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The Newsletter of the CD adapco Group
STAR-Works:
Mainstream CAD for CFD
CD adapco Group
launches expert
system, eess--ttoooollss
New MINI optimized
using STAR-CD
and eess--uuhhoooodd
CFD modeling
of a new bridge
in complex terrain
STAR-CD helps
design new shoes
for Clarks
4
5
10
13
16
ISSUE 17 Summer 2002
1 STAR-CD Dynamics � Spring 2002
CORPORATE NEWS
contents...CORPORATE NEWS
Heavy liquid metal project 3
New offices for CD adapco Group 3
North American user conference 3
STAR-CD performance webpages 3
IPAQ winner 3
PRODUCT NEWS
STAR-Works 4
es-tools 5
New combustion model for STAR-CD 6
Chemistry enhancement for STAR-CD 7
APPLICATION STORIES
BIOMEDICAL
CFD simulation of flow in a heart 8
COVER STORY
CFD analysis of hydraulic tank of an earth moving vehicle 9
A theme to a User Group Meeting
A distinct feature of the CD adapco Group’s 10th Annual European User Group Meeting was that
so many of the presentations seemed tuned to the theme of how CFD is becoming integrated
into the design process.
Clients such as DaimlerChrysler and Volvo made clear that they see STAR-CD as part of their
"virtual engineering toolbox" and highlighted its importance in developing an effective and
efficient product development process. The CD adapco Group demonstrated its commitment to
this through demonstration of its integrated "Expert System" es-tools (described on page 5),
which capture and make available high level application-specific methodologies. Integration
also featured in presentations involving the coupling of CFD with other CAE tools to enable
calculations of aeroacoustic noise sources, fluid/structure interaction, and CFD with chemistry.
A presentation on the FRONTIER optimization tool gave a vision of how engineers of the future
will be empowered within integrated design environments to bring high quality products to
market even faster.
The general question "Where is CFD going?” was posed and answered in several ways. My
own comments about the practicality of virtual engineering were complemented by Milovan
Peric's keynote presentation affirming that creativity will continue to shape the future of CFD.
In his words, "The future is bright for both developers and users of CFD tools - CFD will never
become boring and both the need and possibility of improvements can hardly be exhausted".
The CD adapco Group aims to be both creative and practical. Both attributes will be essential if
we are to serve you well in the virtual engineering environment that is now becoming a reality.
The social highlight of the European User Group Meeting was a boat trip on the Thames.
The night was unusually balmy for late November and London truly excelled itself in floodlit
beauty. On board, staff and clients soon became immersed in an enjoyable atmosphere. We felt
it was a night to remember and we hope you felt that way too. Looking forward to seeing you
all in London again next year!
P. S. MacDonald, Director and General Manager
CD adapco Group
STAR-CD Dynamics � Spring 2002 2
CORPORATE NEWS
AUTOMOTIVE
New MINI uses STAR-CD 10
RAIL
Bombardier - on track with CFD 11
ENVIRONMENTAL
Guiding fish through the Bonneville 12dam
CFD modeling of new bridge in complex terrain 13
FOOD PROCESSING
LES simulation of airborne particles 14
MARINE
Minimising traverse flow effectsof passing ships 15
OTHERS
STAR-CD designs new shoesfor Clarks 16
TECHNICAL TIPS
Dr. Mesh 17
New technical publications 18
3 STAR-CD Dynamics � Spring 2002
CORPORATE NEWS
Heavy (Liquid) Metal Project
The CD adapco Group has joined an EU sponsored Framework-5
program for 2002 called "ASCHLIM". This aims to assess the ability of
leading CFD codes to simulate heavy liquid metals, as used for example
in high-power spallation targets. The project involves a consortium of
major European atomic research centers including users of STAR-CD at
CEA (France), ENEA (Italy), NRG (Holland), CRS4 (Sardinia, Italy) and
UPV (Bilbao, Spain).
The technical interest derives from the need to understand and
predict turbulence, free surface and bubble flows in such liquids. The
research institutes have extensive experimental data and from our
viewpoint this will enable us to validate STAR-CD's multiphase
capabilities in a new area of applications, and in regimes where
intuition is a poor guide to the real flow.
STAR-CD Performance Webpages
The CD adapco Group has launched a STAR-CD performance area on its
website. Hardware vendors are actively being encouraged to use this
area to show the versatility and robustness of STAR-CD on various
hardware platforms and CPU configurations.
Users are also encouraged to submit datasets for inclusion, with
the understanding that the data may be used freely in the public
domain. We trust that STAR-CD users will find the new webpages useful
when making decisions about hardware selection.
The pages may be viewed at: www.cd-adapco.com/support/bench
New Offices for the Group
The expansion of the CD adapco Group and its commitment to providing
global support on a local basis has recently seen the opening of new
offices in San Diego, CA, Hamburg in Germany and Lyon in France. The
new offices will be linked electronically to existing offices via the
Group’s virtual private network (VPN), thus ensuring that local support
can be supplemented when necessary by specialized industrial CFD
expertise from anywhere in the group.
North American User Conference6th-7th May 2002
The CD adapco Group takes great pleasure in inviting you to its annual
STAR-CD North American User Conference, to be held at The Atheneum
Hotel and Conference Center in Detroit.
The Conference will include two days of presentations from clients
across a variety of industries, as well as demonstrations from hardware
and software vendors, and a User Forum.
