Computational Fluid-structure Interaction Simulations for Wind Induced Vibrations in Silo Groups

During a storm in October 2002, wind induced ovalling vibrations were observed on several empty silos of a closely spaced group consisting of 8 by 5 silos in the port of Antwerp (Belgium). First, a thorough understanding of the fluid flow around the group is required to clarify the underlying mechanisms for the vibration. Since the configuration and orientation of the group drastically change the pressure distribution on the silos of the group, the flow regime around and within the silo group has been simulated for 7 angles of incidence between 0 and 90, leaving other parameters unchanged (e.g. spacing ratio, Reynolds number,...). The flow regime shows similarities with the flow within tube arrays (e.g. heat exchangers) and the flow around rectangular cylinders. By a ‘one way coupling’ of static (time averaged) and dynamic (fluctuating) pressure loadings on the cylinder surfaces, two probable causes of wind induced silo vibrations in the group are observed. The first, as a result of large static wind pressures and fluctuating drag and lift coefficients, might lead to rigid body motions of the statically deformed silos. The second, due to higher dynamic pressure oscillations, can excite ovalling oscillations in the third and fourth eigenmodes at the lee side of the group, corresponding with the lowest eigenfrequencies of the silos and the visually observed vibrations in 2002. Although it is shown by this ‘one way coupling’ that ovalling vibrations can be excited in the group, more advanced ‘two way coupled’ fluid-structure interaction simulations are required to determine the underlying mechanism inducing these aeroelastic deformations.