Contour Cross-sections Research Articles

Development and validation of pedestrian sedan bucks using finite-element simulations: a numerical investigation of the influence of vehicle automatic braking on the kinematics of the pedestrian involved in vehicle collisions

Previous vehicle-to-pedestrian impact simulations and experiments using pedestrian dummies and cadavers have shown that factors such as vehicle shape, pedestrian anthropometry and pre-impact conditions influence pedestrian kinematics and injury mechanisms. Generic pedestrian bucks, which approximate the geometrical and stiffness properties of current vehicles, would be useful in studying the influence of vehicle front-end structures on pedestrian kinematics and loading. This study explores the design of pedestrian bucks, intended to represent the basic vehicle front-end structures, consisting of five components: lower stiffener, bumper, hood leading edge and grille, hood and windshield. The deformable parts of the bucks were designed using types of currently manufactured materials, which allow fabricating the bucks in the future. The geometry of pedestrian bucks was approximated according to the contour cross-sections of two sedan vehicles used in previous pedestrian dummy and cadaver impact tests. Other cross-sectional dimensions and the stiffness of the buck components were determined by parameter identification using finite-element (FE) simulations of each sedan model. In the absence of a validated FE model of human, the FE model of the POLAR II pedestrian dummy was used to validate a mid-size sedan (MS) pedestrian buck. A good correlation of the pedestrian dummy kinematics and contact forces obtained in dummy–MS pedestrian buck with the corresponding data from dummy–MS vehicle simulation was achieved. A parametric study using the POLAR II FE model and different buck models – an MS buck and a large-size sedan (LS) buck – were run to study the influence of an automatic braking system for reducing the pedestrian injuries. The vehicle braking conditions showed reductions in the relative velocity of the head to the vehicle and increases in the time of head impact and in the wrap-around-distances (WAD) to primary head contact. The head impact velocity showed a greater sensitivity to the different buck shapes (e.g. LS buck versus MS buck) than to the braking deceleration. The buck FE models developed in this study are expected to be used in sensitivity and optimisation studies for the development of new pedestrian protection systems.

Dynamics of the middle atmosphere at Saskatoon (52°N, 107°W): a spectral study during 1981, 1982

Planetary waves (2 day–30 day) and tidal wave (8 h, 12 h, 24 h) oscillations are studied by forming height (60–110 km) and time (January–December) contour cross-sections and comparing with mean winds for 1981, but also on occasion 1982. Strong seasonal variations with evident wave-mean flow couplings are demonstrated. The zonal mean wind momentum budget (80–90 km) is assessed using cross-sections of northward-eastward covariances for wind fluctuations in the planetary and tidal wave period ranges and also gravity wave cross-sections. Dominant contributions are due to coriolis torque in the meridional mean flow and vertical divergence of the gravity wave momentum flux, although planetary wave contributions may be large also in winter months.