CHAPTER 1 INTRODUCTION

 At the end of this chapter, you should be able to: 1. Understand the basic concepts of fluid mechanics and recognize the various type of fluid flow problems encountered in practice. 2. Model engineering problems and solve them in a systematic manner. 3. Have a working knowledge of accuracy, precision, and significant digits, and recognize the importance of dimensional homogeneity in engineering calculations

 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.

 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 = F n /dA (in fluid at rest, it is called pressure) Shear stress, τ = F t /dA (for fluid at rest=0)

Examples:  Natural flows & weather  Aircraft & spacecraft  Boats  Human body  Piping & plumbing systems  Wind turbines  and many more…..

57:020 Fluid Mechanics6 Tornadoes HurricanesGlobal Climate Thunderstorm

57:020 Fluid Mechanics7 Aircraft Submarines High-speed rail Surface ships

57:020 Fluid Mechanics8 Air pollution River hydraulics

57:020 Fluid Mechanics9 Blood pumpVentricular assist device

57:020 Fluid Mechanics10 Water sports Auto racing Offshore racingCycling Surfing

 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.

A. Viscous vs inviscid regions of flow  Viscosity -a measure of internal stickiness of fluid  Viscous flow region–significant frictional effect  Inviscid flow region – negligible viscous forces B. Internal vs external flow C. 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

D. Laminar vs turbulent flow  Determined by Reynolds number, Re  Re 6000 (turbulent); between laminar and turbulent is transitional E. Natural (or unforced) vs forced flow F. 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)

Good luck!

1) What is fluid? 2) Stress is force per unit area. Name 2 types of stress in fluid and their equations. 3) Give 3 examples of application areas of fluid mechanics. 4) Please explain about the “no-slip condition”. You have 10 minutes. TQ!