Methane (CH4) emissions from pig production are about 13% of the agricultural sector's total greenhouse gas (GHG) emissions. Most CH4 emissions from pig farms originate from manure storage inside the pig housing and outdoor storage. Researchers have endeavoured to identify the mechanisms of CH4 generation within manure. The knowledge generated from these studies is essential for understanding the mechanisms but is yet to be applied in practice, because, for example, sampling and analysis of manure are required. The objective of this study is to develop an approach to predict CH4 emissions using computational fluid dynamics (CFD) to obtain sub-models of the mass transfer coefficient and, based on available experimental data from sections with two pig pens, CH4 concentration at slurry surface. The inputs for predicting CH4 concentration at slurry surface include pig weight, manure age and amount, climatic parameters such as temperature and humidity, ventilation rates, which can be easier to be monitored on site. The results show that the mass transfer coefficient of CH4 is positively correlated with both ventilation rate and slurry volume. The sensitivity analysis shows CH4 concentrations at the slurry surface are primarily influenced by slurry volume and slurry age. The models to estimate CH4 emission is explicit, physically interpretable, and performs reasonably well under sidewall jet ventilation (R2 of 0.88, RMSE of 1093.19 mg/h), while predictive accuracy declines under diffuse ceiling ventilation (R2 of 0.78, RMSE of 1548.96 mg/h).

The impact of balconies on outdoor microclimate has typically been overlooked in previous studies. This study investigated how balconies affect airflow and pollutant dispersion within an idealized street canyon using computational fluid dynamics (CFD) with fully coupled radiative, convective, and conductive heat transfer processes. Steady-state CFD simulations were conducted using weather data from a typical day in June in Guangzhou, China, at four representative times of the day (0800, 1200, 1600 and 2000 Local Solar Time (LST)). The results showed that outdoor air quality was influenced by time of the day, balcony form and location. The best and worst outdoor air quality occurred at 0800 LST and 2000 LST, respectively, and pollutant concentrations at pedestrian zone overwhelmingly exceeded those at vertically distributed balcony zones. When only the nearfa & ccedil;ade pedestrian zone was evaluated, the presence of balconies worsened the outdoor air quality significantly. When all the balcony zones were evaluated, the presence of balconies worsened the outdoor air quality at 0800 LST but improved it at 1200 LST. Generally, the All-sealed balcony is most effective in promoting better air quality in the near-fa & ccedil;ade areas. Pronounced thermal stratifications on building surfaces developed not only during periods of solar radiation but also at night, driven by temperature differences between interior and exterior surfaces. Overall, the findings highlight the importance of accurately representing fa & ccedil;ade geometry and dynamic thermal boundary conditions in CFD studies of urban microclimate. Future work should investigate how aspect ratio, balcony configuration, and building materials jointly influence outdoor microclimate.

Rising outdoor temperatures, the absence of effective overheating mitigation strategies and upcoming renovations contribute to a decrease in summer thermal comfort in homes. This heightens the need to provide occupants with adequate passive cooling strategies to avoid the use of energy-intensive active cooling systems. Louvred openings enable occupants to extend the well-established passive cooling strategy of natural ventilation to nighttime, periods of absence, and non-ideal weather conditions. As numerical investigations of indoor environmental quality for these systems are rare and validated CFD models do not exist, this study aims to validate a CFD model by conducting full-scale experiments, testing different turbulence models, and assessing the impact of radiation. Furthermore, various strategies to reduce the large number of mesh cells, caused by the complex geometry of the louvre, are studied. The final model shows good performance for low-velocity zones. In zones with higher velocity, namely the flow entry zone after the louvre, the model tends to overpredict velocities. No turbulence model is superior. Radiation modelling did not significantly improve the model performance but drastically increased the computational resources. The best strategy to reduce the mesh (by 63%) was the porous media model, which also improved the prediction of the high-velocity inflow zone. Additionally, allowing for higher surface curvature deviation did not significantly impact the flow but resulted in a 30% reduction of mesh cells.

