Fluids in motion

There are three states of matter under most conditions around us near the surface of the Earth. Solids, Liquids, and Gases. Here I write about fluid motion. Why is this relevant? With a few approximations we can understand simple properties of flow. This understanding can come handy in our daily life. Before describing flow, I write what is a liquid and use this description to relate to flow.

All matter is made out of atoms. That means that understanding the motion of the atoms helps us understand fluid motion. In the case of liquids, which are a type of fluid, the forces between the parts of the liquid are weaker than the forces inside the parts. These parts then, usually molecules like H₂O , are free to move away from each other, but not away from the surface of the liquid where tension forces keep the molecules inside the volume occupied by the liquid.

Fluids in Motion

The parts of the fluid in a state of streamline, or laminar motion, move in a regular manner. They do not go around in circles, that requires a difference between the motion above and below the streamline. Particles above the streamline would move in the opposite direction as particles below the line. This is like a hurricane or a tornado, and is not regular streamline motion. It is unavoidable to get some circulation in most flows, they are called eddies, and cause turbulence and friction. This is difficult to describe. It is easier to understand streamlined unifrom motion.