CE 230-Engineering Fluid Mechanics Lecture # 18 CONTINUITY EQUATION Section 5.3 (p.154) in text

Time rate of change of a system extensive property = time rate of change of that property in CV + Net outflow rate of that property across CS Property B can be selected as mass, momentum, energy etc

Selecting the extensive property, B, to me the system mass M And therefore the intensive property, b, to be 1 If we substitute in the control volume equation we get the continuity equation Rate of mass accumulation in CV + net outflow rate of mass across CS=0 Assuming constant velocity over flow area Deriving mass balance equation

Example 5.9 A 120-cm pipe in series with a 60 cm pipe. The flow rate of water is 2 m 3 /s. What is the velocity in each pipe?

Example 5.5 what is the rate of water accumulation in the tank?

Example 5.6 what is the rate of water rise in reservoir?

Example 5.7 A 10-cm water jet leaves the 1-m diameter tank as shown. If the jet velocity to be (2gh) 0.5. How long will it take to drop the water surface from 2m to 0.5 m?