An informal reception will be held at the end of the first day where
you are welcome to meet other users, chat with CD adapco Group
employees, and enjoy the food and drink prepared by the catering staff
at the beautiful Atheneum.
For information about registration, presentations, etc., contact
Rachel Oliver, [email protected] or (+1)734-453-2100, ext.208 or visit
our website at www.cd-adapco.com/company/ugmintl.htm
Winner of Centrom Prize Draw
Following a prize draw held at the STAR-CD European User Group
meeting 19th-20th November, Centrom is pleased to announce that the
winner of the iPAQ Pocket PC is Darren Wolfe of ARUP. Darren is
pictured below right, receiving his prize from Neil Foster, HPTC Business
Manager at Centrom Technical Computing (TC) Ltd.
Centrom TC, a Compaq partner in the Technical Computing market,
is a leading systems integrator providing high-end, server-based
solutions tailored specifically to the requirements of Technical
Computing customers.
For further information about Centrom TC and its work in the High
Performance Technical Computing sector, please contact Neil Foster on
01737 823244 or visit www.centromtc.com
5 STAR-CD Dynamics � Spring 2002
PRODUCT NEWS
What’s in a name?Expert Systems!
The CD adapco Group is involved in the development of advanced
application-specific tools. These have brought together all the
methodologies required from automatic meshing to post-processing to
help the user achieve an optimized CFD solution. Initially, we adopted
the name "EZ-tools", where EZ, pronounced the American way,
suggested "easy". But then we started thinking. The tools actually
offered a new approach to CFD applications, with all the characteristics
of an expert system, namely the ability to "deliver ways of doing
particular things". So, we changed the name to Expert System Tools, or
eess--ttoooollss!
Below is a brief description of the eess--ttoooollss now available:
The eess--aaeerroo tool is an expert system for solution of external
aerodynamics problems. Starting from a good CAD surface, eess--aaeerroo has
an easy–to-use GUI to guide the user through geometry import, surface
preparation, template generation, mesh generation, run set-up and
post-processing.
eess--bbaarrtt (building and room thermofluids) offers the architectural
engineer a modern CFD application customized to simulate air flow and
temperature prediction in building spaces. Working in conjunction with
AutoCad Architectural Desktop, eess--bbaarrtt is therefore enabled to work
within this industry’s preferred CAD environment.
The eess--ffssii tool enables STAR-CD to analyze linear (small displacement)
fluid-structure interaction problems by efficient coupling to FEA
structural analysis codes such as ANSYS. Solutions can be achieved
with no more computer resource than is required for a typical CFD run.
Applications include operation of pressure-actuated valves, flutter of
turbomachinery fan blades, sloshing in fuel tanks and flow-induced
vibration of tube bundles.
The eess--iiccee expert system automates setting up and running the
sophisticated moving mesh technology required for engine simulation. It
automatically produces a parameterized meshed template that can be
altered for specific engine configurations. eess--iiccee empowers engineers as
never before to achieve rapid, accurate CFD analysis of internal
combustion engines of all types. The technology enables engineers to
quickly evaluate and optimize new internal combustion engine designs.
The eess--uuhhoooodd tool is an expert system to help STAR-CD users achieve
CFD solutions for complex automotive underhood geometries. Starting
from a CAD surface, eess--uuhhoooodd provides an easy-to-use GUI that guides
the user through importing geometry, template generation, closing the
surface, mesh generation and the mapping of boundary conditions,
ready for CFD solution.
eess--ttuurrbboo is an expert system to help turbomachinery engineers generate
accurate CFD simulation of internal aerodynamic flows for both axial and
radial turbomachinery components. eess--ttuurrbboo reads the CAD surface
description or interface directly with the users’ design system to import
flowpath and blade geometry definitions. The grid is created
automatically.
Watch out for more details on each of these eess--ttoooollss in forthcoming
issues of the newsletter.
New Combustion Model for STAR-CD
STAR-CD Dynamics � Spring 2002 6
PRODUCT NEWS
The ECFM (Extended Coherent Flame Model) is STAR-CD’s new capability
for predicting combustion processes.
In recent years, stratified charge engines, particularly Direct Injection
engines, have attracted great interest due to tightened controls on
pollutant emissions and the demand for a reduction of fuel consumption.
In such engines, the fuel can be distributed within the cylinder in a wide
range of equivalence ratios, from very lean to very rich mixtures. This
strategy allows better control of the pressure peak, the temperature of
burnt gases and the concentration of pollutants under different loads. As
a consequence, the engine performance and its fuel efficiency and
emission levels are improved.
In order to understand the complex processes involved, a model with
comprehensive capability is required.
The ECFM was implemented in STAR-CD in collaboration with
Renault. It is a combustion model for inhomogeneous turbulent premixed
combustion based on a conditional thermochemical approach. STAR-CD
solves a transport equation for the flame surface density and transport
equations for 12 chemical species involved in the fuel oxidation
mechanism. The combustion is carried out in two stages:
S.Duranti, C.Kralj, F.Lange, Y.Liang, STAR-CD Development team
1. the fuel oxidation stage, for which the reaction rates are expressed in
terms of the flame surface density and laminar flame speed.
2. the post-flame stage which accounts for further oxidation of fuel in
very rich mixtures, for O2 and N2 dissociation, for NOx excess and for
local chemical equilibrium.
