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EFD.Lab at Grohe
Flow simulation right from the predevelopment phase
People who believe that bathroom and kitchen taps are only simple water dispensers will discover from Grohe
that this is not the case. Grohe, a company renowned for its high quality and functionality as well as the attractive
design, has continued to pursue its innovative strategic policy and presented its latest developments at the ISH
trade fair in the spring.
Translated by BKL Übersetzungen Claudia Siegert GmbH
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These include amongst other things the Grotherm thermostats, which will be available in new bathroom fittings
from the autumn of 2005 onwards. High performance software solutions such as the EFD.Lab system of NIKA GmbH are
already employed by Grohe in the pre-development phase so that the water flows reliably in the desired quantities
and at the desired temperature at all times. Approx. 5 years ago an additional optimisation of the entire development
and construction sector was launched after high performance 3-D systems for CAD modelling became available with
Solid Edge and Unigraphics. The objectives of the new project were
amongst others to increase expertise in the field of
development and to reduce costs for the entire product development. In this case structural analyses (FEM), flow
simulations (CFD) and the use of rapid prototyping parts formed the main pillars of the optimisation process.
“Approx. ten years ago computer systems for flow simulation were still unaffordable for us and the external commissioning
of calculations was very expensive, ensuring that we could hardly use these options”, as Kai Huck, who deals with the flow
analysis in the Westphalian town of Menden, reported.
In the course
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A completely new Grohtherm generation of thermostats has been created at Grohe
with the aid of the flow specialists and the EFD.Lab software.
Picture: Grohe
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of the “Virtual Product Development” project the CFD
systems available were inspected and the suppliers each received the same benchmark as the calculation task.
“Ultimately the decision was not that difficult to make” as Kai Huck explained, “ as the NIKA software was also best suited -
due to the user-friendliness and the ease with which people could adapt to it - to meet the Grohe requirements. It was clear
to us right from the start that we did not want to form a full-time calculation group, but that instead the respective
employee works with the CFD solution for around 30% to 50% of the time spent on development work.”
The exchange of experience between users makes it easier to start using it
In the case of the other solutions available it took much more time to generate networks and master the program so that
unforeseeable time delays had to be anticipated. Kai Huck views the evaluation of the results as being the greatest
challenge for all people who are new to the field of flow simulation. He stressed, “In this respect my colleague
Stefan Steinhoff and I have learnt how to walk, step by step, and in the starting phase we repeatedly compared the
simulation results with the real test results of prototypes or series products”. “For this reason we installed two CFD
workstations right from the start so that the users could always exchange ideas. Otherwise we would have completely overtaxed
the support team of NIKA, which performs very good work, with the many questions that arose during the daily simulations.”
Two different paths are taken with respect to the implementation of flow simulations at Grohe. In the case of the first one
the calculation specialists received complete products, i.e. modules from the construction, which could then be read in,
processed for the calculation and subsequently analysed. However, these procedures do not only apply for the product development,
but also for the tool design of cast parts, for instance in order to carry out flow analyses in the core. The Parasolid core
of UGS serves as the exchange platform as EFD.Lab,
Nika’s CFD solution, has integrated the CAD software of SolidWorks as a
geometry modeller and both SolidWorks and also Solid Edge and Unigraphics are based on the Parasolid core.
In the case of the
second path, which has been taken at least just as many times as the first one, the calculation department itself begins with the
geometry generation for concept studies by means of which flow tests are then carried out in order to optimise the geometry
in accordance with the results gained. The outlines of the concept studies that are generated in this way are subsequently
transferred to the design department and integrated within the CAD product model within Solid Edge there.
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The sound properties were optimised with EFD.Lab
with this functional specimen of a single-lever mixer.
Picture: Grohe
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Overall basic principle of flow was determined
In the thermostat sector the existing overall system was analysed by flow specialists at Grohe to begin with, in order to
integrate the findings that had been gained from this within the new development. In this way a completely new Grohtherm
generation of thermostats has come into being, which will be launched onto the market this year. The heart of the new generation of
thermostats is formed by the thermostat cartouche, a completely new development whereby the entire basic principle of flow was
determined in advance with EFD.Lab. “Frequently just a few contours are necessary in order to calculate whether the assumptions
made also correspond to the results of the flow analysis”, as Kai Huck explained.
“This approach offers very great assistance especially in the early development phase with respect to the improvement of the
control quality for instance. The new compact cartouche reacts twice as quickly to fluctuations in pressure compared to its
predecessor, for example.”
In addition, strict separation was observed in the case of the cartouche. A special heat-resistant plastic was selected for
parts which are flowed through and where it is important that the contours are precisely observed.
