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In view of the difficult problem of gas and dust exceeding the limit during the digging process of a gas tunnel in Guizhou Province, Southwest China, the CFD numerical simulation method was applied to study the gas tunnel airflow, dust and gas transport law during the digging process. A physical simulation experimental platform was established to verify the numerical simulation results, and research was carried out in terms of gas-containing gas-carrying dust disaster prevention and control, and ventilation optimization was carried out for this gas tunnel. The results showed that the maximum gas concentration in the tunnel face under press-in ventilation could be about 1%, and the local dust concentration can be up to 900 mg/m 3 . The gas mass fraction in localised areas of the tunnel exceeded 0.9% under mixed ventilation pressure-extraction ratios of 9:1 and 8:2. When the pressure to pumping ratio is 6:4, the dust was concentrated on the return side of the tunnel at a distance of 40–60 m from the head of the tunnel, and the highest local dust concentration reaches 700 mg/m 3 . When the pressure pumping ratio was 7:3, the dust pollution problem could be controlled more effectively, and at the same time, there was no higher concentration of gas gathering in the tunnel. A comprehensive analysis of the differences between dust and gas-enriched areas in gas tunnels could provide some guidance on the synergistic control of gas and dust in gas tunnels.

The mine ventilation system is a vital component in ensuring mine safety, and optimizing it is crucial for reducing energy consumption and improving efficiency. However, traditional optimization methods face limitations when applied to complex mine ventilation systems, making it challenging to achieve optimal results. This paper presents an optimization method for mine ventilation systems utilizing an enhanced Dung Beetle Optimizer (DBO). Several enhancement strategies have been made to address issues such as uncoordinated global search, limited local exploitation, and slow convergence speed in the standard DBO, including chaotic initialization, random walk strategy, and cross-strategy. The Strategy-Combined Dung Beetle Optimizer (SCDBO) is used to optimize mine ventilation systems by reducing energy consumption through improved air distribution and resistance management within the network. Experimental results show that SCDBO can effectively reduce the energy consumption of mine ventilation systems, achieving a 27% energy savings and providing a practical new approach for optimizing mine ventilation.

Increasing global temperatures and unpredictable weather threaten agricultural production, intensifying the reliance on greenhouse cultivation. While naturally ventilated greenhouses offer an energy-efficient solution, their thermal performance under high heat loads is a growing concern. This study developed and validated a 3D CFD model to investigate the temperature distribution inside a single-span, naturally ventilated greenhouse. The model, implemented in ANSYS Fluent, considered the influence of external meteorological conditions, including solar radiation and wind, on the internal microclimate. The model demonstrated high accuracy, with an RMSE of 0.847°C and an MAE of 0.714°C for temperature when compared to experimental data. Diurnal analysis confirmed the dominant role of solar radiation, showing a strong correlation between indoor temperature and external solar radiation (r = 0.96) on sunny days. Spatially, the simulation revealed extreme thermal heterogeneity under high solar load, with a total internal temperature variation of up to 25°C (from 296 K to 321 K). The distribution was characterized by a distinct vertical stratification due to buoyancy and a strong longitudinal gradient, with the hottest air accumulating in the upper leeward corner. These findings highlight areas of potential crop heat stress and demonstrate the limitations of side-ventilation alone. The validated model serves as a valuable tool for optimizing ventilation strategies and improving climate control system design.  

With the rapid development of tunnel construction, more and more long tunnels are being designed and built. In contrast to ordinary tunnels, long tunnels are characterized by large construction distances and difficult ventilation. In this study, gallery ventilation systems in the construction of long tunnels were studied. Combined with the CFD software FLUENT, a three-dimensional model of tunnel ventilation of a double tunnel was established, and a numerical simulation analysis of the ventilation flow field was carried out and optimized the flow field of gallery ventilation. We found that the main circulation air flow of gallery ventilation was formed by the jet fan, which was installed near the air flow-in tunnel. We also determined the main factors that affect the ventilation effect in gallery ventilation, including the wind wall formed by the high-speed airflow at the cross-aisle and found that the draft fan in front of the cross-aisle could eliminate the wind wall and improve the ventilation effect. The influence of the location and type of the draft fan on the elimination of air flow structure was studied, and the best fan layout scheme suitable for the site was determined. The ventilation scheme of the tunnel was optimized.

