Course Introduction January 22 – 24, 2008 Today’s Class Course Introduction • First class day items: roll, outline, etc. • Class goals and learning objectives Larry Caretto • Assessment quiz Mechanical Engineering 390 • Discussion of dimensions and units Fluid Mechanics – Physical quantities have dimensions – Several units measure same dimension January 22 and 24, 2008 – Use SI system of units (meter, kilogram, ... – Also use engineering units (feet, pounds ... 2 Thursday Class Basic Information • Fluid properties • Larry Caretto, Jacaranda (Engineering) 3333, – Density [email protected], 818.677.6448 – Bulk modulus • Office hours Monday and Wednesday, 4:30 to 5:15 pm; Tuesday and Thursday 2:45 to – Viscosity 3:45 pm; other times by email, phone, drop-in, – Vapor pressure or appointment – Viscosity • http://www.csun.edu/~lcaretto/me390 –Surface Tension • Munson, Young, and Okiisii, Fundamentals of • Start discussion of fluid statics on using Fluid Mechanics (fifth edition), Wiley, 2006. next set of notes 3 4 Email Course Learning Objectives • Campus policy requires students to • Understand the and be able to formu- monitor their CSUN email addresses late and solve problems using basic – These addresses will be used class email fluid properties: density, specific weight, list [email protected] viscosity and mechanical quantities: • Setup your CSUN email account if you pressure, velocity, force and stress have not done so already • solve problems to determine pressures • If desired, forward CSUN email to in static fluids and manometers another address • understand limits of and solve problems with Bernoulli equation 5 6 ME 390 – Fluid Mechanics 1 Course Introduction January 22 – 24, 2008 More Learning Objectives Still More Learning Objectives • understand definition and be able to use • understand the differences between concepts of system and control volume laminar and turbulent flows and be able to determine if a flow is laminar or • use continuity equation to use mass turbulent based on the Reynolds conservation in problem solving number for the flow • solve problems to determine forces in • solve problems in laminar and turbulent moving fluids using control volumes flows in pipes • use dimensionless parameters and apply • be familiar with the basic ideas of the concept of similitude for fluid boundary layers and irrotational flows mechanics experimentation outside these boundary layers 7 8 Learning Objectives Concluded Thermodynamics • solve problems of lift and drag in • Often a prerequisite for fluids, but not external flows presently a prerequisite at CSUN • understand the important variables used to solve problems in open channel and • Students advised to complete ME 370 compressible flows prior to taking ME 390 • solve problems in one of the following • Instead of a 370 review this course will areas (a) compressible flows (b) open use “just-in-time” Thermodynamics channel flows • Cover specific topics as required for course in nature of review 9 10 Class Operation Quizzes • Tuesday: lecture on new material • Twelve during the semester – Review text and notes before class • Based on group work and homework • Thursday: group problem solving – Homework assigned, but not collected or graded • Tuesday: 30-minute quiz at start of • Solutions available on line class followed by new material lecture • Count ten highest quiz grades for final • Starts next week – No makeup quizzes; final quiz grade based – Introduction during first week only on quizzes taken if fewer than ten • First quiz is on Tuesday, February 5 • First few quizzes closed book; remainder will be open book and equation sheet 11 12 ME 390 – Fluid Mechanics 2 Course Introduction January 22 – 24, 2008 Grading See the Course Outline • Quiz grades 45% • Download from course web site • Midterm (March 13) 22% – http://www.csun.edu/~lcaretto/me390 • Contains lecture schedule and homework • Final (May 13) 33% assignments (homework also on web) • Plus/minus grading will be used • Also read information on the following items • Grading criteria in course outline – Class participation and courtesy – Collaboration versus plagiarism: students found • No make-up quizzes or exams cheating receive F grade in course • Students are responsible for changes to outline announced in class 13 14 You cannot Goals for this Course teach people • My goal is to help all students find within themselves sufficient knowledge of fluid anything; you mechanics so that they will all get an A can only help grade in the course • What is your goal for this course? Galileo Galilei them find it within (1564-1642) • What will you do to achieve that goal? themselves. http://space.about.com/od/astronomyhistory/a/galileoquotes.htm 15 16 How to get your A How to Get your A, Part II • Spend six to