Darcey, Henry Philibert Gaspard (1803-1858)

French engineer

Henry Philibert Gaspard Darcy (1803–1858) was an accomplished French engineer, researcher, and civil servant, who is credited with building roads, water systems, and railroads. He is best known for a number of major contributions and advances in the understanding of fluid flow in pipes, open channels, and porous media. Darcy was the first researcher to suspect the existence of the boundary layer in fluid flow. His work contributed in the development of the Darcy-Weisbach equation, recognized as the best empirical relation for pipe flow resistance. Darcy also made major contributions to open channel flow research and provided the first quantitative measurements of artesian well flow. An enduring legacy of his work, Darcy's Law for flow in porous media, a cornerstone for several fields of study including groundwater hydrology, soil physics , and petroleum engineering remains widely used.

Darcy was born on June 10, 1803 in Dijon, France, the son of a civil servant. In 1821, he entered L'Ecole Polytechnique in Paris. In 1823 he was admitted to the prestigious L'Ecole des Ponts et Chaussee's (School of Bridges and Roads) in Paris, where he graduated with a degree in Civil Engineering in 1826. After graduation, he took a position with the Corps of Bridges and Roads in Dijon. There, Darcy began work on a project to develop a system for a safe and adequate water supply for the city. That effort eventually resulted in completion in 1844 of a model, completely enclosed, gravity driven system that provided water to major buildings and street hydrants throughout the city. Darcy's work was so advanced that it was 20 years before Paris had similar service. Despite his impressive achievements, Darcy refused to accept payment for his work as designer and manager of the water system project. The amount of money Darcy refused would translate to over a million dollars at modern exchange rates.

Darcy completed numerous other civil works in and near Dijon including roadways, bridges, sewers, and a railroad, passing through Dijon, linking Paris with Lyon, the largest industrial city to the south. His design for the railroad included a 2.5-mile-long (4 km) tunnel through the mountains at a time when tunnels of any significant length were considered unacceptable. However, Darcy had enlisted the aid of a geologist and mining engineer for a detailed survey of the site that indicated ideal conditions for constructing a tunnel. He had conceived the best engineering solution by rejecting an old generalization (tunnel length) and analyzed the problem on a site-specific basis. Because of Darcy's plan, the railroad passed through Dijon, ensuring the city's economic future. In 1844, he was awarded the Legion of Honor.

The St. Pierre Basin Fountain was considered a technological marvel for the time. Darcy designed separate valves for controlling an inner and outer ring of jets that allowed variations in the height of the fountain display. In an 1856 report, Darcy provided a theoretical analysis and experimental verification of the jet flow in this artesian system as a function of the height of the water system's two source reservoirs.

In 1848, Darcy was appointed Chief Director for Water and Pavements in Paris. There he began his systematic study of turbulent flow in pipes. He made significant advances in the design of the Pitot tube, used to measure the flow velocity in pipes. Those improvements made possible accurate, detailed measurements of point velocity distributions in pipes, leading to advances in pipe hydraulics and to his recognition of the existence of the boundary layer.

In 1855, Darcy returned to Dijon to carry out his famous sand column experiments that ultimately resulted in Darcy's law for flow in porous media. For one-dimensional flow, the law relates the volumetric flow rate to the cross-sectional area of a tube or column to the drop in hydraulic head over the length of the flow path, and introduces a proportionality constant for hydraulic conductivity. Subsequent to his work, engineers and scientists have demonstrated the theoretical basis and applicability of Darcy's law in several fields. The law has since been generalized to allow for differential solutions, vector analysis, and unsaturated and multiphase flow.

Darcy died unexpectedly of pneumonia, on January 3, 1858. He is buried in Dijon.

See also Hydrogeology; Hydrostatic pressure