ANSYS FLUENT 16.0 Preview 4 -...

© 2011 ANSYS, Inc. September 19, 2014 1

ANSYS FLUENT 16.0 Preview 4


Parallel/HPC


HDF5-Based Case/Data IO

• HDF5-based case/data file IO is introduced in R16.0

• Fully supports parallel IO for case/data read/write

• Sectioned data compression is implemented natively through HDF5

• Provides different modes of IO capability:

1. Host : only host does the IO, and data are collected or distributed

2. Node0: only node0 does IO, skipping the communication overhead with host

3. Parallel independent: all nodes fully parallel independent IO

4. Parallel collective: all nodes do IO collectively


HDF5 IO Interface

• Fluent recognizes the .h5 suffix

• TUI for basic read/write:

• read-case box.cas.h5

• read-data box.dat.h5

• write-case box.cas.h5

• write-data box.dat.h5

• TUI for further options:

• /file/hdfio-options>

• compression-level

• io-mode

GUI for read/write


HDF5 IO Performance

Node ZeroParallel

IndependentLegacy

16 9.6 8.8 11.21

32 8.5 7.7 10.44

02468

1012

Tim

e in

se

con

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sedan_4m case read

Node ZeroParallel

IndependentLegacy

16 2.2 1.6 21.3

32 1.9 1.3 24

05

1015202530

Tim

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con

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sedan_4m case write

Node ZeroParallel

IndependentLegacy

16 1.4 0.8 2.3

32 1.4 0.7 2.3

0

0.5

1

1.5

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2.5

Tim

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sedan_4m data read

Node ZeroParallel

IndependentLegacy

16 2.2 1.8 5.8

32 2.1 1.8 4.8

01234567

Tim

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sedan_4m data write


HDF5 IO Performance

Caseread

Dataread

Casewrite

Datawrite

Legacy 39.2 35.6 92.8 35.3

Parallel collective 25.5 8.2 56.4 26.2

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LM6000_46M

Caseread

Dataread

Casewrite

Datawrite

Legacy 595.464 77.279 496.223 84.11

Par collective 300.14 56.27 431.983 80.6087

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700

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HEXCORE_400M t512 t1024


• Optimized communication algorithms

• Implemented multithreaded calculation

• Wall distance computations now scale better at high core counts (even 1024 and above)

• Speed ups simulations using enhanced wall treatments or turbulence models like SST

Wall Distance Computation Speedup

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100

200

300

400

500

600

96x 192xTim

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r so

luti

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init

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atio

n (

s)

Core count

R15

R16

Time taken in solution initialization of a 140M F1 benchmark case


• Can now export a multi-grid FV file so customers can now post process using parallel FieldView session

• FV export now scales better than before

• Simulations with frequent FV exports benefit by this performance improvement

Multi-Grid FieldView Export

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96x

Tim

e f

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FV e

xpo

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s)

Core count

R15

R16

Time taken to export 16 fields + 3 velocities for 111M truck case


• Improvement of accuracy of node-based gradients in the presence of mesh interfaces

– Minimizes/eliminates residual jump at restarts

– Helps convergence of node-based gradient cases with mesh interfaces

Node-Based Gradients & Mesh Interfaces Accuracy Improvement

SAS Term for a 2D case with mesh interface in the middle

without special treatment

with special treatment


• Helps performance of cases requiring edge information, e.g. shells and adaption

• Helps improve performance and scalability at high core counts

Improvement in Neighbor Edge Filling Algorithm


• Partitioning based on grouping by Laplace coefficients – This avoids partition interfaces through high cell aspect ratio areas

– It improves convergence for cases with highly stretched cells

Laplace Partitioning


AMG GPGPU Options

• Per equation user controls for AMG-GPGPU parameters


Parallel Check

• Checks for system usage, interconnect speeds and load balance


Other Parallel Enhancements

• Improved robustness for parallel solver

– Automatic handling of AMG divergence

• Cache flush

– Automatically checks for cache file buildup and warns users of potential performance impact

– New flag “-cflush” added to perform cache flush and restore the memory

• Results in more consistent and improved performance in affected cases


Platform and Protocol Support

• CISCO usNIC

– Added support for newer CISCO usNIC protocol over Ethernet (an offering from CISCO to compete with Infiniband)

