Chapter 1: Introduction Note to Students (the points emphasized in syllabus):• The classroom time should be used to amplify the text book material by discussing related materials and applying basic principles to the solution of problems.

• The textbook should be a clear, concise presentation of the fundamentals that the student can read.

• Your willingness to read the text before going to classOne learns best by doing --- you must solve problems!

• Follow formal solution procedure of the text.

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Main Topics

Definition of a FluidScope of Fluid MechanicsBasic LawsMethods of AnalysisDimensions and Units

 Definition of a Fluid  

 Scope of Fluid Mechanics  

To present basic laws and associated physical concepts that provide the basis or starting point in analysis of any problem in fluid mechanics Applications: Aircraft, surface ships/submarines, and automobiles (engines)Fluid machinery including pumps, fans, blowers, compressors, and turbinesThermal/chemical processes: boilers, heat exchangers, refinery, …Bio-fluids, blood flowCivil engineering, HVAC, flow in a pipeAnything that involves a fluid, such as a hurricane or tornado, …

 Images of Some Typical Flows (Google) 

 Basic Laws

The conservation of massNewton’s second law of motionThe principle of angular momentumThe first law of thermodynamicsThe second law of thermodynamicsThe equation of state, such as pv = RT The basic laws are the same as those used in mechanics (mechanics of materials) and thermodynamics. Our task will be to formulate these laws in suitable forms to solve fluid problemsThe last frontier of mechanics – more complex than any other mechanics

  SystemMethods of Analysis System: A system is defined as a fixed quantity of mass – Closed system/Controlled mass The system boundaries separate the system from surroundings. The boundaries of the system may be fixed or movable; however, no mass crosses the system boundaries.

(In mechanics courses – free-body diagram – system approach – the number of bodies is limited – in

fluid, however, millions of particles – difficult to use the

system approach)

 Control volume

A control volume is a (or an arbitrary) volume in space through which fluid flows.The geometric boundary of the control volume is called the control surface – may be real or imaginary – may be at rest or in motion

© Fox, McDonald & Pritchard

Dimensions and Units

Systems of Dimensions[M], [L], [t], and [T][F], [L], [t], and [T][F],[M], [L], [t], and [T]

© Fox, McDonald & Pritchard

Dimensions and Units

Systems of UnitsMLtT• SI (kg, m, s, K)

FLtT• British Gravitational (lbf, ft, s, oR)

FMLtT• English Engineering (lbf, lbm, ft, s, oR)

© Fox, McDonald & Pritchard

Dimensions and Units

Preferred Systems of UnitsSI (kg, m, s, K)

British Gravitational (lbf, ft, s, oR)

  Dimensions and Units

SI system:Unit of mass: kg; unit of length: m; unit of time: s, and the unit of temperature is the Kelvin K). Force (a secondary dimension) is the Newton (N).

F = ma 1 N = 1 kg-m/s2

The Absolute metric system:Unit of mass: gram ; unit of length: cm; unit of time: s, and the unit of temperature is the Kelvin K). Force (a secondary dimension) is the dyne1 dyne = 1 g-cm/s2

The British Gravitational system:Unit of force: the pound (lbf); unit of length: foot (ft); unit of time: s, and the unit of temperature is the degree Rankine (oR). Mass (a secondary dimension) is the slug1 slug = 1 lbf-s2/ft

  Dimensions and UnitsThe English Engineering system:The unit of force: lbf, the unit of mass: lbm, the unit of length: ft, unit of time: s, and the unit of temperature is the degree Rankine oR). Since both force and mass are chosen as primary dimensions, Newton’s second law is written as

F = ma/gc

A force of one pound (1 lbf) is the force that gives a pound mass (1lbm) an acceleration equal to the standard acceleration of gravity on Earh, 32.2 ft/s2. From Newton’s second law

gc = 32.2 ft-lbm/lbf-s2

-- the constant of proportionality

1 slug = 32.2 lbm

Preferred systems of units:Both the SI and the British Gravitational systems. In either case, gc = 1.