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• Single shotgun pellet ricochet marks can imply their impact angles. • Pinch points/ nucleus ricochet marks can be seen following shotgun pellet ricochets. • Extents of impacting and ricocheting shot spreads have significant reconstructive values. Compared to popular handguns and rifle bullets, quantitative and empirical-based ricochet studies using shotgun pellet ricochets are observed to be far fewer. This empirical study examines the ricochet behaviour and impact evidence when shotgun pellets (Buckshot) ricochet off standard floor tiles, providing a series of novel findings related to the resultant ricochet marks. Among these findings, a novel and statistically significant relationship between the lengths and widths of individual ricochet marks and the shot impact angles is demonstrated, offering useful forensic application. Ricochet mark shapes and morphologies highlighted in this study at different impact angles demonstrate the interactions between the ricocheting spherical pellets and tile surfaces, and the effects of acting frictional forces and degree of energy transfer in the production of impact evidence on the tile surface. Relationships with high statistical significance were also reported between the shot spreads on the tile surfaces and the post-ricochet cardboard witness screens, with shot impact angles. Finally, this work reports on the first documented observations of 'Pinch Points' and 'Nucleus' ricochet marks with shotgun pellet ricochets as angle-specific phenomena. [ABSTRACT FROM AUTHOR]

• Ricocheting bullets off sheet metal produces low ricochet angles than incident angles. • Three-head ricochet mark is unique to M 16 bullets ricocheting off 1 mm sheet metal. • Length of rifle bullet ricochet marks can use to estimate the bullet's incident angle. • M-16 bullets fragment when impacting 1 mm sheet metal from 5 degrees onwards. [ABSTRACT FROM AUTHOR]

Abstract In this study, the influence of different roof pitches on the mean pressure distributions around isolated buildings subject to different wind directions were investigated with wind tunnel tests, 3D steady Reynolds-averaged Navier-Stokes (RANS) simulation and large eddy simulation (LES). Wind tunnel experiments were conducted to obtain mean pressure distributions around buildings having three commonly used roof pitches, namely, 1:5, 2:5 and 3:5. The critical high suction areas created by conical vortices were identified, and the influence of roof pitch on these critical areas with high localised pressures was investigated under various wind directions. In addition, computational fluid dynamics (CFD) analysis was performed, and the performance of RANS and LES were evaluated and compared with the results measured from the wind tunnel tests by considering both the accuracy of results and computational cost. The assessment on RANS and LES was used to determine the best guidelines for the flow problems involved in this study. Results from the RANS show good agreement with the experimental results on pressure distribution when the building is subject to perpendicular wind directions. However, a significant improvement was found using LES over RANS in the prediction of near-building flow field and localised pressure under oblique wind directions but with an increased computational cost by a factor of more than 80. Furthermore, the high suction pressures are observed to be more critical on buildings with a lower roof pitch under both perpendicular and oblique wind directions. This indicates that a low roof pitch should be applied with caution especially in windstorm-prone areas. Highlights • Influence of roof pitch on wind induced pressure on gable roof buildings was investigated. • Both perpendicular and oblique wind directions were taken into consideration. • The performances of steady state RANS and large eddy simulation (LES) were compared with experimental results. • The high suctions caused by corner vortices are found to be more critical on the roof with lower roof pitch. • LES can provide better accuracy on pressure prediction and flow field generation over RANS under oblique wind directions. [ABSTRACT FROM AUTHOR]

In this study, the influence of opening position and wind direction on pressure distribution around isolated gable roof buildings with and without openings were investigated. Computational Fluid Dynamics (CFD) simulations were performed and compared with wind tunnel experimental results. One of the aims of this study was to develop well-defined design guidelines for typical gable roof structures, identifying critical localised pressure rises due to different wind attack angles. Existing international standards provide limited design guidelines for localised wind pressure distribution of such buildings, especially in cases where there are openings. Wind tunnel experiments were conducted to obtain mean pressure distributions of critical areas of the building under different wind directions with four different opening configurations, namely, an enclosed building, a building with one windward opening, a building with one windward opening and one sidewall opening, and a building with one windward opening and two sidewall openings. A CFD-based numerical simulation approach was used to create a virtual wind tunnel in the computational domain. Sensitivity analyses for grid resolutions and turbulence models of simulations were performed for the building with a windward opening. Results from the numerical simulations show good agreement with the experimental results on pressure distribution. The validated models were used to identify critical areas of the buildings that must be considered in the design stage. The relevant pressure coefficients are presented and compared with the standards. The importance of performing a comprehensive wind study using a numerical approach or wind tunnel tests is highlighted. [ABSTRACT FROM AUTHOR]