Airborne transmission of respiratory pathogens in indoor environments remains a significant global health challenge. While existing research broadly addresses ventilation effectiveness, there is a critical need to understand how specific diffuser placements influence early-phase aerosol dispersion immediately following a cough event. This study uses Computational Fluid Dynamics (CFD) with an Eulerian–Lagrangian approach and the Discrete Phase Model to analyze initial droplet transport, evaporation, and nuclei concentration under different air distribution configurations. The results demonstrate that conventional parallel exhaust configurations, though effective at reducing overall particle mass, can fail to control the lateral spread of infectious nuclei in the short term. In contrast, placing exhaust diffusers above the cough source reduces the lateral particle spread by approximately 40% compared to conventional layouts. Additionally, maintaining the WHO-recommended two-meter distance results in an 82–89% reduction in particle number concentration during the early dispersion phase. These findings underscore the importance of diffuser placement for controlling short-term particle dispersion immediately after a cough event in mechanically ventilated office environments. The study’s scope is limited to early-phase dispersion dynamics within a 10-second simulation period, and further research is needed to assess long-term aerosol suspension, removal mechanisms, and infection risk. Nonetheless, the results offer practical insights for HVAC design and support the integration of ventilation strategies with physical distancing measures to reduce near-field exposure risks.

•Ventilation, fan modes & exhalation types on droplet spread are studied.•Ceiling fans reduce infection risk or boost ventilation performance.•Higher fan speed impairs droplet control effectiveness.•CFIAC systems control cough droplets better than speaking droplets.•Upper-supply & lower-exhaust ventilation optimizes droplet control. Ceiling Fan-Integrated Air Conditioning (CFIAC) is a coupling configuration of air conditioning ventilation systems and ceiling fans that combines fresh air supply (from the air conditioning system) with indoor airflow distribution adjustment (via ceiling fans). This study employed Computational Fluid Dynamics to simulate the transient respiratory droplet dispersion under CFIAC systems. By combining infection risk for the exposed person and droplet fate indicators (suspension, sedimentation, escape), the impacts of different ventilation configurations, ceiling fan speeds, and exhalation types on droplet transmission were investigated. Ceiling fan activation was found to either mitigate local infection risk or enhance airflow circulation: downward operation at 72 rpm reduced local infection risk by 96.6 %, while upward rotation decreased the fraction of suspended droplets by 39.29 % (boosting droplet escape by 10.88-fold relative to fan-off conditions). Excessively high fan speeds (122 rpm) negated these benefits, increasing infection risk by 4.25-fold compared to the 72 rpm condition. CFIAC systems exhibited more effective control over coughing droplets than over speaking droplets, with the infection risk associated with speaking being 15.5 % higher than that of coughing. Among the tested configurations, upper-supply and ceiling-exhaust ventilation excelled in reducing local infection risk, while upper-supply and lower-exhaust ventilation optimized overall respiratory droplet control. These results provide practical guidance for optimizing CFIAC operation and formulating targeted infection prevention strategies. Schematic of the indoor CFIAC system and key findings: (1) The lower-supply and upper-exhaust ventilation outperforms other modes in droplet control; (2) Moderate bidirectional ceiling fan rotation reduces local infection risk by 96.6 % and improves droplet control (settling, suspension, escape); (3) Droplets from speaking have a higher suspension ratio than coughing, leading to higher infection risk for M2. [Display omitted]

