Numerical simulation of wind loads and aerodynamic characteristics of streamlined bridge decks under tornado-like vortices

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This paper mainly investigates interactions between a tornado and a streamlined single-box bridge deck using large-eddy simulation (LES). Simulation is carried out with respect to an ISU-type tornado vortex simulator with an embedded bridge deck model. Aerodynamic loading characteristics of the bridge deck are compared with available experimental data, in forms of surface pressure coefficients as well as sectional aerodynamic load coefficients. The presence of the bridge deck as well as the horizontal distance from tornado center to bridge deck are then taken into account to reveal the interference of the bridge deck with the tornado flow field. It is shown that the numerical results fit well with the experimental data in most cases, while discrepancies recorded in some cases are potentially due to the limitations of experimental measurement and uncontrollability of flow field similitude. The presence of the bridge deck would destroy the vortex structure generated in an empty simulator and form two new flow regimes with distinct vortex structures above and below the deck. The effects of the variation of spatial relationship between the bridge deck and the tornado-like vortices on two newly formed flow regimes appear to be different, and the difference between the pressure deficits of these two flow regimes result in discrepancies between the surface pressures on the upper and lower surfaces of the bridge deck. The angle of attack and the magnitude of velocity of incoming wind flows are determined for the further purpose of simple parameterization of tornadic effects on bridge decks, and both seem to be influenced by the presence of the bridge deck.