Rapid development of the pig industry in China has led to numerous challenges in managing livestock manure and slurry. Field application of slurry has proven to be an economical, effective and environmentally beneficial approach to sustainable resource recycling globally. However, China remains largely dependent on fertilizer inputs from mineral sources, with limited adoption of slurry application practices. A common challenge with slurry field application isits typically higher emission of ammonia and greenhouse gases (GHGs) compared to mineral fertilizers. This work investigated selected treatments with specific ratios of pig slurry and mineral fertilizers aimed at reducing the use of mineral fertilizers and emission following basal fertilizer application and topdressing after maize planting specifically, the ratios of pig slurry included 30%, 50% and 100%. The methods of fertilizer application involved a comparison of acidified versus non-acidified pig slurry for field application, as well as a comparison between sprinkler and drip irrigation. The results showed that replacing 30% of mineral fertilizers with pig slurry (RC30) reduced total GHG emission by 62% and NH3 emission by 60.4% compared to a full slurry substitution during field application. Meanwhile, the RC30 group recorded the lowest total NH3 emission, totaling 5.08 kg & centerdot;ha-1, among all treatments using pig slurry. The acidification of pig slurry significantly reduced NH3emission, decreasing them by 42.1% compared to the direct application of untreated pig slurry. Drip irrigation proved to be more effective in reducing total GHG emission compared to sprinkler irrigation. Drip irrigation reduced NH3emission by 38.9%-42.6%, N2O emission by 12.4%-18.6%, and GHG emission by 21.5%-34.7%. In summary, this study demonstrated that replacing 30% of mineral fertilizers with pre-acidified pig slurry, combined with drip irrigation, reduced GHG and NH3 emission. (c) The Author(s) 2026. Published by Higher Education Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0)

Natural ventilation is a passive ventilation mode, as it does not require additional energy and is, therefore, very popular in mitigating the overheating of buildings. In residential buildings, natural ventilation is usually facilitated by manual window opening, which can raise concerns about intrusion, rain, and noise. Alternatives can include flaps, louvres, or grills providing environmental protection, such as enhanced acoustic performance and protection against rain, particles, or burglary. Therefore, these components allow the operational hours for ventilative cooling to be extended to the night, periods when occupants are absent, and non-ideal weather conditions during the summer. This study is part of the research on the potential of louvred openings utilised for Danish residential buildings. It aims to generate well-documented experimental data for CFD modelling of louvred openings specifically designed for ventilation. Hence, this study collects experimental data, measuring the velocity profiles, air temperature profiles and surface temperatures in a room equipped with a louvre element designed for ventilation. The experimental data are used to validate a CFD model. Future studies will focus on simplified modelling of the louvre geometry and will also employ the validated model to investigate the influence of changing boundary conditions on thermal comfort during the summer.

Properly ventilated classrooms to ascertain the indoor air quality (IAQ) are key to healthy schools. In Iceland, some projects of renovating schools are being carried out to provide proper IAQ and thermal comfort. This study was to utilize airflow network modelling, CONTAM, to simulate the IAQ at a school in Iceland before renovation. To assess the IAQ, the concentrations of CO2, formaldehyde (HCHO) and total volatile organic compounds (TVOC) were simulated and the exposure to those gaseous concentrations was examined. The simulation of CONTAM was first validated by employing a case study with well documented experimental data found in literature. The simulation results of our CONTAM modelling agreed well with the experimental data as well as the simulation results obtained by the same authors of the experimental study. The program of CONTAM was then further applied to simulate 13 scenarios designed for our study on the school building in Iceland. The results indicated that pure natural ventilation system might not be able to maintain CO2 concentration lower than 1000 ppm during the entire period and thus mechanical ventilation system is needed in such a building. The simulation results also support that the ventilation rate of 15 l s-1 person-1 is needed with current occupant numbers in classrooms. The concentrations of HCHO and TVOC could be maintained to be reasonable with air exchange rate of 0.5 h-1 if the doors of classrooms could be open during the night. The results achieved from this study provide guidance for the renovation of the school and design/regulation of the ventilation system after renovation.

