Fluid mechanics

The basics of fluid mechanics are summarized, with particular emphasis on the energy aspect, since the engineer must most often consider non-isothermal fluid flows. We have endeavored to present clearly the unity of concepts that concern all fluids, and whose application here concerns only Newtonian single-phase fluids.

It is essential that the engineer always keeps a critical eye on the assumptions he introduces to facilitate his calculations, or on the suitability of the formula he employs in the particular case studied; fluid mechanics is a field where common sense can easily be misled. The validity of a hypothesis must be verified once the solution to the problem has been obtained. A common example is that of determining the flow rate of a flow that is assumed to be turbulent to start the calculations; is it really? We need to be sure, through the value of the Reynolds number, that the possibility of laminar flow is excluded.

Software currently on the market can be used to solve the equations of complex technical problems. They have been designed with theoretical foundations in mind, but with the introduction of empirical hypotheses and formulas that have their limits of validity, just like the algorithms used to solve them. The use of software requires vigilance on the part of engineers who are not specialists in fluid mechanics. The following text has been written to provide guidelines and simple calculation tools for rapid evaluation at first order.

The applications given are limited to the most common cases, and the reader is of course invited to seek further information in the chapters listed in the General Alphabetical Index under the following keywords: acoustics, aviation, aeroacoustics, aerodynamics, aero-cooler, air, coolant, channels, heat, air-conditioning, compressibility, heat exchanger, flows, ejectors, fluid, gas, swell, hydraulics, lubrication, magnetohydrodynamics, thermodynamics, not forgetting the field of measurement.