Open Water Disposal of Sediments in Ports and Harbors

Numerical and Analytical Studies of Single and Multiphase Starting Jets and Plumes Ruo-Qian (Roger) WangDept. of Civil and Environ. Eng., MIT

Thesis Committee: Dr. Heidi NepfDr. Ole MadsonDr. Adrian Wing-Keung LawDr. Roman StockerPhD advisor: Dr. Eric Adams

Thank you for your introduction. Hi everyone! Thank you for being here. Today, I am very happy to share my research on the physics of sediment disposal in ports and harbors.

Use Your mouth, raise your voice more often!!! Think about whats next!1

Jets and Plumes2Oil spill plume

Jack Cook, WHOI

Sneezing (http://blogs.discovermagazine.com)Spores spreading (http://blogs.discovermagazine.com)

Whats dredging and sediment disposal?3

A dredge working on Lake Michigan. (EPA)

First of all, whats dredging? Dredging operations include two components. First, it means excavation from the bottom of the water. And second, it means disposal of the dredged materials. The picture shows a dredger barge excavating sediments in the Lake Michigan.3

Where do we need dredging? I. Land reclamation4stefaniestoelen.blogspot.com

Dredging is applied in various fields. The first application is in land reclamation. I believe many of you have seen this picture before. Do you know where it is? Yes, this is the Palm island in Dubai. Dredging can be used to build such beautiful artificial island.4

A Singapore Example

http://www.wildsingapore.com/wildfacts/concepts/loss.htm5

Lets see another example from Singapore. This is the coastal line of Singapore in 1950 and this is 2002. You can see all the red areas are created by land reclamation, including the new airport and all the industrial islands. Singapore still has an ambitious plan to expand its land area, but they have no sand resources. So they have to import from its neighbors like Malaysia and Indonesia. Recently, these two countries stop selling sands to Singapore, because a small island disappeared in Indonesia due to sand smuggling. As a result, Singapore has to purchase sediment from farther countries like Vietnam or Cambodia, which dramatically increased the cost of sediment, from $ 0.8/m^3 to $8.5 per cubic meter. Therefore, they need to conserve the use of sediment in their future projects. 5

Where do we need dredging? II. Navigation6http://www.travelskyline.net/view-crystal_symphony_panama_canal-1024x768.html

Another important application of dredging is in Navigation. This is the Panama canal. This canal is not only important in global trade, it also sets the standard of the ship manufacturing industry. The size of the canal limit the size of the ship that can go through. Now, the canal is under expansion and larger boats can be manufactured. It means the US also need larger and deeper ports to accommodate the enlarged ships. These projects require a lot of dredging.

If your ship is too big and cannot pass through this canal, then it is useless to transportation from the New York to the LA. Now this canal is under expansion, which itself requires a lot of dredging. In addition, ports in the US need have to be bigger and deeper for the future trading demand.6

Where do we need dredging? III. Environmental Restoration

7Lindsey B., Grade 8, North Carolina. One of the 2012-2013 winners in the Keep the Sea Free of Debris art contest

Dredging is also an important tool for environmental remediation. I really like this picture. Look at those cute shellfish busy cleaning the bottom of the harbor! Why is that? Because the sediment is dirty! By estimation, the US dredges around 200 million m3 of sediments every year. And 10 to 20% are contaminated by PCB, DDT, or heavy metals. Therefore, people need a special treatment to those dredged materials.7

http://www.bostonharborbeacon.com/A story about the Boston Harbor Navigation Improvement Project

8Source: Great Lakes Dredge and Dock Company

www2.epa.gov

This issue is especially significant in the Boston Harbor Navigation Improvement Project. The sediment in Boston Harbor is heavily contaminated by toxic materials due to a poor waste water treatment plan in the past. The toxic dredged materials were disposed using a technique called Aquatic Cell Disposal. The basic produces are shown here. This technique is encouraged by the Corps of Engineers and promoted by EPA.

