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27
STAR-CCM+
enables ICON to develop a complete-cabin CFD simulation process
for Airbus
Article by ICON
- Simon Weston, Thomas Schumacher.
Fig:01
Cabin Ventilation for the all new Airbus A350XWB
ICON provides independent and confidential technology and process consulting.
Since 1992, the company has been delivering tailor-made solutions and advice to
OEMs, SMEs and research organisations worldwide. CD-adapco software has enabled
ICON to deliver solutions for our customers most demanding requests. www.iconCFD.com
ICON
would like to thank Airbus-Deutschland for kindly allowing this
work to be presented.
A long-standing co-operation with Airbus
has seen ICON working on the design and improvement of ventilation
systems for a number of different aircraft programmes such as the
A380, A380-F, A340/330, A400M, A350XWB.
In the case of the A380, Airbus’ next generation full double-deck passenger aircraft, simulation engineers faced many new challenges. In its standard version the A380 holds 555 passengers in three classes, on two decks. In theory, a layout holding more than 800 economy class passengers is also possible. It is well documented that Airbus wants to offer airlines and passengers an improved level of cabin comfort and as a result significant demands are placed on the cabin ventilation system.
The
ventilation system has to fulfil not only the requirements imposed
by the authorities, like minimum air exchange rates or maximum pollutant
concentrations, but also Airbus’ self imposed limits like maximum
velocity, minimum humidity, etc.
In addition, the nature of the
cabin flow field has to be designed to ensure the risk for spreading
airborne transmitted diseases is kept to a minimum. Public concern
over the spread of Severe Acute Respiratory Syndrome (SARS) during
2003, ensured that aircraft cabin ventilation systems became the
focus of public interest.
The fast turn-around times required in the early design stages of large cabin models are often not feasible due to the high amount of cells required to resolve small features like air inlets. In the past, the hardware resources and software capabilities were not always available to run extensive cabin models, which resulted in the problem of “boundary condition closure”. Simulating just a slice of the cabin leaves two major boundaries (front & back) in the open. This problem can be addressed by using no-slip walls, symmetry planes, prescribed in- and outflow or cyclic boundary conditions. However, each solution comes with certain compromises on either the accuracy and/or comparability of results. This is especially true if the area of interest is close to a cabin feature such as the galley, lavatory or, in the special case of the A380, stairhouses. The availability of low-cost CPU power and the release of STAR-CCM+ allowed ICON to approach the problem by creating a complete cabin model for a double deck aircraft seating 484 passengers in three classes.
The
intention of this work was to:
*
investigate the practicality of handling models for very
* develop
an efficient work process including testing the suitability of CD-adapco’s
new STAR-CCM+ solver
* investigate the cabin flow field in a
complete “closed” domain by erasing the problems associated with
additional unknown
boundary conditions
*investigate
the flow in the stairhouses and its effect on the adjacent cabin
areas
Due to asymmetric geometry features in some galley
areas and most notably the rear stairhouse, it was not possible
to model just half of the aircraft. Only hex-dominant meshes were
considered suitable to meet the required refinement levels near
inlets and outlets and keep the overall mesh size within reasonable
limits. The final mesh consisted of 75 million cells with over 90%
being hexahedral cells (with aspect ratio equal to 1).
Using
CD-adapco’s next generation software STAR-CCM+ and exploiting its
new approach to parallel processing, ICON was able to use modest
hardware to perform a detailed CFD study of the flow field in the
whole cabin. This included assessment of comfort related parameters
such as PMV (Predicted Mean Vote), PPD (Percentage People Dissatisfied),
Age of Air etc. These results helped ICON to understand the special
flow phenomena existing in complex cabin geometries such as the
A380. It can also be seen as a “worst” case scenario in terms
of domain size, since the only similar sized aircraft in the foreseeable
future will be -900 stretch version of the A380. Finally, as CPU
power becomes cheaper and more readily available, models of complete
aircraft cabins will become even more detailed and/or quicker to
run.
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