Basic Ideas in Fluid Mechanics

Fluid mechanics is based largely on working out the detailed consequences of four basic ideas  

Each of these four ideas is a generalization of experimental data. No one of them can be deduced from the others or from any other prior principle. None can be proved mathematically. Rather, they stand on their ability to predict correctly the results of any experiment ever run to test them. 

Sometimes in fluid mechanics we may start with these four ideas and the measured physical properties of the materials under consideration and proceed directly to solve mathematically for the desired forces, velocities, and so on. This is generally possible only in the case of very simple flows. The observed behavior of a great many fluid flows is too complex to be solved directly from these four principles, so we must resort to experimental tests. Through the use of techniques called dimensional analysis (Chap. 13) often we can use the results of one experiment to predict the results of a much different experiment. Thus, careful experimental work is very important in fluid mechanics. With the development of supercomputers, we are now able to solve many complex problems mathematically by using the methods outlined in Chaps. 10 and 11, which previously would have required experimental tests. As computers become faster and cheaper, we will probably see additional complex fluid mechanics problems solved on supercomputers. Ultimately, the computer solutions must be tested experimentally. 

These four ideas are applied to fluid mechanics problems as follows In Chap. 1 we discuss some of the measurable properties of fluids and some definitions. In Chap. 2 we apply Newton s law of motion to the particularly simple case of a fluid which is not moving. In Chap. 3 we explain and apply the principle of the conservation of mass. In Chap. 4 we consider the principle of the conservation of energy. In Chaps. 5 and 6 we apply the principle of the conservation of energy to a class of relatively simple fluid flows which includes many flows of great practical importance. In Chap. 7 we recast Newton s laws 

The first eight chapters form the core of the book. The remaining nine are intended as extra reading which will introduce the student to further topics in fluid mechanics. No nbw principles are introduced in these last chapters, but special topics and techniques in fluid mechanics are discussed. These chapters show the reader the connections between the basic material in Chaps. 1 to 8 and the sometimes special terminology and special ideas in other areas of fluid mechanics.,  

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