A number of correlations are used to get the laminar flame speed, and
its reduction due to EGR is also considered. A special treatment is
included in STAR-CD to determine the chemical reaction mechanism at
different equivalence ratios. Wall quenching effects on flame surface
density and on laminar flame speed are considered in order to avoid
over-predictions of reaction rate and heat release close to walls.
Compared with other combustion models in commercial CFD codes,
the ECFM model will be capable of predicting more realistic values for
thermodynamic quantities as well as a wider range of species,
including NOx.
Flame surface density fieldVelocity fieldTemperature field
Results at different crank angles after ignition in collaboration with Renault
Enhancement ofChemistry Modeling inSTAR-CD
Major enhancements have been made to the complex-chemistry
capabilities of STAR-CD, both through new stand-alone features and
links to the well-known CHEMKIN package, as follows:
1) Shared solver and transportproperty libraries with CHEMKIN
Users wanting to exploit the full power and versatility of the well-known
CHEMKIN chemical reaction package in conjunction with STAR-CD can
now do so via shared-library facilities. These allow STAR-CD to use the
advanced CHEMKIN coupled solvers and transport property database
directly, by running the two codes in a coupled fashion. These features,
together with the full CHEMKIN interface built into PROSTAR, provide
unparalleled ease of use and enable the combined codes to perform
complex flow/chemistry calculations.
2) New coupled complex-chemistrysolvers and data input facilities
STAR-CD’s ability to perform complex chemistry calculations in a stand-
alone mode has also been enhanced through the provision of three
robust and fast coupled-chemistry solvers. These can be applied to
transient and steady-state reaction systems of ‘arbitrary’ complexity, in
terms of both number of species and reactions. A special decoupled
reaction module is designed to separate those reactions that are
considered to have negligible effect on the main reaction system from
the calculation, thus allowing for a substantial reduction in
computing time. Chemical kinetic rate information in standard
CHEMKIN format can be imported using the built-in CHEMKIN interface.
In addition, a new General-Purpose Interface allows the user's own
chemistry package to be linked to STAR-CD.
7 STAR-CD Dynamics � Spring 2002
PRODUCT NEWS
Yongjun Liang, STAR-CD Development team
3) Easier to use and more versatiletransport property module
STAR-CD now has an expanded database of transport properties, such
as viscosity, heat conductivity and species diffusivity, as polynomial
functions of temperature. These properties can be readily available
selected or defined by the user via PROSTAR. In addition, the General-
Purpose Interface makes it possible for users easily to incorporate the
user’s own transport property package into STAR-CD.
As an illustration of the new capabilities, an axisymmetric confined
laminar jet diffusion flame was simulated using STAR-CD’s built-in,
coupled-chemistry solver where a detailed reaction mechanism (see
Table 1) and the complete transport processes (including multi-
component diffusion) were considered. In this case, the fuel stream - a
mixture of CH4, H2 and N2 - discharges through the central tube into a
co-flowing air stream. Figures 1 and 2 show the temperature contours
and the radial profile of temperature at an axial location, respectively.
The results agree well with experimental data.
Figure 2: Radial distribution of temperature at an axial location.
Figure 1: Flame temperature contours at an axial location.
Figure 2: CFD mesh
of left ventricle at one
instant of time
including portions of
aortal and atrial
passages
STAR-CD Dynamics � Spring 2002 8
APPLICATIONS
STAR-CD Simulates the Human Engine
STAR-CD is widely-known for its unique capabilities to simulate the
complexities of gas motion and other in-cylinder processes in
automobile engines. Recently, a group of researchers at the Imperial
College of Science, Technology and Medicine in London
have exploited some of those same capabilities to
calculate the flow in another kind of engine – the
human heart. It is intended that the simulations will
be used initially to assist in clinical diagnosis and
ultimately also as a component of virtual surgery, to
help in planning the real thing.
The approach developed involves the
combined use of CFD and Magnetic
Resonance Imaging (MRI), which is the
technique employed in Computer-Aided
Tomography (CAT) scanning machines.
The information obtained by MRI is in
the form of thin two-dimensional
image ‘slices’, like the example shown
in Figure 1, on which the inner surface
of one of the heart chambers selected
for study, the left ventricle, has been
traced. Sets of these slices at various
levels through the ventricle are obtained
at discrete times spanning the filling and
emptying phases of the heart cycle. Image
processing and geometry reconstruction
techniques are then used to determine the
complete chamber topology at each time.
CFD, in the form of STAR-CD, then takes
over. The time-varying ventricle volume is fitted
with a moving mesh (Figure 2), including arbitrary
sliding interfaces to accommodate the ‘inlet’ (left atrium)
and ‘outlet’ (aorta) passages, at which the boundary
conditions are applied. Calculations are performed over a
number of heart ‘beats’, until a cyclically-repeating solution is
obtained. A snapshot of the predicted flow in a vertical plane during the
inflow (diastolic) phase, is shown in Figure 3 and alongside are
corresponding measurements obtained using MRI. The agreement is,
as they say, heartening!
Professor David Gosman, Imperial College, London
Figure 1: MR slice image of heart with
outline of left ventricle (LV).
Figure 3: Simulated (right)
and measured (left) flow fields
Caterpillar is well known for world leadership in the
production of equipment for the construction and mining
industries, including huge earth-moving vehicles. The
bigger and more complex the machine, the more
sophistication in design is required to ensure
reliability. Here we describe how CFD analysis was
used during vehicle
development to avoid
damage caused by
cavitation within the
hydraulic system.
