This text is intended for mechanical engineering students in their second year of study. This is a basic study level, in which the educational target of the subject "Fluid Mechanics" is an introduction to the basic principles on which fluid mechanics science is built, explanation of fundamental concepts and relations. What makes fluid mechanics at higher levels difficult are complicated spatial effects taking place in flowing fluid. To make the basic problems more understandable, these effects are not treated in the present text and are left for higher, later stages. The treatment of the fluid flow is here one-dimensional
Fig.A-1 An example of flow which cannot be computed and
evaluated by the present approach because its computation re-
presents a two-dimensional problem: vortices visualised in slow
(velocity only 14 mm/s) flow past a cylinder.
(in fact, in certain parts the treatment is only "zero-dimensional", not taking spatial relations into account). This means that some very essential problems were to be skipped over - for example the dynamics of vortical motions, in spite of its importance position for flow past bodies (cf. Fig.A-1). This also means that it is here impossible to explain the principles of modern numerical flowfield computations (Figs.A-2, A-4, A-5). The discussed problems also avoid those cases in which there are important compressibility effects (..these are important e.g. in high-velocity flow of a gas, the treatment of which requires knowledge from thermodynamics - but this students do not encounter until later stages of their studies. It is expected that apart from gaining basic concepts, necessary for higher stages of their studies, understanding of the present text enables students to solve problems in particular associated with flows in ducts, which are more or less one-dimensional. It is assumed that this basic stage will be immediately followed in the course of the next term by another subject oriented towards two- and three-dimensional flow and its computer solution,
Fig.A-2 Decomposition of an aeroplane surface into elements used in
numerical three-dimensional flowfield computations (Avions Marcel Dassault, France).
Among further stages, gas dynamics (studies of compressible flow), convective heat and mass transfer and at least in some study directions also the aerodynamics of shear flows, experimental fluid mechanics and problems of turbulence are subject which it is also highly advisable to enter. It should be mentioned that until quite recently, standard fluid mechanics textbooks did not treat the above mentioned more difficult subjects and limited their sphere of interest to classical hydraulics, which is basically the contents of the present text. This is because fluid mechanics has recently underwent a fundamental change of its character. It used to be a science based almost exclusively upon knowledge acquired experimentally (to the degree that - some of its parts at least - were described as "science of empirical coefficients"). Practical engineeting tasks (unless they were mere interpolations between existing experimental data) were solved by investigating the flow on models in wind tunnels (Fig.A-3) or in hydrodynamic tow tanks


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from textbook Vaclav TESAR : "BASIC FLUID MECHANICS"
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