flow-3d ® version 9.4 michael barkhudarov vp for research and development flow science, inc. 2009...

FLOW-3DFLOW-3D®® Version 9.4Version 9.4

Michael BarkhudarovMichael BarkhudarovVP for Research and DevelopmentVP for Research and Development

Flow Science, Inc.Flow Science, Inc.

2009 FLOW-3D European User Conference2009 FLOW-3D European User Conference

2009 Releases (August 2009)2009 Releases (August 2009)

Distributed memory (MPI) parallel version FLOW-3D/MP 4.0:

•based on version 9.3.2 of the serial/SMP version•CPU-optimized inter-block data transfer•greatly reduced MPI communication•automatic domain decomposition tool (ADT)•scaling up to 32 ranks

Version 9.4 serial/SMP parallel:

•merged pre-processor and solver executables•multi-species sediment scour and bed-load transport•turbulence: reduce sensitivity to “turbulent mixing length”•sand core gas model•temperature-dependent fluid and solid component properties•GMO model extensions•non-linear Stokes wave model•auto-termination at steady-state•additional output for open channel (hydraulic) flows


Integration of Pre-processor and SolverIntegration of Pre-processor and Solver

Pre-9.4 execution sequence:

Pre-9.4 execution sequence:

inputinputprepinprepin

geometry geometry datadata

pre-processorpre-processor

prep3d.exeprep3d.exe

output filesoutput fileshd3in.dathd3in.dathd3inb.dathd3inb.dat

restart instructionsrestart instructions

solversolver

hydr3d.exehydr3d.exe

restartrestartflsgrfflsgrf

flscon.exeflscon.exe

hd3rsthd3rst

9.4 execution sequence:

9.4 execution sequence:

inputinputprepinprepin

geometry geometry datadata

pre-processor and solverpre-processor and solverhydr3d.exehydr3d.exe

restartrestartflsgrfflsgrf

ExitExitin preview modein preview mode


Benefits of a Single Solver ExecutableBenefits of a Single Solver Executable

• eliminates writing and reading intermediate files which can be several GB in size

• faster simulation startup• easier code distribution and updates• opens new possibilities to extend the restart logic:

multiple restart data source files flsgrf multiple restart times

• simplifies code development• no change in how the user runs simulation from the GUI and

the command line


Advection of sediment due to fluid motion

Settling of sediment due to gravity

Entrainment of sediment into fluid

Bed-load transport of sediment along bottom

Multi-component Scour and Bed-load TransportMulti-component Scour and Bed-load Transport


• Replaces the old single-sediment scour model• Up to 10 sediment species:

average particle size density sedimentation properties

• Bed-load transport larger size debris transported along the bottom

• Improvements in accuracy and usability non-linear drift-flux model special geometry components to define packed bed

• Scour potential model (or excess shear stress output)


Multi-component Scour and Bed-load TransportMulti-component Scour and Bed-load Transport

Packed sediment volume fraction

downstream from a 10 m high weir

Presence 10.5 mm pebbles reduces erosion

Erosion of sand river bed, no bed load sediment


Scour Potential ModelScour Potential Model

Excess shear stress on the eroded river bed

•A passive model that evaluates shear stresses on solid and packed sediment

beds in excess of a user-defined value•Each geometry component can have its own critical value•When the critical shear stress is zero (default), the output is just the shear stress

Excess shear stress on the river bed downstream of a power plant

L0

H

H

d

Stokes Surface WavesStokes Surface Waves

•5th order Stokes wave approximation extends the linear wave solution primarily

to larger amplitude waves, but also to somewhat longer wave lengths.•The solution naturally includes a constant current


Linear wavesLinear wavesStokes wavesStokes wavesFourier SeriesFourier Series

Linear wavesLinear wavesStokes wavesStokes wavesFourier SeriesFourier Series

5-th Order Stokes Surface Waves(John D. Fenton’s fifth-order Stokes Theory)

5-th Order Stokes Surface Waves(John D. Fenton’s fifth-order Stokes Theory)

: wave length

H: wave height (from trough to peak)

: water elevation

U: mean stream velocity

: angular velocity, =2/T

k: wave number, k=2/ c: wave speed, c=/T

H

x

z c

U

Assumptions: incompressible, inviscid and irrotational

Perturbation parameter: wave steepness

Potential function :

Laplace equation:

Solution:

02

0.12/ kH)(,)(),,(),,( 6

5

1

uOtzxxUtzxi

ii

,)sin()cosh(),,(1

5

1

2/1

30

i

jij

i

i jkXjkzAk

gCxUtzx )( tkxkX


Wave Boundary ConditionsWave Boundary Conditions



Stokes Solution Describes Well the Predominant Wave Patterns in Deep Sea

Stokes Solution Describes Well the Predominant Wave Patterns in Deep Sea

Comparison of Experimental and Numerical time Comparison of Experimental and Numerical time history of Pitch motion (in radian) of device.history of Pitch motion (in radian) of device.

