1Fluid Mechanics – Lecture 4

Fluid mechanics(wb1225)

Lecture 4:control volume analysis

Momentum equation

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Conservation of momentum

1 2

3 4

5

1

2

3 [1]

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Conservation of momentum

momentum flux:

• pressure forces• forces due to viscous stresses• forces by solid bodies that protrude through surface

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Example 3.9

maximum momentum transfer when jet direction is reversed

small angle deflection; forceis normal to vane, and F ~ θ

[2]

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Example

[1]

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Hydraulic jump

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2004 Tsunami

[1]

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Hydraulic jump

[1]

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Example 3.11

1D inlet

streamline, no mass flux,no shear

2D outlet

streamline, V = 0shear forces

Boundary layer over a flat plate

[2]

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Example 3.11

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Example 3.12

[2]

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Example: Pelton wheel

[3]

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Summary• Chapter 3: 3.1-3.4

• Examples: 3.1-3.6

• Problems: 3.36, 3.50, 3.51, 3.73, 3.86

14Fluid Mechanics – Lecture 4

Source1. Multimedia Fluid Mechanics DVD-ROM, G. M. Homsy, University of California, Santa Barbara2. Frank M. White, Fluid Mechanics, McGraw-Hill Series in Mechanical Engineering3. Pelton Turbine, http://www.eumarine.com