livestock houses, the slatted floor is one of the challenges to be modelled in CFD due to its small sizes of slots and large number of solid surfaces. Porous media modelling, with resistance coefficients derived from scaled experimental tests and full-scale CFD simulations, offers a practical approach to addressing these challenges. Clarifying the relationship between the resistance coefficients of slatted floors at different scales is crucial for optimising computational resource consumption and simplifying the research process. This paper, using similarity theory, explores the relationship of resistance coefficients of porous media modelling at different geometric scales. The similarity analysis revealed that the viscous resistance coefficient similarity constant is inversely proportional to the square of the geometric similarity constant (cD = 1/cl2), while the inertial resistance coefficient similarity constant is inverselIn %y proportional to the geometric similarity constant (cC = 1/cl). And, CFD simulations of slatted floors at three different geometric similarity scales (1:1, 1:2.5, and 1:5) confirmed the validity of these relationships. The predictions of similarity theory showed strong agreement with the simulation results, with an average error of 2.1 % for the 1:1 scale (prototype) and 1.6 % for the 1:5 scale. Furthermore, a detailed CFD validation was conducted using a 1:2.5 scaled pig pen model by incorporating the resistance coefficients derived from direct geometric modelling into a porous media model. Comparison with experimental data demonstrated good agreement in both air velocity and temperature, with a maximum air velocity error of 0.34 m/s and an overall relative air temperature error of 1.98 %.

Methane conversion under ambient conditions has garnered significant attention due to complex catalyst design, costly oxidants, and unwanted byproducts remain. In this study, we established a newly discovered process for the direct conversion of methane under ambient conditions by leveraging the concept of piezo-photocatalysis, which synergistically integrates energy input from both light irradiation and ultrasonic vibration. An efficient formaldehyde (HCHO) yield of 11.07 mu mol center dot g-1 center dot h-1 was achieved by using the piezo-photocatalyst system BaTiO3/g-C3N4 (2BTO/CN), which is approximately 3.5 times higher than that under ultrasonic vibration alone (3.2 mu mol center dot g-1 center dot h-1) and 2.6 times higher than that under simulated solar irradiation alone (4.27 mu mol center dot g-1 center dot h-1). Under optimal conditions, the yield can reach a maximum of 60.79 mu mol center dot g-1 center dot h-1. The enhanced performance is attributed to the ultrasonic vibration-induced generation of polarized electric fields within g-C3N4 which sustain the built-in electric field intensity at the heterojunction interface. This facilitates more efficient migration of photogenerated charge carriers, improving charge separation efficiency and enabling the synergistic catalytic effect of piezoelectricity under simulated solar irradiation. Electron paramagnetic resonance (EPR) spectroscopy revealed enhanced signals from hydroxyl radicals (center dot OH) and superoxide radicals (center dot O2-) under synergistic conditions. Additionally, density functional theory (DFT) calculations demonstrated that, under ultrasound-assisted conditions, the energy barrier for the rate-determining step of methane photocatalytic conversion on BaTiO3/g-C3N4 is significantly reduced. The implications of this methodology, with its potential for broader application in gas-phase catalytic reactions, underscore a significant advance in catalysis.

