FRIDAYS 14:00 to 15:40. FRIDAYS 16:10 to 17:50

Size: px

Start display at page:

Download "FRIDAYS 14:00 to 15:40. FRIDAYS 16:10 to 17:50"

Dinah Robbins
5 years ago
Views:

1 Brad Peterson, P.E.

2 FRIDAYS 14:00 to 15:40 FRIDAYS 16:10 to 17:50

3 BRAD PETERSON, P.E., PTOE Brigham Young University, 1975 Highway and Bridge Design Montana, Utah, Idaho, Wyoming Worked 27 Years in Helena, Montana Worked 4 Years in Salt Lake City, Utah Partner in a 400-Person Civil-Design Firm Left firm in July 2009

4 It s a Small World

5 USA

6 My House in Summer

7 MyHouseinWinter

8 My Family:

9 Fluid Mechanics, Friday Class Time (14:00 or 16:10) Name in Chinese Characters Chinese Name in Pinyini English Name (if you use one) Student Identification Number Year in School (1st, 2nd, 3 rd, 4 th, Masters, PhD, Other) Major and the University it

10 CLASS INFO: Class Website: Mr. Peterson s Address: bradpeterson@engineer.com

11 Class Goal Primarily: To learn and practice the concepts and principles of Fluid Mechanics. Secondarily: To increase skills in the English language as related to these engineering i principles. i

12 Guidelines: Attend all classes. Check with the instructor on how you can make up a class, before you miss the class. Be punctual (be on time). SHOE - Speak Here Only English. Do not be fearful about making mistakes when speaking English.

13 Guidelines: Participate in class discussions and ask questions when you do not understand. Check for and download information at the class website. DO NOT smoke eat spit use cell DO NOT smoke, eat, spit, use cell phone or sleep in class.

14 Guidelines: Be prompt in handing in written assignments due at the beginning of each class. Learn and have fun!

15 Grading In-Class Tests 30% Homework 30% Final Exam 40%

16 CLASS SCHEDULE Lesson 1, Properties of Fluids Lesson 2, Fluid Statics Lesson 3, Hydrostatic Force on Surfaces Lesson 4, Buoyancy and Flotation Lesson 5, Translation and Rotation ti of Liquid id Masses Lesson 6, Dimensional Analysis and Hydraulic Similitude Lesson 7, Fundamentals of Fluid Flow Lesson 8, Flow in Closed Conduits Lesson 9, Complex Pipeline Systems Lesson 10, Flow in Open Channels Lesson 11, Flow of Compressible Fluids Lesson 12, Measurement of Flow of Fluids Lesson 13, Forces Developed by Moving Fluids Lesson 14, Fluid Machinery

17 Class Text:

18 About the Class Text Clear, concise and straightforward But not long <400 pages vs If feasible, purchase a copy Useable now, and for entire career See my website for one purchase site Local bookstores may also have it? Or can get it?

19 Other Sources of Info Other search engines and data bases Some info is good, some not-so-good. Be careful and let s discuss, if questions.

20 Lesson 1, Properties of Fluids 1. Fluid Mechanics 8. Vapor Pressure 2. Definition of a Fluid 9. Surface Tension 3. Systems of Units 10. Capillarity 4. Specific or Unit Weight 11. Modulus of Elasticity 12. Isothermal Conditions 5. Mass Density 13. Adiabatic or Isentropic 6. Specific Gravity Conditions 7. Viscosity 14. Pressure Disturbances

21 Items of Importance For this lesson, items considered of most importance for civil engineering students (items dealing with liquids and specifically water) are generally shown in white text like this. Items related to gases and liquids id other than water are dealt with in less detail and are shown in green text. The student is encouraged to research these topics individually, as needed.

22 Fluid Mechanics Deals with the properties of fluids at Deals with the properties of fluids, at rest and in motion.

23 1.2. Definition of a Fluid Capable of flowing Conforms to shape of a vessel Cannot sustain shear forces Little resistance to change of form. Two Classifications: Liquid, not compressible, definite volume Gas, compressible, expands to volume of vessel.

24 Important Fluid Properties Specific Weight Density Viscosity

25 1.3. Systems of Units British Engineering (or FPS) Not used in this class

26 1.3. Systems of Units (Cont) International System of Units (SI) Length = meter (m) Mass = kilogram (kg) Time = second (s) All other units derived d from these, thus: Area = m 2 Volume = m 3 Acceleration = m/s 2 Acceleration of gravity (g) = 9.81m/s 2 Force = Newton (N) = mass X acceleration = kg. m/s 2 Work = joule (J) = N. m Pressure = pascal (Pa) = N/m 2

27 1.4. Specific or Unit Weight Specific (or unit) weight (Ƴ) = Weight of a unit volume of a substance For liquids, Ƴ is constant Specific weight of water = 9.79 kn/m 3

28 1.5. Mass Density Mass per unit volume = Ƴ/g For Water, mass density = 1000 kg/m3

29 Weight, Acceleration Of Gravity & Mass Acceleration of gravity at sea level g 9.81 m/ s 2 g decreases slightly as elevation increases In our textbook, g is assumed to be 9.81 m / s 2

30 Weight, Acceleration Of Gravity & Mass (cont) 3 o Weight of water 9.81 / at 0 kn m C 3 o kn / at t20 kn m C 3 o 9.73 / at 40 kn m C kn / m at 100 o C Our textbook uses 9.79 kn / m 3

