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Unformatted text preview: V 1 f1L1
2g d1 z1 hJ h2 2
V 2 f2L2
2g d2 z2 hJ h3 2
V 3 f3L3
2g d3 z3 hJ (6.111) We guess the position hJ and solve Eqs. (6.111) for V1, V2, and V3 and hence Q1, Q2,
and Q3, iterating until the flow rates balance at the junction according to Eq. (6.110).
If we guess hJ too high, the sum Q1 Q2 Q3 will be negative and the remedy is to
reduce hJ, and vice versa.
Take the same three pipes as in Example 6.17, and assume that they connect three reservoirs at
these surface elevations
z1 20 m z2 100 m z3 40 m Find the resulting flow rates in each pipe, neglecting minor losses. Solution
As a first guess, take hJ equal to the middle reservoir height, z3
calculation (Q3 0) and enables us to get the lay of the land: Reservoir hJ, m 1
40 zi hJ, m
0 fi hJ Qi, m3/h Vi, m/s 0.0267
0.0241 40 m. This saves one 3.43
17.1 Li /di
2000 | v v Since the sum of the flow rates toward the junction is negative, we guessed hJ too high. Reduce
hJ to 30 m and repeat: | e-Text Main Menu | Textb...
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- Spring '08