UNIT VI PIPE FLOW – Q.1 Define (i) Hydraulic gradient (ii) Energy gradient (July 2013,July 2014,Jan 2015) Ans:(i) Hydraulic gradient: A Line joining the peizometric heads at various points in a flow is known as Hydraulic Grade Line (HGL) (ii) Energy gradient: It is a line joining the elevation of total energy of a flow measured above a datum, i.e. 2 EGL Line lies above HGL by an amount V /2g. Q. 2Distinguish between compound pipe and equivalent pipe (July 2014, Jan 2015) Ans: Compound pipe Equivalent pipe lent pipe is such that the entire system is replaced by a single pipe of uniform diameter D, but of the same length L=L1+ L2+ L3 such that the head loss due to friction for both the pipes, viz equivalent pipe & the compound pipe are the same. For a compound pipe or pipes in series.    hf hf1 hf2 hf3  8 h fL1Q 8 8 fL2Q fL3Q    (1) g D5 g D5 g D5 2 f 2 2 For an equivalent pipe 8  h fLQ (2)    g D5 f 2 Equating (1) & (2) and simplifying L L1 L2 L3 1  5 5 5 5 5  1 2 3 L  D   L  L L     1 2 3  D5 D5 D5    1 2 3
UNIT – VI PIPE FLOW Q.1 Define (i) Hydraulic gradient (ii) Energy gradient (July 2013,July 2014,Jan 2015) Ans:(i) Hydraulic gradient: A Line joining the peizometric heads at various points in a flow is known as Hydraulic Grade Line (HGL) (ii) Energy gradient: It is a line joining the elevation of total energy of a flow measured above a datum, i.e. 2 EGL Line lies above HGL by an amount V /2g. Q. 2Distinguish between compound pipe and equivalent pipe (July 2014, Jan 2015) Ans: Compound pipe Equivalent pipe lent pipe is such that the entire system is replaced by a single pipe of uniform diameter D, but of the same length L=L1+ L2+ L3 such that the head loss due to friction for both the pipes, viz equivalent pipe & the compound pipe are the same. For a compound pipe or pipes in series. hf  hf1  hf2  hf3 h  8 fL1Q 8 fL2Q 8 fL3Q    (1) f g 2 D5 g 2 D5 g 2 D5 For an equivalent pipe h  8 fLQ    (2) f g 2 D5 Equating (1) & (2) and simplifying L L1 L2 L3 5 5 5 5 1 2 3   D   L 1 5 L  L L   1  2  3   D5 D5 D5   1 2 3 
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