Physics
Fluid Systems
Fluid systems refer to a collection of interconnected components that work together to transport and control the flow of fluids, such as liquids and gases. These systems are governed by principles of fluid mechanics and can be found in various applications, including hydraulic systems, pipelines, and ventilation systems. Understanding fluid systems is crucial for designing and optimizing fluid-based technologies.
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9 Key excerpts on "Fluid Systems"
- Michael Clifford, Kathy Simmons, Philip Shipway(Authors)
- 2009(Publication Date)
- CRC Press(Publisher)
Fluids (the generic name given to both liquids and gases) are all around us – the air we breathe, the water in lakes, rivers and the sea, the liquids we drink. They are a familiar part of everyday life and the way in which fluids behave is understood by everyday experiences. For instance, liquids have a defined volume but take the shape of the container they are in; a kilogram of water generally has a fixed volume but it can be confined inside a bottle or spread out over a large area if spilled on the floor. Some fluids flow more easily than others: water is easy to pour, but syrup moves more slowly. Fluids that are moving create forces on solid objects: the umbrella blows inside out on a windy day! In engineering it is important to understand the behaviour of fluids in a scientific way, to be able to quantify the effects so that calculations can be undertaken to design systems involving fluids and to predict their performance. For instance, if water needs to be pumped 25 metres uphill at a rate of 10 litres per second, how big does the pump have to be and how much energy is needed to pump the water? Could the system be designed to be more sustainable and use less energy? If an oil storage tank needs to be built, how thick will the walls need to be? How much force does the oil exert on the walls? In this chapter the behaviour of fluids will be explained in a mathematical way and tools will be introduced to enable design calculations to be performed. These will be related to some of the everyday experiences that we have of fluids to help understanding. The chapter is divided into five main sections. Following the introduction in Section 3.1, Section 3.2 looks at fluid statics. The concept of pressure is described, showing how to calculate the forces created by the pressure of a fluid on a solid surface and how pressure can be measured using a manometer. The concept of buoyancy and why some things float and others sink is explained.
eBook - PDF- Tian-Chyi Yeh, Raziuddin Khaleel, Kenneth C. Carroll(Authors)
- 2015(Publication Date)
- Cambridge University Press(Publisher)
1 Fluid statics and dynamics 1.1 Introduction 2 1.1.1 Fluids and Solids 2 1.1.2 Dimensions and Units 3 1.1.3 Fluid as a Continuum 4 1.1.4 Fluid Properties 5 1.2 Fluid Statics 10 1.2.1 Forces on Fluids 11 1.2.2 Hydrostatic Equation 13 1.2.3 Various Forms of Energy and Their Relation to Force 15 1.3 Fluid Dynamics 16 1.3.1 Coordinates: Lagrangian and Eulerian viewpoints 16 1.3.2 Time Derivatives 17 1.3.3 Acceleration 19 1.3.4 Bernoulli Equation 19 1.3.5 Heads (Energy/Weight) 22 1.3.6 Water Manometer (Piezometer) 24 1.3.7 Head Loss 24 1.3.8 Inertial and Viscous Forces and Flow Behavior 27 1.3.9 Physical Meaning of the Reynolds Number 28 1.4 Summary 29 1.5 Exercises 30 1 1.1 Introduction Our experience suggests that most students from geosciences, natural sciences, and other backgrounds are not required to take a fluid mechanics class, and most engineer- ing students who took a fluid mechanics class earlier may still need to reinforce their physical understanding of the fluid mechanics concepts. Thereby, this chapter is intended to provide readers with some basics of fluid mechanics (particularly, in terms of physics) that are essential to understand and appreciate flow through geologic media. Fluid Mechanics is the study of the forces on fluids. These fluids can be either a gas or a liquid. Fluid Mechanics includes both fluid statics (the study of fluids at rest) and fluid dynamics (the study of fluids in motion). Notice that the fluid mechanics serves as the fundamental principles in a number of disciplines in science and engineering. For instance, atmospheric science is built upon fluid mechanics, as is cardiology – the study of the blood flow through our veins and arteries. The study of the infiltration of water and its subsequent movement in unsaturated subsurface media (vadose zone hydrology) also relies on fluid mechanics, as do studies of the movement of groundwater in geologic media (groundwater hydrology).
