QUESTIONS

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QUESTIONS

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Homework

• Jack load 12.2kN
• Gage pressure 27.7kPa

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SG 0.8
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Examples

• Mercury manometer is connected to an air duct to
  measure its insice pressure. The manometer
  deflection is 15mm. Atmospheric pressure is
  100kPa. Find the ducts absolute pressure. Hg ?
  13,600kg/m3.

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Manometer

• Liquid flow deflection large manometer fluid can
  be Hg, SG 13.6
• Gas flow deflection small manometer fluid SG lt
  0.9. Use inclined manometer

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Example

• Mott 3.71 Figure 3.36 Gage fluid has a SG 0.87
  and L 115mm. ? 15o. Find PA.

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Fluid statics

• Liquid at rest ?F 0
• Horizontal equal in all directions
• Horizontal dependent on depth
• Vertical pressure prism
• P ?h

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Hydrostatic forces

• Pressure prism
• Distributed forces
• Force ? vector
• Direction
• Magnitude
• Line of action center of pressure

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Fluid statics

• F ?hcA magnitude
• hcp hc (I/ hcA) center of pressure

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Submerged surface location

• Top edge at liquid surface
• Top edge submerged
• Pressurized surface equivalent depth of fluid
• Inclined surface
• Curved surface

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Example

• A heavy car veers off the road into a lake. It
  settles upright on the bottom. The front car door
  is 1.2m high and 1m wide. The top of the door is
  8m below the lake surface. What is the force
  holding the door closed? Can the driver open the
  door? What can he do to survive?

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Example

• A rectangular gate is installed in a vertical
  wall of a reservoir. Find the magnitude of the
  resultant force and the center of pressure. What
  is the force of each latch?

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Example

• The square gate is eccentrically pivoted so that
  it automatically opens at a certain value of h.
  What is that value in terms of l ?

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Homework

• A gate for the spillway holds water at a normal
  high level mark. The spillway crest elevation is
  2090.0 ft. The gate span is 30 ft. What is the
  force on the two pins holding the gate in place?

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Homework

• The air above the liquid is at 40kPa. The SG of
  the liquid is 0.8. The rectangular gate is 1.0m
  wide y1 1.0m and y2 3m. What force P is
  needed to hold gate in place?

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Homework

• The inclined wall is 4m wide. Find the magnitude
  of the resultant force and the center of pressure.

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Centroid of compound area

• Moment of compound area about any axis is equal
  to sum of the moments of its parts around the
  same axis
• (A1 x1 A2 x2)/ AT

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Assignment

• Mott Chapters 3 4
• Ch.4 16,20,40,47

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References

• Images examples
• Fluid Mechanics Fundamentals Applications, 6th
  Edition, Cengel Cimbala, McGraw Hill
• Applied Fluid Mechanics, 6th Edition, Mott,
  Prentice Hall
• Engineering Fluid Mechanics, 5th Edition Crowe,
  Roberson, Wiley