dsd-int 2016 investigation of sediment transport processes in mine pit lakes induced by wind waves -...

Investigation of sediment transport processes in mine pit lakes induced by wind waves

Delft3D - User Days

Torsten Heyer & Carsten Schulz

Faculty of Civil Engineering Institute of Hydraulic Engineering and Technical Hydromechanics

Delft, November 2nd, 2016

Outline

• Introduction

• Model setup

• Results

• Summary & perspectives

Delft, 02/11/2016 Sediment transport in mine pit lakes Slide 2 of 21

Introduction

Model setup

Results

Summary & perspectives

Introduction

Delft, 02/11/2016 Sediment transport in mine pit lakes

source: www.sitemap.de

Slide 3 of 21

Lusatia

Introduction

Model setup

Results


Introduction


source: www.umweltveraendern.de

Slide 4 of 21

IntroductionInvestigation area


• former Lusatia brown coal mining area near Cottbus

• open-cast pits – ongoing flooding to create lakes for recreational purposes establishment of tourism industry

Lake Meuro

Introduction

Model setup

Results


Slide 5 of 21


• Flooding period:

2007-2017

• Final water level:100,50 m NHN

• Maximum depth:≈ 50 m

• Main wind direction:

o W – SW

• Fetch length:

o NW-SO ≈ 5,1 km

o NO-SW ≈ 2,5 kmLake Meuro, current and final (red) water level

[source: Google Earth, 2015]

IntroductionLake Meuro

Introduction

Model setup

Results


Slide 6 of 21


• Stability of bank slopes (fine-grained excavation material)

• Erosion and deposition of sediments (inlets, marinas) long- and cross-

shore transport

• Acidification due to pyrit activation (waves, groundwater inflow)

...and many more

Lake Meuro, current and final (red) water level[source: Google Earth, 2015]

IntroductionChallenges

Introduction

Model setup

Results


numerical simulations using Delft3D (WAVE & FLOW)

Slide 7 of 21

Model SetupComputational grids

Storm simulation Long-term simulation

Wave forecast

Vertical discretization (s-Layer, 15)


Introduction

Model setup

Results


source: Delft3D manual

Slide 8 of 21

• WSP=94/98/100,5 m NHN

WSP=94 mNHN

WSP=98 mNHN WSP=100,5 mNHN

Model SetupBathymetry & shoreline


Introduction

Model setup

Results


Slide 9 of 21

• Base data: samples along the shoreline

Model SetupSediment data

Region D50

[mm]

Sediment 1 0,175

Sediment 2 0,212

Sediment 3 0,405

• Non-cohesivematerial

• Soil types:

o SU

o SU*/ST

o SE


Introduction

Model setup

Results


Slide 10 of 21

• Revetment zones no erosion; deposition possible

Model SetupSediment data


Introduction

Model setup

Results


Slide 11 of 21

• Simulation (WSP=100,5 m NHN) of:

• Storm event (Tn=20 years) design parameters (revetments, etc.)

• 1 year wind event (year 1990; measured) long-term sediment

transport

• Storm event: w10.20a= 29,2 m/s (steady wind field)

• Wind year: w10.max= 18,2 m/s (unsteady wind field)


Model SetupWind data

0

5

10

15

20

25

30

35

0° 60° 120° 180° 240° 300° 360°

W10

[m/s

]

Direction

T = 1aT = 2aT = 5aT = 10aT = 20aT= 100a

Introduction

Model setup

Results


Slide 12 of 21

Model SetupTransport formula


Introduction

Model setup

Results


Slide 13 of 21



• Best fit: Bijker (1971); also tested: van Rijn, Soulsby

Introduction

Model setup

Results


Slide 14 of 21

• Example: WSP 98,0 m NHN; 260°; w10,20a=29,2 m/s; tE=2,5h

ResultsWave forecast


Introduction

Model setup

Results


Slide 15 of 21

• Example: WSP 98,0 m NHN; long-term simulation (year 1990)

• Calculation of total transported volume and check of volume balance

ResultsErosion/deposition


erosion deposition

Introduction

Model setup

Results


Slide 16 of 21

• Example: WSP 98,0 m NHN; Long-term simulation (year 1990)

ResultsErosion/deposition


Introduction

Model setup

Results


Slide 17 of 21

• Example: WSP 98,0 m NHN; Long-term simulation (year 1990)

ResultsSediment transport rate


Introduction

Model setup

Results


Slide 18 of 21

• Effects of piers and floating breakwaters

Wave height, KZ, 260° Erosion/Deposition, LZ

withoutmeasures

withmeasures

ResultsExamination of variants


Introduction

Model setup

Results


Slide 19 of 21

• Wind-induced sediment transport (longshore, cross-shore) could be simulated by Delft3D (Wave/Flow)



Introduction

Model setup

Results


Further investigations planned regarding:

• appropriate transport formula(validation of the physical model test in wave flume)

• Possibility of model calibration(recalculation of an eroding shoreline over 6 years)

• Water quality issues

Questions/tasks:

• Reduction of computational effort (time) for long-term simulations (subgrids, scale factor, …)

• Mixed sediments effect of decomposition

• (result) file size reduction (preselected parameters only?)Slide 20 of 21


Slide 21 of 21

Thank youfor your attention!

Technische Universitaet DresdenInstitute of Hydraulic Engineering and Technical Hydromechanics (IWD)August-Bebel-Straße 3001219 DresdenGermany

: +49-(0)351-463 33874: +49-(0)351-463 37120: https://tu-dresden.de/bu/bauingenieurwesen/iwd: [email protected]


Grid parameters Unit Morphodynamics Wave prediction

Storm simulation

Long-term simulation

Number of M-nodes 152 73 51

Number N-nodes 302 138 101

minimum Area [m²] 45 114 943

mean Area [m²] 386 1.417 3.431

maximum Area [m²] 665 5.000 7.961

Number of nodes 45.904 10.074 5.151

Number of elements 32.075 8.446 5.000

Model SetupComputational grids


Introduction

Model setup

Results


Slide 23



• Best fit: Bijker (1971); also tested: van Rijn, Soulsby

Introduction

Model setup

Results


Slide 24

dsd-int 2016 investigation of sediment transport processes in mine pit lakes induced by wind waves -...

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