Incompressible Fluid Flow: a Basic Idea
A flow is called incompressible when the density of the fluid remain fixed during it motion as it is the property of the flow not of the fluid. The rate of change of density of a fluid element is always decided depending on the material derivative properties. According to fluid mechanics Incompressible fluid flow is a specific kind of flow where an infinitesimal volume moves with the velocity of the concerned fluid. Incompressible flow is also called isochoric flow.
All fluids are compressible to some extent, that is, changes in pressure or temperature will result in changes in density. However, in many situations the changes in pressure and temperature are sufficiently small that the changes in density are negligible. In this case the flow can be modeled as an incompressible flow.
Fluid flow research process plays an imperative role in multiple fields of engineering industrial design. For example, gaseous flows are observed and studied for the improvement of aircraft, cars, and space craft as well as for the designing of delicate engineering machines like combustion engines and turbines. The research of liquid flows is extremely important in the designing of a ship and also for the use of civil engineers working for harbor design and devices for coastal protection. There are abundant other applications of fluid flow study such as chemistry and medicine. The prime and central issue in all kinds of fluid flow research is visualization.
Conventionally, fluid flow modeling patterns have been visualized via different experimental methods by using scale models within controlled test environments such as wave tanks. Different types of experimental flow visualization methods are found in practice, and these are:
- The adding of identifiable/external material such as dye or smoke into the flow for in dicatingthestream lines and path lines in between.
- The use of visual techniques based on the effect that a change in density causes in the light refraction index.
- • Electron beam methods - here collisions of the electron beam with gaseous flow particles creates thermionic emissions.
If the flow is compressible, the density is a non-constant factor related to of the pressure, the temperature, phase, composition, etc. When a fluid particle of some mass interacts with surrounding fluid particles via pressure forces, heat exchange, chemical reaction, etc., it goes through either compression or the process of dilatation. Consequently, its specific volume gets changed as per the changed pressure, temperature, etc., what it encounters with.
In case of an incompressible fluid flow, we can safely describe it as an idealized case, where the difference of temperature, pressure, etc., encountered by a specific particle impacts zero- change in the density of the particle. There is no such thing in practical world what is called an ideal incompressible fluid. In an incompressible flow pattern, we cannot find any change (in respect to time) in the exact volume (and so is the density) of each fluid particle.