Wind-structure interaction simulations for the prediction of ovalling vibrations in silo groups

Wind-induced ovalling vibrations were observed during a storm in October 2002 on several empty silos of a closely spaced group consisting of 8 by 5 thin-walled silos in the port of Antwerp (Belgium). The purpose of the present research is to investigate if such ovalling vibrations can be predicted by means of numerical simulations. More specifically, the necessity of performing computationally demanding wind-structure interaction (WSI) simulations is assessed. For this purpose, both one-way and two-way coupled simulations are performed. Before considering the entire silo group, a single silo in crosswind is simulated. The simulation results are in reasonably good agreement with observations and WSI simulations seem to be required for a correct prediction of the observed ovalling vibrations

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 it is examined if the excitation of ovalling vibrations in the silo group is possible. Two probable causes of observable 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 detected 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

Unsteady Reynolds averaged navier-stokes simulation of the post-critical flow around a closely spaced group of silos

During a storm in October 2002, wind induced ovalling oscillations were observed on several empty silos of a closely spaced group of 8 by 5 silos in the port of Antwerp (Belgium). Present day standards describe only basic wind load cases, unable to explain this ovalling phenomenon. In order to improve the design of engineering structures with cylinders placed in groups, a thorough understanding of the fluid flow around such groups is required. 2D unsteady Reynolds averaged Navier-Stokes (URANS) equations usingMenter’s shear stress transport turbulencemodel were performed, considering the wind flow around the rectangular group for a range of angles of incidence (0 a 90). The 2D highly turbulent post-critical flow (Re = 1.24×107) around a single cylinder was computed to elucidate the influence of the applied turbulence model and to validate the spatial and temporal discretization. Since, the flow regime around and within the silo group is similar to the flow around rectangular cylinders and the flow within tube arrays (e.g. heat exchangers), similarities and differences are used to assess the influence of the angle of incidence on the flow pattern around the cylinder group. The large velocities in the interstitial flow between cylinders as well as the formation of large scale vortex shedding in the wake of the group are discussed for various angles of incidence. Static and dynamic loadings on separate silos of the group are studied to explain the existence and the location of ovalling oscillations in closely spaced silo groups