Fluid Mechanics and Thermodynamics

Assignment Brief

In this paper you are required to define the main terms of the topic Fluid Mechanics and Thermal Dynamics that are process, real gas, laws of thermal dynamics, Thermal equilibrium, control volume, fluids and flows. Additionally, you have to answer the given questions in details regarding the theme with the help of graphs and scales.

Instructions 

ASSIGNMENT: Coursework on Fluid Mechanics and Thermal Dynamics

Give the definitions to the concepts used in thermodynamics and fluid mechanics:

• Process
• Cycle
• Real gas
• Perfect gas
• 1st law of thermal dynamics
• Thermal equilibrium
• Viscosity
• Inviscid fluid
• Control volume
• Steady flow

Answer all following questions

1. If you put cold water into a blender and mix it rapidly for several minutes, the water will become warm. Where does the additional thermal energy come from? [4 marks]
2. State the conditions that should be met to apply Bernoulli’s equation. [7 marks]
3. State the conditions which must be applied if a thermodynamic operation is to be reversible.

Question 2 (25 marks)

For the manometer shown in the figure below, calculate the pressure difference pA-pB.

• The water density is taken as 1000 kg/m3 . The specific gravities for mercury and oil are 13.6 and 0.86 respectively.

A bucket is filled from a garden water butt as shown in Fig Q2 (b).

• The butt is filled with water to a level of hfill = 1.5 m. The water is discharged via a 10 mm round pipe (Dpipe) near the bottom of the tank.

Question 3 (25 marks)

• A Venture meter shown in Fig. Q3 is essentially a convergent-divergent construction in a pipeline. The change in pressure in the liquid as it passes through the meter can be used to determine the flow rate.

Sample Answer

Coursework on Fluid Mechanics and Thermodynamics

Introduction

Fluid Mechanics and Thermodynamics are fundamental topics in engineering and applied sciences, focusing on the behaviour of fluids (liquids and gases) and the principles of energy transfer. Understanding key terms and applying scientific laws allow us to analyse and predict physical processes involving heat, pressure, and fluid motion. This paper defines essential terms and concepts, answers practical application questions, and presents sample calculations in line with coursework requirements.

Definitions of Key Terms

1. Process
   A process refers to the change that a thermodynamic system undergoes from one equilibrium state to another. For example, heating water from 20°C to 100°C is a thermal process.

2. Cycle
   A thermodynamic cycle is a series of processes that return a system to its initial state. Examples include the Carnot cycle or the Rankine cycle used in steam turbines.

3. Real Gas
   A real gas is a gas that does not follow the ideal gas law exactly, especially under high pressure or low temperature. Real gases exhibit intermolecular forces and occupy physical volume.

4. Perfect Gas (Ideal Gas)
   A perfect gas obeys the ideal gas law $PV=nRT$ precisely. It assumes no intermolecular forces and that gas particles have negligible volume.

5. First Law of Thermodynamics
   This law states that energy cannot be created or destroyed, only transferred or converted. Mathematically,

ΔQ=ΔU+ΔW

where ΔQ is heat added, ΔU is change in internal energy, and ΔW is work done by the system.

6. Thermal Equilibrium
   A state in which two objects in contact do not exchange heat, i.e., they are at the same temperature.

7. Viscosity
   Viscosity is the measure of a fluid’s resistance to flow. For example, honey has higher viscosity than water. Units: Pa·s (Pascal-seconds).

8. Inviscid Fluid
   An inviscid fluid is an ideal fluid with zero viscosity. This assumption simplifies analysis but does not exist in reality.

9. Control Volume
   A control volume is a defined region in space where fluid flow is analysed. Mass, energy, and momentum can cross its boundaries.

10. Steady Flow
    In steady flow, fluid properties (velocity, pressure, density) at a point do not change over time. Example: water flowing through a constant-diameter pipe at uniform speed.

Question 1: Detailed Answers

1. Thermal Energy in a Blender

When cold water is rapidly mixed in a blender, mechanical energy from the motor is converted into thermal energy due to viscous friction between water molecules and the blender blades. This internal friction causes the water molecules to vibrate more, increasing the internal energy of the system, and thus, the temperature rises.

Continued...