Hydrodynamics is the study of how forces (pushes and pulls) affect "incompressible fluids". What is an "incompressible fluid"? A fluid is a liquid or a gas. Incompressible means that when a force is applied to an object, the object doesn't take up less of a volume; it doesn't compress and its density does not change. There are certain instances when the velocity of a gas is very slow and the gas can be treated as if it was incompressible. So although most of the time "hydrodynamics" is applied to the study of how forces affect a liquid it can also refer to a gas.

These liquids could be moving around an object like a boat hull or a submarine. They could be moving through something like pipes or hoses. Or they might be contained, like water behind a dam. In each case, there are rules and laws for the behavior of the fluid or liquid. Engineers study and apply these rules and laws when they design boats, pipes, dams, or anything that uses a liquid.

The study of hydrodynamics is sometimes confused with aerodynamics, especially when people are designing boats. The behaviors, rules, and laws are very similar in both fields. That's why some design engineers call themselves aerodynamicists, even though they are working with liquids rather than gases.

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Last modified: Mon Jun 15 20:45:02 PDT 1998

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