One of the
components of the
hydraulic system is a
partially filled tank, which receives the
return flow of the fluid from the implement pump. The flow shoots into
the top of the tank with high velocity, creating strong flow circulation.
Perforated rectangular baffles aim to calm the flow, but aeration can
occur. Aerated fluid is then carried via suction lines to the implement
and fan pumps, increasing the chance of cavitation in the pumps.
Caterpillar's design challenge was to use STAR-CD to catch the problem
at its source, by finding ways to calm the strong fluid circulation inside
the tank and reduce aeration.
STAR-CD was used to predict qualitatively and quantitatively the
fluid circulation in the tank, and specifically to find the fluid pressure
and velocity distribution for standard flow rates. The model represented
the flow conditions in the tank, including details of the perforated
baffles (modeled as porous media), suction lines, flow rates and fluid
properties.
In addition to modeling the baseline configuration, three new
designs were simulated:
■ With baffles encircled by a porous circular tube to more uniformly
distribute the high flow jets from baffle holes
9 STAR-CD Dynamics � Spring 2002
APPLICATIONS
■ The whole left and right sides of the baffle plates perforated to
increase the area open to the fluid
■ Extra holes added on each left and right baffles to provide more open
flow area
STAR-CD was able to predict significant differences of flow circulation
as well as other flow parameters in each case.
The magnitude of the flow circulation dictates the severity of
aeration in the tank, and a comparison of the vector plots from STAR-CD
showed that the first design variation has lowest circulation and is
therefore the best solution of the aeration problem. Furthermore, the
porosity of the circular tube was found to play a major role in
determining the pressure drop in the tank; as porosity increases the
pressure drop decreases. This aspect of the design could also be
optimized. In this preferred design, high flow jets are dispersed and
flow proceeds uniformly inside the tank.
In summary, Caterpillar found that the CFD approach using STAR-CD
provides detailed understanding of the flows and allows optimization
of the design before building and testing prototypes. Overall time
and cost of design modifications and the number of actual
hardware tests could be reduced.
CFD Moves the Earth for CaterpillarPriyatosh Barman
Hydraulics and Hydraulic Systems, Caterpillar Inc
Figure 1: Velocity contours of the baseline model
Figure 2: Velocity contours of preferred model
STAR-CD Dynamics � Spring 2002 10
APPLICATIONS
Underhood ThermalAnalysis of new MINI
That style icon of the sixties, the Austin MINI, achieved greatness
without the help of CFD. However, its stylistic successor the new MINI
had to be a thoroughly modern car developed using the latest software
tools. The CD adapco Group welcomed the opportunity to use its new
Expert System CFD tool, eess--uuhhoooodd to test the car’s underhood cooling
performance.
During the product definition phase for the new MINI, a complete
CAD representation was sent to the CD adapco Group. Once this had
been read into eess--uuhhoooodd, the next task was to produce a closed surface
of the geometry read for meshing using the surface wrapping tools.
Figure 1 shows the underhood CAD data provided and figure 2 shows
the closed surface produced. Next, the fluid mesh was built using an
automatic custom mesh to locate increasing levels of refinement
around areas of high surface curvature or thin gaps between surfaces.
The MINI model totaled 5.5 million cells and featured a detailed
underhood area and underfloor region as well as a large external
domain. Once the mesh was complete, the model was run at three
different conditions to simulate the planned test program. The model
included a fan mesh which, in the ‘car at idle’ simulation, was drawing
air into the underhood environment.
This type of full three-dimensional analysis is allowing engineers to
evaluate particular components in the MINI’s underhood as follows:
■ The location of the fan and design of its blades could be assessed
during the underbonnet installation, something very difficult to do
using traditional testing techniques.
■ Leakage paths around the radiator, which would reduce the radiator’s
efficiency, could be identified. This included the redesign of the radiator
grill or sealing the flow paths around the radiator. Minor modifications
to the model could be easily processed and the model re-run from the
previous solution to achieve a rapidly converged new solution.
Steve Hartridge, Senior Engineer, CD adapco Group
Figure 1: The
underhood CAD
data provided
In the case of the MINI, the major leakage paths around the radiator
were identified where high velocity air was moving around the radiator
package rather than through it. After this was highlighted, additional
sealing strips were added around the radiator pack, and testing proved
that there was an improvement in heat release.
■ As well as investigating the flow through the
underhood area under driving conditions,
the model could be used
to investigate a
s t a t i o n a r y
condition when
the vehicle’s fan
is operating. This
can show a very
different flow field
from the ones
under driving conditions and again highlights areas of reverse
flow through the radiator, which will reduce the efficiency of the
cooling pack.
■ In addition to looking at the side effects of airflow in this vehicle, the
engine coolant flow could be modeled. This included the crucial heat
transfer between air and coolant and made possible the investigation of
any area of the radiator not expelling its share of heat. The end tanks of
the heat exchangers were also included so that any maldistribution of
coolant throughout the matrix would be obvious.
The use of eess--uuhhoooodd enables detailed underhood analysis predictions
of cars under design. Such high level analysis allows design engineers
to understand how particular components will survive in the conditions
they will be subjected to during service. It also allows Powertrain
engineers to predict the efficiency of a cooling system in an underhood
environment.
eess--uuhhoooodd continues to demonstrate its powerful capabilities, and
the CD adapco Group looks forward to supporting its clients in the
automotive industry as they take up this new technology to get a head
start in underhood analysis.
