user's manual for corhyd: an internal diffuser hydraulics model - IfH

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A reasonably good discharge distribution along the diffuser (first bar-chart, Fig. 26) with maximum deviations from the mean discharge of not more than 5 % of the mean discharge (second bar-chart, Fig. 26) is obtained. Due to different pressure losses along the diffuser pipe and the port/riser configurations (line in second bar-chart, Fig. 26) the discharge is increasing here to the seaward end. Usually diffuser cannot be laid horizontally as assumed here, because of the sloping bathymetries. Therefore another calculation is shown in Fig. 26 on the right side, with a sloped diffuser with an assumed elevation difference of 3 m along the diffuser length of 449 m (= 6.7 % 0 ). The discharge deviation in this case is almost neglectable, which is due to a higher pressure difference between the sewage in the diffuser pipe and the heavier ambient water especially in deeper waters at the seaward diffuser end. The flow velocities in the diffuser pipe continuously decrease in seaward direction (fourth bar-chart, Fig. 26). For the last 25 port locations velocities below 0.5 m/s are predicted, which might cause sedimentation of particles in the diffuser. This number reduces for peak flows (Q = 12 m³/s), (Fig. 27), to about 16 but still the last 75 m of the diffuser have velocities much lower than 0.5 m/s. That means, that even for maximum discharges scouring velocities are not obtained for the end part of the diffuser. Considering, that the present treatment is only coarse screening, this might cause problems for the diffuser end part. Fig. 26: Flow characteristics for design flow. Left: horizontal diffuser, right: sloped diffuser 3m/449m. Top-down: Individual riser flow distribution along diffuser, riser flow deviation from mean, losses in port/riser configurations (line), port and jet discharge velocities and diffuser pipe velocities, port and diffuser diameter (lines) Institut für Hydromechanik, Universität Karlsruhe 55
Fig. 27: Flow characteristics for different flows. Left: maximum flow Q max = 12 m³/s, right: design flow Q d = 8 m³/s. Top-down: Individual riser flow distribution along diffuser, riser flow deviation from mean, losses in port/riser configurations (line), port and jet discharge velocities and diffuser pipe velocities, port and diffuser diameter (lines) Fig. 28 shows the flow characteristics for several intermediate flowrates. A slight variation of the discharge distribution can be observed for these flow variations only for the sloped diffuser. The changes of the total head for increasing discharges are shown in Fig. 29. But the most critical point stays the low scouring velocity, which affects almost 40 % of the diffuser (169 m and about 60 ports) for the flowrate of 6 m³/s, which is presently the average flow. Institut für Hydromechanik, Universität Karlsruhe 56
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Universität Karlsruhe Institut fü
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Acknowledgments The authors like to
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10.1 Local loss formulations: Divis
Page 7 and 8: 1 Introduction CorHyd is a computer
Page 9 and 10: Fig. 1: Outfall configuration showi
Page 11 and 12: where j 0 denotes the buoyancy flux
Page 13 and 14: 2.4 Manifold processes Pipe hydraul
Page 15 and 16: Fig. 8: Local port/riser branch los
Page 17 and 18: Table 2: Local loss formulations Ty
Page 19 and 20: Gradual contraction (Idelchik 1986)
Page 21 and 22: Where H denotes the headloss, V duc
Page 23 and 24: Table 3: Equivalent sand roughness
Page 25 and 26: Institut für Hydromechanik, Univer
Page 27 and 28: For a constant sea water level and
Page 29 and 30: (16) solved for r in (15) and assum
Page 31 and 32: 3.1.4 Automatic implementation of l
Page 33 and 34: elevation difference between diffus
Page 35 and 36: The iteration stops if the differen
Page 37 and 38: Table 4: CorHyd subroutines and the
Page 39 and 40: 4 Data Input Input can either be do
Page 41 and 42: (ρ 0,max > ρ 0 ). Further sensiti
Page 43 and 44: should allow for riser velocities,
Page 45 and 46: Fig. 19: First input sub-window for
Page 47 and 48: 10 7050.000 0.000 -2.500 11 7000.00
Page 49 and 50: Fig. 22: Graphical output: Energy a
Page 51 and 52: given dilution requirements and maj
Page 53 and 54: 6.3 Off design conditions It was co
Page 55 and 56: Table 5: Sensitivity of involved pa
Page 57: Fig. 24: Side view and cross sectio
Page 61 and 62: under different flow conditions. Th
Page 63 and 64: Fig. 32: Side view and cross sectio
Page 65 and 66: Fig. 34: Flow characteristics for:
Page 71 and 72: Table 6: Comparison of construction
Page 73 and 74: seaward end, which can be prevented
Page 75 and 76: Especially for this long diffuser a
Page 77 and 78: Jirka, G.H., Doneker, R.L. and Hint
Page 79 and 80: 10 Annex 10.1 Local loss formulatio
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user's manual for corhyd: an internal diffuser hydraulics model - IfH

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