Set against this the other parts, which must absorb force, were designed in stainless steel. Both components for their part
are linked with each other by means of a form closure. Should the compact cartouche really need attention the service engineer
can react quickly on the spot, and either replace the cartouche or simply inspect its functionality.
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The arrows point towards the modified area, which led to an improvement of the noise behaviour
of the fittings corresponding to an entire sound class by means of the changes demonstrated
and the linked change of the flow rate.
Picture: Grohe
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An additional novelty
is termed a “cool touch”. It guarantees that the external temperature at each point of the thermostat is a maximum of one
degree above the selected temperature of the water flowing out. This is achieved due to the fact that the inlet for the cold
water acts as a complete cooling jacket within the thermostat fitting. “To this end we have simulated the surface temperature
of a fitting that has been completely flowed through with EFD.Lab in order to recognise at which points temperature fields
arise and in which areas the design of duct would have to be changed in order to reach the respective temperature target”
as Kai Huck explained. Additional Grohtherm innovations including 2000 Wanne and 3000 Wanne (bathtubs) are the aquadimmer
with a touch catch, a handle, by means of which three functions can be controlled: the water flow, the water quantity and the
tapping point – i.e. the bathtub or the shower head. An additional Eco-Button on the shower head fittings reduces the water
flow rate by approx. 50 per cent.
Hardly any deviations between the measuring results and the calculations
“Up to now we have been able to carry out all the desired calculations with EFD.Lab by generating the corresponding
specimen models”, as Kai Huck reported. “One of the most important parameters for us is always the volume flow rate,
which can be measured easily. In addition we have an excellent hydraulic laboratory for the testing of prototypes.
The deviations from our calculations almost always remain below three per cent”. Kai Huck named a cast housing of a
fitting as an example. This was manufactured as a rapid prototyping model so that the geometry in reality precisely
corresponded with the CAD model. The subsequent measurements in the hydraulic laboratory only differed from the calculation
measurements with EFD.Lab by approx. 2 per cent. In addition noise tests were carried out with the NIKA software,
for example on simple washstand fittings. As a result it was possible to reduce the noise generated by approx. 50% by
means of slight geometry modifications. Despite the ease of use and ease with which people can learn how to use it,
extensive experience using the CFD software is necessary, in particular in the event of more complex geometries or
components. This applies as already mentioned to the evaluation and assessment of the calculation results, but also
to the preparatory work on the geometry model. “The main work often involves the preparation of the construction
geometry for the flow calculations”, is how Kai Huck described his experiences. “For instance, all tangential contacts
must be avoided, O rings should be completely removed and these areas should be levelled out extensively following
this so that no more cracks should be present if at all possible”. In this case you constantly need to consider whether
the geometry details in question influence the flow. In most cases the respective assumptions can be inspected based on
a small, simple model, which is quickly generated.
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This pressure compensation control was developed by Grohe’s Canadian subsidiary Tempress.
The networking with EFD.Lab comprises more than a million cells.
Picture: Grohe
The cross-section through the pressure compensation control reveals the temperature distribution during the flow analysis.
Picture: Grohe
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Manual network adaptations can be carried out at all times
“If EFD.Lab’s networking function comes across a crack, it attempts to generate webs that are as finely structured
as possible, which occupy unnecessary memory and tie up computer capacities”, as Kai Huck can report based on his
experiences. “This leads to a situation whereby either no result is achieved or a result only comes about after
“an age”. In such cases the user must manually adjust the network that has been automatically generated”. Viewed
in overall terms it has been possible to reduce the number of genuine prototypes at Grohe step by step and thus
also the time involved working on them and expenditure. The EFD.Lab CFD system, but also the close contact with the
flow specialists at NIKA in Frankfurt as well as trouble-free links to the NIKA development team in Moscow has contributed
towards this. Kai Huck also views the simplified communication with Grohe’s management when it concerns the initiation of
new projects as an additional essential advantage. The graphic representations provide a lot more insights than a lot of
verbal arguments about complex technical matters. They are not just colourful images, but are also very realistic so that
the decision makers who do not come from the technical field can be convinced by representations of the flow path. On this
basis technicians and non-technicians can jointly discuss the advantages and also their doubts with respect to new product
ideas with the aid of the EFD.Lab software. “The Grohe name stands for high quality engineering, the technical components
are therefore developed and manufactured in-house, which we consider to be a unique selling point” as Kai Huck explained
by way of a conclusion. “Software tools such as EFD.Lab are imperative for us so that we can still retain our high quality
standards at reasonable prices”.
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The speed of flow is represented on the left and the temperature distribution is represented
once again on the right with a diagonal cross-section.
Picture: Grohe
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» Special edition from CAD-CAM Report 6/2005 (PDF, 5.072KB)
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