Organic fertilizers were produced through maggot-composting (MC) and natural composting (NC) using swine manure, and the migration, contamination, and health risks of heavy metals (Zn, Cu, Cd, Cr, Pb) were evaluated within a fertilizer - soil - ryegrass - Rex rabbit system. After 70 days of treatment, heavy metals were concentrated by 43.23 % to 100 % in MC and 52.82 % to 90.91 % in NC, higher concentration rate was observed in Cr and Cu in NC. The residual fractions of Zn, Cu, CD, Cr, Pb increased by 0.4 % to 30.2 % in MC, and 3.4 % to 29.7 % in NC. More stable forms of Zn, Cr, and Cu were observed in NC, whereas Pb showed greater stability in MC. Post-fertilization, statistically higher levels of the five elements were obtained in NC treatment. Even their concentrations decreased in the soil, however, high initial background levels caused Cr and Zn to exceed standard thresholds in both treatments. Despite this, the geo-accumulation index (Igeo) and pollution load index (PLI) below 1, did not indicate a pollution risk. Cr levels exceeded feed limits in both roots and leaves, although the low BCF value in roots suggested limited risk. In rabbits fed with 48 % ryegrass, significantly higher levels of Zn and Cu were detected in NC, with elevated Cr levels posed moderate to severe pollution risks in two treatments. Health risk assessments, including non-carcinogenic (HQf) and carcinogenic risks (CRf), revealed Cr was the most cautionary element for both children and adults, even no significant carcinogenic risk exist. These findings provide key insights into mitigating heavy metal contamination from animal waste to rabbit meat.

As outdoor temperatures rise and heat waves become more frequent, the absence of overheating prevention measures and impending renovations pose challenges to summer thermal comfort in residential buildings. Manual window opening, as the preferred method to address high temperatures, comes with concerns such as increased safety risks, potential noise disturbances, and vulnerability to adverse weather conditions. To address this, a combined system of louvre and ventilation hatches (named louvred opening hereafter) is proposed as an alternative to energy-intensive air conditioning and traditional window ventilation. This system enables ventilation even during occupants' absence, adverse weather conditions, and potential noise disturbances. The study investigates the implementation of louvred openings in existing residential buildings and their potential to mitigate overheating during the warm season. The systems’ impact on load-bearing structure, architectural value, daylight availability, and overheating is analysed using the Danish building stock and two Danish case study buildings. Additionally, influential factors such as occupant behaviour and opening characteristics are scrutinised in the overheating study. The findings revealed that the load-bearing structure and the architectural value of post-1950 Danish buildings are well-suited for incorporating louvred openings. However, placing louvred openings in existing window spaces significantly reduces daylight availability, indicating that buildings from earlier construction periods with smaller glazed areas may necessitate adding new external wall openings. Nevertheless, louvred openings demonstrate superior performance in mitigating overheating compared to conventional window ventilation, especially when occupants utilise night ventilation effectively.

Many dairy farms use the combined sprinkler-fan cooling system to mitigate the heat stress in dairy cows by enhancing evaporative heat transfer. Effectively controlling the system depends on key parameters such as the time period for water to completely evaporate (hereafter drying time), heat transfer rate, and the strategy for regulating spraying duration. Developing an effective control strategy can not only enhance cooling efficiency but also save water. The heat transfer rate and drying time are influenced by several determining parameters, such as the hair coat's initial water content, air temperature, relative humidity (RH), and air velocity. However, the correlation between drying time, heat transfer rate, and the aforementioned determining parameters has not been thoroughly analysed. Consequently, this study aimed to propose models that use computational fluiddynamics (CFD) simulations to predict drying time and total heat flux, and then propose an improved spray cooling strategy. The simulation results indicated that the total heat flux (W m- 2) released via evaporation and convection from the skin surface of a cow can be 162 % higher than the value of pure convection under conditions of air temperature in 30 degrees C, relative humidity of 70 %, air velocity of 2 m s- 1, with an initial water content in the hair coat of 0.07 kg m- 2. The size of the wetted skin surface area did not significantly affect the heat flux (W m- 2) and drying time but a larger wetting area will increase the total heat transfer (W). The drying time increased with higher RH and initial water content but decreased with higher air velocity. The drying time initially decreased and then increased as the air temperature rose. The total heat flux increased as the air velocity and initial water content increased and decreased as air temperature and RH increased. The results indicated that the sprinklers should be opened before the total heat flux from the wetted area falls below the minimum requirements to ensure the cooling efficiency while saving the water consumption because an increase of 19 % in average heat loss from the wetted area was obtained when relative humidity was 70 %, air temperature was 40 degrees C, air velocity was 2.0 m s- 1, and initial water content was 0.05 kg m- 2.

