Fahy Air

The Excellent Canopy
1. Auflage 2013
ISBN: 978-1-78242-434-5
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 144 Seiten

We take it for granted, but without it we perish and if we continue to abuse it, it may kill us in the end. This fascinating text provides an understanding and appreciation of the role that air plays in our environment and its importance in relation to human life and technology. Aimed at those who are scientifically curious but who have no specialist training, it contains no mathematical equations and relies upon the qualitative descriptions and analogies to explain the more technical parts of the text together with simple home experiments to illustrate a range of air-based phenomena. Liberally illustrated with a range of line drawings and photographs, it recommends further reading for those who are motivated to learn more. This book offers invaluable background reading for both physics teachers and students. - Provides an understanding and appreciation of the role that air plays in our environment and its importance in relation to human life and technology - An introductory text for those who are scientifically curious but have no specialist training - Delivers qualitative descriptions and analogies and simple experiments that illustrate a range of air-based phenomena

Frank Fahy University of Southampton, UK

Autoren/Hrsg.

Fahy, Frank

Leseproben

Glossary

Note: a number of the following words/terms have more than one definition. The ones given here relate specifically to the subject of the book

Ablation: melting and evaporation of material due to heating by friction

Acceleration: the rate of change of velocity (m/s2)

Amplitude: the maximum deviation from the rest value of a quantity undergoing simple harmonic variation (see ‘Simple harmonic’)

Angle of incidence (attack): the angle between the direction of motion of an aerofoil relative to the undisturbed air (or angle between the direction of the airflow approaching an aerofoil) and a line from the leading to trailing edges of the aerofoil

Angular momentum (of a body about an axis about which it rotates): the sum over the whole elements of a body of the product of the mass of each element, its velocity and the perpendicular distance to the axis of rotation

Boundary layer: a thin layer of fluid that covers the surface of a solid body that moves relative to the fluid and in which viscous forces and turbulence are dominant features

Celsius (Swedish astronomer): scale of temperature in which water freezes at zero and boils at 100 under specified conditions

Centre of curvature: the centre of a circle that passes through a point on a curved line of any shape, has the same curvature and is tangential to the curve at that point

Coefficient: a factor that defines a proportional relationship of one variable quantity to another

Contiguous: touching

Convex: curved outwards like the exterior surface of a ball

Decibel: a logarithmic measure of the temporal variation of sound pressure divided by a reference sound pressure

Diffraction: a property of waves whereby their pattern of propagation in a supporting medium is altered by the presence of ‘foreign’ bodies in the medium

Diffusion: spreading in all directions (especially by interaction between randomly moving particles of a fluid)

Dimensions (physics): fundamental physical quantities in terms of which all others may be expressed, e.g., mass, length, time. For example, from Newton’s Law, force has the dimensions of mass (M) times acceleration. Acceleration has the dimensions of velocity/time (LT-1/T). So force has the dimensions MLT-2

Element: a very small region of fluid

Empirical: resulting from, or relating to, observation and experiment, not to theory

Energy (mechanical): a physical quantity that is a measure of the capacity to do mechanical work (see ‘Work)

Equilibrium: at rest or undeformed

Even/odd multiples: 2,4,6, 8, …/1,3,5,7,..... times

Fatigue (mechanical): damage to the basic structure of a material by repeated reversal of applied force/stress ultimately causing failure

Fluid: any non-particulate material that flows

Fluorocarbons: chemical compounds of fluorine and carbon

Fractional variation: the variation of a quantity divided by its equilibrium or time – average value

Frame of reference (rectangular Cartesian): a set of three mutually perpendicular axes (like three edges of a room that meet at a point) by means of which the position of any point in space may be defined by the perpendicular distances of the point from the three planes defined by the axes (e.g. distances to two joining walls and the floor)

Gradient: the rate of change of one physical quantity with change of another

Hand wing: the outer part of the bird wing which tends to be flatter in section than the inner ‘arm wing’ and has a shaper leading edge than the latter

Harmonic: (i) abbreviation for ‘simple harmonic; (ii) a frequency component of a periodic signal. The fundamental frequency is the first harmonic and the frequencies of the higher harmonics are multiples of this frequency. The set of harmonics is known as a ‘harmonic series’

Heat: a form of energy involving the random motion of molecules; also, the amount of energy in this form capable of doing work

Hydrodynamic: to do with the relation between forces and motions of fluids

Inversely proportional: proportional to unity divided by the value of a quantity

Kinetic energy: energy of motion

Latent heat: the heat absorbed or released in the process of change of phase (e.g. evaporation of water, condensation of steam)

Leading edge: the edge of a wing that an approaching flow meets first

Loudness: a subjective perception of the strength of a sound. A doubling of loudness correspond approximately to an increase of sound pressure level of 10 decibels (see ‘Sound pressure level’)

Micron: one millionth of a metre

Modulation: a time variation in the amplitude of an oscillation

Momentum: the sum over a body of the products of the mass of each element of the body and its associated velocity (vector quantity)

Natural frequency: the frequency with which a system continues to oscillate following the cessation of an action that disturbs it from a state of equilibrium

Newton: a unit of force which is roughly equal to the weight of a medium size apple

Newton’s Laws of Motion: (i) a body continues in a state of rest or uniform velocity unless acted upon by a force; (ii) the acceleration of a body produced by a force is proportional to that force, in the direction of the force and inversely proportional to the mass of the body; (iii) action and reaction (forces) are equal and opposite (e.g. at an interface between contiguous bodies). Note: it would be more precise to specify the ‘body’ as a small particle and the concept of ‘rest’ implies the existence of an inertial frame of reference that undergoes zero acceleration. Although this cannot be defined, the assumption of its existence is often good enough to allow accurate analyses of motions to be made (see Chapter 5 and ‘Coriolis’)

Nonlinear: a relation between the variation of one quantity and that of another that cannot be expressed in terms of a constant factor

Overtones: similar to harmonics but not necessarily forming a harmonic series

Pantograph: the frame mounted on top of a vehicle that can be raised to contact a cable that carries the electric current that drives the vehicle

Parabolic relation: a proportional relation between the variation of one quantity and the square of another

Parameter: a measure of a physical system that characterises the system and/or its behaviour. It is usually non-dimensional meaning that is a pure number because it comprises a combination of physical quantities in such a way that the units cancel out. For example, the Strouhal number of an airflow across a cylinder that generates an oscillatory flow is given by St = frequency of oscillation (f) times cylinder diameter (d) over flow speed (U) in which the units cancel out. St is about 0.2 for such a flow. This means that the frequency of oscillation is given by f = 0.2 *U/d in all cases

Pascal: a unit of pressure which equals one Newton per square metre or approximately 145 millionths of a pound per square inch

Peripheral speed: the speed of the periphery of a rotating body

Permafrost: a state or region of the surface of the Earth of which the temperature is permanently below zero Celsius

Phase: a state of matter (e.g. liquid, gas, solid); a measure of the time difference between one harmonic oscillation and another of the same frequency

Potential energy: energy possessed by a body or system by virtue of its position (e.g. height above the ground) or...