Figure 2: The
closed surface
produced
Copyright of BMW AG
Bombardier on Track with CFD
At the Centre-of-Competence for Aerodynamics
and Thermodynamics (CoC-ATh) at Bombardier
Transportation (BT), we use state-of-the-art
predictive CAE tools such as CFD and CAA to
optimise product design for the rail industry. Our
goal is to match customer requirements whilst
reducing operating and design costs. Here we
describe the diverse mix of some recent
investigations.
Comfort and Safety for ourCustomers
For vehicle cooling and climate comfort analysis
we use steady state CFD methods. Figure 1 shows
the temperature within the compartment of the
latest generation of BT’s regional trains assessed
during the vehicle’s pre-design phase. CFD allows
optimization of new climate control concepts and supports the
specification of HVAC systems with best balance between performance
and cost. Three interrelated programs are used: SWF for the prediction
of the heat load of the passenger saloon; STAR-CD for the internal flow
field and temperature distribution; TIM for thermal load and comfort
status of selected occupants1.
To assess the safety of Bombardier’s trains in
all weather conditions, the aerodynamic
loads on the critical leading car
have to be determined by wind
tunnel experiments and CFD cal-
culations illustrated in figure 2.
The computations reveal that the
predictive accuracy of steady-
state CFD decreases with
increasing yaw angles (above 20°),
when transient phenomena, e.g.
vortex shedding, start to dominate the
flow.
CFD for Noise Source Prediction – a Technology Frontier
Transient flows have been studied at CoC-ATh to predict aeroacoustic
noise sources. For example, figure 3 shows CFD results for a high speed
11 STAR-CD Dynamics � Spring 2002
APPLICATIONS
pantograph where the
contact strip exposed
to cross flow causes
pronounced vortex
shedding.
HVAC fan
noise is another
noise problem. The
key here is to avoid penetration of
unsteady large-scale vortices into
the HVAC duct. Large-Eddy-
Simulation (LES) was used to
investigate transient internal
flows. Figure 4 shows the velocity
distribution in the HVAC inlet
section for Metro Berlin.
Unfortunately, LES is generally too computationally intensive to
solve inherently unsteady external flows at high Reynolds numbers.
DES and URANS methods were therefore applied in a collaborative
effort with the Technical University of Berlin and DaimlerChrysler
Research and Technology. The results were encouraging and
demonstrated the superiority of DES over URANS methodology, applied
to the same mesh and model set-up.
Currently, there is also collaboration underway with the CD adapco
Group to implement DES into STAR-CD.
Further Down the Track?
At Coc-ATh, Our business is to meet our clients’ demands in areas such
as operational safety and thermal and acoustic comfort. With CAE tools
such as STAR-CD we hope to deliver these in an ever more cost-effective
and timely manner.
1 SWF and TIM have been developed by DaimlerChrysler Research and Technology.
Alexander Orellano, Bombardier Transportation
Figure 1: Velocity and
temperature distribution
within the compartment of
the regional train ITINO
Figure 3: Pressure
distribution at
the German
high-speed
pantograph
DSA 350
Figure 4: Velocity
distribution of the HVAC
inlet section of the Metro
Berlin obtained from
RANS (left) and LES
(right, snapshot at an
arbitrary miscellaneous
time)
Figure 2: Streamlines of a high-speed
double-decker train experiencing
strong cross-wind gust
Our approach was at 2 scales: a numerical flume model was used to test
the implementations or parameterizations of intake modifications; then
those parameterizations were implemented in a full forebay model and
various operational and structural scenarios run. The numerical model
was used to test the sensitivity of the flow near the powerhouse to
changes in spill volume, and the spill volume with the largest lateral
components at the powerhouse was then used in all of the remaining
scenarios. These included combinations of removable structural
features and operational alternatives. In total, 15 combinations of
operational scenarios and structural alternatives were run.
The results from all of the operational scenarios highlighted that
project operations were the most significant cause of lateral flow in the
intakes at B2. The various structural or operational configurations had
little influence on the lateral flow inside the intake. In addition, the
lateral flow tends to be eliminated by the time the flow gets to the
gatewell slot. With the lateral flow being minimized if not eliminated at
the gatewell slot, the same design prototype tested at Unit 15 was
installed at Unit 17, and will be tested this year.
For further information please contact:
[email protected] (Laurie Ebner)
Figure 3: Plan view for partial load
STAR-CD Dynamics � Spring 2002 12
APPLICATIONS
Guiding Fish through the Bonneville Dam
The Columbia-Snake River system, in the Pacific Northwest of the U.S.,
plays a vital role in the economic well-being of the region. Various types
of numerical and physical model investigations and field efforts are
being conducted by the US Army Corps of Engineers to re-establish fish
runs. One of these studies addresses improvements to a fish guidance
system and in this article, it is explained how CFD studies for the
Bonneville Project are being used to support engineering and
operational decisions.
Multiple structural modifications have been made to Unit 15 of
Bonneville’s 2nd Powerhouse (B2) that have improved the fish guidance
efficiency. These structural improvements have been designed to
increase the overall gatewell flow and maintain uniform velocities into
the gatewell. These conditions are believed to increase the number of
fish guided into the gatewell and the uniform velocity is believed to
decrease the possibility of escape from the gatewell into the turbine.
The majority of the design effort was conducted in a physical model
with all flow going directly into the turbine intake.
