Assignment 2, fluid
1. Explain the fluid continuum assumption?
The fluid continuum assumption is when you treat the fluids as continuous even though they
are composed of molecules. The fluid properties can vary throughout the volume elements
and are the average value of the molecular properties.
2. A cylindrical tank of methanol has a mass of 60kg and a volume of 75L. Determine the
methanol’s weight, density, and specific gravity. Take the gravitational acceleration to be
9.81m/s2.
Weight: 60kg*9,81m/s^2 = 588,6
Density: 60kg/75L = 0,8 kg/L
Specific gravity: 0,8 kg/L / 0.792 kg/L = 1,0101
1. What is cavitation? What causes it?
Cavitation is the formation of bubbles in the fluid at the low-pressure regions. It occurs in
places where the fluid has accelerated to high velocities. Examples where it occurs are
centrifugal pumps, water turbines and marine propellers.
4. A pump is used to transport water to a higher reservoir. If the water temperature is 20o
Celsius, determine the lowest pressure that can exist in the pump without cavitation.
Cavitation occurs when the pressure falls below the saturation pressure. Therefor the lowest
pressure that can exist is 2,34 kpa. Value found for the saturation pressure in table 2-2.
5. What is total energy of a system? Identify the different forms of energy that constitute
the total energy. Furthermore, Saturated water vapor at 150o Celsius (enthalpy h =
2745.9kJ/kg) flows in a pipe at 35m/s at an elevation of z = 25m. determine the total
energy of a vapor in J/kg relative to the ground level.
The total energy in a system is the sum of all the different types of energy. Which includes
thermal, mechanical, kinetic, potential, electric, magnetic, chemical, and nuclear.
e= h+((V^2)/2) + gz
e= 2745900 + ((35^2)/2) + 9,81*25 = 2746480,93 J/kg