Pitch Motion of WRASPA against 10mm Wave

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

9 10 11 12 13 14 15 16 17 18 19 20

time (s)

Po

siti

ion

(ra

d)

Experimental ResultsNumerical Results

Numerical Modelling of WRASPA using FLOW-3DNumerical Modelling of WRASPA using FLOW-3D

GMO Model AdditionsGMO Model Additions

• Tethered GMO model (springs and ropes)

• Control forces at user-defined points (up to three)

• Buoyancy point and metacenter output for ship stability evaluation



• Each tether is characterized by:

- locations of its two ends: one end is on a coupled-motion GMO second either on another GMO or fixed

- spring coefficient

- free length

- block length

- initial torque (for a torsion spring)

• Multiple tethers are allowed

• Spring mass is neglected

Tethered GMO components: Ropes and SpringsTethered GMO components: Ropes and Springs


Rope: Stretches elastically, force vanishes when there is slack,block length is 0.0:

Springs:

1. compression and extension spring2. compression spring (one end is free)

3. extension spring

4. torsion spring

Types of TethersTypes of Tethers

LLkF free ,0.0 min

LLkF 0,0.0max

),max( LLL

LLkF

block

free

blockfree LL

00 kTT

L

L0


Types of TethersTypes of Tethers

Spring and ropes are defined under Geometry, and are listed in a separate branch, together with Geometry components, Mesh and Baffles.

Tethered GMO Model ApplicationsTethered GMO Model Applications

• sea keeping• wave energy harvesting• spring loaded valves and levers• possibly:

linked moving objects micro-collisions

Untethered Tethered to the seabed by four cables (ropes)

Oil platform interacting with (Stokes) waves



Possibility: Using Springs to Model Linked GMOPossibility: Using Springs to Model Linked GMO

The spring model may offer a way to model linked moving objects.

In this example two coupled-motion GMO are connected by a stiff spring simulating a hinge. Multiple springs may provide a way to model more complex connections


Ship Stability EvaluationShip Stability Evaluation

Buoyant stability of a floating object is evaluated by computing the meta-centric height GM. The calculation is done assuming small angles of heel and a close to horizontal free surface.

Metacenter is computed separately for pitch and roll.

G - mass center

B - buoyancy center

M - metacenter


Control Forces at Fixed Application PointsControl Forces at Fixed Application Points

•Alternative to defining the total force and torque and the mass center

•Up to three control forces can be defined

•Each can be either in the space or body system

•Time-dependent


• Prescribed sinusoidal motion• Improved accuracy of the pressure force calculation using

hydrostatic interpolation at the GMO surface• Individual wetting conditions on each subcomponent of a GMO

component• Output for both shear and pressure hydraulic force components

(also applies to the stationary components)• Added wall adhesion to the hydraulic force on moving and static

components• New user-customizable subroutines for GMO forces and velocities

Other GMO Model AdditionsOther GMO Model Additions


Turbulence Model ImprovementsTurbulence Model Improvements

• Remove laminar sub-layer calculation• Reduce the dependency on turbulent mixing length TLEN• Tests are still under way

Turbulent flow in a cylindrical pipe, Re=10,000

Sensitivity to mesh resolution with and without the sub-layer Sensitivity to TLEN


Automatic Termination at Steady-stateAutomatic Termination at Steady-state

User selects:• watch list variables• variation threshold• time window over which steady-state

is determined

4.40E-01 1563 1 2.81E-04/cd 2.81E-04 3.0E-01 1.1E+01 15:09:374.40E-01 1563 1 2.81E-04/cd 2.81E-04 3.0E-01 1.1E+01 15:09:37 4.55E-01 1617 1 2.81E-04/cd 2.81E-04 3.0E-01 1.1E+01 15:09:374.55E-01 1617 1 2.81E-04/cd 2.81E-04 3.0E-01 1.1E+01 15:09:37 4.71E-01 1671 1 2.81E-04/cd 2.81E-04 3.0E-01 1.2E+01 15:09:374.71E-01 1671 1 2.81E-04/cd 2.81E-04 3.0E-01 1.2E+01 15:09:37 ****** restart and spatial data available at t= 4.82781E-01restart and spatial data available at t= 4.82781E-01 ****** 4.83E-01 1714 1 2.81E-04/cd 2.81E-04 3.0E-01 1.2E+01 15:09:384.83E-01 1714 1 2.81E-04/cd 2.81E-04 3.0E-01 1.2E+01 15:09:38

end of calculation at t= 4.828E-01 cycle = 1714end of calculation at t= 4.828E-01 cycle = 1714 mass-averaged mean kinetic energy has become steady mass-averaged mean kinetic energy has become steady

elapsed time (seconds) = 1.300E+01elapsed time (seconds) = 1.300E+01 cpu= 1.192E+01cpu= 1.192E+01

Additional Hydraulic Data OutputAdditional Hydraulic Data Output

Depth-average velocity Velocity at an offset from the river bed

These are computed when the user selects Hydraulic data output:•fluid depth•free surface elevation•Froude number•depth-averaged velocity•velocity at an offset from the bottom

A new option to output hydraulic head will also be added. It is computed in every cell as the spatial field variable.

