#blog Archives - L'hypercube

Dans la continuité des stages de Marc ALECIAN (2021), puis Mina CHAPON (2021), un outil Python a été développé pour calculer les facteurs de formes de rayonnement entre « facettes » planes.

Incontournables dans la détermination de la température moyenne radiante, les facteurs de formes sont un paramètre de première importance dans la détermination du confort thermique, notamment pour le rayonnement CLO & GLO (Courtes Longueurs d’Ondes and Grandes Longueurs d’Ondes – plus d’explications sur la page dédiée : Calcul de la MRT).

Après avoir été présenté à la conférence IBPSA France 2022, le code est désormais disponible sur Gitlab : https://gitlab.com/arep-dev/pyViewFactor et sur PyPi avec un simple pip install pyviewfactor !

La documentation complète de la librairie est accessible here.

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IBPSA France 2022

25 May 20223 January 2023 Mateusz Bogdan

AREP L'hypercube attended the IBPSA France 2022 conference (at Châlons-en-Champagne, may 19th-20th), to present a paper entitled " Computation of View Factors between polygons - Application to urban thermal and comfort studies« .

Des travaux sont en cours pour rendre ces codes open-source, sous forme de librairie Python : pyViewFactor

Abacus of VF between a wall and an individual (cylinder)

Comparison of surface temperatures with and without taking into account the exact view factors

MRT computation with view factors

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The PET comfort index included to the pyThermalComfort Python library

20 April 202225 May 2022 Édouard Walther

Our version of the Physiological Equivalent Temperature (PET) comfort index, published in 2018 in Building&Environment has made it to pythermalcomforta project from the Center for the Built Environment (CBE) at UC Berkeley (amongst others S. Tartarini & S. Schiavon)

pyThermalComfort includes many other comfort metrics (PMV/PPD, SET, DR... a bit lost? A recap here) and the steady state PET is naturally added for a wider diffusion of this reference model.

IBPSA 2021 Conference

13 August 20213 January 2023 Édouard Walther

We will be participating to theInternational Building Performance Simulation Association conference in Bruges in September this year.

Three paper will be presented, exposing part of the research done last year:

Urban Heat Island modeling with: Simulation of outdoor thermal comfort: A tweak with EnergyPlus
Spatialised computation of indoor comfort levels in semi-open spaces: Spatial distribution of thermal comfort: A case study in Paris’ station
Infrared radiation and polymer materials such as ETFE: A Spectral Model for Longwave Radiant Heat Transfer: Influence of New generation Polymers in BES

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"Building Physics" publication

11 August 20213 January 2023 Édouard Walther

This post promotes a non-commercial announcement!

The result of a year's work is an open-source book published by a member of the team, dealing with problems in building physics and soberly entitled:

« Building Physics – Applications in Python »

The main features of the book are the following:

freely available as a PDF file,
source code is provided on github,
Jupyter Notebooks allow for direct applications, without install! (link to the 1st example).

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Web visualisation

2 April 20213 January 2023 Édouard Walther

Amongst the current developments of the team: creating a visualisation server for projects for our customers, designed for an interactive exploitation of results.

Based on Paraview Glance and the VTK file format, it will allow to access simulation results remotely and securely, as well as performing real-time statistical analyses.

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Kriging interpolation

2 April 20213 January 2023 Édouard Walther

Currently explored by the team: kriging, a method from the mining sector, used for field projection and interpolation.

In order to have an alternative at our disposal, different from the methods described "next door", an exploration of kriging was lead with the SMT lib. Definitely worth a try!

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Non-isothermal air flow in the urban environment

2 April 20214 January 2023 Édouard Walther

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!).

Mailles de calculs aéraulique urbaine anisotherme — Diagram of the heat balance on a mesh cell for the calculation of the air temperature.

Températures d'air — Example of results: 3D air isotherms in a built environment.

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Urban scale infra-red radiation

2 April 20213 January 2023 Édouard Walther

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

2 April 20213 January 2023 Édouard Walther

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.