SOLUTION MANUAL FOR
Engineering Fluid Mechanics
by Donald F. Elger
12th Edition
, Notes To Instructors
Introduction
The Following Ideas And Information Are Provided To Assist The Instructor In The Design And
Implementation Of The Course. Traditionally This Course Is Taught At Washington State University And The
University Of Idaho As A Three-Credit Semester Course Which Means 3 Hours Of Lecture Per Week For 15
Weeks. Basically The First 11 Chapters And Chapter 13 (Flow Measurements) Are Covered In Mechanical
Engineering. Chapters 12 (Compressible Flow) And Chapter 14 (Turbomachinery) May Be Covered Depending
On The Time Available And Exposure To Compressible Flow In Other Courses (Thermodynamics). Open
Channel Flow (Chapter 15) Is Generally Not Covered In Mechanical Engineering. When The Text Is Used In Civil
Engineering, Chapters 1-11 And 13 Are Nominally Covered And Chapters 14 And 15 May Be Included If Time
Permits And Exposure To Open Channel Flow May Not Be Available In Other Courses. The Book Can Be Used For
10-Week Quarter Courses By Selecting The Chapters, Or Parts Of The Chapters, Most Appropriate For The Course.
Author Contact
Every Effort Has Been Made To Insure That The Solution Manual Is Error Free. If Errors Are Found
(And They Will Be!) Please Contact Professors Crowe Or Elger.
Donald Elger Clayton Crowe
Mechanical Engineering Dept School Of Mechanical Eng. & Matl. Science
University Of Idaho Washington State University
Moscow, ID 83844-0902 Pullman, WA 99164-2920
Phone (208) 885-7889 Phone (509) 335-3214
Fax (208) 885-9031 Fax (509) 335-4662
E-Mail: E-Mail:
Design And Computer Problems
Design Problems (Marked In The Text In Blue) Are Those Problems That Require Engineering Practices
Such As Estimation, Making Asummptions And Considering Realistic Materials And Components. These
Problems Provide A Platform For Student Discussion And Group Activity. One Approach Is To Divide The Class
Into Small Groups Of Three Or Four And Have These Groups Work On The Design Problems Together. Each
Group Can Then Report On Their Design To The Rest Of The Class. The Role Of The Professor Is To Help The
Student Learn The Practices Of The Design Review—That Is, Teach The Student To Ask In-Depth Questions And
Teach Them How To Develop Meaningful And In-Depth Answers. This Dialogue Stimulates Interest And Class
Discussion. Solutions To Most Design Problems Are Included In The Solution Manual.
Computer-Oriented Problems (Marked In The Text Is Blue) Are Those Problems May Best Be Solved
Using Software Such As Spreadsheets, TK Solver Or Mathcad. The Choice Is Left To The Student. The Answer
Book Also Includes The Results For The Computer-Oriented Problems.
1
,PROBLEM 2.1
Situation: An Engineer Needs Density For An Experiment With A
Glider. Local Temperature = 74.3 ◦F = 296.7 K.
Local Pressure = 27.3 In.-Hg = 92.45 Kpa.
Find: (A) Calculate Density Using Local Conditions.
(B) Compare Calculated Density With The Value From Table A.2, And Make A Recom-
Mendation.
Properties: From Table A.2, Rair = 287 J ,
kg· K
Ρ = 1.22 Kg/ M3.
Apply The Ideal Gas Law For Local Conditions.
a.) Ideal Gas
Law
P
Ρ =
RT
92, 450 N/ M2
=
(287 Kg/ M3) (296.7 K)
= 1.086 Kg/M3
ρ = 1.09 kg/m3 (local conditions)
b.) Table Value. From Table A.2
ρ = 1.22 kg/m3 (table value)
1. The Density Difference (Local Conditions Versus Table Value) Is About 12%.
Most Of This Difference Is Due To The Effect Of Elevation On Atmospheric
Pressure.
2. Answer ⇒ Recommendation—Use The Local Value Of Density Because The
Effects Of Elevation Are Significant.
1
, PROBLEM 2.2
Situation: Carbon Dioxide Is At 300 Kpa And
60oc. Find: Density And Specific Weight Of CO2.
Properties: From Table A.2, RCO2 = 189 J/Kg·K.
First, Apply The Ideal Gas Law To Find Density. Then, Calculate Specific Weight Using
R = Ρg.