– usNIC has a latency of 2.3 us

– usNIC is currently supported by OpenMPI only

• MPI Upgrades

– Both Platform (IBM) and Intel MPI libraries are upgraded to latest versions (which has resolutions for some of the bugs encountered in earlier versions)

• Upgraded IBM-MPI to 9.1.2

• Upgraded Intel-MPI to 4.1.3

– For distributed mode runs, now ssh is used as default as it is more secure compared to rsh (rsh is still provided as an option)


Platform and Protocol Support

• 64-bit integer support for Windows platform

– 64-bit integer support is added to be able to solve very large cases on Windows platform

• Intel v14.0 compiler upgrade for both Linux and Windows platforms

– Currently evaluation of latest Intel v14.0 compiler is underway.

– This complier has support for AVX2, Intel Haswell chips and Intel Xeon Phi


Numerics


Flow Forcing Boundary Condition

• New transparent flow forcing BC allows for correct modeling of transient wave dynamics

– Removes artificial reflection of outgoing waves from the boundary, allowing incoming waves to come into the domain

• Artificial reflection can be twice as big as the incoming wave

• Incoming waves are specified using a time-dependent profile or a UDF at non-reflecting boundaries

– Allows the use of smaller computational domains for transient flows

– Benefits combustion dynamics and transient external aero auto applications

• Notes:

– Available only in the pressure-based solver

– Incompatible with steady state flow, multiphase and compressible liquid models


Flow Forcing Boundary Condition

• Right propagating wave in a pipe with an open end

• Incoming wave specified at the velocity-inlet on the left end

• Pressure-outlet at the right end

Comparison with 1D analytic solution

Transparent forcing Standard v-inlet BC NRBC


Average Pressure Specification

• Average Pressure Specification at Pressure Boundary – Allows the exit pressure to vary across the boundary, but maintains

an average equivalent to the specified exit pressure value

– The Average Pressure Specification option now can also be used with Pressure profile(Radial or Axial) or Radial Equilibrium Pressure Distribution option

– Less reflective than previous version and improved results

– Benefits turbomachinery applications

• Important limitations and concerns – Pressure blending factor ‘f’ (default value 0.0) may need to change

f > 0.0 in cases where stability is degraded

– Not available with multiphase flows


2D Blade Passage(PBNS)

f = 0.0 f = 0.5 (old)

Where ‘f’ is Pressure Blending factor, f = 0(default) recovers the fully averaged pressure, f = 1 recovers the specified pressure

This is because of the shock reflections from the outlet boundary


Whites Case (DBNS)

f = 0.0 f = 0.5

Significantly more reflections, compare to results with value f = 0.0

These two example shows that, the pressure variation allowed in this boundary implementation slightly diminishes the reflectivity of the boundary as compared with the default ‘Constant Pressure Specification’ or when f = 0.5 is used as pressure blending factor


3D Goldman Stator (DBNS)

bin avg pressure Specified profile on bin In this example exit pressure is specified as

radial Profile and Average Pressure Specification option is used. Contour plot shows the pressure variation at the outlet boundary, however averaged value of pressure matches closely with the specified pressure profiles on bins(see XY-Plot).


Poor Mesh Numerics

• Criteria for marking of poor elements – Default (ON, No user control) : Cells with negative volume, non-convex

cells, cells with left handed faces

– Cell Quality Based (User choice) : Cells with low orthogonal quality

– User Defined : User’s own criteria

• Improves specification of cell-based quality criterion for marking bad elements, which in turn provides better robustness

• Text user interface has also been improved


Poor Mesh Numerics Improvements

Equiangle Skewness

Orthogonal Quality

Old Criterion

New Criterion


Improved text user interface

Poor Mesh Numerics Improvements


Jet Impingement over Flat Plate

Problematic case : - Diverged without poor mesh numerics

irrespective of solver settings - Diverged with poor mesh numerics

treatment in R15 - Smooth convergence with improved poor

mesh numerics treatment in R16.0


Compressible Flow Numerics Improvements

• Extension of work done at R15 – Treatment for SIMPLEC, PISO

– Treatment for user-defined compressible gas/liquid

– Treatment for multiphase flow

• Objective is to improve robustness for compressible flow simulations by controlling the rate of change of pressure and temperature within iterations and also by increasing diagonal dominance for coupled solver

