Дополнительные тексты

Текст 1

1.Дайте русские эквиваленты следующим английским словам и словосочетаниям, которые являются ключевыми для данного текста:

Equilibrium and motion of liquids and gases, fluid flow, application, applied science, division, constrain, construction, velocity of flow, means of scientific research, investigate, investigation,

2. Подберите соответствующий заголовок к каждому

Абзацу или группе абзацев:

а) Сравнение трудностей исследования потока жидкостей, газов и твердых тел

б) Два пути, по которым проходило развитие гидравлики как науки

в) Предмет гидравлики. Основные проблемы, которые решает гидравлика

г) Метод исследования потока жидкостей, применяемый в гидравлике

д) Гидравлика – эмпирическая и прикладная наука

3. Составьте реферат по тексту: The Subject of Hydraulics

The branch of mechanics which treats of the equilibrium and motion of liquids and gases and the force interactions between them and bodies through or around which they flow is called hydromechanics or fluid mechanics. Hydraulics is an applied division of fluid mechanics covering a specific range of engineering problems and methods of their solution. It studies the laws of equilibrium and motion of fluids and their application to the solution of practical problems.

The principle concern of hydraulics is fluid flow constrained by surrounding surface, i.e. flow in open and closed channels and conduits including rivers, canals, flumes, as well as pipes, nozzles and hydraulic machine elements.

Thus hydraulic is mainly concerned with the internal flow of fluids and it investigates what might be called “internal” problems as distinct from “external” problems involving the flow of a continuous medium about submerged bodies, as in the case of a solid body moving in water or in the air. These “external” problems are treated in hydrodynamics and aerodynamics in connection with aircraft and ship design.

The science of hydraulics concerns itself mainly with the motion of liquids. The internal flow of gases is studied only in so far as the velocity of flow is much less than that of sound and consequently their compressibility can be disregarded. Such cases are frequently encountered in engineering as for example in the flow of air in ventilation systems and in gas mains.

Investigation of the flow of liquids and gases is much more difficult and complicated task than studying the motion of rigid bodies. In rigid body mechanics one deals with systems of rigidly connected particles. In fluid mechanics the objects of investigation is a medium consisting of multitude of particles in constant relative motion. Fluid mechanics as a science developed along two different paths. The first was the purely theoretical path of precise mathematical analysis based on laws of mechanics, it led to the emergence of theoretical hydromechanics, which for a long time existed as an independent science. Its methods provided an attractive means of scientific research. A theoretical analysis of fluid motor, however, does not always answer the questions arising in real situations.

The urgent requirements of engineering practice, therefore, can give rise to a new science of fluid motion, hydraulics in which researchers took to the second path, that of extensive experimenting and accumulation of factual data for application to engineering problems. At the origin hydraulics was a purely empirical science. Today whenever necessary it employs the methods of theoretical hydromechanics for the solution of various problems and conversely in theoretical hydromechanics experiments are widely used to verify the validity of its conclusions. Thus, the difference in the methods employed by either silence is gradually disappearing and with it the boundary line between them. The method of investigating fluid flow in hydraulics today is essentially as follows: the phenomenon under the investigation is first simplified and idealized and the laws of theoretical mechanics are applied. The results are then compared with experimental data, the discrepancies are established and the theoretical formulas and solutions adjusted so as to make them suitable for practical application.

Many phenomena are so involved as to practically defy theoretical analysis and are investigated in hydraulics on the sole basis of experimental measurement, the results being expressed in empirical formulas. Thus, hydraulics can be called a semi empirical science.

At the same time it is an applied science in so far as it emerged from the demands of life and is widely used in engineering. Hydraulics provides the methods of calculating and designing a wide range of hydraulic structures (dams, canals, wires and pipelines for transporting fluids), machinery (pumps, turbines, fluid couplings) and other devices used in many branches of engineering, in machine-tool design, foundry practice, the manufacture of plastics, etc. Modern aircraft design with its fluid drives, fuel and lubricating systems, hydraulic shock absorbers, etc relies extensively on the science of hydraulics. 4303

Текст 2