Ideal Gas Law
P
Ρco2 =
RT
300, 000
=
189(60 + 273)
= 4.767 kg/m3
Specific
R = Ρg
Weight Thus
Rco2 = Ρco2 × G
= 4.767 × 9.81
= 46.764 N/m3
2
Engineering Fluid Mechanics
by Donald F. Elger
12th Edition
, Notes To Instructors
Introduction
The Following Ideas And Information Are Provided To Assist The Instructor In The Design And
Implementation Of The Course. Traditionally This Course Is Taught At Washington State University And The
University Of Idaho As A Three-Credit Semester Course Which Means 3 Hours Of Lecture Per Week For 15
Weeks. Basically The First 11 Chapters And Chapter 13 (Flow Measurements) Are Covered In Mechanical
Engineering. Chapters 12 (Compressible Flow) And Chapter 14 (Turbomachinery) May Be Covered Depending
On The Time Available And Exposure To Compressible Flow In Other Courses (Thermodynamics). Open
Channel Flow (Chapter 15) Is Generally Not Covered In Mechanical Engineering. When The Text Is Used In Civil
Engineering, Chapters 1-11 And 13 Are Nominally Covered And Chapters 14 And 15 May Be Included If Time
Permits And Exposure To Open Channel Flow May Not Be Available In Other Courses. The Book Can Be Used For
10-Week Quarter Courses By Selecting The Chapters, Or Parts Of The Chapters, Most Appropriate For The Course.
Author Contact
Every Effort Has Been Made To Insure That The Solution Manual Is Error Free. If Errors Are Found
(And They Will Be!) Please Contact Professors Crowe Or Elger.
Donald Elger Clayton Crowe
Mechanical Engineering Dept School Of Mechanical Eng. & Matl. Science
University Of Idaho Washington State University
Moscow, ID 83844-0902 Pullman, WA 99164-2920
Phone (208) 885-7889 Phone (509) 335-3214
Fax (208) 885-9031 Fax (509) 335-4662
E-Mail: E-Mail:
Design And Computer Problems
Design Problems (Marked In The Text In Blue) Are Those Problems That Require Engineering Practices
Such As Estimation, Making Asummptions And Considering Realistic Materials And Components. These
Problems Provide A Platform For Student Discussion And Group Activity. One Approach Is To Divide The Class
Into Small Groups Of Three Or Four And Have These Groups Work On The Design Problems Together. Each
Group Can Then Report On Their Design To The Rest Of The Class. The Role Of The Professor Is To Help The
Student Learn The Practices Of The Design Review—That Is, Teach The Student To Ask In-Depth Questions And
Teach Them How To Develop Meaningful And In-Depth Answers. This Dialogue Stimulates Interest And Class
Discussion. Solutions To Most Design Problems Are Included In The Solution Manual.
Computer-Oriented Problems (Marked In The Text Is Blue) Are Those Problems May Best Be Solved
Using Software Such As Spreadsheets, TK Solver Or Mathcad. The Choice Is Left To The Student. The Answer
Book Also Includes The Results For The Computer-Oriented Problems.
1
,PROBLEM 2.1
Situation: An Engineer Needs Density For An Experiment With A
Glider. Local Temperature = 74.3 ◦F = 296.7 K.
Local Pressure = 27.3 In.-Hg = 92.45 Kpa.
Find: (A) Calculate Density Using Local Conditions.
(B) Compare Calculated Density With The Value From Table A.2, And Make A Recom-
Mendation.
Properties: From Table A.2, Rair = 287 J ,
kg· K
Ρ = 1.22 Kg/ M3.
Apply The Ideal Gas Law For Local Conditions.
a.) Ideal Gas
Law
P
Ρ =
RT
92, 450 N/ M2
=
(287 Kg/ M3) (296.7 K)
= 1.086 Kg/M3
ρ = 1.09 kg/m3 (local conditions)
b.) Table Value. From Table A.2
ρ = 1.22 kg/m3 (table value)
1. The Density Difference (Local Conditions Versus Table Value) Is About 12%.
Most Of This Difference Is Due To The Effect Of Elevation On Atmospheric
Pressure.
2. Answer ⇒ Recommendation—Use The Local Value Of Density Because The
Effects Of Elevation Are Significant.
1
, PROBLEM 2.2
Situation: Carbon Dioxide Is At 300 Kpa And
60oc. Find: Density And Specific Weight Of CO2.
Properties: From Table A.2, RCO2 = 189 J/Kg·K.
First, Apply The Ideal Gas Law To Find Density. Then, Calculate Specific Weight Using
R = Ρg.
Ideal Gas Law
P
Ρco2 =
RT
300, 000
=
189(60 + 273)
= 4.767 kg/m3
Specific
R = Ρg
Weight Thus
Rco2 = Ρco2 × G
= 4.767 × 9.81
= 46.764 N/m3
2
