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The release of FLUENT 6.0 sets a new benchmark for commercial CFD codes,
delivering world-class, unstructured, parallelized solver technology to
a broad new range of applications in the areas of multiphase flow, flow
in rotating equipment, reacting flow,flow involving heat transfer and
phase change, and transient flow. Specific industrial applications in these
focus areas were targeted as part of a comprehensive planning and testing
process.
For each of FLUENT’s target application areas, clients and industry experts
were interviewed to identify their software requirements. Relevant “industrial-strength”
test cases were obtained from clients and were used as the final acceptance
criteria for each area. This process ensured not just the functionality
of the individual features, but the overall applicability of FLUENT 6.0
for the targeted and related applications. Some highlights of the new
modeling capabilities are described below.
- Multiphase Flows
- Rotating Equipment
- Reacting Flows
- Heat Transfer/Phase Change
- Transient Flows
Multiphase Flows
Targeted applications include bubble column reactors, fluidized beds,
mixing, and steel manufacturing/continuous casting.
The most significant new capability in FLUENT 6.0 is the availability
of Eulerian multiphase models in a fully unstructured framework.FLUENT
6.0 can be used to model the hydrodynamics of isothermal, non-reacting
gas-liquid, liquid-liquid, gas-solid and liquid-solid flows. Indeed, it
is the first software with an unstructured solver to offer a granular
model for a secondary phase of solids. In addition to two-phase mixtures,
it also has the capability to handle three-phase flows (gas-liquid-solid
mixtures), allowing users to model such complex devices as slurry bubble
columns and trickle bed reactors.
Solids volume fraction in a circulating fluidized bed,
computed using the Eulerian granular multiphase model in FLUENT 6.0
Numerous enhancements have been added to the multiphase models in FLUENT
6.0, accessible through a simple and intuitive interface, that go beyond
the capabilities of FLUENT 4.5. For example, three different formulations
are available for each of the different k-e turbulence models in order
to more accurately address different regimes of phase loading. A new phase-coupled
momentum solver has been implemented, providing for more robust and efficient
convergence.The models are also highly customizable; material properties
and source terms can all be accessed using user-defined functions (UDFs).
The mixture model (formerly called the algebraic slip mixture model)
that was introduced in FLUENT 5.0 has been enhanced in FLUENT 6.0.The
model now allows for heat transfer between phases and the ability to model
multiple secondary phases. User-defined access to the volumetric source
terms is also provided.This model can be used instead of the Eulerian
multiphase model when the secondary phases have small particle relaxation
times, delivering faster convergence than the Eulerian approach.
The discrete phase model (DPM) and the volume of fluid (VOF) model have
been extended. For DPM, a new liquid spray model has been added. Primary
atomization models are available to capture the initial formation of droplets
from a liquid jet, and secondary atomization models are available to capture
the behavior of the droplets after their initial formation. For VOF simulations,
the effect of heat transfer, including radiation, can now be included.
Compressibility can be considered and compatibility with the melting/
solidification model has been introduced.
"Fluent has entered into a league of their own with
the release of FLUENT 6.0. In my testing efforts, I found that even when
using the Eulerian model for complex geometries, along with FLUENT's
fully unstructured code, the calculation time was substantially faster
than FLUENT 4.5. In addition to these major enhancements, the code remains
easy to use and continues to employ its intuitive setup."
-M. Karim Essemiani
Vivendi Water, France
Rotating Equipment
Targeted applications include turbomachinery and gas turbine combustion.
FLUENT 6.0 delivers several new post-processing capabilities designed
specifically for the turbomachinery community. Users can create surfaces
and display contours along the meridional, pitchwise, or spanwise coordinate
directions while still taking advantage of the flexibility of a fully
unstructured mesh. Pitchwise averaged 2D contour plots and XY plots can
also easily be computed and displayed. In addition, a set of turbomachinery-specific
integral quantities, including torque and efficiency, can be computed
with a single mouse-click.
Static pressure contours on the hub and blade surfaces
of an axial compressor stage (rotor + stator), simulated using the mixing
plane model in FLUENT 6.0
In addition to the post-processing enhancements, several modifications
have been implemented in the solver. Non-reflecting boundary conditions
allow pressure waves to pass through pressure boundaries, preventing spurious
reflections at the boundaries and locally at the leading and/or trailing
edge of the blade. The mixing plane model has been enhanced to include
options for conservation of mass and conservation of swirl throughout
the mixing plane. Mesh generation for periodic boundaries will get easier,as
non-conformal (i.e. non-matching) meshes can now be used at periodic boundaries.
Reacting Flows
Targeted applications include gas turbine combustion, pulverized coal
combustion, laminar flames, and surface reactions/stiff chemistry in chemical
vapor deposition reactors.
The eddy dissipation concept model, widely know as the EDC model, has
been implemented for the modeling of turbulent finite rate chemistry.
It is completely different from the eddy dissipation model that has long
been available in FLUENT. Based on the assumption of small turbulent structures,
or fine scales in the turbulence field, the EDC model allows users to
better account for complex, stiff chemistry through the use of a robust
algorithm.
