ES 202 Fluid and Thermal Systems Lecture 4: Pressure Distributions on Submerged Surface (12/09/2002)

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ES 202 Fluid and Thermal Systems Lecture 4: Pressure Distributions on Submerged Surface (12/09/2002). Assignments. Reading: Mechanics: definition of center of mass, moment of inertia Cengel & Turner Section 5-4 ES 201 notes Homework: 10-11, 10-19, 10-37 in Cengel & Turner.

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## ES 202 Fluid and Thermal Systems Lecture 4: Pressure Distributions on Submerged Surface (12/09/2002)

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### ES 202Fluid and Thermal SystemsLecture 4:Pressure Distributions on Submerged Surface(12/09/2002)

Assignments
• Mechanics: definition of center of mass, moment of inertia
• Cengel & Turner Section 5-4
• ES 201 notes
• Homework:
• 10-11, 10-19, 10-37 in Cengel & Turner
• Announcements
• Examples and exercises (from first principle to generalization)
• Force and moment on vertically submerged surface
• Concept of resultant force, centroid and center of pressure
• FR = Pavg * Awhere Pavgis measured at the centroid of the submerged surface
• Center of pressure is located lower than the centroid according to

yp = yc + Ixx,c / yc Awhere yc is the location of centroid and

Ixx,c / yc Ais the downward shift of center of pressure relative to centroid

• Force and moment on obliquely submerged surface
• Force and moment on curved surface
• Horizontal component is the same
• Vertical component is different according to the weight of fluid that is above surface
Announcements
• First homework set due by 5 pm today at my office
When a fluid is in static equilibrium,

the hydrostatic pressure increases/decreases____________ with depth;

the pressure gradient (rate of change) depends on the ____________ of the fluid.

A manometer is a device which measure small pressure difference based on the difference in ____________ between fluid columns

For a given pressure difference, the difference in height between the fluid columns will be greater if a fluid of lower/higher density is used.

The pressure equation:

P2 = P1 +/- r g h

describes the pressure variation in a manometer. The minus (-) sign is used when Point 2 lies above/below Point 1 and vice versa.

Quiz on Lecture 3

Vertically Submerged Surface

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

Obliquely Submerged Surface

• Same old fish tank problem

If one of the sides of the fish tank is slightly sloped at 30o, how will the followings be different?

• Analysis
• Results (take a first guess before you work out the details)

Curved Surface

• Same old fish tank problem

If the slope is replaced by a

• concave surface
• convex surface

What do you expect the results to be?