The plan was to make the same improvements at Unit17 although,
given the large lateral flow components known to exist near the unit, it
is unknown if the improvements will work as well as those of Unit 15. A
STAR-CD model of the Bonneville Forebay was used to investigate the
lateral flow component near the B2 powerhouse and into the gatewell
slot (Figure 1). Complex flows near the powerhouse result from the
excavated bathymetry in front of the turbine intakes and the Bonneville
Project operations. The flow at B2 is most uniform when all of the B2
turbine units (Units 11-18) are operating. When the total powerhouse
discharge requires that not all turbines be used, then the load is
typically split between the end units (11,12,17, and 18). This split flow
operation results in lateral flow across the non-operational center units
(13-16), and partially across Units 12 and 17.
Laurie Ebner, US Army Corps of Engineers, Portland District,USA
Cindy Rakowski, Pacific Northwest National Laboratory
Richland, Washington, USA
Figure 1:
Streamlines for
partial load
Figure 2:
Vertical slice
through Unit 15
for full load
Figure 4: Horizontal slice for partial load
UNIT 11 UNIT 15 UNIT 17
A new bridge is to be built over the Svinesund fjord, on the border
between Sweden and Norway. The total length of the bridge will be 680
meters and the span will be 242 meters. SMHI have calculated the wind
and turbulence conditions in the area around the bridge. The purpose
of the study was to predict wind load for the bridge. An image of the
planned bridge is shown in figure 1.
From height data, a mesh measuring 10km by 10 km with a height
of 1 km was built. As seen from figure 2, the terrain is complex. The light
blue colour is the water at sea level and the highest area (red) is about
160 m above sea level.
Land use data for every 25 metres in 20 different classes were used
to define ground surface roughness. The data were based on satellite
images. Examples of different land use classes are: water (light blue),
bog area (blue), different kinds of coniferous forest (green colours),
deciduous wood (yellow), rockface (red), open area (light brown) etc.
Figure 3 shows the variety of land use data used in
the model.
Figure 4 shows that wind speed is high over the sea due to low
friction. When the airflow enters land it is affected by the higher friction
there and the topographic landscape. The turbulence increases and the
wind speed decreases near the ground. A new boundary layer is built
over land. Figure 4 shows how the wind speed differs a lot at the 10
meter level above ground due to differences in the landscape.
In one site not far from the bridge, the three wind components were
measured 10 meters above ground. From these data sets we could
calculate the turbulent kinetic energy (blue dots) and compare with the
CFD calculations (red line). In figure 5, one can see that the agreement
between model and measurements is very good for the given wind
direction.
Figure 6 shows the vertical wind velocity component in a vertical
cross section just where the bridge will be built. The horizontal line is
50 metres above sea level and approximately the height of the bridge.
For more information visit www.smhi.se/cfd, or contact
[email protected] [email protected]
Figure 1 - Artists impression of planned bridge
13 STAR-CD Dynamics � Spring 2002
APPLICATIONS
CFD Modeling of a New Bridge in a Complex TerrainLennart Wern and Mikael Magnusson
Swedish Meteorological and Hydrological Institute
Figure 2: The terrain
Figure 3: Land use data
Figure 4: Windspeed calculations
Figure 5: Model comparison measurements
Figure 6: Vertical wind component in a vertical cross section
Figure 4 shows
locations of
deposited
par t ic les .
Red particles are released 2mm from the wall while
green, blue and cyan colored particles are released 4, 6 and 8 mm from
the wall. The conclusions drawn from figures 2 and 3 are clear.
Releasing particles after t=10 s (steady flow) results in a deposition of
about 0.6% of those released. Releasing particles from t = 0 (impulsive
start) produces a deposition of 21.7% in a far more regular pattern
which reflects more organized large-scale eddy structures. These
structures are related to the higher velocities near the plate and petri
dish.
The conclusion of these studies is that LES is an indispensable
tool for flows of this type. For this particular case, which
simulated airborne contamination of food, it showed that
reversal of the flow increases particle deposition as
compared to steady flow situations.
Further information: Contact Poul
Scheel Larsen, [email protected]
Figure 2: Tracks from
particles initially placed
8 mm above the
wall.
STAR-CD Dynamics � Spring 2002 14
APPLICATIONS
Particle Deposition In Low-SpeedHigh-Turbulence Flows
Particle deposition on walls bounding turbulent flows appears in many
industrial process components and in outdoor and indoor
environments. Of particular importance for food-processing industries
is the airborne
contamination of food
products when exposed
to the ventilated indoor
environment. The
Technical University of
Denmark has recently
been using STAR-CD to
calculate the con-
centration of airborne
particles.
A frequently
employed particle-sampling device is the petri dish (diameter 100 mm,
height 16.7 mm). The purpose of the computational study described
was to predict the specific deposition flux in a petri dish on wall setup
using LES (Figure 1). A simple Gaussian random number algorithm
without spatial and temporal correlations generated the 100%
turbulence intensity of the specified inlet velocity of 0.2 m/s, which is
found to be typical from field measurements. As a result, large-scale
structures developed only slowly. The present LES scheme employed
the standard Smagorinsky sub-grid scale model, a time step of 0.005 s,
and second order accuracy in space and time.
Preliminary studies using RANS with a k-ε model showed
deposition patterns unlike those observed in exploratory experiments
under similar flow conditions. This confirmed the anticipation that near-
wall coherent structures govern particle deposition in a turbulent flow.
