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Kinematic characteristics of flows in transition sections of unlined canals
Conclusions In the case of a nonprismatic form of the cross section of a canal on transitions the form of the free surface is determined by the slope of the bottom of the transition (sustaining or adverse), and the rate of contraction or expansion of the channel affects mainly the steepness of the particular type of curve of the free surface of the flow, as well as its dimensions along the length of the canal.In the case of transitions of a canal from narrow and shallow to wider and deeper, for all variants of the change in the angle of expansion and, consequently, sustaining slope of the bottom of the transition there are extremely unfavorable hydraulic conditions of the flow on the transition and in the downstream stretch of the canal, which is determined at the entrance of the transition by separation of the boundary layer from the bulk of the flow with the formation of a nonworking zone with reverse currents along the banks on a length of more than 30B1.On transitions with an adverse slope of the bottom, the length of the transition is determined by the angle of expansion of the sides of the transition. On transitions with a sustaining slope of the bottom, their length is determined by the slope of the bottom.In the case of joining canals with a transition gradually expanding in plan and an adverse slope of the bottom, it is recommended to take an angle of expansion of the sides of 4–6°.In the case of joining canals with a transition gradually narrowing in plan and a sustaining slope of the bottom, the necessary length of the transition is determined by the ratio of the widths of the upstream and downstream stretches of the canal, as well as by the difference in the maximum depths of these sections, making possible a determination of the slope of the bottom of the transition and its length (Fig. 5).It is recommended to design transitions within stronger soils.
Kinematic characteristics of flows in transition sections of unlined canals
Conclusions In the case of a nonprismatic form of the cross section of a canal on transitions the form of the free surface is determined by the slope of the bottom of the transition (sustaining or adverse), and the rate of contraction or expansion of the channel affects mainly the steepness of the particular type of curve of the free surface of the flow, as well as its dimensions along the length of the canal.In the case of transitions of a canal from narrow and shallow to wider and deeper, for all variants of the change in the angle of expansion and, consequently, sustaining slope of the bottom of the transition there are extremely unfavorable hydraulic conditions of the flow on the transition and in the downstream stretch of the canal, which is determined at the entrance of the transition by separation of the boundary layer from the bulk of the flow with the formation of a nonworking zone with reverse currents along the banks on a length of more than 30B1.On transitions with an adverse slope of the bottom, the length of the transition is determined by the angle of expansion of the sides of the transition. On transitions with a sustaining slope of the bottom, their length is determined by the slope of the bottom.In the case of joining canals with a transition gradually expanding in plan and an adverse slope of the bottom, it is recommended to take an angle of expansion of the sides of 4–6°.In the case of joining canals with a transition gradually narrowing in plan and a sustaining slope of the bottom, the necessary length of the transition is determined by the ratio of the widths of the upstream and downstream stretches of the canal, as well as by the difference in the maximum depths of these sections, making possible a determination of the slope of the bottom of the transition and its length (Fig. 5).It is recommended to design transitions within stronger soils.
Kinematic characteristics of flows in transition sections of unlined canals
Elimov, V. I. (author) / Rabkova, E. K. (author)
1989
Article (Journal)
English
BKL:
56.30
Wasserbau
Local classification TIB:
770/6550/8000
Kinematic characteristics of flows in transition sections of unlined canals
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