Book cover for Fluid Mechanics

Fluid Mechanics

Frank M. White

ISBN #9789385965494

8th Edition

1,418 Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

External flows around immersed bodies are characterized by the development of a boundary layer, whose behavior is strongly influenced by the Reynolds number and the geometry of the body. While viscous effects are dominant close to the body, the flow becomes nearly inviscid far away. Flow separation, which results from adverse pressure gradients, is a key contributor to drag. The interplay between laminar and turbulent behavior in the boundary layer dictates aerodynamic and hydrodynamic performance, and experimental data often guide the final design decisions. Understanding these concepts allows engineers to design more efficient vehicles, buildings, and fluid systems.

Learning Objectives

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Key Concepts

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DEFINITION

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Example Problems

Example 1

An engineer claims that the flow of SAE $30 \mathrm{W}$ oil, at $20^{\circ} \mathrm{C}$ through a 5 -cm-diameter smooth pipe at 1 million $\mathrm{N} / \mathrm{h}$, is laminar. Do you agree? A million newtons is a lot, so this sounds like an awfully high flow rate.

Example 2

The present pumping rate of crude oil through the Alaska Pipeline, with an ID of 48 in, is 550,000 barrels per day $(1 \text { barrel }=42 \text { U.S. gallons })$ $(a)$ Is this a turbulent flow? (b) What would be the maximum rate if the flow were constrained to be laminar? Assume that Alaskan oil fits Fig. A.1 of the Appendix at $60^{\circ} \mathrm{C}$

Example 3

The Keystone Pipeline in the chapter opener photo has a maximum proposed flow rate of 1.3 million barrels of crude oil per day. Estimate the Reynolds number and whether the flow is laminar. Assume that Keystone crude oil fits Fig. A.1 of the Appendix at $40^{\circ} \mathrm{C}$

Example 4

For flow of SAE 30 oil through a 5 -cm-diameter pipe, from Fig. A.1, for what flow rate in $\mathrm{m}^{3} / \mathrm{h}$ would we expect transition to turbulence at $(a) 20^{\circ} \mathrm{C}$ and $(b) 100^{\circ} \mathrm{C} ?$

Example 5

In flow past a body or wall, early transition to turbulence can be induced by placing a trip wire on the wall across the flow, as in Fig. P6.5. If the trip wire in Fig. P6.5 is placed where the local velocity is $U,$ it will trigger turbulence if $U d / \nu=850,$ where $d$ is the wire diameter $[3, p .388] .$ If the sphere diameter is $20 \mathrm{cm}$ and transition is observed at $\mathrm{Re}_{D}=90,000,$ what is the diameter of the trip wire in $\mathrm{mm} ?$
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Step-by-Step Explanations

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Common Mistakes

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