A point vortex model for aerodynamic derivatives for tandem multi-deck structures

The problem of aerodynamic flutter has received much attention and continues to be important for slender structures, such as long-span suspension bridges. The wind flow across the structure can approximately be described as a two-dimensional flow across a moving flat plate, and the bridge motion can be expanded in heave and pitch motions, leading to the traditional aerodynamic derivatives description. In this paper, the classical Theodorsen model [NACA report no. 496, 1934] is revisited, and an extended method is proposed, allowing computation of the aerodynamic derivatives for more complex planar geometries, such as tandem configuration multi-deck bridges. In keeping with the Theodorsen model, the vorticity in the wake is modelled as a vortex sheet advected passively with the free-stream velocity. The bridge deck influence on the wind flow is described by a number of point vortices, and the aerodynamic forces and moments on the bridge are obtained as the rate-of-change of their aerodynamic impulse and angular impulse. Twin-deck bridges are considered for a number of inter-deck spacings. A set of critical reduced wind speeds, depending on the spacing between decks, are identified. Preliminary wind tunnel test results are reported and shown to correspond well to the point vortex model predictions.


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  • Accession Number: 01715647
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 14 2019 3:04PM