Navigation Improvement project. Because this city used to have a poor waste water treatment plan, now the dredged materials are toxic. To solve this problem, the project used a technique called confined aquatic cell disposal, which is encouraged by corps of engineers and promoted by EPA. 8

Where do we need dredging? IV. Flood Prevention and Beach Nourishment

9http://www.theguardian.com/environment/2014/jan/29/flooding-england-private-funding-scheme

Dredging is important for flood prevention. A poorly dredged river can cause the rise of river bed and therefore flooding. The people live near this river in England are obviously not happy. They need dredgers!9

Coastal Protection

Eroded beach after the Hurricane Sandy in Montauk10

Long island also needs dredging for flood prevention and beach nourishment. This is the beach in Montauk after the Hurricane Sandy. The similar challenges can be seen in many places here. The corps of engineers is considering a series of coastal line protection projects as shown here. Therefore, dredging will be a local civil engineering topic for years.10

Applications of DredgingLand reclamationNavigationEnvironmental restorationFlood prevention and beach nourishmentMiningFishingConstruction (e.g. ports, bridges, and other infrastructures)11

11

OutlineResearch objectivesNumerical method a multi-scale challengePhysics of settling particle cloudsMain cloudTrailing stemTheoretical model of vortex ringsSummary and a case study12

In the following talk, I will first introduce our research objectives and the numerical method. Then, I will talk about our numerical results and the physics of settling particle clouds, including the main cloud and the trailing stem. Next, I will introduce a theoretical model that we have derived. At last, I will summarize my talk and outline my future research plan.12

Research ObjectivesAccurate placementTurbidity reductionDissolved contaminants trackingOperation guidance

Save costReduce environmental impact

13

----- Meeting Notes (3/6/14 15:17) -----remove "the", put Koh and Chan 197313

State of knowledge in particle cloudsKoh and Chang (1973)Ad hoc loss mechanism: Abdelrhman and Dettmann (1993) and Johnson and Fong (1995) STFATE

GravityParticle Cloud

Drag + Added Mass

Entrainment

Phase separation in the main cloudTrailing stem

Traditionally, people used Koh and Changs model to describe the particle cloud. They treat the cloud as a mixture of particles and fluid and take account of the drag and added mass force, and the entrainment to allow its growth. Later on, researchers added ad hoc loss mechanism to allow the particles and fluid to separate. However, we found some significant discrepancies between their model and our lab observation. The right-hand side is a photo image from our lab. We released the particles together with rodamin dye. So the blue area in the photo are the particles and the red area is the tracer dye, which represents the dissolved contaminants released with the sediment disposal. From this picture, we can see the Koh and Changs model misses two important characteristics: first, the phase separation between the particle and the fluid phase is not captured. Second, the trailing stem behind the main cloud is not included in their model. Therefore, we try to use our own study to improve the model. 14

Numerical models can help our understandingCFDEMCFD-DEM couplingOpenFOAMLarge Eddy SimulationsLIGGGHTSParticle TrackingOne-wayTwo-wayFour-wayFour-way+Passive ParticlesParticle-fluid interactionParticle-fluid Interaction+Particle-collisionParticle-fluid Interaction+Particle-collision+Coalesce and break up15

----- Meeting Notes (3/6/14 16:17) -----break up15

Governing Equations

// Lagrangian Track// Neglect History and Wall interaction termsFluidSolid// Fractioned N-S equation

My Contributions16

16

Particle Collision

17

17

A Multi-scale Dilemma

kE2/EnergyInputParticleSizeGrid cell

18

18

A proposed scale-separation solution

Characteristic cell volume @ center ~=1.5 particle volume 2nd order discretization in space

4th order discretization in space

kE2/EnergyInputParticleSizeGrid cell

19

19

Comparison to experiments validates the present numerical schemeNumerical SimulationLab Experiment

20

Explain colorbar, pausein middle explain20

A series of numerical simulations was performed 15 CasesParticle diameter dp=0.26-0.73 mmTotal massMtotal=2-3 gRelease radius R0=3.9-9 mmAspect ratioA=H/R0=1.2-1521

H2R0

No details of numbers----- Meeting Notes (3/6/14 16:17) -----small S

Definition of the phase separation

22Phase separationin the main cloudTrailing stem

22

Phase SeparationSeparation time bySeparation height and time

23(Wang et al., submitted to IJMF)

Rayleigh number is important variable, A is new. Original form23

Two-phase Particle Cloud Structure

24

24

Settlement of Clouds

Solid PhaseFluid Phase

25

A is newTwo-phases are new, fonts

25

Growth of Clouds

Solid PhaseFluid Phase26(Wang et al., submitted to IJMF)

Solid and fluid, remove mono-disp, figures first, collaps26

What happen if the particles are not the same in size?