- Jonathan Wickert, Jonathan Wickert, Kemper Lewis(Authors)
- 2016(Publication Date)
- Cengage Learning EMEA(Publisher)
220 CHAPTER OBJECTIVES Fluids Engineering CHAPTER 6 6-1 Recognize the application of fluids engineering to such diverse fields as microfluidics, aerodynamics, sports technology, and medicine. 6-2 Explain in technical terms the differences between a solid and a fluid, and the physical meanings of a fluid’s density and viscosity properties. 6-3 Understand the characteristics of laminar and turbulent fluid flows. 6-4 Calculate the dimensionless Reynolds number, which is the most significant numerical value in fluids engineering. 6-5 Determine the magnitudes of the fluid forces known as buoyancy, drag, and lift in certain applications. 6-6 Analyze the volumetric flow rate and pressure drop of fluids flowing through pipes. ▸ ▸ 6.1 Overview I n this chapter, we introduce the subject of fluids engineering and its role in applications as diverse as aerodynamics, biomedical and biological engineering, piping systems, microfluidics, and sports engineering. The study of fluids, which are classified as either liquids or gases, is further broken down into the areas of fluid statics and dynamics. Mechanical engineers apply the principles of fluid statics to calculate the pressure and buoyancy force of fluids acting on stationary objects, including ships, tanks, and dams. Fluid dynamics refers to the behavior of liquids or gases when they are moving or when an object is moving through an otherwise stationary fluid. Hydrodynamics and aerodynamics are the specializations focusing on the motions of water and air, which are the most common fluids encountered in engineering. Those fields encompass not only the design of high-speed vehicles but also the motions of oceans and the atmosphere. Some engineers and scientists apply sophisticated computational models to simulate and understand interactions among the atmosphere, oceans, and global climates (Figure 6.1).
eBook - PDFDynamic Systems
Modeling, Simulation, and Control
- Craig A. Kluever(Author)
- 2019(Publication Date)
- Wiley(Publisher)
As with mechanical systems in Chapter 2 and electrical systems in Chapter 3, we utilize a lumped-parameter approach, and, therefore, the mathematical models derived in this chapter consist of ordinary differential equations (ODEs). Our goal is to develop models of systems and devices that utilize fluid and/or thermal components that are of practical use to mechanical and aerospace engineers. In particular, we focus our discussion on fluid-system actuators. This chapter is the final chapter devoted to modeling physical systems; the subsequent chapters develop the techniques for obtaining and analyzing the system’s dynamic response. 4.2 HYDRAULIC SYSTEMS A general fluid system is composed of fundamental elements: (1) a pump that provides a high-pressure fluid; (2) a fluid capacitance due to fluid energy stored in a reservoir or tank; and (3) hoses, pipes, and valves that connect the various reservoirs and control flow. If the fluid system is a translational actuator (such as a hydraulic servomechanism), it typically involves a cylindrical reservoir where the pressurized fluid moves a piston connected to a mechanical load to perform work. This section presents brief descriptions of the fundamental relationships that govern hydraulic systems where a liquid is the working fluid. We use the basic concepts of fluid mechanics that are developed in university physics courses. The fundamental variables of a hydraulic system are pressure P (in N/m 2 or pascals, Pa), mass-flow rate w = m (in kg/s), and volumetric-flow rate Q = V (in m 3 /s), where m and V are the fluid mass and volume, respectively. It is important to use absolute pressure, or pressure relative to a perfect vacuum, in theoretical calculations (absolute pressure = gage pressure + atmospheric pressure). We use volumetric-flow rate Q to describe the flow of liquids in hydraulic systems. Density is a physical property of a fluid, and it is the amount of mass per unit volume (in kg/m 3 ).