• Final solution is not changed, only the convergence behavior


Enhanced Compressible Numerics

• Improved start-up and run-time robustness for compressible multiphase flows

Eulerian Multiphase Mixture Multiphase VOF


• Beta in R15.0, now full feature

– Impedance Boundary Conditions can model the impact of pressure reflections from outside the domain of interest on the domain of interest without including those zones in the simulation

1-D Wave at a boundary

• L=1m, dx=0.01, N=100

• Inlet Pt=58.6 pa, Tt=300 K, u=10 m/s

• Gaussian wave (FWHM=0.125, 30 points), 154 Db, 1e3 Pa

Impedance Boundary Condition

IBC, R=0 IBC, R=-1 IBC, R=-0.5


Improved Rothalpy Transport

• Improved Rothalpy Transport

– Aims to accurately compute viscous heating at the interface between two frames of references with the relative velocity formulation

– Important for turbomachinery applications


Improved Rolthapy Transport

• Results for Axial Turbine

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120

3000 rpm 3500 rpm 4000 rpm 4500 rpm 5000 rpm 5500 rpm

Cm-Abs

Cm-relative-Legacy

Cm-Relative-R16.0

Cm


Improved Rothalpy Transport

1.35

1.36

1.37

1.38

1.39

1.4

1.41

1.42

1.43

1.44

1.45


MF-Abs

MF-relative-Legacy

MF-Relative-R16.0

Mass Flow Rate

280

285

290

295

300

305

310


To-Abs

To-Relative-Legacy

To-Relative-R16.0

Total Temperature at Stator 2 Exit


Improved Shock Capture

• Roe flux method has been added as an option for the pressure-based solver

– Improves the resolution of shock waves

• Requires only half the cells needed by the traditional Rhie-Chow method

– Benefits external and internal aerodynamic simulations with shocks

BETA


Improved Shock Capture

• Results for air foil simulation

– Mach number 0.8, angle of attach 4 degrees

– Spalart-Allmaras turbulence model

• Shock wave on the upper side is further downstream with Roe flux in PBNS compared with Rhie Chow flux, better matching the DBNS results

Comparison with Rhie-Chow flux Comparison with DBNS

BETA


Non-Reflecting BC with VOF

• Non-Reflecting BC is now compatible with VOF at pressure outlets

– Eliminates artificial reflection from the boundary

– Transient VOF droplets, mixture applications, in particular, will benefit

BETA


Non-Reflecting BC with VOF

• Results for simulation of droplet motion in a pipe

– Inlet flow forcing in a pipe, mean flow: u = 100 m/s

– Velocity-inlet at left with u = 100(1+0.15sin(2pi 1000 t) sets up a right propagating wave on top of mean flow

– Pressure-outlet at right

– VOF with two phases (secondary phase: droplet r=15mm)

NRBC No NRBC

BETA


Turbulence


Turbulence Modeling Improvements

• Speed improvements of SST model

• BSL-w model implementation in Fluent

– Robust general-purpose model which will be the basis of our w-equation based turbulence modelling strategy

• To serve as replacement for RKE

• Basis for EARSM and RSM

• Combined all models with transition, rough walls etc.

• Improvement for Scale-Resolving Simulations (SRS)

– Extension of SRS models to polyhedral cells

• Some of our model use the maximum edge length – this is not suitable in poly meshes, as it does not reflect the size of such cells. Now using a more generic formulation which is backwards compatible with current formulation


Turbulence Modeling Improvements

• Default change – WALE model default for LES

– WALE model offers best ratio of complexity and accuracy

• SAS + Rough walls

– allow combination of both model options

• Consolidate definition of turbulence length scale Lt across codes (was different in Fluent)

• Allow combination of Enhanced Wall Treatment with rough walls

• Implement some missing hooks for user-specified Prandtl/Schmidt numbers

• Change default inlet value for Spalart-Allmaras model

• Allow combination of Enhanced Wall Treatment with rough walls BETA


Stress-Blended Eddy Simulation (SBES)

• New Scale-Resolving Simulation Option

– Separation of RANS, LES and blending

– Separately select a RANS and a LES model in a building block approach

– Visualize the regions where the RANS and where the LES models are active

– Flexibly select RANS and LES zones using UDFs in a zonal fashion

– Can mimic all existing models (WMLES, DDES, DES, …)

– Can provide perfect shielding of BL

Round jet at M=0.9 and Re=1.3 106 : 3D structures are obtained almost immediately downstream of the nozzle.

