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Creation of local meteorological data

En se basant sur les données mesurées historiques, ce début d’année 2022 voit le développement d’une nouvelle offre pour la création de fichiers météorologiques locaux.

La méthode est basée sur les points suivants :

  • Récupération & traitement de données météorologiques historiques
  • Interpolation spatiale par un processus gaussien afin de déterminer les valeurs à une granularité plus fine
  • Validation sur des jeux de et versus les cartographies de températures moyennes de Meteofrance
  • Reproduction de séries temporelles de température, humidités…

Ce pas en avant ouvre la voie à la création de fichiers météorologiques adaptés au « climat urbain » spécifique de chaque ville à l’aide de l’Urban Weather Generator (UWG).

Intéressé.e. ? Pour plus d’information, c’est ici : lhypercube@arep.fr

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Non-isothermal air flow in the urban environment

Amongst the team's current development themes: the calculation of air temperatures in urban environments.

In order to improve the prediction of the consumption calculations of buildings or the exterior thermal comfort, a thermal/aerodynamic coupling is necessary.It is all about taking into account the influence of building surface temperatures on the temperature of the outside air.

The complete anisothermal CFD calculation being prohibitive in computation time, a "weak coupling" approach is adopted, based on energy balances and valorizing the isothermal air velocity field systematically conducted in our studies.

The validation on an experimental dataset is underway (thanks again to our partners from the LaSIE in La Rochelle!).

Diagram of the heat balance on a mesh cell for the calculation of the air temperature.

 

Example of results: 3D air isotherms in a built environment.
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Urban scale infra-red radiation

Among the current development undertaken by the team: computing longwave radiation in the urban environment.

In order to improve the prediction of surface temperature levels for the calculation of building consumption or the evaluation of outdoor comfort, it is necessary to know the radiation view factors between surfaces of an urban scene.

View factor computation being time consuming, we will try to answer following question:

        How can we speed-up the process with a minimum trade-off on precision?

The possibilities yet considered are parallelism and k-means clustering.

Illustration du k-means clustering (source Wikipedia)
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Genetic optimization & natural ventilation

Amongst the team's ongoing research topics: optimizing the modeling of natural ventilation in dynamic thermal simulation.

In order to reduce the computational effort for the pressure coefficient computations by means of CFD simulations, we have to answer the following questions:

"Can we choose the wind directions a priori to limit the number of CFD calculations?"
"With a fixed number of CFD calculations, can we minimize the modeling error compared to a reference case?"

On the agenda : thegenetic optimization coupled to EnergyPlus.

Difference of pressure coefficients on a façade element between the classical approach and the coupled CFD+BES approach.

 

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World UTCI and MRT

A "new" database has been made available by the EU, from the Copernicus project (free access, login required).

UTCI and T_{MRT} , August 31st, 2018

 

This dataset provides a complete historical reconstruction of the UTCI (Universal Thermal Confort Index, a thermal comfort index as well as the MRT (Mean Radiant Temperature, essential for the thermal comfortestimation), from 1979 up to today. Those parameters are computed by the ERA5-HEAT (Humen thErmAl comforT) model. It is based upon a reanalysis of observations from across the world, to provide a globally complete and consistent description of the Earth’s climate and its evolution in recent decades.

 

Technical data:

DATA DESCRIPTION
Data type Gridded
Horizontal coverage Global except for Antarctica (90N-60S, 180W-180E)
Horizontal resolution 0.25° x 0.25°
Vertical resolution Surface level
Temporal coverage 1979-01-01 to near real time for the most recent version.
Temporal resolution Hourly data
File format NetCDF
Conventions Climate and Forecast (CF) Metadata Convention v1.6
Versions UTCI v1.0
Update frequency Intermediate dataset updated daily in near real time, Consolidated dataset monthly updates with 2-3 month delay behind real time.

 

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160 Cores dedicated to building physics

Since 2017, The Hypercube has been performing detailed airflow simulations and implementing numerical optimization procedures. These methods require significant computing power, which until now has been provided by "virtual machines" in Microsoft's Azure cloud. The team thus had 24 bodybuilt "machines" (8 ultra-clocked logic cores and 56 to 112 GB of RAM), switched on on demand and allowing a high reactivity.

This solution, which has been in use for 2 years, limited us in terms of reactivity (IT maintenance) and connectivity (data transfer speed) with a non-negligible associated cost.

The question then arose, with the AREP IT team, of an opportunity to invest in an "on-premises" calculation server... It is now done! It has just been delivered, in kit form.

It is therefore a computing rack with 4 processors, 20 cores each capable of hyperthreading (virtualization of a second core), in other words, 160 cores dedicated to simulating building physics phenomena! This represents the equivalent of more than 25 high-performance computers (for example for 3D visualization).

160 cores in action !

Today, this "beast", with 256 GB of RAM memory, extensible up to 3TB, runs on the open source Linux operating system (Debian 9).

Many thanks to AREP IT Services for their advice, support and energy!

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Autonomous measurement station

An autonomous measuring station for diagnosis

Resulting from a partnership of more than two years between AREP and the electrical engineering speciality of the INSA of Strasbourg, here is an autonomous measuring station, started during previous projects (see L'Hypercube references) which was finalized in January 2019 thanks to the Technological Research Project of François-Alexandre Fournier, a GE5 engineering student at INSA: we thank him here for his unequalled investment!

Including a Raspberry PI base and low power wireless sensors Whisper node from WISEN, this station was custom developed for AREP's needs and includes a dozen temperature and humidity probes as well as a CO2 sensor. Particular attention was paid to energy consumption and robustness of operation during the project. Field tests are planned for 2019.

[ Autonomous station: Raspberry PI + 868 MHz communication with wireless sensors]