3 FLUID STATICS CH EN 374 Fluid Mechanics

3. FLUID STATICS CH EN 374: Fluid Mechanics

Pressure

Pressure at Depth •

Problem • Blood pressure is partly made up of hydrostatic pressure caused by the weight of blood. Calculate the difference in blood pressure between the heart and the head of someone who is 1. 75 m (approximately 5’ 9”) tall. Use units of mm. Hg, the typical units used for blood pressure. • Hearts are located at about ¾ of a person’s total height. • The density of blood is 1050 kg/m 3. • 760 mm. Hg = 1 atm = 101, 325 Pa

Differential Pressure • Forces on the faces of the cube must cancel out. • What forces are acting in the x, y, and z directions?

• For forces in each direction cancel out • pressures forces on x and y faces must be the same • but what about z? Rearranging…

Problem • Find an expression for pressure as a function of z for an incompressible fluid.

Problem •

Problem •

Depth is Depth • In a continuous fluid, pressure at a given depth is always the same.

Problem • The pressure at the bottom of Container 1 is 32. 3 psi. What is the pressure at the bottom of Container 2?

Pascal’s Law • Pressure applied to a confined fluid is distributed equally throughout the fluid.

Pressure Measurement Devices Barometers Manometers

Problem • The gas tank below is connected to a manometer. Find P.