It was therefore decided to use LES, resolving scales down to about 3
wall units, and this approach has shown time-resolved coherent
structures in the near-wall region.
Figures 2-4 show sample results from the LES simulations. Four
rows each of 25 particles (Figure 4) are released at t = 0 s to imitate the
effect of sudden flow reversal, and at every second thereafter. Figure 2
shows particle tracks for a row of
particles released 8 mm above the
wall. Figure 3 shows particle tracks for
a row of particles initially placed 2 mm
above the wall. Quite a few of the
particles shown in figure 2 are seen to
deposit into the petri dish while most
particles in figure 3 are deposited on
the perimeter and just downstream of
the dish.
Mads Reck, Poul S. Larsen, and Dan N. Sørensen
Department of Mechanical Engineering, Fluid Mechanics Section
Technical University of Denmark
Figure 1: Computational domain and boundary
conditions of the flat plate-petri dish set-up.
Figure 3: Tracks from particles initially placed 2
mm above the wall.
Figure 4: Petri-dish and locations of deposited particles and their initial positions.
Flow from left to right.
Improving Traffic Safety on Waterways
Tobias Linke, Antje Mueller and Martin Detert
University of Hannover, Germany
15 STAR-CD Dynamics � Spring 2002
APPLICATIONS
Transverse flows from lateral water discharges into waterways, for
example those caused by storm water outfalls, may cause passing
ships to drift. In order to provide traffic safety, such effects need to be
restricted so that outfall structures create well-balanced flow fields of
low intensity.
Until now, the common practice for developing outfall structures
has been to carry out very time- and cost-consuming physical model
tests, but in future numerical simulations could help to reduce this
overhead. An outfall structure has been developed by the University of
Hannover using physical model tests; it will be put into practice this
year in the Main Danube Canal in the city of Bamberg (Germany). In
order to judge the capabilities of numerical simulations in this
application, the structure has also been studied using STAR-CD.
Figure 1 shows the 36m-wide outfall structure including features
such as the pressure pipe, overfall weir and submerged wall, as well as
the topographic situation 200 metres up- and downstream, which were
all transposed into the numerical simulation. A mesh of about 80,000
cells was generated, with edge lengths between 0.05m and 3m. The
water/air free surface was modelled using the VOF method and the
standard high Reynolds-number k-ε turbulence model was used. The
calculation time was about 20 hours on a SGI Origin 200 Workstation.
Figure 2 shows the weir overfall in the outfall structure for the initial
numerical simulation. It is abundantly clear that the well-balanced weir
outfall seen in the model tests is similarly reproduced, in that the
discrepancy between calculated and measured overfall height never
exceeds 6%. A similarly low divergence between physical model test
and numerical simulation can be recognised when comparing the
calculated and measured flow field within and in the vicinity of the
outfall structure at half-water depth. This is illustrated in Figure 3,
which shows particularly good agreement in both the flow velocities
and directions in the outfall structure itself.
For similar investigations in the future, the use of more numerical
simulations is recommended in order to reduce the amount of very
time-consuming and costly physical model tests. Note, however, that
physical model tests cannot yet be replaced completely, since although
the current simulation methodology makes it possible to develop an
overfall structure from a purely fluid-mechanical point of view, it does
not take into account the influence of ship traffic on the waterway. This
is because the interaction of a moving object and its environment is not
presently implemented. Research is under way to close this gap.
For further information, please contact [email protected]
(Tobias Linke), [email protected] (Antje Mueller) or
[email protected] (Martin Detert).
Figure 1: Outfall structure at the Main Danube Canal in the City of Bamberg (Germany)
Figure 2: Calculated weir overfall in the outfall structure at the beginning
Figure 3: Calculated (Left) and measured (Right) flow field within and in the vicinity of
the outfall structure at half-water depth
In this way, STAR-CD
was able to provide useful
insight into the flow characteristics,
which are driven by the compression of the air channels during the
stepping cycle. Not only were the mass flows forced and drawn into the
sole quantifiable (showing that flow is forced through the sole from
heel to toe), but also the airflow inside the sole could be demonstrated.
In conclusion, this novel application takes full advantage of
STAR-CD's moving mesh capabilities, demonstrating the technology
and yielding insightful results which can also be used as a datum for
comparison against alternative designs.
A Step Forward inShoe Design
STAR-CD has been innovatively used for many challenging
applications. When considering such applications, shoe
design and in particular footwear ventilation, is not the first
thing that springs to mind. Nevertheless, STAR-CD has
recently been used to simulate advanced sole designs on
behalf of Clarks shoes.
A number of applications of CFD to different shoe
designs were considered and here we describe how
STAR-CD was used to simulate the airflow in the ‘Active Air’
brand. Clarks shoes developed their unique ‘Active Air’ systems
over 20 years ago to provide underfoot comfort in men’s shoes. The
footwear is promoted as having the dual effect of cushioning the foot on
ground impact as well as redistributing air inside the shoe through a
network of air channels that are compressed during the stepping cycle.
The effect is that air is also forced out of the channels as the sole
compresses, and more air is drawn into the channel as the sole
expands. Sweaty feet no more!
CFD modeling of the ‘Active Air’ system encompassed the flow
volume inside the network of channels. This was meshed using the
pro-am automatic meshing package and included a representation of
the localized compression of these channels during the stepping cycle.
