Yaojun Ge

Investigation and prevention of deck galloping oscillation with computational and experimental techniques

Abstract Although bridge aerodynamics usually involves such kinds of wind-induced responses as vortex shedding excitation, buffeting and flutter instability, a bluff cross section for even a short-span bridge, combined with a lightweight superstructure in reality, has brought its galloping-type instability as an important issue for bridge aerodynamics. This paper focuses its attention on the galloping-type oscillation taking as an example of the Yadagawa Bridge in Nagoya, Japan. The deck galloping oscillation of this continuous beam bridge has been thoroughly investigated by CFD computational estimation and wind-tunnel experimental confirmation using a sectional model and an aeroelastic model. Three aerodynamic preventive means, including the 40% slotted deck, the 80% slotted deck and the structure with aerodynamic deflectors, have been suggested and studied to improve the galloping characteristics of the bridge deck.

Reynolds Number Effects on the Flow Around Square Cylinder Based on Lattice Boltzmann Method

The Lattice Boltzmann (LB) equation is discussed from the point of molecule kinetic theory at first. Based on the turbulence theory, eddy viscous turbulence model is incorporated into the LB equation to simulate the turbulence flow at high Reynolds number. The flows around square cylinder are simulated in the range of Reynolds number from 10 to 105, and the Reynolds number effects on drag, Strouhal number and flow field are investigated in details. Figure 1 and Figure 2 show that the drag and vortexes shedding frequency of square cylinder are dependent on Reynolds numbers. The turbulence LB method is verified by the comparison of present results with those of other numerical methods and experiments. nOpen image in new window n nFigure 1 nDrag coefficients depending on Re n n nOpen image in new window n nFigure 2 nStroubal number depending on Re

Extended Lattice Boltzmann Method with Application to Predict Aerodynamic Loads of Long Span Bridge

The lattice Boltzmann (LB) method, a new conceptual approach to solve the fluid dynamics problem, is presented at first. The turbulence model is incorporated into the normal LB equation to simulate turbulence flow in the form of turbulence relaxation time determined by the nonequilibrium particle distribution function and Smagorinsky model. The total relaxation time is defined as the contribution of molecule viscosity and turbulence eddy viscosity. The aerodynamic forces on bridge girders are predicted by present LB method and the analysis of flow state is performed. The validity of LB method is verified through comparing the present results with the available experimental data and those obtained from the solutions of Navier‐Stockes equation like Reynolds averaged Navier‐Stokes (RANS) and discrete vortex method (DVM).

Nonlinear Aerodynamic Forces on Bridge Decks due to Transverse Sinusoidal Fluctuation of Wind

The aerodynamic forces on bridge decks generated by transverse sinusoidal fluctuation of wind are investigated by 2-dimesional lattice Boltzmann method. The aerodynamic admittance functions in traditional buffeting force model are identified. The proposed numerical method is verified by comparing the corresponding identified admittance functions of a thin flat-plate with the Sears function. The longitudinal buffeting forces of all the four typical decks simulated here have multiple-frequency phenomenon. The transverse buffeting force and buffeting torque of the blunt п-shape deck also have this nonlinear characteristic. A nonlinear buffeting forces model is proposed to reproduce the nonlinear aerodynamic force due to the transversely fluctuating wind.