LES

ij

RANS

ijij ff 1

BETA


Acoustics


Frequency Band Post Processing

• Frequency band post processing of sound sources – FFT of transient surface pressure fields

– User creates/removes variables for visualization:

• SPL (surface pressure level, in dB) for frequency bands

• Octaves, 1/3-octaves, user-defined bands

• Fourier amplitudes for single selected modes

• Flexible memory control, other service functionality


CGNS Export of Pressure Spectra

• 1-way coupling to ANSYS Mechanical in frequency domain – Scale-resolving transient simulation is performed in Fluent and

pressure histories are exported from a coupling wall zone

– New: FFT of wall pressure field -> exported in CGNS files

– CGNS files are inputs for harmonic and response analysis in ANSYS Mechanical

• Vibration and acoustics for different frequencies

• Targeted at the automotive industry – Cabin noise from external turbulent flow

BETA



• Geometry and Fluent results for car cabin noise example

U = 40

m/s

Fluent domain

ANSYS Mechanical domain (closed box)

“Side mirror”

Resolved separated flow

BETA



• ANSYS Mechanical results for car cabin noise example: Plate displacement at 20 Hz, 70 Hz, 500 Hz

• Microphone sound spectrum in the cavity center, SPL( f ) for 20 Hz – 500 Hz

Sound pressure level

BETA


Discrete Phase Model (DPM)


Wall Film Model Improvements

• Impingement and Splashing UDF – Allows customization of wall-film particle behavior for spray-wall

interaction applications

– Provides several UDF hooks for Lagrangian wall film model

• Specify an impingement regime

• Set particle variables for a regime

• Customize diameter, velocity distributions for splashed particles

– Benefits aerospace and automotive industries

• Gas turbine and automotive fuel injectors application, in particular, will benefit


Impingement and Splashing UDF

O’Rourke/Amsden impingement model (default)

User Defined film behavior for high impact on hot walls (UDF)



• Energy transfer from Lagrangian film to the wall – Refactoring of wall film temperature solution now allows for direct

transfer of energy to wall covered by the film

– Provides increased accuracy for all simulations using Lagrangian wall film

– Compatible with all thermal boundary conditions and all particle types usable in the wall film

– Note: Radiation effects are not accounted for



• New film boiling model for droplet and multi component Lagrangian film particles

– Boiling rate is now computed directly from solution of particle energy equation- includes impact of chosen boundary condition of the wall covered by the film

– Allows a larger range of applications of the Lagrangian wall film at an increased accuracy (before the particle temperature was just limited by its boiling temperature)

– Note: Radiation effects are not accounted for


Heat Transfer to Walls

• Heat transfer from particles to walls can now be accounted for

– When a liquid particle is in contact with a wall it can exchange heat with the wall for the time of contact- the heat exchange is considered in the particle as well as on the wall

– Previously, particles were considered adiabatic when reflected at a wall

– Supported with reflect, wall-jet, or wall-film boundary conditions

– Allows for new applications where heat transfer of particles to walls is important

– Note: Cannot be used within the DDPM framework


Parallel Reproducibility

• New random number generator – Helps users to reproduce tracks as displayed in serial in a parallel run

– Consistent and unique seeding across all but volume injection types

– Provides unique particle ids in serial and parallel to increase reproducibility in serial and parallel


Parallel Scalability

• Extend hybrid parallel tracking to non-adiabatic non/partially-premixed combustion model – Non-adiabatic non/partially-premixed combustion model can now take

advantage of hybrid parallel tracking (before this was disabled internally)

– Users of these model combinations will see improved speedup and scalability


Binary Diffusivity

• DPM binary diffusivity of evaporating species is now dependent on pressure and temperature – Previously, it was only dependent on temperature

– Benefits applications where the pressure dependency is important such as piston engines and gas turbine atomizers


Discrete Phase Particle Rotation

• The effect of particle rotation can now be considered with the DPM model

– Including rotational drag forces and lift forces

– Considering impact during wall reflection

– More accurate results for solid particle simulations in wall-bounded flows

BETA


Dense Phase Particle Rotation

• The effect of particle rotation can now be considered with the DEM model – Including rotational forces during contact evaluation

