Proportional Weirs as Velocity Controlling Devices

by Nagar S. Lakshmana Rao, Prof.; Civ. Engrg. Dept., Indian Inst. of Sci., Bangalore, India,
Duraiswamy Chandrasekaran, Asst. Prof.; Soil and Water Conservation Engrg. Dept., Coimbatore, India,

Serial Information: Journal of the Hydraulics Division, 1977, Vol. 103, Issue 6, Pg. 633-648

Document Type: Journal Paper

Abstract: Of the many factors that govern the settling phenomenon, the flow velocity in the settling tanks can be controlled favorably by fixing suitably designed weirs at the outlets of the tanks. The velocity at the bottom should not dislodge the particles that have already settled. These requirements might be met with by velocities which are controlled to be constant with respect to the depth of flow, or velocities which reduce linearly with increasing depth or velocities that vary inversely with the depth. To achieve these types of velocity control, new proportional weirs have been designed. Very near to the outlet of the tank, over a small length, the flow was found to be turbulent and noncompliant with the expected type of velocity control. This small length of the disturbance may be provided over and above the theoretical settling length of the tank, for efficient sedimentation.

Subject Headings: Fluid velocity | Flow control | Weirs | Sedimentation tanks | Particle velocity | Turbulent flow | Settling velocity | Linear flow |

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