7. Conclusion

The study of the flow of compressible fluids (gases and vapors) calls not only on the basic concepts of fluid mechanics, but also on those of thermodynamics through the equations of state and those of particular transformations such as isothermal and isentropic transformations. As the dynamic viscosity of fluids is very low compared to that of liquids, it is often possible to neglect velocity changes in the vicinity of material walls. Many problems can therefore be treated, to a first approximation, in monodimensional form. That's what we've done in this article, which shows the importance of the speed of sound as a boundary between two very different types of flow: subsonic flow and supersonic flow. While the transition from the former to the latter is gradual, the opposite transition is in most cases abrupt, through a shock wave that dissipates a non-negligible proportion of the energy....