– Makes the DEM model applicable to a wider range of applications

BETA


Reacting Flows


New Equilibrium Solver

• New Equilibrium Solver CEQ is implemented – This replaces existing equilibrium solver CPROP

– CPROP fails in performing equilibrium calculations for many applications such as EGR, Diesel Unsteady Flamelets

– CEQ is more robust, fast and accurate


Soot Model UDF Hooks

• Generalized Soot Model – User can implement their own soot models through this functionality

– The udfs can be provided for each subcomponents of soot model like

• Nucleation, Coagulation

• Surface growth, oxidation

– Fully flexible and has options for adding/replacing the Fluent’s default

– In conjunction with PDF model, it allows to pre-tabulate the soot rates in PDF tables

– Can handle the turbulence chemistry interactions like default models


Finite Rate Chemistry Speed-Up

• Several improvements to improve performance – Replaced sundials with CVODE for ISAT

– Enhancements in the ODE solver performance

– Reaction rates solver improvements

– ISAT optimization

– ODE solver tolerance optimization

– R16 will be much faster than R15 for finite rate chemistry

• All applications that require finite rate chemistry modeling will benefit


• New Method of Moments soot model

– Interpolative closure for soot diameter and surface area

– Moment transport equations solved in Fluent

– Moment source terms consider realistic chemical and physical processes

– Coupled to the flow through radiation heat transfer

• May be at R16 - TBD

New Soot model

BETA


Other Reacting Flow Improvements

• Real gas enhancements: NIST 9.1 update (this was beta in R15)

• Support encrypted mechanisms for Chemkin-CFD

– Available for Chemkin-CFD and other Fluent models:

• Can be used with relax to equilibrium or laminar stiff chemistry

• Surface chemistry is not supported

• Flamelet generation is only serial

• DMR and DR are not supported


Radiation & Heat Transfer


Surface-to-Surface Radiation

• S2S Model Performance

– Improved performance with non-conformal interfaces

• No need to encapsulate coupled wall faces at partition interface

• Better overall load balance (in parallel)

• Significantly improves solver time (i.e. time/iteration)

• Up to 10X faster for (for >64 cores)

– Faster view factor computation for poly meshes with ray tracing method

• No further triangulation needed

• View factor computation for 884K poly mesh is 8-10X faster in R160

– Improved I/O with binary file format support

• Faster reading of view factor file- up to 4x faster in testing

• Writing supported on linux64 only

• Files written on linux64 can be read on win 64

– Particularly beneficial for underhood applications


Performance Gain with Further Optimization

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t8 t16 t32 t64 t128

R160-New

R150

Solver Time Per Iteration

Number of Cores


Multi-Layer Shell Conduction

• Faster I/O and solver time for shell conduction

– Significantly improved case read time and solver time (i.e. time/iteration)

• New UDF hook for heat generation rate

– Allows users to specify profile of heat generation in their simulations

Case read time vs CPUs Solver time per iteration vs CPUs


Other Radiation & Heat Transfer Improvements

• Mapped meshes for CHT modeling – Allows thermal coupling between (indirect) mapped mesh interfaces

– May be at R16 – TBD

• Anisotropic thermal conductivity – Allows users to specify principal values and axes for anisotropic

thermal conductivity

BETA


Mesh Morpher and Optimization (MMO)


MMO Control Points Improvements

• MMO has multiple options to specify control points on the surface of any boundary for improved control over movement of surface mesh node – Including the ability to:

• Specify the control points (e.g. mouse control, XYX coordinates, etc.)

• Specify the parametric motion definitions (translation, rotation, radial)

• Display the control points

– Access to both structured (available with previous releases) as well as unstructured control point specifications (new at R16.0)


Surface Morphing User Interface


Mesh Deformation Using Mouse Probe

Mouse probe can be used to selectively move the internal control points and thus adjacent mesh nodes more accurately


Multiphase


Multiphase Species Mass Transfer

• Multiphase mass transfer laws – Mass transfer processes are modeled using distribution laws- three

such laws have been implemented in Fluent:

• Henry’s Law (Gas-Liquid)

• Raoult’s Law (Ideal Solution)

• Equilibrium Ratio model (Non-Ideal Solution)

– Benefits challenging multicomponent multiphase problems often encountered in chemical and petrochemical industries

