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For the fluid flow network shown in fig. Determine pressure at nodes and flow rates in pipe.

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1 Answer
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Element matrix equation,
[K]e=1Re[1111], where, Re=128μheπd4e

Forelement1,d=15mm,he=7.5m
Re=12881047.5π(0.015)4=4828878.87
[K]1=107[2.072.072.072.07]

Forelement2,d=20mm,he=10m
Re=128810410π(0.02)4=2037183.27
[K]2=107[4.914.914.914.91]

Forelement3,d=12.5mm,he=10m
Re=128810410π(0.0125)4=13350884.29
[K]3=107[0.750.750.750.75]

Forelement4,d=7.5mm,he=7.5m
Re=12881047.5π(0.0075)4=24446199.26
[K]4=107[0.410.410.410.41]

c) Element Stiffness matrix
[K]=107[2.07+4.912.074.9102.072.07+0.7500.754.9104.91+0.410.4100.750.410.75+0.41]

d) Global Stiffness Matrix Equation,
[K]{P}e={Q}
107[6.982.074.9102.072.8200.754.9105.320.4100.750.411.16]{P1P2P3P4}={Q1Q2Q3Q4}

e) Imposing boundary condition,
Q1=0.16103m3/sec,P4=0,Q3=0
Q2=0

f) Frame the equation,
107(6.98P12.07P24.91P3)=0.16103 -(1)
107(2.07P1+2.82P2)=0 -(2)
107(4.91P1+5.32P3)=0 -(3)
107(0.75P20.41P3)=Q4 -(4)

Solving equation (2) and (3) we get,
P1=1722.4N/m2P2=1264.32N/m2P3=1589.662N/m2
Substituting in equation (4), we get,
Q4=1600

Flow rate in pipe,
Q1=P1P2R1=1722.41264.324828878.871000
Q1=0.09486lit/sec

Q2=P1P3R2=1722.41589.6622037183.271000
Q2=0.06516lit/sec

Q3=P2P4R3=1264.32013350884.291000
Q3=0.0947lit/sec

Q4=P3P4R4=1589.662024446199.261000
Q4=0.06502lit/sec

Check,
Q1+Q20.16002lit/sec
Q3+Q40.15972lit/sec

Also,
Q1Q3
Q2Q4 - Hence Verified.

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