31 Weight, Acceleration Of Gravity & Mass (cont) kn / m 3 Mass density of water =1000kg / m at 0 o C m/ s kn / m 3 =998kg / m at 20 o C m/ s kn / m 3 t40 o =992kg / m at C m/ s kn / m 3 o =958kg / m at 100 C m/ s 3 Our textbook uses 1000 kg / m for mass of water

32 Weight, Acceleration Of Gravity & Mass (unit check) Mass of water 9.81 kn / m m/ s 9810( kg m/ s ) / m m/ s 3 =1000kg / m at 0 o C

33 Weight, Acceleration Of Gravity & Mass (conclusion) Some sources use g 9.8 m/ s and, for water 9.8 kn / m however: Our textbook uses: g 9.81 m/ s and, for water 9.79 kn / m 3

34 1.6. Specific Gravity Ratio of weight of a body to the weight of an equal volume of a standard substance Water is usually the standard substance 979kN/m Specific Gravity = weight of substance weight of equal volume of water

35 1.7. Viscosity That property which determines the amount of a fluid s resistance to a shearing force. Absolute viscosity = μ = τ /(dv/dy) where τ =F/A= = shear stress Kinematic Viscosity it = ʋ = m2/s or ft2/sec

37 Viscosity y( (cont) U = velocity A = area of plate y = spacing between plates U / y = dv / dy Experiments have shown that: F α (AU/y = A dv/dy) or F/A α dv/dy

38 Viscosity (cont) Since shear stress = F/A = τ and dif a proportionality constant tμ is introduced, then: F/A α dv/dy becomes: τ = μ x dv / dy or, μ = τ / (dv/dy) Units for μ are Pa-s or lb-sec/ft 2

39 1.8. Vapor Pressure Produced when evaporation takes place within and enclosed space Depends on temperature Increases as temperature increases

40 1.9. Surface Tension Molecules on the surface of a liquid have more energy that molecules within. This creates surface tension. Illustrated by glass of water and needle.

41 Capillarity Causes liquid to rise or fall in a tube. Caused by surface tension and by adhesion to walls of the tube. Adhesion > Cohesion liquid rises in tube Cohesion > Adhesion liquid falls in tube Draw picture to illustrate. Capillarity is important using tubes smaller Capillarity is important using tubes smaller than 10mm diameter

42 Capillarity (picture)

43 Bulk Modulus of Elasticity Expresses the compressibility of a fluid. Ratio of change in unit pressure to corresponding volume change.

44 Pressure Disturbances Isothermal Conditions Adiabatic or Isentropic Conditions Pressure Disturbances These apply mostly to gases and may be discussed at a later date, as needed.

45 Problem 1 If 6 m 3 of oil weighs 47 kn calculate its If 6 m of oil weighs 47 kn, calculate its specific weight Ƴ and specific gravity.

46 Problem 1, Solution specific weight Ƴ = 47 kn = kn/m 3 6 m 3 specific gravity = Ƴoil = kn/m 3 = Ƴwater 9.79 kn/m 3

47 Problem 2 If 1 m 3 of concrete has a mass 2.4 Tons, calculate its specific weight Ƴ and specific gravity.

48 Problem 2, Solution (Cont) 9.81 / specific weight N kg 2300kg kn / m 3 1 m 3 3 con kn / m specific gravity water 9.79 kn / m

49 Problem 3 A cylinder of m radius rotates concentrically inside a fixed cylinder of m radius. Both cylinders are m long. Determine the viscosity of the liquid that fills the space between the cylinders if a torque of N-m is required to maintain an angular velocity of 60 revolutions per minute.

50 Problem 3, Solution Sketch on the Board Torque is transmitted through the fluid layers to the outside cylinder. Since the gap between the cylinders is small, calculation can be made without integration.

51 Problem 3, Solution (cont) Tangential velocity of inner cylinder = rω = 2π x m x 1 rps) = m/s dv/dy = (0.767 m/s) / ( ) = s -1

52 Problem 3, Solution (cont) τ = F/A F = τa torque = F x arm F =torque/arm τa = torque/arm τ = torque / (arm x A) τ = / [(0.125) x (2π x x 0.305)] = 29.4 Pa μ = τ / (dv/dy) = 29.4 / = Pa-s

53 CLASS SCHEDULE Lesson 1, Properties of Fluids 2009 September 04 Lesson 2, Fluid Statics 2009 September 11 Lesson 3, Hydrostatic Force on Surfaces Lesson 4, Buoyancy and Flotation Lesson 5, Translation and Rotation ti of Liquid id Masses Lesson 6, Dimensional Analysis and Hydraulic Similitude Lesson 7, Fundamentals of Fluid Flow Lesson 8, Flow in Closed Conduits Lesson 9, Complex Pipeline Systems Lesson 10, Flow in Open Channels Lesson 11, Flow of Compressible Fluids Lesson 12, Measurement of Flow of Fluids Lesson 13, Forces Developed by Moving Fluids Lesson 14, Fluid Machinery

54 Vocabulary for Next Week Fluid Pressure Pressure Gages Pressure Head Compressible Vacuum Piezometers Manometers Absolute Pressure Gage Pressure Barometers Standard Atmospheric Pressure

Fluid Mechanics Introduction

Fluid Mechanics Introduction Fluid mechanics study the fluid under all conditions of rest and motion. Its approach is analytical, mathematical, and empirical (experimental and observation). Fluid can be