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Flow simulation in industrial use
Automated functions support the engineer
Translated by BKL Übersetzungen Claudia Siegert GmbH
For some time now there has been a trend to shifting flow simulation calculations
to the developing engineer's workplace. The core functions of many products and processes are based on or
influenced by flow or thermodynamic configurations, so that this trend is in fact an expression of changing
reality in industry. The introduction of product lifecycle management (PLM) concepts usually also includes
physical simulations conducted as part of virtual prototyping for fundamental and principle development,
function verification, variation studies and also problem identification.
Dr. Ivo Weinhold, Produktmanager NIKA GmbH
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Fig. 1: Ascertaining the aerodynamic coefficients of a flying object – Interferogram –
Depicting the density distribution and numerical evaluation of the resistance coefficients.
Picture: NIKA
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But it should always be clear that in particular flow and heat transfer configurations are often highly complex and
therefore difficult to access. For flow simulation programs to be suitable routine tools under practical industrial
conditions, they require certain properties for broad use in development departments and must offer corresponding
additional benefits over and beyond classical CFD (computational fluid dynamics) expert tools. This is because a
development engineer can usually only concentrate on the physical and technical problems. Non-related tasks during
a simulation project, such as network generation or solution parameterisation must be performed automatically by
the simulation software itself. In other words, the software must ensure that users are provided efficiently with
viable simulation results simply on the basis of a knowledge of their corresponding area.
On the technical engineering level, a simulation program cannot replace the qualified development engineer when it
comes to analysing physical contexts, stipulating a suitable demarcation of tasks or evaluating the results and
reaching conclusions for an improved design. Such tasks are and always will be the responsibility of the software
user, with all his technical know-how.
In practice
For some years now, the simulation packages in the engineering fluid dynamics (EFD) family by NIKA have been used
productively on a world-wide scale in many areas of industry and in research and teaching. One very long-standing
user is Ralf Stierle from Bayern-Chemie Protac in Aschau am Inn. The company develops and produces drive systems
for solid-propellant rockets, Fig. 1, with the corresponding components, and uses NIKA flow simulation software
for example to optimise intake components for flying objects with ram rocket drives, for calculating thrust vectors
of angled nozzles or ascertaining the aerodynamic coefficients of flying objects.
The geometric data are supplied by a multi-CAD environment with "CATIA V4", "CATIA V5" and "Pro/ENGINEER", and compiled
and processed with "SolidWorks" for the specific calculation process. A core element of the EFD concept is automatic
detection of the internal flow spaces with "intelligent" identification of the areas and parts actually involved in
flow and heat transfer processes, without having to fill the flow cavities with separately modelled parts for later
networking. All cavities in the CAD model which are not involved in the flow process are automatically excluded from
the simulation model.
The calculation network is generated completely automatically, with consideration of special flow-specific requirements
made locally and globally in network quality thanks to a two-stage adaptive network refinement procedure. The result is
an optimised CFD calculation network as prerequisite for a stable, efficient solution process, with top quality results,
Fig. 2.
Fig. 2: Simulation of the thrust vector error of an angled nozzle – excerpt of the calculation network and depiction of flow paths
Picture: NIKA
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Automatic configuration and control
Another key element in the EFD concept is the definition of engineering goals as the basis for automatic configuration and
control of the solution procedure. These engineering goals are used to describe key engineering and physical parameters whose
definition and optimisation are focal aspects of the simulation project.
On the one hand, such parameters can consist of directly calculated physical variables, such as wall temperatures, forces
and moments of parts or volume flows in openings. On the other hand, this function can also be used for direct definition
of any derived variables such as characteristic indexes, de-dimensioned values or differential variables (e.g. loss of pressure)
with a graphic presentation of their development.
At Bayern-Chemie Protac, this helpful function is used among others for on-going observation of the aerodynamic parameters of
flying objectss during the solution process (Fig. 1). This makes a noticeable contribution to conducting simulation projects
efficiently with the possibility of detecting unsuitable variations or also possible modelling errors at an early stage.
The simulation results are always illustrated in the 3D CAD model with a large number of possible graphic functions which also
meet special demands. For example, Bayern-Chemie Protac evaluates the calculated density distribution around flying objectss
using an interferogram (Fig. 1). Video sequences of animated flow paths produced by the integrated post-processor, or interactive
drawing of cutting planes considerably enhance an understanding of the 3D character of complex flows.
Quantitative evaluation of the results using "Microsoft Excel" and "Word" is also extensively automated. The integrated report
generator produces documentation of all project data on the basis of templates, including the required graphic presentations of
reports and numerical evaluations. The report templates can be adapted so as to fulfil existing documentation and archiving
standards for simulation projects. Once created, these templates act as basis for future fully automatic reporting in accordance
with the corresponding internal requirements. Engineering fluid dynamics technologies with the corresponding simulation packages
by NIKA offer all prerequisites for low-cost, efficient flow simulation in the framework of modern PLM concepts.
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» Special edition from VDI-Z Integrierte Produktion, 3/2005 (PDF, 1.635KB)
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