TABLE OF CONTENTS Fluid flows are commonly observed phenomena in this world. Giving typical examples, the wind is a flow of the air and the river stream is a flow of water. On the other hand, the motion of clouds or smoke particles floating in the air can be regarded as visualizing the flow that carries them. When we say flow of a matter, it implies usually time development of the displacement and deformation of matter. Namely, a number of particles compose the body of matter, and are moving and continuously changing their relative positions, and are evolving with time always. Flows are observed in diverse phenomena in addition to the wind and river above: air flows in a living room, flows of blood or respiratory air in a body, flows of microscopic suspension particles in a chemical test-tube, flows of bathtub water, atmospheric flows and sea currents, solar wind, gas flows in inter-stellar space, and so on.
From the technological aspect, vehicles such as ships, aeroplanes, jetliners and rockets utilize flows in order to obtain thrust to move from one place to other while carrying loads. Glider planes or soaring birds use winds passively to get lift.
On the other hand, from the biological aspect, swimming fishes are considered to be using water motions ( eddies) to get thrust for their motion. Animals such as insects or birds commonly use air flows in order to get lift for...
