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Case side-channel Afferden-Deest

Impact of grid refinement

Deltares Software Dagen

Universiteit Twente: Erik ten Hagen, Suzanne Hulscher, Jord Warmink HKV lijn in water: Freek Huthoff, Joana Vieira da Silva, Andries Paarlberg Deltares: Aukje Spruyt, Arthur van Dam, Herman Kernkamp

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Contents

Part 1

• Test models

– Differences WAQUA - Delft3D - Flexible Mesh

Part 2

• Case Afferden-Deest

– Comparison Flexible Mesh - WAQUA

– Impact grid refinement

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test models

Simple rectangular model

– Comparison with analytical estimation

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test models

Simple rectangular model

– Comparison with analytical estimation

Test model Waal

– Differences WAQUA - Delft3D - Flexible Mesh in complex model

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Rectangular test model

• 2000x200 meter

• Horizontal bed (h=5.0 m) with sill (h = 5.3 m)

• Constant discharge upstream (1515 m3/s)

• Constant waterlevel downstream (11.70 m)

• Uniform roughness (Colebrook-White, k = 0.2 m)

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Rectangular test model

Analytical estimation:

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Rectangular test model

Chézy roughness using Colebrook-White:

Used in Delft3D and Flexible Mesh

Used in WAQUA

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Rectangular test model

Chézy roughness using Colebrook-White:

Used in Delft3D and Flexible Mesh

Used in WAQUA

Larger friction in Delft3D and Flexible Mesh!

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Rectangular test model

Results (Default settings)

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Rectangular test model

Colebrook-White formula of WAQUA in Flexible Mesh

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test model Waal

Differences WAQUA–Delft3D–Flexible Mesh for a

more complex model

– Schematization of 40 km Waal (Nijmegen – Tiel)

– Constant upstream discharge (16000 m3/s at Lobith)

– Constant downstream waterlevel (10.38 m +NAP)

– Friction

• Uniform Colebrook-White roughness (k = 0.2 m)

• Trachytopes (spatially variable and depth dependent roughness)

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test model Waal (Colebrook-White)

Results (default settings)

Maximum water level difference FM - WAQUA = 21.5 cm

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Conveyance2D

WAQUA

Flexible Mesh

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Weirs and dry points

Weirs

Dry points

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test model Waal (Colebrook-White)

Water level difference (Flexible Mesh – WAQUA)

Conveyance2D Colebrook-White

Overlaten Droge punten

Default settings FM FM X X

Overlaten FM FM X

Droge punten FM FM X

Bodeminstelling WAQUA FM X X

Colebrook-White FM WAQUA X X

Bodeminstelling + Colebrook-White

WAQUA WAQUA X X

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test model Waal (Trachytopes)

Results (default settings)

Maximum water level difference FM - WAQUA = 37.6 cm

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test model Waal (Trachytopes)

Waterlevel difference Flexible Mesh-WAQUA

Conveyance2D Colebrook-White

Overlaten Droge punten

Default settings FM FM X X

Bodeminstelling + Colebrook-White

WAQUA WAQUA X X

Overlaten WAQUA WAQUA X

Droge punten WAQUA WAQUA X

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Conclusion test models

• Large differences from bed and friction settings (Conveyance2D and Colebrook-White formula)

• Differences from modelling energy losses by weirs

• Use WAQUA setting for bed and Colebrook-White formula to compare Flexible Mesh with WAQUA

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Case Afferden-Deest

• Side-channel at Afferden and Deest (River Waal)

Bron: Rijkswaterstaat

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Case Afferden-Deest in WAQUA

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Research plan – comparison

Compare Flexible Mesh results with WAQUA

• Waalmodel without side-channel (reference) – Run Flexible Mesh with WAQUA-settings for design high

water wave (16000 m3/s at Lobith) and 1995 flood wave

– Compare Flexible Mesh with calibrated WAQUA model and 1995 measurements

• Waalmodel with side-channel – Run Flexible Mesh with WAQUA-settings for design high

water wave (16000 m3/s at Lobith) and 1995 flood wave

– Compare Flexible Mesh with WAQUA model

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Research plan – study area

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First results (comparison)

Waalmodel without side-channel (Pannerdense Kop)

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First results (comparison)

Waalmodel with side-channel (Pannerdense Kop)

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First results (comparison)

Waal without side channel

Waal with side channel

Pannerdense Kop 13.8 cm 17.6 cm

Nijmegen 9.1 cm 7.5 cm

Tiel 2.9 cm -0.8 cm

Water level difference Flexible Mesh - WAQUA

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First results (comparison)

Flow velocity (m/s) in side channel

WAQUA

Flexible Mesh

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Research Plan – Grid refinement

Assess impact grid refinement

• Waalmodel without side-channel (reference) – Refine grid Waal-channel at Afferden-Deest

– Determine when convergence is reached

• Waalmodel with side-channel – Refine grid side-channel Afferden-Deest

– Determine when convergence is reached

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Grid refinement

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Grid refinement

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Grid refinement

Example allignment

Bron: Herman Kernkamp, 2014

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Summary

• Differences from bed setting and Colebrook-White formula WAQUA settings used in

Flexible Mesh

• Higher water levels in Flexible Mesh

• Flexible Mesh solution for representation complex geometry

More accurate results for side-channel in

Flexible Mesh??