• DAF tanks, bioreactors, distillation columns/trays


Coupled Level Set Improvement

• Coupled Level Set Improvement

– Reduces Spurious currents from surface tension dominated low velocity flows

– Useful for surface tension dominated flow, micro fluidics


PVT Lookup Table

• Ability to use a lookup table with the NIST real gas model to specify phase properties as a function of PVT

– Less expensive (much faster) than using the NIST model directly

– Required to solver problems involving condensation, evaporation, flash evaporation (single component) and to perform high fidelity oil and gas reservoir simulations


Multiphase in Porous Media

• Multiphase flow in porous media can be modeled – Based on the full Navier-Stokes equations

– Takes into account:

• Relative permeability of the different phases

• Relative viscosity between phases

• Capillary pressure

– Models for relative permeability are:

• Cory-Brooks model for two-phase simulations

• Stone I and Stone II for three phase simulations

BETA


Other Multiphase Improvements

• NITA (Non-Iterative Transient Advancement) is now available for multiphase flows

– Significant speed up for all transient Eulerian multiphase simulations

• More robust modeling of mixing tanks and bubble column separators

– Implicit treatment of the virtual mass force

– Nphase continuity solver

• Computes the solution of continuity equations for all phases

• Reduces mass imbalance problems that commonly occur in with these simulations

• Flow regime transition model

– Captures the dynamic flow regime transitions for two-phase gas-liquid flow

– Developed within the framework of the VOF and multifluid VOF model

– Useful for simulating glows in vertical risers, oil wells and pipelines


VOF and Multi-Fluid VOF Restructuring

• New option to choose interface modeling type

– Available discretization schemes and drag laws based on interface modeling type

– Allows for more intuitive set up and helps avoid user errors

Interface Modeling Type

Implicit Formulation Explicit Formulation

Sharp Compressive (default) HRIC, BGM

Geo-Reconstruct (default) CICSAM, Compressive, HRIC

Sharp/Dispersed Compressive (default) Modified HRIC

Dispersed 1st order upwind (default) Second order upwind Quick

1st order upwind (default) Quick

Interface Modeling Type

Drag Laws for Multi-Fluid VOF

Sharp Symmetric, Anisotropic

Sharp/Dispersed All the drag laws available

Dispersed All the drag laws but Anisotropic


Free Surface Options

• Free surface regime modeling options

– Options to address cases where interface modeling may depend on cell zone or phase pair

• Zonal discretization

• Phase localized discretization

• Free surface expert options

– Sub-time step calculation method

– Solve VOF every iteration


• Generalized variant of compressive scheme has been developed – Applicable to both Sharp and Dispersed regimes.

– Adaptive: produces desired behavior depending on the regime type (Sharp, Dispersed and Sharp/Dispersed)

– Bounded: an improvement over the HRIC/R15-compressive for dispersed flow regimes

• New default for sharp/dispersed regime type

• Default unchanged for sharp regime

• Crucial for flow regime modeling in oil & gas industry

Modified Compressive Scheme


Straight pipe with liquid VOF=0.5 at the inlet. The modified compressive scheme ensures the boundedness compared to other schemes.

Modified Compressive Scheme in Dispersed Regime

Compressive Modified Compressive

CICSAM HRIC

Max vof = 0.654 Max vof = 0.58

Max vof = 0.98 Max vof = 0.5


Modified compressive scheme also works very well for a sharp regime Images below show comparison of modified compressive (red curves) vs compressive (white curves)

Modified Compressive Scheme in Sharp Interfacial Regime

Slotted circle after one rotation Wigley Hull


Slurry (Water + Solids)

Gas bubble

Phase Localized Compressive Discretization • Bubble & Slurry

• Max Slope Limiter Beta= 2 • This is Compressive/Modified

Compressive • Slurry (Water & Solids):

• Max Slope Limiter Beta = 0 or 1 • First order (0) or second order (1)

Contours of Solid Volume Fraction

Beta (2,0) Beta (2,1) Beta (2,1)

With standard compressive

With modified compressive

Unphysical sharpening of solids

Modified compressive shows appropriate settling of solids

Modified Compressive Scheme in Sharp Interfacial Regime


• Available with VOF and Eulerian multiphase with multi-fluid VOF option – Feature was available with Explicit

formulation- it has been extended to implicit formulation

• Will help estimate proper time step size for implicit VOF calculation and will speed up the transient calculations

