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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 202Fluid and Thermal SystemsLecture 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
Road Map of Lecture 4 • 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. Something about manometer: 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?