Technology & Engineering
Flow Over Body
Flow over body refers to the movement of fluid, such as air or water, around a solid object. This phenomenon is important in engineering and aerodynamics, as it affects the performance and efficiency of vehicles, aircraft, and structures. Understanding the flow over body helps in designing streamlined shapes and reducing drag for improved functionality and energy efficiency.
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4 Key excerpts on "Flow Over Body"
- John I. Hochstein, Andrew L. Gerhart(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
322 In this chapter we consider various aspects of the flow over bodies that are completely im- mersed in a fluid. Examples include the flow of air around airplanes, automobiles, and falling snowflakes or the flow of water around submarines and fish. In these situations the object is completely surrounded by the fluid and the flows are termed external flows. Numerical techniques such as CFD can provide some of the needed information about flows over many objects. However, for complicated flow situations, the amount of informa- tion obtained from numerical analysis is limited. Information about the details of the flow then needs to come from experiments. Typically, the flow over the object is evaluated in a wind tunnel, as shown in Fig. 9.1a. The experimental results from wind tunnel testing would be compared to CFD predictions of the flow pattern, as illustrated in Fig. 9b. Thus, much of the information about external flows comes from experiments carried out, for the most part, on scale models of the actual objects. 9.1 General External Flow Characteristics A body immersed in a moving fluid experiences a resultant force due to the interaction between the body and the fluid surrounding it. For convenience, we can fix the coordinate For external flows it is usually easiest to use a coordinate system fixed to the object. • calculate boundary layer parameters for flow past a flat plate. • explain the physical process of boundary layer separation. • calculate the lift and drag forces for various objects. • identify and discuss the features of external flow. • explain the fundamental characteristics of a boundary layer, including laminar, transitional, and turbulent regimes. LEARNING OBJECTIVES After completing this chapter, you should be able to: Flow over Immersed Bodies CHAPTER 9 FIGURE 9.1 (a) Flow past a full-sized streamlined vehicle in a wind tunnel.
- Christina G. Georgantopoulou, George A. Georgantopoulos(Authors)
- 2018(Publication Date)
- Wiley-ISTE(Publisher)
4 Flow Around Solid Bodies4.1. IntroductionWhen a solid body of random shape moves with a constant velocity inside a fluid, a flow force R and a momentum Μ are often applied on it. From the technological perspective, the analysis and study of these forces is one of the significant interests of the applied fluid mechanics community.Therefore, in this chapter, we will deal with some basic theorems, which offer us expressions for the calculation of these forces, as well as with the definition and analysis of the forces and momentums applied on a body during its movement inside the fluid.The study of this flow, which is called external flow, in contrast to the fluid’s flow inside pipes, is of technological interest for many cases, such as the flow around airplanes, cars, submarines, chimney buildings, blades or airplane wings. The flow around solid particles, bubbles and water drops is also very interesting, which is important in environmental technologies, the process of mass and heat transfer, and heterogeneous chemical reactions.The geometry of the flow around the body depends on the form of a surface of the body immersed in a fluid, which is a criterion to characterize a body as two- or three-dimensional when the flow around it is two- or three-dimensional, respectively. So, if there is a cylinder of very large length, when the flow projects vertically to its axis, it will be considered as a two-dimensional body because the flow around its edges does not influence the geometry of the flow field and the distribution of the pressure around the central part of the body. In comparison, if there is a cylinder of small length, it will be considered as a three-dimensional body because the influence of the flow around its edges is significant. For the study of this flow, we consider the flow around an airfoil of an airplane’s wing.4.2. Geometrical characteristics of an airfoil
- Philip M. Gerhart, Andrew L. Gerhart, John I. Hochstein(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
482 In this chapter we consider various aspects of the flow over bodies that are completely immersed in a fluid. Examples include the flow of air around airplanes, automobiles, and falling snowflakes or the flow of water around submarines and fish. In these situations the object is completely sur-rounded by the fluid and the flows are termed external flows. External flows involving air are often termed aerodynamics in response to the important external flows produced when an object such as an airplane flies through the atmosphere. Although this field of external flows is extremely important, there are many other examples that are of equal importance. The fluid force (lift and drag) on surface vehicles (cars, trucks, bicycles) has become a very important topic. By correctly designing cars and trucks, it has become possible to greatly decrease the fuel consumption and improve the handling characteristics of the vehicle. Similar efforts have resulted in improved ships, whether they are surface vessels (surrounded by two fluids, air and water) or submersible vessels (surrounded completely by water). Other applications of external flows involve objects that are not completely surrounded by fluid, although they are placed in some external-type flow. For example, the proper design of a building (whether it is your house or a tall skyscraper) must include consideration of the various wind effects involved. As with other areas of fluid mechanics, various approaches (theoretical, numerical, and experimental) are used to obtain information on the fluid forces developed by external flows. Theoretical (i.e., analytical) techniques can provide some of the needed information about such flows. However, because of the complexities of the governing equations and the complexities of the geometry of the objects involved, the amount of information obtained from purely theoretical methods is limited.
- Andrew L. Gerhart, John I. Hochstein, Philip M. Gerhart(Authors)
- 2023(Publication Date)
- Wiley(Publisher)
462 = = In this chapter we consider various aspects of the flow over bodies that are completely immersed in a fluid. Examples include the flow of air around airplanes, automobiles, and falling snowflakes or the flow of water around submarines and fish. In these situations the object is completely sur- rounded by the fluid and the flows are termed external flows. External flows involving air are often termed aerodynamics. Examples include an air- plane flying through the atmosphere or a surface vehicle (e.g., car, truck, bicycle) moving through air. The fluid forces (primarily lift and drag) on these vehicles have become a very important topic. By correctly designing airplanes, cars, and trucks, it has become possible to greatly decrease the fuel consumption and improve the handling characteristics of the vehicle. Similar efforts have resulted in improved ships, whether they are surface vessels (surrounded by two fluids, air and water) or submersible vessels (surrounded completely by water). Other applications of external flows involve objects that are not completely surrounded by fluid, although they are placed in some external-type flow. For example, the proper design of a building (whether it is your house or a tall skyscraper) must include consideration of the various wind effects involved. As with other areas of fluid mechanics, various approaches (theoretical, numerical, and experimental) are used to obtain information on the fluid forces developed by external flows. Theoretical (i.e., analytical) techniques can provide some of the needed information about such flows. However, because of the complexities of the governing equations, the flows, and the geometry of the objects involved, the amount of information obtained from purely theo- retical methods is limited. Much of the information about external flows comes from experiments carried out, for the most part, on scale models of the actual objects.
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