Elementary Mechanics of Fluids CE 319 F Daene McKinney Elementary Mechanics of Fluids 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, Absolute & Gage

Pressure Variation with Elevation Static fluid – pressure varies only with elevation in the fluid.

Pressure Variation with Elevation If g is a constant z = z1, p = p1 1 z = z2, p = p2 2 Piezometric head Elevation head Pressure head z = 0

Piezometric Head z = 0 1 2 Open Tank

Piezometric Head z = 0 3 2 1 Pressurized Tank

Example (3.6) Tank contins fluid with gA > gB Which graph depicts the correct pressure distribution?

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 Gasoline SG=0.68 1 water 2 3 ft

Example (3.5) Find l Forces at surface inside tube l Fw d=0.5 mm Fa water Fw

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:

Temperature variation with altitude for the U.S. standard atmosphere Compressible Fluids Assume constant and integrate Assume linear and integrate Temperature variation with altitude for the U.S. standard atmosphere