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HL 2016 09 13

Free surface vortices pose a risk in systems that draw water, such as hydropower intakes and pump stations. Vortex formation is caused by non-uniform flow transitions, high velocity gradients, and obstructions in the flow. Understanding the causes of vortices is crucial for designing effective intake structures.

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9 views1 page

HL 2016 09 13

Free surface vortices pose a risk in systems that draw water, such as hydropower intakes and pump stations. Vortex formation is caused by non-uniform flow transitions, high velocity gradients, and obstructions in the flow. Understanding the causes of vortices is crucial for designing effective intake structures.

Uploaded by

neerajkumar.rs.mec23
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Introduction

Free surface vortices are a concern for any system that draws water by either
gravity or pumping. These can include outlet works at non-hydropower facilities,
hydropower intakes, pump stations, navigation locks, spillway intakes, or any
intake located below a free water surface. With the variety of structure types,
there are also many different types of intake designs. For many hydropower
facilities, a horizontal or an angled penstock is common, while for many pump
facilities, a vertical or inverted vertical intake are common as shown in Figure 1.

Figure 1. Horizontal and Vertical Intake Designs (note, inverted vertical intake not
shown). D represents the pipe diameter, Do is the diameter of the bellmouth intake,
and S is the submergence to the intake (Rindels and Gulliver, 1983)

A vortex is defined as a region of flow that is rotating around an axis that can
either be straight or curved. Vortex formation occurs when the transition from
open channel (free surface) flow to pressure flow is not smooth and uniform.
When flow does not maintain gradual transitions that attempt to keep a uniform
velocity distribution and acceleration, then vortices can occur (Bottazzi, Floreale
and Molina, 2007). The main causes of vortex formation are non-uniform
approach flow to the intake, shear layers of high velocity gradients and rotational
wakes caused by obstructions in the approach flow (Durgin and Hecker, 1978).
Chang (1977) lists these sources as well as flow passing diffusers and baffles that
can also cause small eddies to shed and that any swirl action in the approach flow
can be magnified as it converges at the intake due to the conservation of angular
momentum. Vortices can also be formed as flow passes piers between intake
gates as they are located directly adjacent to the opening and span the full depth

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