1. Fluid Mechanics-I Spring 2010 Lecture # 01

2. 2 Course Outline  Introduction to Fluids and Fluid Properties  Fluid Statics  Integral Relations for fluid flow  Dimensional Analysis and Similarity  Differential Relations for fluid flow  Pipe Flows & Potential Flow

3. 3 Books FLUID MECHANICS Frank M. White Yunus A. Cengel Reference Book: Fluid Mechanics by Munson & Young BY

4. 4 Why Study Fluid Mechanics?  Fluid Mechanics is omnipresent Aerodynamics Bioengineering and biological systems Combustion Energy generation Geology Hydraulics and Hydrology Hydrodynamics Meteorology Ocean and Coastal Engineering …numerous other examples…  Fluid Mechanics is beautiful

5. 5 Aerodynamics

6. 6 Bioengineering

7. 7 Energy Engineering

8. 8 Geology

9. 9 River Hydraulics

10. 10 Hydrodynamics

11. 11 Meteorology

12. 12 Hydraulic Structures

13. 13 Fluid Mechanics is Beautiful

14. 14 Ways of Studying Fluid Mechanics

15. 15 Matter SolidLiquidGasPlasma Fluid States of Matter

16. 16 Microscopic Difference Fixed Position Molecules in Solids Molecules move about each other in Liquids Molecules are in random motion in Gases

17. 17 What is a Fluid? Solid Firm and stable in shape Fluid Able to flow or alter shape freely

18. 18 Difference between a Liquid & a Gas  Relatively strong cohesive forces in molecules.  Retain its volume and make a free surface if unconfined from top.  Molecules are widely spaced.  Does not retain its volume if unconfined from top.  No gravitational effects except buoyancy. LiquidGas

19. 19 Types of Forces on Materials

20. 20 Stress The internal resistance of a material to the applied force is called Stress.

21. 21 Solid Fluid (Stress is proportional to strain) (Stress is proportional to strain rate) Shear force on a Solid & Fluid

22. 22 Definition of a Fluid Any substance that is continuously deformed when subjected to shear stress is called a fluid.

23. 23 Fluid Mechanics Mechanics is the branch of physics that is concerned with the analysis of the action of forces on matter. Fluid Mechanics is the analysis of action of forces on fluids.

24. 24 Branches of Fluid Mechanics Fluid Statics: The analysis of action of forces on fluids at rest e.g. Water stored in a tank Fluid Dynamics: The analysis of action of forces on moving fluids e.g. water flowing in a river or a pipe flow

25. 25 Basic laws of Mechanics  Conservation of Mass  Conservation of Momentum  Conservation of Energy  Laws of Thermodynamics

26. 26 Properties of the Fluid  The analysis of the fluid flow is the determination of fluid properties as a function of position and time. Outlet Inlet Throat X Y

27. 27 Fluid Flow Variables  Pressure  Velocity  Temperature  Density All flow variables are functions of space (x,y,z) & time (t)

28. 28 Types of Properties  Extensive Properties Depends upon the size of the system or amount of the material e.g. mass, length, volume etc  Intensive Properties Independent of the size of the system or amount of the material e.g. Temperature, pressure, velocity, viscosity, density etc

29. 29 Specific Properties  Extensive properties per unit mass are called specific properties. Examples include specific volume v= V/m and specific total energy e=E/m.

30. 30 Specific gravity  The ratio of the density of a substance to the density of some standard substance at a specified temperature (usually water at 4°C), i.e., SG=ρ/ρ water

31. 31 Specific weight  The weight per unit volume.

32. 32 Why it is?  Easier to move in air at rest.  Difficult to move in Water at rest.  More difficult to move in Oil at rest.  Honey flows slowly than water  Always difficult to move in a running fluid towards you.

33. 33 Viscosity  Relationship between the local stresses to strain rate of the fluid element. A quantitative measure of fluid’s resistance to flow  Order of viscosity of different fluids is e.g. Air<Water<SAE30<glycerin <blackstrap molasses

34. 34 Drag Force  The force a flowing fluid exerts on a body in the flow direction is called the drag force, and the magnitude of this force depends, in part, on viscosity.

35. 35 Relation for a Viscosity

36. 36 Velocity Distribution

37. 37 Coefficient of Viscosity Units: Kg/(m.s) or Pa.s Also known as absolute or dynamic viscosity

38. 38 Kinematic Viscosity  The ratio of absolute viscosity to the density is known as Kinematic Viscosity. Units: m 2 /s

39. 39 Viscous Classification of Fluids