Darcys law

The law of flow of water through soil was first studied by Darcy in 1856.

1. Presentation On DARCY’S LAW Presented by: Md Imran Hossain Rakib Roll No -18531045 Course code- Bangladesh University Of Professionals

2. WHO WAS DARCY? Henry Philibert Gaspard Darcy was born June 10, 1803 in Dijon , France . Admitted to the French School of Bridges and Roads in Paris, part of the Corps of Bridges and Roads. After graduation, he was eventually assigned by the Corps to a position in Dijon . In 1828, Darcy designed a 12.7 km system of aqueducts to supply the city of Dijon with surface water. The system included 28,000 m of pressurized surface lines and required no pumps or filters.

3. Made important contributions to flow and friction loss in pipes, created an improved pitot tube design, and was the first to postulate the existence of a boundary layer in fluid flow . In 1856, carried out experiments while researching sand filters that lead to Darcy’s Law . Henry Philibert Gaspard Darcy (1803–1858)

4. DARCY’S LAW The law of flow of water through soil was first studied by Darcy in 1856 . The Darcy’s law is , “ For laminar flow through saturated soil mass, the discharge per unit time is proportional to the hydraulic gradient ”.

5. Equation Q=KA(h 1 -h 2 )/L Here, Q is Flow rate A is area H1,h2 are groundwater heads K is the hydraulic conductivity L is distance between groundwater heads.

6. ASSUMPTIONS OF DARCY’S LAW :- The following assumptions are made in Darcy’s law: The soil is saturated . The flow through soil is laminar. The flow is continuous and steady. The total cross sectional area of soil mass is considered . The temperature at the time of testing is 2 70C.

7. VALIDITY OF DARCY’S LAW 1 . Darcy’s law is valid if the flow through soils is laminar : The flow of water through soils depends upon the dimension of particles. In fine grained soils the dimensions of the interstices (voids) are very small and flow is necessarily laminar. In course- grained soil, the flow is also laminar. However, in very coarse grained soils, such as gravels , the flow may be turbulent. For flow through soils, the flow is laminar if the Reynolds number is less than unity

8. 2.As per Allen Hazen, the maximum diameter of the particle for the flow to be laminar is about 0.50 mm. 3. It is valid for flow in clays, slits and fine sands. In coarse sands, gravels and boulders, the flow may be turbulent and Darcy’s law may not be applicable. 4. For Darcy’s law to be valid, the relationship between velocity (v) and hydraulic gradient( i ) should be linear. 5. In extremely fine-grained soils, such as colloidal clay, the interstices are very small. The velocity is therefore very small. In such soils, the Darcy’s law is not valid

9. Limitations of Darcy’s Law Due to skin formation permeability in vicinity of wellbore is changing (decreasing) At higher flow rates inertial force, acting due to convective acceleration of fluid particles through porous medium, have to be taken into account.

10. Application Of Darcy’s Law The study of flow in porous media is important in a wide range of applications including- Ground water flow Exploitation of petroleum reservoirs Filter design Capillary circulation Chemical reactors

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