Each flux surface will have the area-averaged hydraulic head calculated as a function of time.


Material PropertiesMaterial Properties

• Reorganized the Fluid Properties tree to separate properties specific to fluid 1 and 2 and to both fluids.

• Reorganized material database to have a separate file for each material.

• Can access and load fluid or solid material properties from anywhere in the GUI


Temperature-dependent Fluid PropertiesTemperature-dependent Fluid Properties

• All fluid properties except for the electrical can be defined as a function of temperature using tables

• User can either type the data directly or load it from the database

• Tabular data is saved to the prepin file and can also be added to the material database.

• User can easily switch between constant and variable property definitions

• Viscosity can be a tabular function of either temperature or strain rate


Temperature-dependent Solid PropertiesTemperature-dependent Solid Properties

Similar capabilities for the solid properties:- thermal conductivity- density*specific heat- heat transfer coefficient to fluid 1 and 2


Sand cores are used to make complex castings. Resin binders are typically used to hold sand together. When metal comes in contact with a core during the casting process, the heated binder decomposes into gases (CO, H2, CO2, etc.). The gases can penetrate into the still liquid casting and create defects such as porosity, cracks and blisters.

Goal: predict the evolution of core gas within the core, its venting and possible penetration into the casting.

Sand Core Gas ModelingSand Core Gas Modeling


• Gas is generated due to the heating of the core, using the Arrhenius model for the chemical reaction.

• Flow of the compressible air and binder gases through the porous media of the core is computed.

• Flow of gas is evaluated at the core surface into the prints, ambient air and metal based on the pressure difference

• Can be used together with the filling and solidification analyses.

Core Gas ModelCore Gas Model


Comparison of the predicted rate of gas generation in a sample core with the experiment.

A sample is heated from outside. As the

heat penetrates deeper into the sand, it triggers the generation

of gas.

Core Gas Model, continuedCore Gas Model, continued

Gas pressure at the core surfaces

Gas mass flux at the core surface


Core Gas Model, continuedCore Gas Model, continued

During filling there is a ‘race’ between the rising gas pressure inside the core and the metal hydrostatic pressure outside. The model will help engineers to come up with optimum parameters to minimize the risk of gas blow.


Other Additions and ImprovementsOther Additions and Improvements

Solver:

• Reduced convective volume error• CPU-optimized inter-block data transfer• Pressure effect to the air entrainment model (mainly for HPDC)• User-defined time-step size control for the implicit advection model• Fill missing values in the time-dependent tabular input using linear

interpolation, instead of constants:

time value

1 0.1

2 …

3 0.3

4 0.25

Fill with 0.2, instead of 0.1


Sloshing analysis

• Use STL files to define initial fluid regions• High resolution screenshots• Wireframe iso-surface display• Check and fix STL files from Meshing & Geometry using admesh• Interactive seeding of streamlines• Visualize streamlines with spheres• Simultaneous 3D viewing of two datasets• Combined plots of metal and mold temperature

Additions and Improvements to GUI and Post-processorAdditions and Improvements to GUI and Post-processor


• Load data from the same or different data files• Synchronized side-by-side viewing• Synchronized animations

Simultaneous 3D viewing of two datasetsSimultaneous 3D viewing of two datasets


Wireframe Iso-surface DisplayWireframe Iso-surface Display


• 9.3+ ported to MPI code• Auto-Decomposition Tool (ADT) for better load balancing• optimized inter-block data transfer• removed unnecessary communication between ranks• reduced the number of synchronizations

release – August ’09beta release – June ‘09

FLOW-3D/MP 4.0FLOW-3D/MP 4.0

4.4.00

3.3.22


Improvement in scaling for a consumer products simulation

Domain decomposition with ADT on 16 ranks

Scaling for a coupled-motion boat simulation

• Parametric optimization• Small-amplitude FE elastic stress model for

solidified metal and mold• Stead-state solver for hydraulic applications• Sand core drying model• Salt dissolution model• Represent baffles using STL files• More surface waves types: tsunami, cnoidal,

solitons, etc.• Extend SMP parallelization scaling to > 4 cores

FLOW-3D/MP• Hybrid parallelization, MPI/SMP• Domain decomposition not based on multi-block

meshes

2010 Development Plans2010 Development Plans


Thank you!Thank you!


flow-3d ® version 9.4 michael barkhudarov vp for research and development flow science, inc. 2009...

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