Hydraulic analysis of skimming flows along stepped chutes

Department of Hydraulics and Sanitation University of São Paulo

Raquel Jahara Lobosco, Prof. Harry Edmar Schulz

Topics:

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1- Introduction

- The hydraulic structure

- Flow over stepped chutes

2- Air Entrainment

3- Research purposes

4-Mathematical models

- The statistical model

- Air concentration

5- Preliminary tests

- Cavitation effects

- Air distribution

- Interface capturing

7- Final considerations

The hydraulic structure:

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Picture acknowledgement: Images (2) and (3) – Engevix Company Image (1) - Stuart Longley

(2)

(3)

(1) Labyrinth spillway

Traditional Chute

Stepped Spillway

The stepped chutes:

Structure

Energy dissipation

Reduction in size Basin

Costs reduction

Enviromental impacts

Steps

Ealier areation

Increase turbulence

Decrease residual energy

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Nappe

Skimming

Large water discharges

Flow Regimes:

Air Entrainment:

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Inlet Profile

Boundary layer

Aeation

Water quality and cavitation

Research purposes:

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The statistical Model:

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Proposed by Chanson (2006)

Air concentration:

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90´

´2

2tanh1)(

hD

yKyC

Comparison with a air buble diffusion model

Proposed by Chanson (2000)

C(y) – A function of the local air concentration

Cavitation damage:

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Adaptation of Chen et al. (2002) results

Air distribution:

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Interface capturing:

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Final considerations:

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There is no simulation literature

data

Cavitation Boundary

layer region Inception

point

Acknowledgements:

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- Financial support was provided by Brazilian research funding agencies

- São Carlos School of Engineering

- Department of Hydraulics and Sanitation

- Rheology and and Turbulence Laboratory