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This study introduces recent efforts of the Architectural Institute of Japan (AIJ) to develop guidelines for largeeddy simulation (LES) of pedestrian wind environments (PWEs). Reynolds-averaged Navier-Stokes (RANS) models have been widely used for predicting urban wind environments following best practice guidelines (BPGs) by Franke et al. [Int J Environ Pollut 44, 1-4 (2011)] and Tominaga et al. [J Wind Eng Ind Aerodyn 96 (10-11), 1749-1761 (2008)]. Although RANS models can predict mean wind velocity and some turbulence statistics based on empirical assumptions, LES provides higher accuracy in resolving transient turbulence structures larger than the grid scale. With increasing urbanization, understanding instantaneous complex wind and wind-related phenomena around buildings is essential for ensuring pedestrian wind comfort and safety. However, LES applications face challenges owing to a lack of BPGs. This study outlines key recommendations for simulation setups and post-processing, including domain size, building modeling, grid generation, boundary conditions, turbulence modeling, discretization, convergence criteria, and reliability evaluation. Additionally, new benchmark cases are provided to support validation for PWEs. The AIJ working group systematically evaluated LES performance across urban scenarios to ensure practical applicability while balancing computational costs. These guidelines aim to enhance prediction reliability, thereby contributing to the standardization of LES applications for PWE and advancement of computational wind engineering.
The shear stress transport (SST) k-w turbulence model has been increasingly applied in urban environmental computational fluid dynamics (CFD) simulations as an alternative to conventional k-e-type closures, due to its robustness and availability in most CFD software. Although its performance has been examined in specific contexts, unified assessments across multiple urban environmental targets remain limited. This study evaluated the performance of both steady and unsteady SST k-w simulations in predicting flow, pollutant dispersion, and surface pressure around simplified urban blocks. Results were compared against three steady Reynolds-averaged Navier-Stokes k-e models (standard, realizable, and calibrated), large-eddy simulation (LES), and wind tunnel experiments conducted by the authors. The steady SST k-w model improved the prediction of rooftop and leeward recirculating flows compared to the k-e models, but overestimated near-ground wind speeds and underestimated downwind pollutant dispersion, which may affect wind comfort and exposure assessments. The unsteady SST k-w simulation showed better agreement with LES and experimental data, particularly for transient scalar dispersion patterns and surface pressure coefficients. Overall, the SST k-w model more accurately captured flow separation and reattachment zones than did the k-e models but exhibited limitations in reproducing peak wind speeds and scalar spread. By separating the effects of turbulence modeling and transient resolution, this study provides a comprehensive and unified evaluation of SST k-w model capabilities and limitations for practical CFD applications in urban environmental design and assessment.
PurposeSecurity concerns in Africa call attention to the need for smart technologies in mosque infrastructure, yet adoption through facilities management (FM) remains limited despite threats. This study examines the integration of FM practices into mosque security systems in Ghana, focusing on safety, access control, and emergency response.Design/methodology/approachA quantitative research design, underpinned by Rogers' Diffusion of Innovations theory and the Unified Model of Organisational Effectiveness (UMOE), was employed. Data were collected through a structured questionnaire administered to 385 stakeholders, including management committee members, facilities staff, security personnel, and worshippers, across 15 mosques in Greater Accra. Purposive and stratified sampling ensured representation from urban, peri-urban, and rural mosques. The data were analysed using descriptive and inferential statistics (correlation and chi-square tests) in the Statistical Package for the Social Sciences Version 26 to assess relationships among FM practices, smart technology adoption, and safety outcomes.FindingsThe results show that smart FM technologies are linked to better safety, access control, and emergency response. Strong correlations were found between team coordination, system integration, and smart monitoring, confirming that collaborative management and technological interconnectivity significantly enhance security outcomes. However, persistent challenges, such as financial constraints, limited technical expertise, and weak institutional support, hamper implementation. There were also differences based on gender, with women showing more support for innovation and stakeholder engagement. This shows that inclusivity is a key factor in technology adoption.Originality/valueThis paper is the first of its kind in Africa to contribute to the literature by examining the operational, technological, and sociocultural dynamics of mosque safety in FM. It offers practical implications for religious facility managers and policy stakeholders through the implementation of the proposed framework.
The FU Orionis star V883 Ori provides a unique opportunity to probe the water snowline in a protoplanetary disk. During an accretion burst, the enhanced stellar luminosity heats the disk, sublimating ices and bringing volatile species into the gas phase. The water snowline, located at similar to 80 au in the midplane, represents a key boundary for dust growth and volatile delivery to forming planets. We present Atacama Large Millimeter/submillimeter Array Band 7 observations of V883 Ori that detect two targeted water isotopologue transitions: para-H2 18O 51,5-42,2 at 322 GHz and HDO 33,1-42,2 at 335 GHz. After correcting for Keplerian rotation, we detect HDO and H2 18O at 23.6 sigma and 9.3 sigma, respectively. Rotational-diagram analysis using a Markov Chain Monte Carlo approach yields Trot = 116.89 +/- 12.81 K and N = (4.90 +/- 1.69) x 1015 cm-2 for H2 18O and Trot = 87.46 +/- 4.95 K and N = (4.47 +/- 0.62) x 1015 cm-2 for HDO. These results imply water vapor abundances of NH2O/NH2 similar to 3x10-7 -5 x 10-6 and an HDO/H2O ratio of (0.4-2.0) x 10-3 just inside the water snowline, broadly consistent with inheritance from protostellar envelopes. The HDO line in Band 7 is significantly weaker than predicted from Band 6 extrapolation, showing only similar to 26% of the expected strength. This attenuation can be explained by a more compact, hotter emitting region with an effective radius of similar to 53 au and/or frequency-dependent dust absorption that enlarges the apparent inner cavity at a higher frequency. Our results highlight both the diagnostic power of water isotopologue lines and the need for higher angular resolution observations to resolve the water snowline and test these scenarios.
The influence of thermal-spot shape on medium is evaluated by magnetization transition fluctuation (jitter-like medium noise) in a dual-layer heat-assisted magnetic recording (DL-HAMR) system applied to a magnetic recording medium with dual recording layers on one side. The thermal-spot shape on the medium assuming an areal recording density of 2 Tbit/inch2 per layer, follows a two-dimensional Gaussian profile. The jitter-like medium noise is measured along with the effective recording field gradient by varying the standard deviations ( σx, σy) in the down-track and cross-track directions, respectively. To ensure sufficient track width in the shingled magnetic recording (SMR) configuration, σy is fixed at 22 nm. It is clarified that decreasing σx results in a steeper effective recording field gradient and consequently reduced jitter-like medium noise.
