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Elementary Mechanics of Fluids. CE 319 F Daene McKinney. Pressure. Pressure. Fluid at rest – can not support shear stress Normal stress on any plane is pressure (+ for compression). Example (3.4). Prob. 3.4: How many bolts are needed at B-B?. 20 bolts, 2.5 cm dia.
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Elementary Mechanics of Fluids CE 319 F Daene McKinney Pressure
Pressure • Fluid at rest – can not support shear stress • Normal stress on any plane is pressure (+ for compression)
Example (3.4) • Prob. 3.4: How many bolts are needed at B-B? 20 bolts, 2.5 cm dia
Pressure Variation with Elevation • Static fluid – pressure varies only with elevation in the fluid.
1 2 Elevation head Pressure head Piezometric head Pressure Variation with Elevation • If g is a constant z = z1, p = p1 z = z2, p = p2 z = 0
1 2 z = 0 Piezometric Head Open Tank
3 2 1 z = 0 Piezometric Head Pressurized Tank
Example (3.6) • Tank contins fluid with gA > gB • Which graph depicts the correct pressure distribution?
0 1 2 Leaking Storage Tank • Water has seeped in to the depth shown • Find: Pressure at gas-water interface, pressure at bottom of tank • Assume: Fluids are at rest 17 ft GasolineSG=0.68 water 3 ft
Example (3.5) • Find l • Forces at surface inside tube d=0.5 mm l Fa Fw water
Example (3.8) • What is maximum force F2 that can be supported?
Compressible Fluids • Density is nearly proportional to pressure • For perfect gasses • Need to know T = T(z) • Constant (Isothermal): • Linear:
Compressible Fluids • Assume constant and integrate • Assume linear and integrate Temperature variation with altitude for the U.S. standard atmosphere