eBook - PDFFluid Power Circuits and Controls
Fundamentals and Applications
- John S. Cundiff(Author)
- 2001(Publication Date)
- CRC Press(Publisher)
15 2 Fluid Power Basics 2.1 Introduction Fluid power systems are designed using all the principles learned in fluid mechanics. It is appropriate to briefly review these principles before proceed-ing with our study of the applications. It is required that a student who reads this treatment of fluid power have had an undergraduate course in fluid mechanics. One of the underlying pos-tulates of fluid mechanics is that, for a particular position within a fluid at rest, the pressure is the same in all directions. This follows directly from Pas-cal’s Law. A second postulate states that fluids can support shear forces only when in motion. These two postulates define the characteristics of the fluid media used to transmit power and control motion. Traditional concepts such as static pressure, viscosity, momentum, continuity, Bernoulli’s equation, and head loss are used to analyze the problems encountered in fluid power sys-tems. The reader should continuously keep in mind that the fundamental concepts are being applied. New methodology is used, but no new concepts are introduced. Dimensions and units provide the engineer with a convenient method to track the progress of, and report the results of, analyses. Today, there is a tran-sition occurring in the U.S. from English to metric systems of units. While the scientific community universally embraces the metric system, trade contin-ues to occur in the English system of units in some places. Engineering stu-dents must be competent working in both U.S. Customary units and the metric SI (from the Le Système International d’Unités ), which is also known as the International System . Perhaps the main difficulty encountered by young engineers is handling mass versus force. For example, in the U.S. Customary system, it is custom-ary to weigh objects and report the magnitude of force generated by the object in the Earth’s gravitational field. On the other hand, the SI system of measurements relies on determination of mass directly.
eBook - PDFComputational Fluid Dynamics and Energy Modelling in Buildings
Fundamentals and Applications
- Parham A. Mirzaei(Author)
- 2022(Publication Date)
- Wiley-Blackwell(Publisher)
2 An Overview on Fundamentals of Fluid Mechanics in Buildings 2 An Overview of Fluid 2.1 Definition of Fluid From a molecular perspective, materials with a dense molecular structure and large inter- molecular cohesive forces are known to exist in the solid state while in conditions when the distance between structures of the molecule is higher and therefore the intermolecular forces are relatively weaker, the material is known to be in the liquid state (see Figure 2.1). The weaker internal forces grant liquid molecules more freedom to take the shape of their containers, although to a certain extent, and to not be easily compressed. Once the distance is further increased, mainly due to the external conditions, and molecules found more freedom to move under negligible intermolecular forces, then the material is in its gaseous state. Consequently, gases can be deformed and take the shape of their containers similar to liquids. In general, both liquids and gases are known as fluids and their behaviour and characteristics will be further investigated in this chapter. 2.1.1 System of Units In the SI system, the primary quantities and their units are defined as length (L), mass (M), time (T), and temperature (Θ). These primary units can be used to define secondary quantities. Table 2.1 shows a range of common secondary quantities widely used in engineering problems. Example 2.1 Find the dimension of the secondary quantity of ‘pressure’. Solution Pressure is defined as the perpendicular force over the unit of area: p = Force Area = F A = ma A ⟹p = MLT - 2 L 2 = ML - 1 T - 2 25 Computational Fluid Dynamics and Energy Modelling in Buildings: Fundamentals and Applications, First Edition. Parham A. Mirzaei. © 2023 John Wiley & Sons Ltd. Published 2023 by John Wiley & Sons Ltd. 2.2 Properties of Fluid 2.2.1 Density Mass per unit of volume is called density and is shown with the Greek symbol of ρ ‘rho’.
eBook - PDFBasic Aerodynamics
Incompressible Flow
- Gary A. Flandro, Howard M. McMahon, Robert L. Roach(Authors)
- 2011(Publication Date)
- Cambridge University Press(Publisher)
A proper set of approximations may make unnecessary the use of some laws to produce a practical yet accurate solution for a given problem. This approach is possible only if a clear understanding of the physics of a fluid motion is attained. It is, of course, possible to construct a mathematically correct solution to an incorrectly formulated problem or a solution that is based 16 Physics of Fluids on an inappropriate set of assumptions. In such cases, the results can be confusing or misleading or can even lead to costly mistakes. There is no substitute in aero- dynamics for a sound understanding of the fundamental physical laws on which fluid mechanics is based. It also may be necessary to introduce additional mathematical models or relationships to supplement those in the preceding list. For example, it often is necessary to use equations that characterize a working fluid. These equations of state, or constitutive equations, describe the physical attributes of a fluid. For example, it often is the case in practical problems that the fluid is an ideal or perfect gas, for which the equation of state is: p = ρRT, (2.1) which is a special relationship among the thermodynamic-state variables, pressure p, density ρ, and temperature T, needed to describe the behavior of a gas. R is the gas constant—a constant of proportionality—that is determined by the molecular con- figuration of the gas. This and other equations are discussed in considerable detail as needed throughout this chapter. With regard to details of the molecular structure of a working fluid, we can choose to approach problems from the standpoint of the molecular motion, or a continuum model can be applied that does not attempt to address directly the actual small-scale particle motion. The former is called statistical mechanics, or the kinetic theory of gases.