This study evaluates the impact of personnel on air quality in air-conditioned restaurant environments during winter, summer, and transitional seasons, characterized by the peculiarities of personnel movement, high concentration of personnel in a short period of time, poor ventilation and high personnel density, leading to the accumulation of pollutants that can severely damage personnel health. This study examines carbon dioxide (CO2) 2 ) and particulate matter (PM) concentrations and proposes an online adaptive model for their prediction. Environmental influence factors are analyzed through correlations of measured data, and appropriate input parameters (time-lagged cumulative number of people) are selected. The Auto-Regressive with Exogenous Inputs (ARX) model is used to predict the change of air quality with the movement and number of people, compared with classical models (LR, DT, SVM, ENS, GPR, NN, VARX). Results show that the ARX model performs excellently in predicting restaurant environments; the effect of different environmental factors on the predictive effectiveness of the model was also explored. When combined with real-time sensor data and AIC-based adaptive optimization, the prediction accuracy is further improved by more than 25 %. The R2 2 of the ARX model is 0.9549, the MAE is 0.8352 mu g/m3 3 and the MAPE is 3.17 %. The adaptively optimized model can be adapted to different environments, overcoming the problem of poor adaptability of such models. Our results enable effective environmental control strategies in public spaces, contributing to Sustainable Development Goal (SDG) 3: Good Health and Well-being by reducing health risks associated with indoor air pollution.

Field-applied liquid animal manure (slurry) is a significant source of ammonia (NH3) emission, which is harmful to the environment and human health. To evaluate mitigation options, reliable emission measurement methods are needed. A new system of dynamic flux chambers (DFCs) with high-temporal-resolution online measurements was developed. The system was investigated in silico with computational fluid dynamics and tested using three respective field trials, with each trial assessing the variability in the measured emission after application with trailing hose at different scales: manual (handheld) application, a 3 m experimental slurry boom, and a 30 m farm-scale commercial slurry boom. For the experiments with machine application, parallel NH3 emission measurements were made using an inverse dispersion modeling method (backward Lagrangian stochastic, bLS, modeling). The lowest coefficient of variation among replicate DFC measurements was obtained with manual application (5 %), followed by the 3 m slurry boom (14 %), and lastly the 30 m slurry boom (20 %). Conditions in DFCs resulted in a consistently higher NH3 flux than that measured with the inverse dispersion technique, but both methods showed a similar emission reduction by injection compared with the trailing hose: 89 % by DFC and 97 % by bLS modeling. The new measurement system facilitates NH3 emission measurement with replication after both manual and farm-scale slurry application with relatively high precision.

The spray-cooling method is used by most large-scale dairy farms currently in operation because it is regarded as one of the most effective methods for mitigating heat stress. This method, which more rapidly evaporates water sprayed onto the cow's skin surface and in so doing removes body heat by evaporative and film cooling, depends greatly on the distribution of water onto the cow's skin. The objectives we set forth in this study involved using computational fluid-dynamic simulations to assess the effectiveness (spray water-wastage rate and water distribution on the cow's body surface) of commonly used nozzles and subsequently finding a means of optimizing efficiency and water distribution during operation. Our simulations indicated that, given a traditional installation condition (the installation angle of 30 degrees and the water flow rate of 1.3 L min -1 ), the average water wastage rates occurring between 9 to 25 s during spraying were 74.80 % and 80.93 % for nozzle 1 (spray angle: 135 degrees , dispersion angle: 20 degrees ) and for nozzle 2 (spray angle: 180 degrees , dispersion angle: 15 degrees ), respectively. The angle at which a nozzle was set had limited influence on the water wastage rate; however, when the angle was increased (from 30 degrees to 45 degrees ), the water was not only distributed over a larger area of the skin surface but was also distributed more uniformly. When the spray direction was altered from perpendicular to parallel, the water wastage rate dropped significantly, and the rates achieved by nozzle 1 and nozzle 2 at 25 s fell by 35.72 % and 29.55 %, respectively, with the water film covering the entire back of the cow. Moreover, the water wastage rate achieved by nozzle 3 (the improved nozzle type proposed in this study), at a spray angle of 70 degrees and a dispersion angle of 16 degrees , was up to only 9.68 %, which was 87.99 % and 81.31 % lower than those achieved by nozzle 1 in the perpendicular and parallel spray directions, respectively. Based on our research findings, enhancing the nozzle's properties in accordance with the size of the cow's body or altering the spray direction to parallel can yield a significant improvement in water distribution on the cow's surface and water efficiency.

