Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

CFD has it all wrapped up

03.03.2014

Wrapped in a tightly meshed grid, the volunteer is enveloped by lots of little cells that tuck snugly around the body, filling all the available space.

Scientists from the Fraunhofer Institute for Building Physics IBP want to understand every little detail, and so have every millimeter covered. Because they know their test person’s exact measurements and understand how these change in different positions.


This diagram clearly shows just how tightly the grid enmeshes the virtual test subjects, or mannequins.

Fraunhofer IBP


CFD simulations require all boundary conditions to be known: the above diagram shows the factors that influence indoor climate in a passenger cabin.

Fraunhofer IBP

The meshed grid in question consists of a million or more cells and took the scientists several weeks to knit around their test subject. How fortunate, then, that in this case the volunteers aren’t real people, but characters in a computational fluid dynamics (CFD) simulation. CFD is used whenever scientists and engineers need to understand and predict the flow behavior of fluids such as air, water and oil. It’s a technique that Sebastian Stratbücker, head of the Simulation group, and his team mainly use when investigating issues relating to indoor climate. In most cases, this involves looking at air and the way it behaves in enclosed spaces. “Our simulations help to optimize the indoor climate for people and technical equipment,” explains Stratbücker. “Evaluation parameters include thermal comfort, energy efficiency, humidity, CO2 and pollutant concentration.”

But what do we need CFD simulations for anyway? “In most cases, taking a trial and error approach just isn’t practicable,” explains Stratbücker. “Even in terms of setting up the test, it would often prove far too expensive and labor-intensive.”

... more about:
»Building »CFD »IBP »conditions »heating »temperature »ventilation

Say you want to construct a new building, for example. The planning phase is all-important, and requires those involved to make a lot of important decisions before work has even begun, such as which ventilation system to install. Planners need solutions that will help them make such choices in advance; they have to be able to determine whether the system they intend to install is up to the job while also being efficient and ideally cost-effective at the same time.

CFD offers just such assistance, and enables planners to measure and evaluate rooms in great detail with the help of the grid described above. This system allows them to call up the indoor climate conditions for any point in the room at any given point in time, highlighting factors ranging from air velocity, temperature and pressure through air exchange rate and the concentrations of specific substances in the air. 

Of course, the boundary conditions for the simulation must be clearly defined; these parameters are often determined by measurements taken in laboratories or in field tests. Fraunhofer IBP scientists also use their own specially developed DressMAN 2.0 measuring system for this purpose. In other cases, they rely on their own databases of building physics reference data, types of construction, building services, and usage profiles. They draw additional data from their customers’ plans. All this allows the computer program to evaluate factors such as the geometry of the space in question, including any air inlets and outlets, exchanges of air between the outside and inside environments, the heating and cooling capacity of the chosen system, the periods when the space is in use, the materials used in its construction, and many more features.

Even the physical properties of the windows or the type of clothing worn by the people using the building can be taken into account if required. “It goes without saying that CFD is also quite an intensive process, but one that’s worth it compared to the trial-and-error principle, as it means we avoid making mistakes from the outset,” Stratbücker explains, adding: “Simulating different scenarios lets us work up a range of proposed solutions and analyze them, so we end up with the optimum system design.”

Of course, this does not just apply to the planning phase of new constructions. Fraunhofer researchers use CFD to identify and develop solutions to problems that arise in existing buildings, too.


Possible applications for CFD also extend beyond the realm of buildings; Stratbücker and his team use this form of flow simulation to analyze and evaluate aircraft and motor vehicle interiors as well. Much of the validation testing for simulations is conducted at the IBP’s Flight Test Facility FTF, a one-of-a-kind test site in Holzkirchen south of Munich. In return, the scientists applied CFD beyond Fraunhofer IBP’s usual setting of air flow simulations when they optimized numerous system components for the FTF’s new Ground Thermal Test Bench so it could be brought into service last year.

In order for the aircraft calorimeter (ACC) at the FTF to simulate the most extreme conditions such as thermal shock (rapid changes of temperature), the cooling and heating functions along the aircraft’s outer skin had to work without a hitch. The Simulation group used CFD to optimize the Ground Thermal Test Bench’s coolant tank and the recirculation of the cooling agent inside it in such a way that the liquid is cooled to exactly the required temperature before being fed back to the aircraft.

This demonstrates how flow simulation can benefit individual components, such as those in a ventilation system, as well as large systems, such as entire rooms. “We use CFD in any situation where we’re not certain if the system works in the way we think it should,” says Stratbücker. “But we also use other methods, depending on the issue we’re addressing.” For instance, particle image velocimetry (PIV) can be used to measure and visualize flow field velocities – which means it can help to verify CFD results at critical points.

IBP scientists developed VEPZO, the VElocity Propagating ZOnal Model, in order to be able to quickly evaluate indoor air flow patterns and temperature distributions. The model can evaluate ventilation concepts and visualize them at a local resolution. “We use it whenever air node models are too basic a solution and CFD too sophisticated. With VEPZO, we can demonstrate fairly quickly the effect that factors can have, such as planting concepts or a heating system that adjusts according to whether a room is empty or occupied.”

Stratbücker and his colleagues are already looking forward to using CFD in some exciting new projects. For instance, heating the interiors of old church buildings is often a big problem. Heating systems are generally used only on a temporary basis, and the heating effect is instantly lost to the large spaces. “If the system were tailored to requirements and designed according to users’ local needs, then a large church could be heated in a user-friendly manner without excessive heat loss. CFD can simulate how this might work in practice.”

Weitere Informationen:

http://www.ibp.fraunhofer.de/en/Press/Research_in_focus.html

| Fraunhofer-Institut

Further reports about: Building CFD IBP conditions heating temperature ventilation

More articles from Architecture and Construction:

nachricht Modular storage tank for tight spaces
16.03.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH

nachricht Smart homes will “LISTEN” to your voice
17.01.2017 | EML European Media Laboratory GmbH

All articles from Architecture and Construction >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>