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International audience; Poultry production buildings must promote growth while maintaining animal welfare. The specific design of the building and the equipment used determine the operating conditions that will provide the internal environment required by the animals. The present work summarises a series of computational fluid dynamics (CFD) studies under transient conditions which investigate each of the main elements that modify the internal climate and air quality of a naturally ventilated poultry house. Interactions between the interior and exterior were modelled, taking account of radiative, convective and conductive heat transfer. Furthermore, the investigation included contributions (e.g. heat and water vapour) pertaining to the animals and the rearing system (e.g. accumulated litter) in the animal occupied zone. Thus, internal climate was described by means of internal temperature and absolute humidity, which also served to quantify sensible and latent heat. Validation was undertaken on the basis of the distributed temperature and humidity patterns. Gas exchanges were studied by analysing water vapour concentrations and estimating ventilation rates. A derived study was also undertaken to assess the impact of wind direction on the internal climate and consequently on the predictions of gas discharge, together with the capacity of the building to renew air. The overall investigation serves to enhance predictions related to climate and air quality. These contributions may also serve as a reference for strategic further research on internal climate and gas exchanges occurring in livestock buildings.

International audience; To prevent the build-up of excess heat and noxious gases, the air inside livestock buildings must be exchanged on a regular basis. A successful use of natural ventilation to accomplish this task depends on reliable measurements of outside wind velocity and direction, as both mainly control the internal air renewal rate of the building. To accomplish the required analyses, the present work relied on a study that used computational fluid dynamics (CFD) to replicate the internal climate dynamics of a typical poultry house. The model developed in this study focused on solving the equations that govern momentum, heat and mass transport and also included data pertaining to radiative transfers and animal-generated heat. The study considered three fixed angles of wind direction (0°, 36° & 56°- with 0° corresponding to wind blowing perpendicular to the ridgeline). A wind blowing at an angle of 36° was chosen to validate the model against experimental data. CFD predictions achieved a RMSE of 1.2°C and 0.6 g [H2O] kg-1 [dry air] for internal temperature and absolute humidity; respectively. Consequently, the same 3D CFD model (with the same input key climatic variables) was used to predict the impact of two additional fixed-wind directions (0° & 56°). Predictions achieved by the model were used to assess the potential change in capacity of the poultry house to renew air, and it was found that during a period of 3h, the air renewal rate oscillated from 39.5 (±1.9), 34.9 (±2.2) and 33.6 (±1.7) air exchanges per hour when air blew at 0°, 36° and 56°; respectively. These outcomes can serve to determine the range of wind directions that could imperil animals housed in naturally ventilated buildings.

International audience; Raising poultry on a commercial basis requires a careful management of the climate and air quality inside the poultry house because the hens are typically confined at relatively high densities and emit heat and noxious gases at rates that can quickly imperil the animals. In recent years, advanced modelling has been used to predict internal climate and gas dynamics, with special attention paid to the capacity of the building to renew air; however, few studies have investigated the negative effects of discharging heat and gases and particles (potentially pathogens) on the outside environment adjacent to the poultry house. This work proposes to replicate the operating conditions that can exist inside and outside a typical poultry house by using an advanced model to consider the external climate, the particular features of the test building and the heat and gas emissions produced by the animals housed in it. The investigation was achieved by first creating a three-dimensional representation of the building and then modelling momentum, heat and mass transport, and also by taking into account the radiative transfers as well as heat and mass generated by animals. The integration of these components into a single model made it possible to replicate the operating conditions of the building and find a numerical solution by means of computational fluid dynamics (CFD). The 3D CFD model, once it was validated, was then used to predict the environmental impact of the discharges, given external wind velocity and direction. The results provided information about how the gases would likely spread under certain external climate conditions, allowing the possibility of using subsequent predictions to define regions of potentially high concentration that could endanger neighbouring habitable facilities.

International audience; Um das Raumklima eines Geflügelstalls zu simulieren, wurde ein 2-D-CFD-Modell entwickelt. Für die Validierung des CFD-Modells wurde ein Versuch im Frühjahr 2014 in Westfrankreich durchgeführt. Zwei Versuchsszenarien wurden dabei evaluiert: in der frühen (19. Tag) und der späten (69. Tag) Produktionsstufe. Im Fall II (späte Produktionsstufe) wurden zusätzlich drei unterschiedliche Besatzdichten (33 %, 66 % und 100 % der 10 m-2 untersucht. Das Hauptaugenmerk lag dabei auf dem Verlauf der Temperatur und der Luftfeuchte und demzufolge dem sensiblen und latenten Wärmeverlust. Im Fall I wurden mit dem Modell 10,6 Luftwechsel pro Stunde (± 0,45 Standardabweichung) mit geschätzten 76 % sensiblen bzw. 24 % latenten Wärmeverlusten vorhergesagt. Im Fall II hingegen 25,2 Luftwechsel pro Stunde (± 2,6 Standardabweichung) mit geschätzten 64 % sensiblen bzw. 36 % latenten Wärmeverlusten.; A 2D CFD model was developed to simulate interior climate of a poultry house. To validate the CFD model, an experiment was conducted in West of France during spring 2014. Two cases were evaluated: Case I and II at the early (19th day) and late (69th day) stage of production, respectively. For Case II, the CFD model evaluated three different densities of animals (33 %, 66 % and 100 % of the 10 hens m-2). This work was focused on the temperature and humidity gradients, and then, estimate sensible and latent heat losses. With respect to Case I, the model predicted 10.6 air changes per hour (± 0.45 standard deviation) and also estimated that sensible and latent heat losses of 76 % and 24 %, respectively. With respect to Case II, the model predicted 25.2 air changes per hour (± 2.6 standard deviation) and estimated sensible and latent heat losses approximately of 64 % and 36 %, respectively.

International audience; Mithilfe der numerischen Strömungsmechanik (Computational Fluid Dynamics; CFD) untersuchten wir die Ausbreitung von Gasen in und um einen Geflügelstall. Ein 3D- CFD-Modell berücksichtigt die natürliche Belüftung in Kombination mit von den Tieren erzeugten Wärme und Wasserdampf. Um dieses 3-D-CFD-Modell zu validieren, wurden während eines Produktionszyklus in einem Betrieb im Westfrankreichs im Frühjahr 2014 Daten erhoben. Zunächst erfolgte die Überprüfung des dreidimensionalen CFD-Modells auf der Basis des Raumklimas. In der zweiten Stufe sollte die Verteilung der Gase in der Umgebung untersucht werden. Dazu wurde der Wasserdampf räumlich und zeitlich genau im Gebäudeinnenbereich registriert, um die Fahnenentwicklung in der Umgebung des Gebäudes vorherzusagen.; Using Computational Fluid Dynamics (CFD), we investigated the spread of gases inside and around of a poultry house. A 3D CFD model takes account of the natural ventilation combined with heat and water vapour produced by the animals. In order to validate a 3D CFD model a cycle of production for experimental purposes located West of France during the spring, 2014 was used to retrieve data. In the first step, there is a validation of a 3D CFD model based on the interior climate. In the second step, the aim was to identify how the gases might be dispersed in the surrounding environment. Water vapour was accurately logged in space and time for the interior of the building, and then utilized to predict the plume development in the building’s surroundings.