Swiss Army CFD
Once the specialized tool of aerospace corporations, CFD has become an indispensable tool
for product designers and industry.
The first successful modeling of fluid and gas flows was accom- plished by the aerospace industry, which recognized the advantages uch understanding could have for successful aircraft design. Now, the once exotic application of Navier-Stokes equations
for the modeling of flows is performed on just about anything, from the
world’s largest hydropower plant to a mundane rear-view mirror on a car.
The availability of computer-aided single-phase flow modeling, also
called computational fluid dynamics (CFD), has prompted companies
who develop these tools to expand their product line. One such company
is ANSYS, Cecil Township, Pa., which offers two CFD packages: FLUENT
CFX is a gen-
program with a
solver that has
been in industrial
use for more than
20 years. Over
time, the basic
tools have been
wrapped in an
user interface that allows for customization and automation.
FLUENT, meanwhile, was added to ANSYS’ portfolio in a 2006 acquisition of Fluent Inc., which was known for its own CFD solution. Already
popular with engineers, FLUENT is a broad-based physical modeling
tool for flow, turbulence, heat transfer, and reactions.
Instead of refining an existing product, these scientists are often pushing
the envelope of fundamental physical understanding.
“Out-of-the-box solution capabilities meet the needs of many CFD
engineers, but most researchers are taking their complex simulations to
another level,” says Wim Slagter, lead product manager, ANSYS Inc.
Academic researchers, he says, need to ensure that their solution of
choice has the breadth, depth, and scale needed to accommodate their
sophisticated CFD simulations.
Flow streamlines modeled using ANSYS CFD software show critical locations for a powerhouse in relation to the Haa-ak-suuk Creek waterfall on Vancouver
Island, B.C. Image: ANSYS
Applications, from modest to intractable
In recent years, as products have become extraordinarily complicated, CFD
has been seen as a way to fine-tune performance of existing technologies.
Turbochargers in automobiles, for example, have been steadily improving with help from CFD simulations, and are now being regularly used
in pickup trucks and economy cars. The improvements have been largely
incremental, but sometimes the improvements are dramatic. Polyurethane
wetsuits, developed with the help of CFD tools, were banned from the
2012 Olympics because the performance advantage for swimmers was too
pronounced. Too many records were broken in Beijing in 2008.
Such widespread appeal has led ANSYS to build a centralized suite, the
ANSYS Workbench, to help handle the many different tools that developers want to access while conducting research. In addition to the CFD
packages, simulators, workflow, and data management are all accessible
These improvements appeal to researchers in the academic setting as
well because they give extra flexibility to the way a CFD study unfolds.
Academic research, in particular, tests the limits of what CFD can do.
CFD: A good fit for hydropower
Large industries, especially those involved in process technologies like
steel, oil and gas, and chemicals, also benefit from CFD tools. The hydropower industry, in particular, depends on them for obvious reason. Efficient turbine operation depends on the ability to accurately understand
water flow through changing conditions and time. But other aspects of
hydropower operations must also account for flow, some of which might
Every dam is designed to accommodate flooding. But even if a dam is
designed to withstand and manage the worst of nature’s onslaught, the
outbuildings, powerhouses, and infrastructure adjacent to the dam could
be inundated. To reduce this risk, planners use CFD to determine where
and how flood waters will flow in a worst-case scenario.
In a recent project that used ANSYS’ tools, a Canadian client of Kawa
Engineering Ltd., Vancouver, B.C., needed to locate a powerhouse close
to a waterfall in an area with minimal flood risk. If flooding did occur in
the powerhouse, it would be costly. Finding a suitable location away from
flooding also decreases the need for additional components to protect
electrical equipment (if flooding does occur). This helps, in the end, to
reduce the construction costs.
To begin their work, a Kawa Engineering designer used ANSYS CFX
to create a model of the riverbed’s surface and shores, near where the
powerhouse will be positioned, using data collected via laser scanning
and imported into CAD software. Then ANSYS DesignModeler software
helped simulate the flooding environment and determine where to place
ANSYS CFD came into play when Kawa engineers used the Eulerian-Eulerian multiphase model to define the interaction between flood water
and the ambient air for open channel flow. Floodwater makes an initial
hydraulic “jump” as it flows through a feature like a waterfall. By running
the CFD simulation on a 32-core cluster computer and repeating the
simulation multiple times using different river conditions, the designers
discovered the maximum hydraulic jump that could occur.
Kerem Karakoc, Mechanical Designer,
Eric Chen, Structural Engineer,
Kawa Engineering Ltd.