Fluid Fundamentals
Fluid fundamentals refer to the basic principles and properties of fluids, including liquids and gases. This encompasses concepts such as fluid mechanics, fluid dynamics, and the behavior of fluids under different conditions. Understanding fluid fundamentals is crucial in various engineering applications, such as designing hydraulic systems, analyzing fluid flow in pipes, and developing aerodynamic structures.
3 Key excerpts on "Fluid Fundamentals"
eBook - ePub- William S. Janna(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...1 Fundamental Concepts Fluid mechanics is the branch of engineering that deals with the study of fluids—both liquids and gases. Such a study is important because of the prevalence of fluids and our dependence on them. The air we breathe, the liquids we drink, the water transported through pipes, and the blood in our veins are examples of common fluids. Further, fluids in motion are potential sources of energy that can be converted into useful work—for example, by a waterwheel or a windmill. Clearly, fluids are important, and a study of them is essential to the engineer. After completing this chapter, you should be able to: Describe commonly used unit systems; Define a fluid; Discuss common properties of fluids; Establish features that distinguish liquids from gases; and Present the concept of a continuum. 1.1 DIMENSIONS AND UNITS Before we begin the exciting study of fluid mechanics, it is prudent to discuss dimensions and units. In this text, we use two unit systems: the British gravitational system and the international system (SI). Whatever the unit system, dimensions can be considered as either fundamental or derived. In the British system, the fundamental dimensions are length, time, and force. The units for each dimension are given in the following table: British Gravitational System Dimension Abbreviation Unit Length L foot (ft) Time T second (s) Force F pound-force (lbf) Mass is a derived dimension with units of slug and defined in terms of the primary dimensions as 1 slug = 1 1 bf ⋅ s 2 ft (1.1) Converting from the unit of mass to the unit of force is readily accomplished because the slug is defined in terms of the lbf (pound-force). Example 1.1 An individual weighs 150 lbf. a. What is the person’s mass at a location where the acceleration due to gravity is 32.2 ft/s 2 ? b. On the moon, the acceleration due to gravity is one-sixth of that on earth. What is the weight of this person on the moon? Solution a...
eBook - ePub- Clifford Matthews(Author)
- 2011(Publication Date)
- Wiley-Blackwell(Publisher)
...Section 9 Basic Fluid Mechanics and Aerodynamics 9.1 Basic Properties 9.1.1 Basic Relationships Fluids are divided into (a) liquids, which are virtually incompressible and (b) gases, which are compressible. A fluid consists of a collection of molecules in constant motion. A liquid adopts the shape of the vessel containing it, while a gas expands to fill any container in which it is placed. Some basic fluid relationships are given in Table 9.1. Table 9.1 Basic fluid relationships. Density (ρ) Mass per unit volume. Units kg/m 3 (lb/in 3) Specific gravity (s) Ratio of density to that of water i.e. s = ρ/ρ water Specific volume (v) Reciprocal of density i.e. s = 1/ρ. Units m 3 /kg (in 3 /lb) Dynamic viscosity (µ) A force per unit area or shear stress of a fluid. Units Ns/m 2 (lbf.s/ft 2) Kinematic viscosity (ν) A ratio of dynamic viscosity to density i.e. ν = µ/ρ. Units m 2 /s (ft 2 /s) 9.1.2 Perfect gas A perfect, or ‘ideal’, gas is one which follows Boyles/Charles law pv = RT where p = pressure of the gas v = specific volume T = absolute temperature R = the universal gas constant Although no actual gases follow this law totally, the behaviour of most gases at temperatures well above their liquification temperature will approximate to it and so they can be considered as a perfect gas. 9.1.3 Changes of State When a perfect gas changes state its behaviour approximates to where n is known as the polytropic exponent. Figure 9.1 shows the four main changes of state relevant to aeronautics; isothermal, adiabatic, polytropic, and isobaric. Figure 9.1 9.1.4 Compressibility The extent to which a fluid can be compressed in volume is expressed using the compressibility coefficient β. where Δ V = change in volume v = initial volume Δ p = change in pressure K = bulk modulus Also and where a. = the velocity of propagation of a pressure wave in the fluid. 9.1.5 Fluid Statics Fluid statics is the study of fluids that are at rest (i.e. not flowing) relative to the vessel containing them...
eBook - ePub- B.H Brown, R.H Smallwood, D.C. Barber, P.V Lawford, D.R Hose(Authors)
- 2017(Publication Date)
- CRC Press(Publisher)
...As in structural mechanics, the aeronautical engineers have been there before us. Many of the modern computational fluid-dynamics (CFD) structures, algorithms and software were developed originally in or for the aeronautical industry. Some simplifications, such as that of inviscid flow, can lead to equations that are still worth solving for complex geometries. Special techniques have been developed, particularly for the solution of two-dimensional problems of this type. These are not discussed here because they are not particularly relevant to problems in biofluid mechanics. Turbulence is a phenomenon of primary interest to aerodynamicists, and this is reflected in the number of turbulence models that are available in commercial software and in the richness of the literature in this field. Moving boundaries (pistons and valves) are of great interest to automobile engineers in the modelling of combustion processes, and again facilities to model events featuring the motion of a boundary have existed for some time in commercial software. Of much more interest to those involved in biofluid mechanics are the problems of the interaction of soft and flexible structures with fluid flow through and around them. Historically structural and fluid-dynamic analyses have been performed by different groups of engineers and physicists, and the two communities had relatively little contact. This situation has changed dramatically in recent years. It is the authors’ belief that we stand on the verge of a revolution in our abilities to handle real problems in biofluid mechanics. 2.8.1 The differential equations For an incompressible fluid the continuity equation is ∂ u ∂ x + ∂ v ∂ y + ∂ w ∂ z = 0 where x, y and z are a set of Cartesian coordinates and u, v and w are the velocities in these three directions. The momentum equation in the x direction for a Newtonian fluid, in the absence of body forces,...