During the operational ventilation process of high-altitude helical tunnels, the installation method of jet fans is a key factor in determining the ventilation efficiency of the tunnel. In this study, the CFD numerical simulation method is adopted to establish three-dimensional ventilation models of helical tunnels with different curvature radii. Through orthogonal experiments, the effects of tunnel curvature radius on the characteristics of the air jet flow field, under the coupled influences of factors such as lateral spacing of jet fans, vertical height of fans, longitudinal spacing, and lateral offset, are investigated. The results show that when R = 500 m, 600 m, 700 m, and 800 m, the longitudinal spacing has the most significant impact on ventilation efficiency, followed by vertical height, with lateral offset and fan spacing having the least impact. The optimal spacing and vertical height of the fan groups remain consistent under different curvature radii, at 1.25D (fan diameter) and 15 cm, respectively. The optimal longitudinal spacing of the fan groups is 90 m, 90 m, 135 m, and 90 m, respectively. Shifting the fan groups 0.25 to 0.75 m towards the inner side of the tunnel helix (for R < 700 m) can optimize the flow field distribution within the tunnel. Finally, expressions for the relationship between the helical radius and the lateral offset and longitudinal spacing of the fan groups are established for the optimal installation parameters of fan spatial positions under different helical tunnel radii.

In the underground mine ventilation area, the absence of robust solutions for nonlinear programming models has impeded progress for decades. To overcome the enduring difficulty of solving nonlinear optimization models for mine ventilation optimization, a major technical bottleneck, we first develop an advanced linear optimization technique. This method transforms the nonlinear ventilation optimization and regulation model into a linear control model, avoiding the limitation of difficulty in solving the nonlinear mathematical model. The linear strategy opens up a new solution idea for the nonlinear calculation of the mine ventilation optimization and regulation. Furthermore, this study introduces evaluation metrics for ventilation scheme quality, including minimal energy consumption, fewest adjustment points, and optimal placement of these points, enhancing flexibility in ventilation network optimization. By analyzing the ventilation model control objectives and constraints, we formulated a linear optimization model and developed a multi-objective mixed-integer programming model for ventilation network optimization. This paper constructs and verifies a calculation example model for mine ventilation optimization, assessing its reliability based on airflow distribution calculations.

In tunnel operation ventilation systems, the arrangement of jet fans plays a decisive role in ensuring ventilation efficiency. Curved tunnels, due to their unique radius of curvature, exhibit significant differences in fan installation parameters and jet flow field distribution compared to traditional straight-line tunnels. In order to investigate the distinct characteristics, this research utilized computational fluid dynamics (CFD) simulation methods to analyze the ventilation performance of both an innovative, adjustable jet fan system and conventional jet fans within the context of curved tunnel configurations. The findings reveal that by adjusting the horizontal deflection angle of the novel jet fan, the flow field distribution can be effectively optimized, and the jet effect can be enhanced, thereby improving ventilation efficiency. Compared to traditional jet fans, the novel fan demonstrates a significantly greater capability in flow field optimization, especially when its horizontal deflection angle is adjusted, showing a trend where the jet effect initially increases and then decreases, with the longitudinal impact range being adjustable within a range of 5 m to 25 m.

Mining activities often deem mine sites as temporary, leading to their eventual reclamation, rehabilitation, or abandonment. This study innovates by proposing the re-purposing of the disused Osarizawa mine in Akita, Japan, leveraging its consistently low tunnel temperatures to establish a data center, thereby offering a sustainable economic avenue to offset reclamation costs. We assessed the feasibility of this transformation by gathering comprehensive environmental data from the site and conducting meticulous ventilation simulations. These simulations explored various scenarios encompassing diverse ventilation configurations, data server room dimensions, thermal outputs, and the inherent cooling capabilities of the proposed humid rooms. By juxtaposing the simulation outcomes with the criteria set forth in the ASHRAE 2011 Thermal Guidelines, we pinpointed the optimal parameters that satisfy the stringent temperature and relative humidity prerequisites essential for a data center’s operation. This research underscores the potential of reimagining abandoned mine sites as strategic assets, providing economic benefits while adhering to critical data center infrastructure standards.