Variable Time Stepping for Implicit VOF


Random Wave Modeling Using Wave Spectrum

• Various frequency/directional spectrum methods are available

– Frequency Spectrums

• Pierson-Moskowitz Spectrum

• Jonswap Spectrum

• TMA Spectrum

– Directional spectrum

• Cosine (frequency independent)

• Hyperbolic (frequency dependent)

• Wave check capability

• Critical for marine industry: ship design, oil skimming

Longitudinal/frequency dependent Frequency + Direction Dependent


Random Wave Modeling Using Wave Spectrum

Long-Crested Unidirectional

Short-Crested


• New treatment allows better accuracy and robustness in case of negative absolute pressures

• Recommended for all MDM and high pressure applications

Case study: Water Hammer

Pipe flow with steady state profiles is suddenly closed at one end, which produces water hammer effect.

Average pressure at outlet accurately predicted using the new improvements

Compressible Liquid Improvements


VOF Initialization Options

With Patch

With Patch and Smoothing

• New volume fraction patch options to minimize start up instabilities

– Patch reconstructed interface

– Volumetric smooth


• Mass transfer improvements with explicit VOF for constant mass transfer rate specification

• Phase-specific surface monitors/reporting for VOF and Mixture models

Other Multiphase Modeling Enhancements

Monitors

Reporting


VOF Interface Accuracy for Poor Mesh

• New option to model interfacial anti-diffusion improves interfacial accuracy for sharp interfaces with the following mesh scenarios – Coarser mesh

– High aspect ratio

– Mesh with large cell volume jump

– Cut-Cell mesh

– Polyhedral mesh

– Skewed mesh


Interface Capturing Comparisons

with interfacial anti-diffusion

without interfacial anti-diffusion


VOF Case Check Summary

• Summarizes case setup and provides additional recommendations

• Verbosity option: 0 (compact) or 1 (detailed)

• Summary is printed on Fluent console

BETA


Sample VOF Summary

• More details are printed below this

BETA


Adjoint Solver


Robust Solution of Large-Scale Problems

• New solution advancement scheme for the adjoint solver – Large-scale problems can be solved more robustly

– Successful simulation of external aerodynamic cases up 100M+ cells


Automated Solution Advancement

• An automated solution advancement “expert system” for the adjoint solver has been developed – Significantly reduces the challenges associated with solving adjoint

problems

– In R15 and earlier the user had to select settings such as Courant number etc., based on how the adjoint solution was advancing

• This made it challenging in many cases for non-expert users to get solutions without help.

– The new feature provides initial choices for settings and updates them dynamically as the adjoint calculation progresses


Automated Solution Advancement

• External aerodynamic simulation of generic racer (half car, 15M cells)

• Drag sensitivity was computed

• Automated solution advancement provides a push-button solution for a problem that was previously been a challenge to solve

Adjoint Pressure Adjoint Residuals


Volume Integral Observable

• Volume integral over a fluid zone or a Cartesian region can be specified as the observable

– Enables specialized questions to be asked about flow losses and wake structures

• Variety of integral types

– Volume integral, average and variance

– Mass integral, average and variance

– Sum

• Variety of integrand types

– Pressure and total pressure

– Vorticity

– Velocity magnitude

– Turbulence production


Management of Design Changes

• New design tool provides much richer functionality than before and greater efficiency for mesh morphing

• Key extensions include: – Multi-objective design

– Prescribed design changes

– Freeform deformation

– Detailed control of the morphing

– Design conditions

– All of the above features can inter-operate!


New Model Support

• Adjoint solver now supports: – Porous media relative velocity formulation

– User-defined sources (with the udf modified to be “adjoint-enabled”)


Solver Meshing


Mesh Interfaces

• Mapped interface option for coupled interfaces for fluid-fluid and fluid-solid

• Enabled usage of sided centroids at coupled interfaces – More accurate and more robust handling of penetrating mesh

interfaces

• Improved performance when deleting mesh interfaces during I/O

• More intuitive interface zone names


Polyhedral Conversion

• Removed parallel bottleneck for meshes >> 50 million cells – Conversion time on 64 CPUs was reduced from 14.3 h to 1.7h for mesh

with > 100 million cells

• Option to preserve prismatic extrusion layer during conversion • Code will do analysis of input mesh to recommend enabling of

preservation

• Enables more robust conversion for very high aspect ratio meshes without cell count increase in extrusion layer

