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Fluid Mechanics SEMESTER II, 2010/2011. CHAPTER 1 INTRODUCTION. OBJECTIVES. At the end of this chapter, you should be able to: Understand the basic concepts of fluid mechanics and recognize the various type of fluid flow problems encountered in practice.
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Fluid MechanicsSEMESTER II, 2010/2011 CHAPTER 1 INTRODUCTION
OBJECTIVES • At the end of this chapter, you should be able to: • Understand the basic concepts of fluid mechanics and recognize the various type of fluid flow problems encountered in practice. • Model engineering problems and solve them in a systematic manner. • Have a working knowledge of accuracy, precision, and significant digits, and recognize the importance of dimensional homogeneity in engineering calculations
What is fluid mechanics? • The science that deals with the behavior of fluids at rest (fluid statics) or in motion (fluid dynamics), and the interaction of fluids with solids or other fluids at the boundaries. • It is divided into several categories: • Examples: hydrodynamics, hydraulics, Gas dynamics, aerodynamics etc.
What is FLUID? • A substance in the liquid or gas phase is referred as FLUID • In fluids, stress is proportional to strain rate. • Stress=force per unit area. Normal stress, σ = Fn/dA (in fluid at rest, it is called pressure) Shear stress, τ = Ft/dA (for fluid at rest=0)
Application areas of Fluid mechanics Examples: • Natural flows & weather • Aircraft & spacecraft • Boats • Human body • Piping & plumbing systems • Wind turbines • and many more…..
Weather & Climate Tornadoes Thunderstorm Global Climate Hurricanes 57:020 Fluid Mechanics
Vehicles Surface ships Aircraft Submarines High-speed rail 57:020 Fluid Mechanics
Environment River hydraulics Air pollution 57:020 Fluid Mechanics
Physiology and Medicine Blood pump Ventricular assist device 57:020 Fluid Mechanics
Sports & Recreation Water sports Cycling Offshore racing Auto racing Surfing 57:020 Fluid Mechanics
NO-SLIP CONDITION • A fluid in motion comes to a complete stop at the surface and assumes a zero velocity relatives to the surface. • Fluid in direct contact with solid “sticks” to the surface due to viscous effect, and there is no slip.
Classification Of Fluid Flows • Viscous vsinviscid regions of flow • Viscosity -a measure of internal stickiness of fluid • Viscous flow region–significant frictional effect • Inviscid flow region – negligible viscous forces • Internal vs external flow • Compressible vs incompressible • Incompressible flow – almost constant density throughout • Compressible flow gas Question:Can gas flow be treated as incompressible flow? • Answer: depends on the Mach number (Ma = V/c ); usually when Ma<0.3 fluid
Classification Of Fluid Flows • Laminar vs turbulent flow • Determined by Reynolds number, Re • Re < 2000 (laminar); Re > 6000 (turbulent); between laminar and turbulent is transitional • Natural (or unforced) vs forced flow • Steady vs unsteady flow • Steady = no change at a point of time • Transient = typically used for developing flows,( e.g. pressure build up inside rocket engine, until it operates steadily)
Quiz time Good luck!
Please answer the following questions…. • What is fluid? • Stress is force per unit area. Name 2 types of stress in fluid and their equations. • Give 3 examples of application areas of fluid mechanics. • Please explain about the “no-slip condition”. You have 10minutes. TQ!