ten hours per week outside • Study with fellow students and try to class studying for the course answer each other’s questions • Prepare for lecture and be ready to ask • Do the homework as well as you can questions before reviewing the on-line solutions – Read the assigned reading before class • Contact me by email, telephone or – Download, print, and review the lecture office visits to ask questions presentations before class • Develop a good working relation with • Use these as notes so that you can follow the lecture; write additional notes on these other members of your self-study group presentations 17 18 ME 390 – Fluid Mechanics 3 Course Introduction January 22 – 24, 2008 What I will do to help Preliminary Assessment • Arrive at class a few minutes early to • Designed to help instruction answer any questions you may have • One set of questions on student • Give lectures that stress application of background basics to problem solving • Second set of questions is ungraded quiz • Return quizzes and exams promptly so that you can learn from your errors • Take about 10 minutes for this assessment • Be available for questions by email, • Hand yours in when finished office visits or phone calls – Will call time when most students are done – Send entire class emails as appropriate 19 20 Dimensions and Units Systems of Units • Any physical quantity has a unique • Arbitrary units for fundamental dimension: e.g., mass, length, time, … dimensions, e.g. mass (M), length (L), • Several units may be available for any time (T), and temperature (Θ). dimension • Units for other physical quantities from – Length is measured in meters, feet, miles, the physical relations to quantities with fathoms, furlongs, yards, light-years, etc. fundamental units – You cannot measure length in units with – Velocity dimensions are length/time, L/T the dimension of mass – Acceleration dimensions are length/time2 – Force dimension of (mass)(length)/(time)2 21 22 More Dimensions Still More Dimensions • Pressure = force per unit area • Another energy term 2 = [force] / [length] – Potential energy = mgh = = [(mass) (length) / (time)2] / (length)2 2 -2 -1 (mass)(acceleration)(length) = = (mass) / [(time) (length)] or MT L (mass)(length)2/(time)2 • Common dimensions for energy terms • Power = (energy)/(time) are (mass)(length)2/(time)2 or ML2T-2 = (mass) (length)2 /(time)3 or ML2T-3 – Work = force times distance = (force)(length) • Thermodynamic work is PdV = (mass)(length)2/(time)2 or ML2T-2 – This is like Fdx where P = F/A and dV = – Kinetic energy = mV2/2 Adx (A is area) 2 = (mass)(velocity) 3 = (mass)(length)2/(time)2 or ML2T-2 – PdV dimensions are (length) (force)/(area) which also is (mass)(length)2/(time)2 23 24 ME 390 – Fluid Mechanics 4 Course Introduction January 22 – 24, 2008 SI Units Other Units • Basic definitions for fundamental units • Light intensity and molar units – Mass: kilogram (kg) = international prototype • Units for velocity and acceleration are – Time: second (s) = time for 9 192 631 770 m/s and m/s2 periods of radiation from Cs133 2 – Length: meter (m) = length light travels in • Units for force are kg·m/s 1/299 792 458 of a second – 1 newton (N) = 1 kg·m/s2 – Temperature: kelvin (K) = 1/273.16 of the • Units for energy are kg(m/s)2 = N·m triple point of water – 1 joule (J) = 1 N·m = 1 kg·m2/s2 – Current: ampere (A) defined in terms of electrostatic force 25 26 Still More Units Some Prefixes • Power: (energy)/(time) = joules/second pico, p nano, n micro, μ milli, m – 1 watt (W) = 1 J/s = 1 N·m/s = 1 kg·m2/s3 • Pressure: (force)/(area) = newtons per square meter (1 atm = 101,325 Pa) 10-12 10-9 10-6 10-3 – 1 pascal (Pa) = 1 N/m2 = 1 kg/(m·s2 ) • Note that Sir Isaac Newton has a capital tera, t giga, g mega, M kilo, k N; 1 newton of force does not, unless it is abbreviated as 1 N (true for all units named after individuals) 1012 109 106 103 27 28 Engineering Units Why Use a Pound Force? • Second is the basic unit of time • From the definition of a pound force, the • The foot = 0.3048 m (exactly) is the weight, W = mg, of a pound mass in a basic unit of length standard gravitational field is 1 lbf • Pound is confusing because it can be 2 32.174 ft lb f ⋅ s used to represent two dimensions W = mg = (m lbm ) 2 = m lbf s 32.174lbm ⋅ ft – Mass: pound-mass (lbm = 0.453592 kg) 2 – Force: pound force (lbf = 32.174 lbm·ft/s ) • This is convenient, but the same name • What is SI equivalent for pound force? for two dimensions is confusing and the 1 lbf = 4.4482 N conversion factor is awkward 29 30 ME 390 – Fluid Mechanics 5 Course Introduction January 22 – 24, 2008 Two Engineering Unit Systems More Engineering Units • English engineering units use mass as • foot-pound is work (energy unit) pound mass and force as pound force • British