Simulating River Ice and Debris Problems using Discrete Element Modeling Mark Hopkins, Steven Daly, and Carrie Vuyovich

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Simulating River Ice and Debris Problems using
Discrete Element Modeling Mark Hopkins, Steven
Daly, and Carrie Vuyovich

• US Army Engineering and Research Center
• Cold Regions Research and Engineering Lab
• Hanover, NH USA

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Discrete Element Modeling of River Problems

• Ice jams
• Debris Accumulations
• Design of breakup ICS
• Design of floating booms
• Operation of locks and dams
• Design of ice control measures such as ice flow
  bubblers
• Interaction of ships, towboats and barges with
  ice and debris

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Discrete Element Modeling of River Problems

• No lower limit on ice or debris concentration or
  requirement on hydrostatic equilibrium
• Wide range of flow conditions can be simulated
• Detailed time-varying information can be
  extracted
• Realistic animations
• Tool for design of control structures and flow
  routing.

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SIMULATION OF RIVER ICE JAM FORMATION

• Simulate Cazenovia Creek Model Study
• Realistic river channel geometry
• Direct comparison of model and simulation stages
  and forces

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Simulation of River Ice Jam Formation

• Discrete element ice model
• Channel model
• Hydraulic model
• Ice/Water interface

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DISCRETE ELEMENT MODELING

• Computer simulation of particle systems such as
  ice jams
• Store position, orientation, shape, and velocity
  of each particle
• Dynamics of system evolves from contact and body
  forces on particles (Fma at each contact)

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Mechanics of the Ice Model

• Three-dimensional, discrete element ice model
• Ice floes are disks with variable aspect ratio,
  friction coef, drag coef, and density
• Floe orientation specified using quaternions (4
  parameter representation of floe orientation)

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SIMULATION AND MODELING OF RIVER ICE
Normal Contact Force Viscous-elastic (Spring and
dashpot) Tangential Contact Force Coulomb
friction
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Mechanics of ice model

• Identify neighboring floes (using 3D grid)
• Determine where contacts exist
• Calculate force at each contact
• Resolve forces and torques on each floe
• Solve equations of motion of each floe
• Advance time one time step (10-3 s)and repeat.

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Channel Model

• Use surveyed channel cross-sections
• Linearly interpolate to regular intervals
• Triangulate between cross-sections
• Fill triangles with discrete elements
• Variable roughness and friction on bed and banks

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Channel Cross-sections
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Discrete Element River Bed
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Hydraulic Model

• Unsteady flow model (able to handle any insult
  the ice dishes out)
• 1-Dimensional depth-averaged continuity and
  momentum equations
• Open under ice flow and porous flow regimes
• 4 point-implicit, finite difference solution with
  Newton-Rapheson iteration

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Ice/Water Interface
ICE
WATER

• Water drag on floes
• Ice Velocity
• Porosity of ice cover
• Bottom profile of ice cover

• Water elevation
• Water velocity
• Porous flow drag
• Hydrostatic pressure differential

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Ice Behind a Temporary Barrier
At the Beginning of a Simulation
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Snapshots from a simulation

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Hydrographs. -90m downstream of ICS, 3m
immediately upstream of ICS 330m upstream of
ICS (downstream of "virtual" ice barrier)
388m upstream of ICS upstream of "virtual" ice
barrier
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Moments on ICS
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Forces acting in simulation
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TESTING ALTERNATIVE BRIDGE DESIGNS AT BUCKLAND, AK

• Realistic river channel from surveyed
  cross-sections.
• 4 Bridge Pier Designs
• Ice runs with uniform sized floes
• Break-up ice runs with mixture of large and small
  floes
• 2 River stages.
• Study for Alaskan DOT

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SIMULATION OF ICE BOOM OPERATION

• Direct comparison between DEM simulations and
  physical model study.
• Used experimental parameters in simulations

• Direct comparison of ice retention and forces

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Forces Rough Walls
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Simulate vessel in ice-filled channel

• Disk-shaped floes
• Forces and moments on vessel
• Ice shove beneath neighboring ice sheets

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Simulation of Lock and Guard Wall
Water velocity field from HYVEL2D courtesy of R.
Stockstill (CHL)
DEM model of lock approach showing guard wall and
lock entrance
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ICE PASSAGE THROUGH A GUARDWALL
Simulating ice passage through a gap in a guard
wall using water velocities from HYVEL2D.
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PROBLEM
Debris accumulation at locks and dams
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DEBRIS PASSAGE THROUGH A GUARDWALL
Simulating debris passage through a gap in a
guard wall using water velocities from ADH
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DEBRIS TRANSPORT IN A CHANNEL
ADH mesh is used to construct the river channel
bed, banks, and piers for the DEM.
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DEBRIS TRANSPORT IN A CHANNEL
Simulating debris transport in a river channel
using water velocities from ADH. Four piers are
located in the center of the picture.
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DEBRIS TRANSPORT IN A CHANNEL
Showing debris transport passing the four piers
located in the river channel. Debris consists of
long sticks and logs.
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DEBRIS TRANSPORT IN A CHANNEL
Complex flow around the piers reflects eddies in
the ADH flow field and collisional effects from
the debris accumulation.
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Simulation of Soo Locks Model Study
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Simulation of Soo Locks Model Study
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Simulation of Tow in Lock Approach
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FY03 ACCOMPLISHMENTS

• Added capability to simulate debris to river ice
  model
• Ran prototype simulations of
• ice passage through gap in guard wall using water
  velocity field from ADH
• debris passage through gap in guard wall using
  water velocity field from ADH
• Extended river ice model to handle wide floe size
  distribution
• Began work on running DEM ice/debris code in HPC
  environment

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REMAINING FY03/04 TASKS

• Demonstrate mixed ice and debris simulation
  capability
• Restructure DEM ice/debris code for optimal
  operation in a parallel environment (HPC)
• Integrate ice/debris modules into ADH
• Develop model initialization and set-up routines
  compatible with SMS