Several other models have been added or improved in FLUENT 6.0. These
include a new partially premixed combustion model and the laminar flamelet
model, which has been extended to include non-adiabatic effects such as
radiation, discrete phase sources, and enthalpy corrections to temperature
and density. The coupled solver has been enhanced to better handle chemical
kinetics in laminar flows. All combustion models in FLUENT 6.0 are now
compatible with LES. In addition, chemical mechanisms can now be imported
into FLUENT in the widely used CHEMKIN format. The NOx model now allows
the use of the two-variable PDF model to account for turbulence-chemistry
interaction even if the PDF model was not used for the main combustion
calculation. For coal combustion, the chemical percolation devolatilization
(CPD) model has been implemented. Predictions of off-gas amounts and composition
using this mechanistic approach have correlated well with measured data
for a wide variety of coals. In the area of surface reactions, significant
improvements in convergence for low-pressure chemical deposition problems
and stiff surface chemistry are now in place. Additionally, surface species
can be selected as both reactants and products in surface reactions, allowing
for bulk etching to be modeled.
"Version 6.0 provides greater breadth to simulate
different types of analyses. New features, such as supersonic flow using
the PDF model, and improvements in post processing, have brought CFD to
a whole new level. I envision that this code will greatly benefit my work
in simulating burner exit profiles and testing previous models."
Jamey Condevaux
Williams International, U.S.A.
Heat Transfer/Phase Change
Targeted applications include steel manufacturing/continuous casting,
underhood flows and engine block flows.
FLUENT 6.0 contains a new surface-to-surface radiation model. It is a
view-factor based model with a built-in capability to cluster surface
faces. The size of the grid that is used for the view factor calculation
is therefore reduced, as is the memory requirement for the calculation.
This model has the potential to be less expensive than the discrete ordinates
model for transient problems, and for parametric studies on the same mesh.
Other features include the ability to use non-conformal meshes at fluid/solid
interfaces, providing for more convenient meshing of conjugate heat transfer
problems in complex geometries. The melting and solidification model,
now accessible from the graphical user-interface, is compatible with the
VOF model. Users can now specify the contact resistance at walls for solidified
material, compute solid pull velocities, and include the effect of Marangoni
convection.
The cavitation model is now compatible with all of the multiphase models
in FLUENT 6.0. It can handle situations where the drift velocity between
the two phases is significant. It can also handle vapor phase compressibility.
"The testing that I have done on the spray model enhancements in
FLUENT 6.0 have shown promise for Jaguar's future powertrain applications.
Qualitatively speaking, the spray geometries were correct, problem setup
was straightforward and logical, and the post-processing capabilities
were excellent. For all scenarios modeled, the solutions converged well
with few problems."
Steven Pierson
Jaguar Cars, U.K.
Transient Flows
Targeted applications include bubble column reactors, fluidized bed
reactors, 1-D code coupling, and flow-induced noise prediction.
FLUENT 6.0 has the ability to predict flow-induced noise using an implementation
of Lighthill's acoustic analogy in conjunction with a transient flow
simulation. The technique is appropriate for modeling far-field noise
from external flows.
An important new solver enhancement is the availability of adaptive time-stepping
to improve the efficiency of transient simulations. A number of important
enhancements for transient post-processing also have been added. The user
can automatically compute time averages (means) and root-mean-squares
of the instantaneous values sampled during the calculation. The ability
to generate animations has become much more automated. Animations can
be written out as a set of hardcopy images in any supported format or
concatenated as an MPEG file.
Coupling with the 1-D engine analysis
code, GT-Power, is now supported on Sun,
Silicon Graphics, Hewlett Packard, Alpha,
and NT workstations.
And Much More
A completely new capability that will be available for beta testing in
FLUENT 6.0 is the ability to model moving/deforming meshes for in-cylinder
flows. The novel approach taken in FLUENT requires the user to specify
only the initial mesh and the boundary condition for the moving wall.
The targeted applications in this area include automotive in-cylinder
flows and simple moving and deforming mesh problems.
FLUENT 6.0 contains many other important enhancements as well. In the
area of turbulence modeling, the k-omega model has been implemented as
a new enhanced near-wall model. An MHD model has been implemented and
new non-Newtonian flow models have been added. The "fix" option
is available so that users can specify values for selected flow variables
in non-boundary cells.
Temperature contours on a flame surface and contours of vorticity magnitude
on the mid-plane of a gas turbine combustor, solved using the LES turbulence
model and the new partially premixed combustion model in FLUENT 6.0
Improvements have also been made in the areas of parallel processing,
including a new feature, dynamic load balancing, or automatic migration
of cells between partitions to maintain a balanced load on each processor.
Numerous post-processing extensions have been added, together with the
ability to export data and graphics in new formats. Data can be imported
from the CGNS format, allowing results from other codes to become more
easily shared with FLUENT.
In summary, FLUENT 6.0 contains an impressive range of new and improved
functionality in several key focus areas. It has been field-tested and
is ready to meet challenging needs. Tutorials have been developed around
many of the cases that were used for the applicability testing. Available
for download from the User Services Center, these tutorials have been
specifically designed to teach users how to model the targeted applications
using the new software. At Fluent, we are very excited about the new capabilities
that are being delivered in this product and look forward to continuing
to provide new functionality in the FLUENT 6 platform during the next
few years.
"The most significant new features, especially for
the users in turbomachinery, are the new 'turbo' post-processing
capabilities, which makes work a lot easier. Additionally, the new features
in turbulence modeling are the result of remarkable technical advances
to FLUENT 6.0."
Rolls-Royce,
Germany
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