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Dam Fluid Mechanics

By Ashar Ali

January 27, 2023



Marvels of Human engineering and architecture, Dams are huge mechanical barriers primarily used to restrict and control the water flow of natural bodies like rivers and lakes, as well as generate electricity through a method called Hydroelectric power production. While the uses of dams are not that secret, the physics involved in producing Hydroelectric Power is often not given its fair share of attention.

This sustainable method of producing electricity starts by storing water in “reservoirs”. A reservoir essentially acts as water’s potential energy store. The reservoir functions similarly to a battery, storing electricity as water when demand is low and providing maximum power during daily and seasonal peak periods. When this water is released, the velocity and depth of the water enable it to spin the turbine in a hydroelectric power plant. The fan of the turbine spins due to the “hydraulic head” created by the pressure of rushing water, and the velocity of the spin varies depending on the size of the fan and the height of the dam. The bigger the fan, the harder it is to move its blades. The taller the dam, the greater the velocity of water when it hits the turbine.

Turbines are connected to electrical generators either directly or through a gearbox or transmission that rotates the shaft and armature of the generator. The flow of electricity generated by the generator's spinning armature relative to its stator is captured by the commutator and brush assembly. Electricity generated immediately turns into grid-level voltages, which are subsequently transmitted through power lines by the local power utility.

Electricity demand is not "flat" or steady. During the day, demand fluctuates, and overnight, there is less need for electricity in homes, companies, and other institutions. For example, at 5:00 PM on a hot August weekend day in Atlanta, Georgia, you can guarantee there is a high demand for electricity to power millions of air conditioners! However, 12 hours later at 5:00 AM.... not so much. Hydroelectric facilities are more efficient than fossil-fuel and nuclear power plants in meeting peak power demands during short periods, and one method is to employ "pumped storage," which reuses the same water several times.


- Hydroelectric Power: How It Works. Hydroelectric Power: How it Works | U.S. Geological Survey. (n.d.). Retrieved January 1, 2023, from c-power-how-it-works

- How do hydroelectric dams work? Retrieved January 1, 2023, from ams-work

- Hydroelectric dam. Hydroelectric dam - Energy Education. (n.d.). Retrieved January 1, 2023, from

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