The latter comes from measured pressure and deflections in the plane
of the insole as a function of time, which lasts for under a second. A
special methodology was developed, using a combination of PROSTAR,
bilinear interpolation and the user subroutine nneewwxxyyzz, to
map the data from the measurement sensors onto the
CFD model. The case took advantage of STAR-CD's
moving mesh capabilities to the full. The air was
modeled as a compressible fluid because
the channel volume compresses in the
heel section first, then punches air
towards the toes, then moves
back again due to the
pressure of the toe
impact and
expansion of
the heel to
its original
volume.
STAR-CD Dynamics � Spring 2002 16
APPLICATIONS
Mike Lewis, Senior Engineer, CD adapco Group
Figure 1: Velocity distribution; gross mass flow
Figure 2: Active Air computational geometry
Figure 3: Clean air
distribution inside sole
after 0.32 seconds
OpenGL and PrintingMany of the fancy images used to promote STAR-CD are made by using
PROSTAR with the OpenGL graphics drivers. At the moment, a lot can be
done using this version and there is extensive development underway
to make more new features available in the OpenGL version. This is
therefore, a good time to have a look at how it can be used.
OpenGL (www.opengl.org) is a high-performance graphics standard
that means developers can write a graphics code which runs well on any
platform from PC to high-end workstation. To use PROSTAR’S OpenGL
drivers on a Unix or Linux box, select the glm driver and on a Windows
PC choose the OpenGL Graphics Driver Setting from the Pre/Post
options.
When you start you will not see any obvious difference. Here is a
plot of pressure over a cycle helmet using 20 colours blended from red
to blue.
To enable the OpenGL functions, you need to turn them on by using
extended mode graphics. This is done by typing term,,,exte. The plot
changes from the standard banded graphics to the smooth OpenGL
plot.
When using OpenGL, you can choose to have lighting and contour plots
on at the same time, so turn a light on (light 1 on 1 1 1) and the mesh off
and you get a plot like this.
The drawback of OpenGL is that the hardware takes control of much of
the drawing, so when it comes to printing, the normal neutral file is of
no use. To print from OpenGL you need to save the screen as a bitmap.
For presentations etc a screen-dump is fine, but when you need high
quality output then numbers do not add up: a typical image from a
screen-dump is say 1200 by 900 pixels. If you have a printer that prints
at 600 dpi, then this image will be just 2 inches wide. If you print it
larger, then you may start seeing the pixels and the image will
look rough.
To overcome this, PROSTAR can be used to produce a series of
images that can be put together to make a much larger image. This is
done by a series of zoom and pans:
7 8 9
4 5 6
1 2 3
The images below show a comparison of a normal screen capture and
one made via the tiling method.
The PROSTAR macro and the code to do this can be found at:
www.cd-adapco.com/support/drmesh.htm
17 STAR-CD Dynamics � Spring 2002
TECHNICAL TIPS
Dr. Mesh
STAR-Works: Mainstream
CAD with CFD
This brochure introduces a new
product, STAR-Works, as
described in the article on page 4
of this newsletter. An illustration
of its ease of use is given in eight
simple steps.
STAR-CD Dynamics � Spring 2002 18
NEW BROCHURES
Technical PublicationsThe following publications are now available and can be obtained by sending an email request to [email protected], stating your preferred brochure and
contact details. Alternatively, you can download them as adobe pdf’s from: www.cd-adapco.com/products/brochuredownload.htm
STAR-CD Engineering
CFD and CAE Solutions
A general overview of STAR-CD’s
ability to provide insight into
complex fluid flow, heat transfer,
chemical reaction and
combustion processes, and how
this has been helping engineers
improve and optimize their
designs.
STAR-CD for the
Automotive Industry
This fold out poster edition gives
an overview of STAR-CD’s
applications in the automotive
industry and illustrates
STAR-CD’s ability to simulate a
range of flow processes in any
area of the automotive sector.
es-ice, expert system for
combustion in IC engines
es-ice is the latest productivity
tool to be released in the CD
adapco Group’s range of Expert
System software. es-ice
automates the sophisticated
moving mesh required for engine
simulation.
CFD applications from the
Chemical Process Industry
Many of our users in the
chemical and process industries
have benefited from the CFD
analyses of their flow problems
using STAR-CD. In this document
they share their experiences.
STAR-CD for the Chemical
Process Industry
With its comprehensive range of
physical models, STAR-CD is an
effective analysis tool for a wide
range of CPI applications.
Examples shown in this brochure
include: mixing, reaction,
separation, heat transfer, etc.
Europe Far East
Yokohama
CD-adapco JAPAN
Nisseki Yokohama, Building 16F
1-1-8, Sakuragi-cho, Naka-Ku
Yokohama, Kanagawa 231, JAPAN
Tel.: (+81) 45 683 1998
Fax: (+81) 45 683 1999
www.cd-adapco.co.jp
New York
adapco
60 Broadhollow Road
Melville, NY 11747, USA
Tel.: (+1) 631 549 2300
Fax: (+1) 631 549 2654
www.cd-adapco.com
London
Computational Dynamics Ltd
200 Shepherds Bush Road
London, W6 7NY, UK
Tel.: (+44) 20 7471 6200
Fax: (+44) 20 7471 6201
www.cd-adapco.com
Global offices of the CD adapco Group
Austin, TX
Cincinnati, OH
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CD-adapco Korea
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China
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Agency offices
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Malaysia
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Russia
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Singapore
CAD-IT CONSULTANTS
South Africa
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Taiwan
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A-Ztech Ltd
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