Passive daytime radiative cooling (PDRC) materials can reduce building cooling demands during hot periods but increase heating needs in colder times, known as heating penalties, limiting their practicality. Temperature adaptive (TA) materials offer a solution, yet optimal TA PDRC properties, such as changes in reflectivity or emissivity from high surface temperature (HST) to low surface temperature (LST) states and the switch temperature at which these changes occur, are under-researched. To address this, a wavelength-dependent PDRC model was coupled with EnergyPlus to identify the optimal reflectivity or emissivity in HST and LST states and determine the appropriate switch temperature. Results show that different reflectivity and emissivity values are needed for various climates to maximize TA PDRC benefits. Switch temperatures from 15 degrees C to 30 degrees C primarily affect cooling benefits with minimal impact on heating penalties. Additionally, the heating penalty and cooling benefit of TA PDRC vary across building types, requiring alignment between TA PDRC operational characteristics and HVAC systems to optimize advantages. Among building types, malls benefit the most from PDRC application.

Photocatalysis employing cost-effective commercial titanium dioxide offers an ideal solution for eliminating trace methane emissions from livestock and poultry farming. However, significant challenges such as the rapid recombination of photogenerated carriers, a limited light absorption spectrum, and weak adsorption capabilities considerably hinder the effectiveness of titanium dioxide in the photocatalytic treatment of trace methane. This study proposes a novel approach to activate plasma pre-treated N-doped commercial anatase TiO2 2 into dual- defect TiO2 2 (N-doped TiO2-x) 2-x ) featuring stable and controllable oxygen vacancies (OV) through photoinduced defect engineering. Characterizations of the photocatalyst confirm the successful creation of surface defects, further evaluated through solar-light-driven CH4 4 (ppm level) removal investigations. The yield of this N-doped TiO2-x 2-x in converting CH4 4 is 4.84 mu mol h- 1 , 44 times greater than that of unmodified TiO2, 2 , significantly outperforming previous studies. UV-Vis diffuse reflection spectra, and photoluminescence indicate that the modified commercial anatase TiO2 2 possesses a narrower band gap, efficient photogenerated carrier separation, and enhanced charge transfer. Furthermore, density functional theory (DFT) calculations demonstrate that the synergistic effects of oxygen vacancies and N doping enhance the adsorption and activation of both O2 2 and CH4 4 in the rate-determining step of the reaction. This innovative strategy holds considerable promise for modifying various materials for more efficient photocatalytic applications.

Conventionally, the airflow fields outside and inside the naturally ventilated livestock buildings are modelled simultaneously in one computational domain using CFD (Computational Fluid Dynamics). The presence of surrounding buildings, indoor facilities and animals for large scale cattle barns make the required computational power extremely high and even unfordable to achieve simulation results with reasonable accuracy. The Domain Decomposition Technique (DDT), dividing simulations into two separate steps, is an alternative CFD framework to provide sufficient accuracy with affordable computations at each step. The objective of this study was to verify the reliability of DDT on modelling the airflow fields inside a naturally ventilated cattle barn (NVCB) by employing wind tunnel measurements. The exterior airflow fields around the targeted NVCB, which was opened with varying opening ratios, were first simulated to obtain the airflow boundary conditions at sidewall openings by applying exterior wind conditions at the inlet of the computational domain. The interior airflow of the targeted NVCB, were secondly simulated by applying the achieved airflow boundary conditions at sidewall openings from the first step simulation. The interior airflow fields obtained by DDT were in good agreement with wind tunnel measurements. This indicates that DDT can provide an alternative for CFD application in large-scale NVCB with presence of surrounding buildings, indoor facilities and animals, though these had not been considered in this study.

