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ES 202 Fluid and Thermal Systems Lecture 2 (12/03/2002). Assignments. Reading: Cengel & Turner Section 10-1 and 10-3 Review Statics (concept of static equilibrium) Homework: 2-41, 2-46, 2-62 in Cengel & Turner. Road Map of Lecture 2. Announcements Finish review section of Lecture 1
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Assignments • Reading: • Cengel & Turner Section 10-1 and 10-3 • Review Statics (concept of static equilibrium) • Homework: • 2-41, 2-46, 2-62 in Cengel & Turner
Road Map of Lecture 2 • Announcements • Finish review section of Lecture 1 • What is a fluid? • Hydrostatics • Forces in a fluid • Concept and properties of pressure • Hydrostatic pressure distribution • Active learning exercises: manometer
Announcements • Lab 1 this week in this classroom • Do the pre-lab before lab session • Check on textbook availability • Instructor’s web page (contains lecture presentations) http://www.rose-hulman.edu/~luic • Corrections on extension: 6998 • Thanks for filling out the questionnaire • Some advice from Rose grads: the different engineering disciplines are not disjoint
Announcements (cont’d) • Example of thermal fluid application in other fields • Learn to work with others • Don’t be tunnel vision in viewing your education; expose yourself to different disciplines (widen your thinking) • Is this course easy or difficult? • Propose to hold review session on major concepts from ES 201 (need your input)
Tips for Success • Keep up with homework daily (best) or weekly (minimum) • See me when you need any help • Give me feedback at anytime (the earlier the better)!
Familiar Terminology • Close system/open system • Control mass/control volume • Storage • Production • Net influx • Conservation of mass • Conservation of linear momentum • Zeroth law of thermodynamics – concept of temperature • First law of thermodynamics – concept of energy • Second law of thermodynamics – concept of entropy • What is entropy, enthalpy and energy? What are they good for?
What is a Fluid? • Give me some descriptions about a fluid • Examples: gas, liquid • Something that flows • Something that fits the shape of its container • It continuously deforms under the application of a force • What is the main difference between a solid and a fluid?
Forces in a Fluid • Start from a control volume analysis • Body force (acts on the contents within the control volume) • Surface force (acts on control surface) • Shear stress • Parallel to a control surface • A new fluid property: viscosity (thin vs thick) • Interpretation of viscosity from microscopic view • Effects of viscosity on fluid flows • Notion of no-slip conditions at solid boundaries • Development of velocity gradient (only when there is fluid motion) • Give rise to viscous stress • Temperature dependency of viscosity • Examples (flow over an airfoil, automobile, flow inside a pipe) • Applications (lubrication in ball bearing, protect engine block) • A small research project (meaning of 10W30, 10W40)
Forces in a Fluid (cont’d) • Normal stress • Normal to a control surface • Pressure is the major component to normal stress • Interpretation of pressure from microscopic view • Pressure is a scalar • Pressure as a point property • Isotropic property of pressure (Pressure at a point is the same in all directions) • How does pressure change in a fluid? • Pressure does not change in the horizontal direction for a fluid at rest (what will happen if pressure varies in the horizontal direction?) • Gage vs absolute pressure
Hydrostatic Pressure Distribution • In horizontal direction: P = constant • In vertical direction: