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FloridaInternationalUniversityDepartmentofCivilandEnvironmentalEngineering
CWR3201FluidMechanics,Fall2018Instructor:ArturoS.Leon,Ph.D.,P.E.,D.WRE
TA:ThaoDo,CEEUndergraduate
HomeworkAssignment6SolutionsMechanicsofFluids(Fifthedition),byM.C.Potter,D.C.WiggertandB.H.Ramadan.
1. 7.20(samenumberinFourthEdition)
๐ท๐๐ โ๐๐๐๐๐ ๐ = ๐ด โ ๐ โ 0.025 =๐4 (0.06)
!๐๐ = 8.84 ๐/๐
๐ ๐ =๐๐ท๐ =
8.84 โ 0.061.005 โ 10!! = 527877
SinceReynoldsnumberisgreaterthan2000,flowisturbulent.๐ ๐ > 10!๐ฟ๐ท = 120๐ฟ = 7.2 ๐
SinceLengthofpipeis50m,whichisgreaterthan7.2m,assumptionofdevelopedflowisacceptable.
2. 7.94(samenumberinFourthEdition)a) ๐ ๐ = !"
!= !.!"#โ!.!"
!"!!= 1000lessthan2000soflowislaminar
RelativeRoughness:!!= !.!"
!"= 0.00625
Frictionfactor:๐ = !"!!"
= !"โ!"!!
!.!"#โ!.!"= 0.064
b) ๐ ๐ = !"!= !.!"โ!.!"
!"!!= 10000TurbulentflowsouseMoodyDiagram
RelativeRoughness:!!= !.!"
!"= 0.00625
Moodydiagram:๐ = 0.04
3. 7.108(samenumberinFourthEdition)
a) ๐ท = 0.66[๐!.!" !!!
!!!
!.!"+ ๐๐!.!( !
!!!)!.!]!.!"
โ! =โ๐๐พ =
2000009810 = 20.38 ๐
๐ท = 0.66[0!.!"๐ฟ๐!
๐โ!
!.!"
+ 10!! โ 0.002!.!100
9.81 โ 20.38
!.!
]!.!" = 0.032๐
Notethattheotherpartshavesamemethodbutdifferingspecificweightsforeachtypeofmedium.
4. 7.113(samenumberinFourthEdition)
โ! =โ๐๐พ =
1009810 = 0.01 ๐
HydraulicDiameter:๐ท = 4 !"#$!"#$%"&"#
= 4 (!.!"โ!.!)!(!.!"!!.!
= 0.057๐FlowRate:
๐ = โ0.965[๐ !!!!!]!.! ln !
!.!!+ !.!"!!!
!!!!!
!.!= โ0.965[9.81 !.!"#
!โ!.!"!
]!.! ln !!.!!
+
!.!"(!"!!)!โ!!.!"โ!.!"#!!.!"
!.!= 7.31 โ 10!! !
!
!
5. 7.117(samenumberinFourthEdition)
๐! =๐๐ด!
= 63.66๐๐
Fromcontinuity:๐! = ๐!!!!
!!!= 15.92 ๐/๐
Idealgaslawtocalculatedensityofair:๐ = !!"#!!!"!#!"
= !"!.!!!"!.!"#โ!"#
= 1.799 !"!!
Headlossduetosuddenenlargement:โ! =!!!!!
!!
๐พ! = (1โ๐!!
๐!!)! = 0.5625
โ! = 116.18Bernoullienergyequation:!!
!"+ !!!
!!+ ๐! = !!
!"+ !!!
!!+ ๐! + โ!
๐! = 51.366 ๐๐๐6. 7.121(samenumberinFourthEdition)
Manometer:๐! + ๐พ!๐ป = ๐พ!!"#๐ป + ๐!โ๐ = 123606๐ป
๐ =๐๐ด = 4.77 ๐/๐
UsingenergyequationandrearrangingtosolveforK:๐พ !!
!!= โ!
!
IfH=4cm:๐พ !.!!!
!โ!.!"= !"#$%$!
!"#$
๐พ = 0.435๐พ = 0.869
7. 7.124(samenumberinFourthEdition)
EnergyEquation:๐ป = ๐พ!" + 2๐พ!"#$% + ๐พ!"!!
!!+ ๐ !
!!!
!!
Assumefrictionfactorf=0.020NominallosscoefficientsK:๐พ!"#$% = 1.0
๐พ!" = 0.8๐พ!" = 1.0
2 = 0.8+ 2(1.0)+ 1๐!
2 โ 9.81+ 0.02200.04
๐!
2 โ 9.81๐ = 1.69 ๐/๐
CheckAssumption:CalculateReynolds๐ ๐ = !"!= !.!"โ!.!"
!.!"โ!"!!= 59298
RelativeRoughness:AssumesmoothpipeMoodydiagram:๐ = 0.019sinceitisclosetotheassumptionOK
๐ = ๐ด๐ =๐4 โ 0.04
! โ 1.69 = 0.0021 ๐!/๐ 8. 7.127(samenumberinFourthEdition)
EnergyEquation:Sincepoint1and3areopentoatmosphereandvelocityatpoint1iszero,theenergyequationreducesto:
๐ป = ๐พ!" + 2๐พ!"#$% + ๐พ!"๐!
2๐ + ๐๐ฟ๐ท๐!
2๐
NominallosscoefficientsK:๐พ!"#$% = 1.39๐พ!" = 0.8๐พ!" = 1.0
Assumef=0.20
6 = 0.8+ 2(1.39)+ 1.0๐!
2 โ 9.81+ 0.026.8+ 2๐ป0.03
๐!
2 โ 9.81
ApplyBernoulliatpoint2andexit:!!"#$!"
+ !!"#$!
!!+ ๐ง!"#$ =
!!!"+ !!!
!!+ ๐ง! +
๐พ!"#$%!!
!!+ ๐ !
!!!
!!
0 + 0 + 0 =1.13 ๐๐๐
(1000)(9.81)+
๐!!
2 โ 9.81+ 6 + ๐ป + (1.39)
๐!
2๐+ 0.02
6 + ๐ป0.03
๐!
2 โ 9.81
Solvingsystemofequations:๐ป = 0.64 ๐๐ = 3.348 ๐/๐
๐ ๐ =๐๐ท๐ =
3.348 โ 0.031.31 โ 10!! = 7.7 โ 10!
๐๐๐๐๐ฆ ๐ท๐๐๐๐๐๐: ๐ = 0.018Recalculateusingnewfrictionfactor:๐ป = 0.78 ๐
๐ = 3.477 ๐/๐
๐ ๐ =๐๐ท๐ =
3.477 โ 0.031.31 โ 10!! = 7.9 โ 10!
๐๐๐๐๐ฆ ๐ท๐๐๐๐๐๐ ๐ = 0.018Frictionfactorhasconvergedso๐ป = 0.78 ๐
9. ProblemDuetolengthofsolution,pleasefollowlinkbelowforcompletesolution:
http://web.eng.fiu.edu/arleon/courses/Hydraulic_engineering/Quizzes/Quiz_3_4_sol.pdf10. 11.41(samenumberinFourthedition)
UsingEPANET:
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