ES 202 Fluid and Thermal Systems Lecture 3: Pressure Distribution on Submerged Surfaces (12/05/2002)

1
ES 202Fluid and Thermal SystemsLecture
3Pressure Distribution on Submerged
Surfaces(12/05/2002)
2
Assignments

• Reading
• Cengel Turner Section 10-4 and 10-5
• Homework
• 10-11, 10-19, 10-37 in Cengel Turner
• Definition of specific gravity and gage pressure

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Road Map of Lecture 3

• Announcements
• Quiz on Lecture 2
• Examples and exercises
• Conceptual exercises
• Pressure distribution at various depths and
  arbitrary shapes
• Pressure distribution in multiple layers of
  different fluids
• Application of manometer
• Force and moment on vertically submerged surface
• Concept of resultant force and center of pressure

4
Announcements

• First homework set due by 5 pm next Monday at my
  office
• Problem 10-37 is moved to Lecture 4 (next Monday)
• Comments on write-up for Lab 1
• Review body force and surface force in ES 201
• For Section 06 only
• Location of Lab 1 at B105, not the lecture
  classroom

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Quiz on Lecture 2

• Forces acted on a system can generally be
  classified as
• body force
• surface force
• Surface force can further be classified as
• shear force
• normal force
• All about pressure
• Pressure is a vector/scalar.
• Pressure is a body/surface force.
• Pressure acts in the shear/normal direction.
• Pressure is a compressive/expansive force.

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Quiz on Lecture 2 (Contd)

• Pressure is the same/different in different
  directions at any single point in a fluid.
• Pressure variation in a static fluid
• Variation in horizontal direction
• P constant
• Variation in vertical direction
• d P / d y - r g
• Give a physical meaning/interpretation to the
  above equation
• It is a balance between surface force and body
  force in a static fluid.

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Conceptual Exercises

• Pressure at various depths and arbitrary shape
• Compare the pressure at various locations as
  indicated
• What does the linear plot represent in the
  figure?
• Does the figure show all the pressure forces
  present in the system?
• If necessary, what modification will you make to
  include all the pressure forces in the system?
• Pressure in multiple layers of different fluids
• Draw the gage pressure distribution as a function
  of fluid depth
• Discussion of pressure at the interface between
  fluids

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Manometer

• Definition Device used to measure small to
  moderate pressure difference based on the
  difference in height of fluid columns
• Manometer problem
• What are the pressure values at the selected
  locations?
• Swim through the fluid as you track down the
  pressure distribution

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Vertically Submerged Surface

• Fish tank problem
• Estimate the total weight of water contained
  (intuition)
• What is the pressure at the bottom of the tank?
• Sketch the pressure distribution on the side
  wall?
• Find the total force on the side wall
• Find the total moment on the side wall about
  Point A
• Find the center of pressure (take a first guess
  at its approximate location)