To effectively mitigate heat stress among lactating sows, this study proposed a novel pen partition-attached jet air supply (PJAS) and compared its performance with commercial ceiling jet air supply (CJAS) by using computational fluid dynamics (CFD). Each PJAS unit, comprising a circular distribution duct with 5 slot orifices at each side, was installed at the pen partition between two adjacent pens to direct air towards lactating sows to enhance convective heat removal. The cooling performances of air supplier were primarily evaluated by assessing the convective heat flux from lying sows. The effect of jet angles induced by PJAS and CJAS on convective heat flux were investigated as well as the consequence of reducing the inlet dimension of CJAS. The results revealed that reducing the inlet dimension of CJAS doubled the speed of supplied air. However, it also limited the amount of air impinging on sow due to the narrowing of the inlet air jet. Consequently, the combined effect only marginally increased the convective heat flux when the inlet area of CJAS was reduced. By placing air supplier closer to lactating sows, the air jet induced by PJAS impinged on sows’ bodies directly and therefore significantly increased the convective heat removal. Compared to CJAS, PJAS required approximately 45% less ventilation rate to induce the same convective heat flux. When the ventilation rate was identical, PJAS could increase the convective heat flux by up to 27.6%. These results highlight PJAS as a promising energy-efficient localized cooling device for mitigating heat stress among lactating sows. To determine the optimal design and control strategy of PJAS based on industrial requirements, further research is still needed.

The slatted floor system is often used in pig housing. Computational Fluid Dynamics (CFD) is a valuable tech-nique for determining the airflow and gas dispersion within the pit headspace through the slatted floor. However, there is a practical issue related to modeling the thousands of small slot openings in real livestock buildings for CFD simulation. It is unpractical to simulate the slatted floor with geometry details due to the large mesh number and the limited computer capacity. In this study, several methods to simplify the model of the slatted floor were explored to reduce the computational cost. The study was based on CFD analysis supported by experimental validation. The slatted floor was modeled in four ways: direct geometry method (DGM), porous-region method (POM), and profiled-porous-region method (including PPOM-cell (PPOM-C) and PPOM-floor (PPOM-F)). To assess the feasibility of the simplification, the four modeling approaches were compared with the experimental data. The results showed that it's feasible to model the slatted floor as POM or PPOM. The accuracy of POM was high, but it was greatly affected by the calculation of the resistance coefficient. PPOM-C has greatly reduced the amount of calculation, which could be used to simplify the large-scale pig house model whose flow fields and gas emissions below the slatted floor could be ignored. The simulation result of PPOM-F was the closest to DGM, however, due to the large number of meshes and complex setup, it was not suitable for practical simulation.

In the context of current intensive livestock farming development, we present a novel energy-efficient ventilation method, named as the partition jet and pit exhaust (PJPE) system, for multi-story pig facilities. The objective is to overcome the limitations of traditional ventilation methods, e.g., mixing ventilation sidewall air supply or tunnel ventilation, in managing heat stress and air quality. Isothermal and non-isothermal experiments were conducted in a 1:2.5 scaled pig pen model to study the airflow distribution characteristics and ventilation effectiveness of the PJPE system. The results demonstrate that the PJPE system enables rapid delivery of fresh air to the animal- occupied zone (AOZ). With the Archimedes numbers (Ar) of supply air ranging between 0.0025 and 0.0052, the jet maintains low air temperatures near the pig's back. Compared to traditional pig house ventilation methods, the PJPE demonstrates better heat removal efficiency (HRE), with an average HRE of 1.20. Additionally, the PJPE effectively inhibits the upward diffusion of ammonia from the slurry pit. These findings indicate that the PJPE system presents a viable, energy-efficient alternative for environmental control in high-density pig housing, highlighting its potential for advancing animal welfare and productivity in intensive livestock farming.