from the Kingdom of Prussia