CasesDistr.dp (mm)d50 (mm)w50 (cm/s)wmax (cm/s)Bu1Top-hat0.26-0.730.618.810.6Bu2Top-hat0.26-0.760.649.311.2Bu3Top-hat0.43-0.600.537.68.7Bg1Gaussian0.46-0.570.527.48.3Bg2Gaussian0.22-0.810.578.212.0

27

Prev are also mono, now its poly, numb distr27

ThermalPoly-dispersion in Thermal and Dispersive stages

Thermal phase d50Dispersive phase dmaxBu1Bu2Bu3Bg1Bg2BeforePhaseSeparationAfterPhaseSeparation28(Wang et al., submitted to IJMF)

Thermal and dispersive, separate from labels28

How to extrapolate experimental results from lab to field scale?29

LabFieldhttp://automaticburger.blogspot.com/http://www.disboards.com/showthread.php?p=42145760

29

Similarity Law from Small- to Full-scaleSolid phase front

CaseR (cm)M (g)Aspectws(cm/s)dp (mm)NpRaB0.931.197.30.5117k41BL43.61921.1914.61.008143k41BL1614.412,2881.1929.22.336736k41

Wang et al. (submitted to JHE)30

30

Suggestion to Improve Field Operationsyosemite.epa.gov

www.southchinashipyard.com31

----- Meeting Notes (3/6/14 16:17) -----OperationsOverlay31

Entrainment Coefficient

32

Entrainment Coefficient

33

Deposition Pattern

34DAMO contribution 191, Oct 2011

How can we get rid of the trailing stem?

35(Wang et al., 2011, Featured on the cover of Physics Fluids.)

----- Meeting Notes (3/6/14 16:17) -----get rid of the trailing stem35

The Aspect Ratio Determines the Presence of the Trailing Stem

LD

L/D=2.0L/D=3.8L/D=12.0Gharib et al. 1998Critical L/D

36

1

2

36

The Buoyancy Effect on the Critical L/D

Wang et al (2009, 2011), Phy. Fluids37

----- Meeting Notes (3/6/14 16:17) -----Stress the experimental data37

Numerical studies can help estimate the particle effect on formation number38

----- Meeting Notes (3/6/14 16:17) -----on formation number38

A series of multi-phase simulations was performedParticle Diameterdp=500 mm (B), 256 mm (D)Volume Fraction=0% - 31%

Particle Densityp=400 2500 kg/m3 49 Cases39

39

Buoyancy of Particles Increases the Critical L/D40

40

Concentration and size of Particles Decreases the Critical L/D41Concentration EffectParticle Size effect

(Wang et al., in preparation)

41

The designs should not be too deepyosemite.epa.gov

www.southchinashipyard.com42L/D < Formation Number

----- Meeting Notes (3/6/14 16:17) -----OperationsOverlay42

Whats the essence of the unified phenomenon?43

----- Meeting Notes (3/6/14 16:17) -----unified43

A steady state solution?

ExperimentNumerical Simulation44

44

At steady state, in high Reynolds number but laminar flow

45

45

The present model matches the numerical simulations better

SimulationsLinear ModelLow Reynolds numberThe Present46(Wang et al., submitted to AMM)

46

SummaryA numerical method for multiphase Large-Eddy Simulations is developed

Physics of two-phase settling particle clouds is analyzedInitial aspect ratio, phase separation, penetration and growth

Trailing stem presence of starting plumes is determined

A theoretical solution to vortex ring is derived47

----- Meeting Notes (3/6/14 16:17) -----Physics of two-phaseTrailing stem prevents the presence of trailing ste,47

A Case Study48

H=30 mAverage particle diameter dp=0.5 mmParticle density p=2.5 g/cm^3Settling velocity ws=7.1 cm/sSettling time Tsp=2.9 minTotal Buoyancy B=1086 NVolume V=0.089 m^3

Check A=1