Book contents
- Frontmatter
- Contents
- Preface
- A Word to the Instructor
- 1 Basic Concepts and Fluid Properties
- 2 The Fluid Dynamic Equation
- 3 Fluid Statics
- 4 Introduction to Fluid in Motion – One-Dimensional (Frictionless) Flow
- 5 Viscous Incompressible Flow: Exact Solutions
- 6 Dimensional Analysis and High-Reynolds-Number Flows
- 7 The (Laminar) Boundary Layer
- 8 High-Reynolds-Number Flow over Bodies (Incompressible)
- 9 Introduction to Computational Fluid Dynamics
- 10 Elements of Inviscid Compressible Flow
- 11 Fluid Machinery
- Appendix A Conversion Factors
- Appendix B Properties of Compressible Isentropic Flow
- Appendix C Properties of Normal Shock Flow
- Index
8 - High-Reynolds-Number Flow over Bodies (Incompressible)
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- A Word to the Instructor
- 1 Basic Concepts and Fluid Properties
- 2 The Fluid Dynamic Equation
- 3 Fluid Statics
- 4 Introduction to Fluid in Motion – One-Dimensional (Frictionless) Flow
- 5 Viscous Incompressible Flow: Exact Solutions
- 6 Dimensional Analysis and High-Reynolds-Number Flows
- 7 The (Laminar) Boundary Layer
- 8 High-Reynolds-Number Flow over Bodies (Incompressible)
- 9 Introduction to Computational Fluid Dynamics
- 10 Elements of Inviscid Compressible Flow
- 11 Fluid Machinery
- Appendix A Conversion Factors
- Appendix B Properties of Compressible Isentropic Flow
- Appendix C Properties of Normal Shock Flow
- Index
Summary
Introduction
The concept of high-Reynolds-number flows was discussed in Chapter 6 and it was concluded that near a solid-body surface for an attached flow a thin boundary layer exists. In Chapter 7 this boundary layer was investigated, and the small-thickness assumption was verified. It was also concluded that the pressure distribution around a vehicle could be obtained by the solution of the inviscid flow outside the thin boundary layer. These modeling conclusions, along with some general features of such flow fields, is summarized in Fig. 8.1.
In term of forces, the boundary layer solution provides the skin-friction estimate and the resulting skin-friction-related drag-force component. However, viscous effects, in addition to the boundary layer, can be present in the wake and in areas of flow separation. For example, we can see the effects of viscous flowmomentum loss by comparing the velocity distribution ahead and behind the vehicle (as shown in the figure). Clearly, in the wake the flow is slower and there is a loss of linear momentum (which is the drag, as was shown in the previous chapter).
Solution of the flow outside this viscous layer should provide information on the velocity and pressure distributions, as depicted by the centerline pressure distribution shown in the upper part of Fig. 8.1 (recall that there is no change in the pressure across the boundary layer). In the case in which the flow is attached, we can define an irrotationl flow model and solve for the velocity distribution.
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- Introductory Fluid Mechanics , pp. 254 - 323Publisher: Cambridge University PressPrint publication year: 2010