- Allan D. Kraus, James R. Welty, Abdul Aziz(Authors)
- 2011(Publication Date)
- CRC Press(Publisher)
12.10 Summary In this chapter we have examined the behavior of static fluids, which are motionless relative to a coordinate system that is either motionless or accelerating uniformly. The basic equation known as the fundamental equation of fluid statics is ∇ P = ( g − a ) (12.19) where the acceleration of the coordinate system is either zero or a constant. The usual situation is where a = 0 in which case ∇ P = g (12.2) Thus, fluid statics deals with problems that are associated with fluids at rest. A common pressure measuring device, the manometer , is based on principles of fluid statics. This chapter also discussed static situation forces on submerged surfaces, buoyancy, and stability. The stability of floating and immersed objects has been examined. A totally immersed system is stable as long as the center of mass is below the center of buoyancy. On the other hand, a floating object can be stable, unstable, or neutrally stable depending on the metacentric height , defined as the distance between the center of mass and the center of buoyancy. The floating body, such as the hull of a vessel, will be stable as long as the metacenter is above the center of buoyancy (as long as the metacentric height is positive). 12.11 Problems General Considerations 12.1: Using standard conditions to determine the density of air, determine the height of the atmosphere if it were incompressible. 12.2: The isothermal compressibility of a substance is given by = ( ∂ P / ∂ ) T = − V ( ∂ P / ∂ V ) T . Determine for a perfect gas. 12.3: In water, the modulus, , defined in Problem 12.2, is nearly constant and has a value of 2 . 068 × 10 6 kPa. Determine the percentage volume change in water due to a pressure of 20,000 kPa. 12.4: On a certain day, the barometric pressure at sea level is 30 in of mercury and the temperature is 20 ◦ C . The pressure gage in an aircraft in flight indicates a pressure of 73 kPa and a temperature gage shows the air to be at 8 ◦ C .
eBook - PDF- Joseph Katz(Author)
- 2010(Publication Date)
- Cambridge University Press(Publisher)
Both gases and liquids behave similarly under load and both are considered fluids. A typical engineering question that we’ll try to answer here is this: What are the forces that are due to fluid motion? Examples could focus on estimating the forces required for propelling a ship or for calculating the size and shape of a wing required for lifting an airplane. So let us start with the first question: What is a fluid? As noted, in general, we refer to liquids and gases as fluids, but we can treat the flow of grain in agricultural machines, a crowd of people leaving a large stadium, or the flow of cars by using the principles of fluid mechanics. Therefore one of the basic features is that we can look at the fluid as a continuum and not analyze each element or molecule (hence the analogy to grain or seeds). The second important feature of fluids is that they deform easily, unlike solids. For example, a static fluid cannot resist a shear force and the particles will simply move. Therefore, to generate shear force, the fluid must be in motion. This is clarified in the following subsections. 1.4.1 Continuum Most of us are acquainted with Newtonian mechanics, and therefore it would be natural for us to look at particle (or group of particles) motion and discuss their dynamics by using the same approach used in courses such as dynamics. Although this approach has some followers, let us first look at some basics. Consideration a: The number of molecules is very large and it would be difficult to apply the laws of dynamics, even when a statistical approach is used. For exam-ple, the number of molecules in one gram-mole (1 g mole) is called the Avogadro number (after the Italian scientist, Amadeo Avogadro, 1776–1856). 1 g mole is the molecular weight multiplied by 1 g. For example, for a hydrogen molecule (H 2 ) the molecular weight is 2; therefore 2 g of hydrogen are 1 g mole. The Avogadro number N A is N A = 6 . 02 × 10 23 molecules/g mole .
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
