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Modelling: AerospAce
which are important for the flow realism and simulation accuracy
over a wing or an aircraft engine for a wider range of flows.
fan or compressor blade.
However, limitations exist complexities of braking
with some advanced RANS control
models, because they cannot Another area where design
simulate a sufficiently wide software contributes to improved
range of turbulent scales. For aircraft is in control systems. To
most engineering flows, with assist engineers in developing
today’s hardware it takes far control systems, The MathWorks
too long to simulate all of these now provides two products
scales using a Direct Numerical specifically for aerospace
Simulation (DNS) approach. engineers: The Aerospace
Meanwhile, hybrid approaches Blockset, its main offering, allows
can now simulate the larger users to model airframes and
scales, which are inherently flight controllers. To support
Air-flow simulation of the propulsive Wing aircraft using star-ccM+ unsteady, and employ models to this, it has blocks for co-ordinate
from cd-adapco.
represent the smaller scales. Best transformations, equations of
known is perhaps the Large Eddy motion, standard atmosphere
➤ aerospace and turbomachinery, maximum power, heat transfer Simulation (LES) method, which models and controller scheduling.
and such advances are having and efficiency. is appropriate for some flows, It works with Simulink to
a major impact in aerospace Hutchinson adds that in but lacks generality because define models and algorithms
simulations, because they general, when other issues such modelling of the small scales is graphically.
now enable the study of large as grid resolution, boundary grid dependant. Next, the Aerospace Toolbox
unsteady problems. conditions, and physical A more flexible method has functions that can be invoked
Hutchinson explains that the geometry are satisfied, the developed at Ansys is the Scale from Matlab and is aimed more
most fundamental and pervasive limiting factor is usually the Adaptive Simulation (SAS) at the aerodynamicist or the
physical model in aerospace is turbulence model. To date, method, which can detect and system engineer. It provides
the turbulence model, because most CFD codes use Reynolds- adjust to the local scales of interfaces to third-party tools
most other models rely upon Averaged Navier-Stokes (RANS) turbulence. Because it is RANS (such as the FlightGear simulator
it. For instance, in turbine simulations in which the effects based, in boundary layers and in described below) and data-
combustors, good turbulence of turbulence are typically other traditional shear flows it storage standards (such as the
models allow engineers to better represented by an eddy-viscosity, produces accurate and economic US Air Force’s Digital Data
represent fuel mixing and also which is often specified with the results, something difficult Compendium, Datcom). The
study cooling effects, because well-known k-epsilon model. and potentially expensive for toolbox provides reference
obstructions and fins induce In this regard, Ansys is glad to LES-type methods. In unsteady standards, environmental
vortices and eddies in the flow have the services of one of the regions where the scales are models and imports aerodynamic
that greatly affect heat transfer. world’s preeminent turbulence larger, the SAS model can adapt coefficients for performing
Advanced methods now allow experts, Dr Florian Menter, and and produce ‘LES-like’ behaviour, advanced aerospace analysis.
the study of not just the main some of his steady-state models all without requiring user input Options for visualising vehicle
flow path, but also cavities and have become standard in the or control. Perhaps the greatest dynamics include a 6 DoF Matlab
secondary flows, where the industry. Recently, advanced benefit is that of increased animation object and interfaces
flow can be more complex and techniques such as Menter’s
unsteady than the main flow, and Shear Stress Transport (SST)
the simulation time scales might model have gained popularity due
differ dramatically in various to superior near-wall and adverse
regions. In addition, the study of pressure gradient properties,
the transition from laminar to enabling higher resolution and
turbulent flow is very important. more detailed representation
It can, for example, control the of flow phenomena such as
acceptable angle of attack for separation, reattachment and
an airfoil and affect efficiency heat transfer. In addition, the
and performance limits; further, SST model has been extended to
because the turbine blades in better capture advanced effects
engines act as rotating wings, such as surface roughness and
An interface to the MathWorks Aerospace Blockset gives the open-source
Flightgear simulator more realistic performance.
their transition point determines laminar-to-turbulent transition,
scienTiFic coMpUTing World october/november 2009
SCWoct09 pp44-47 aerospace.indd 46 10/1/09 12:51:07 PM
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