• Improved parallel performance of optimization step • Avoids encapsulation of very poor polyhedra during optimization

• Added TUI option to skip migration and reordering after conversion


Other Solver Meshing Improvements

• Parallel zone remeshing – Makes it possible to remesh an entire zone without the overhead of

zone encapsulation on a single CPU

• Improved performance of dynamic mesh spring smoothing in parallel


Miscellaneous


System Coupling Improvements

• Porous jump support – Porous jump boundary condition can now be used for 1-way and 2-way

data FSI applications.

• Fluent sends nodal force and/pr consumes nodal displacement data via system coupling

• Deforming porous zones – Porous media can now be used for FSI applications

– Porous jump boundary (with thickness = 0) is used adjacent to porous zone to serve forces and receive displacements from system coupling

– May be at R16.0 - TBD

• Allow Fluent and Mechanical to be used to model filters via System Coupling

BETA


System Coupling Improvements

• Fluent monitor data – All monitor data defined in Fluent can be tracked in System Coupling

• Residuals, statistics, forces, surface and volume monitors

• Monitor data is consistent with Fluent names

• Exchange heat flux/temperature at thermally coupled walls – Allows users to exchange heat flux/temperature values at coupled

walls from Fluent to MAPDL via System Coupling

– Avoids problems with convergence of thermal quantities at the FSI interface

– Displacements due to thermal stresses get passed back to Fluent


Workbench Usability and Performance

Multiple upstream mesh systems

• Connect multiple upstream mesh components with Fluent's Setup cell

• Allows for parametric simulations where only part of domain requires re-meshing


Workbench Parameters and Optimization

Context menu of the Mesh cell allows user to register Fluent Mesher Journal file. The journal is then executed automatically during Project update.

Parametric support for Fluent Meshing

• Parameter Manager in WB now supports Fluent Meshing

• Parametric journals are registered with Mesh cell and automatically executed during Project’s update

Fluent Meshing geometry connectivity

• Fluent Mesh cell can now receive geometry from upstream Geometry cell.

BETA

BETA

FLTG system connected to the upstream Geometry component. Parameters defined in Mesher journal are exposed and controlled in WB.


Transient Convergence Monitoring

• Monitor number of iterations per time step

– Allows user to monitor the residual behavior in time

– Users can see which time steps converged quickly and which time steps took the maximum number of iterations in any transient simulation


Monitoring Iterations per Time Step

not converging in these time steps

User can easily determine which time steps are not converging- this cannot be seen from the standard residual plot on the left

Standard Residuals Iterations per Time Step


Surface Import

• New option to import surfaces for post-processing – Import a surface (in .stl or .msh

format) and create a post-processing surface


Custom Vectors

• Custom vector capability for post-processing

– Three new options are available in the surface integrals panel:

• Custom Vector Based Flux (𝒗𝑐 , 𝜑) = 𝜑𝒗𝑐𝑓 ∙ 𝑨

• Custom Vector Based Flux (𝒗𝑐) = 𝒗𝑐𝑓 ∙ 𝑨

• Custom Vector Weighted Average

(𝒗𝑐 , 𝜑) = 𝒗𝑐∙ 𝑨 𝜑 𝑓

𝒗𝑐∙ 𝑨 𝑓


New Tree-Based UI

• A new tree-based UI is introduced in R16

– The tree replaces the navigation pane

– All the previous navigation pane options are available in the tree

• Branches of the tree provide an overview of the case set up

• New right-click menus allow quick access to most commonly used functionality


New Tree-Based UI


Contour and Vector Objects

• Contour and vector definitions can be saved in and re-displayed from the tree


Default Mesh Display Configurations

• Quick access to different ways of displaying the mesh


3rd Party Tool Support

• Export of polyhedral cells to CGNS – Cases with polyhedral cells can now be exported in the CGNS format

• Support for export of surfaces in FieldView multigrid format – Domain export in multigrid format was already available in R15

• WAVE version upgraded to WAVE2014.1 – Support on linux64 and win64

ANSYS FLUENT 16.0 Preview 4 -...

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