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

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

Wind-structure interaction simulations of ovalling vibrations in silo groups

© 2015 Elsevier Ltd. During a storm in October 2002, wind-induced ovalling vibrations were observed on several empty silos of a closely spaced group of silos in the port of Antwerp (Belgium). In this paper, three-dimensional numerical simulations are used to investigate this complex case of wind-structure interaction. The computed amplitude of the ovalling vibrations of the silos is similar to that in the observations, indicating that the adopted modelling approach can be suitable for the analysis of new silo groups.Both one-way and two-way simulations are presented, for a single silo and for the silo group. In the one-way simulations, the wind pressure is applied on the structure, disregarding the structural displacements in the wind flow simulation. By contrast, the two-way simulations also take into account the effect of the structural motion on the wind flow. For a single silo, the one-way and two-way simulations yield similar results. Conversely, for a silo in the group, the ovalling vibrations are significantly larger in the two-way simulations than in the one-way simulations. Consequently, aeroelastic effects and/or interactions between the wake-induced excitation and the vibration are present in the silo group for the investigated case.Furthermore, it is shown that the aerodynamic loading and vibration amplitudes are considerably larger for silos in the group than for a single isolated silo.status: publishe

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

Computational aspects of simulating wind induced ovalling vibrations in silo groups

© 2012 Elsevier B.V. All rights reserved. During a storm in October 2002, wind induced ovalling vibrations were observed on several empty silos of a closely spaced group of eight by five thin-walled silos in the port of Antwerp (Belgium). To determine realistic dynamic wind loads and hence clarify the cause of the wind induced ovalling vibrations in the silo group, 2D URANS simulations are performed for seven angles of incidence between 0° and 90°. The emphasis in this paper is on the extensive verification and validation of the simulations to ascertain the accuracy of the numerical results. Subsequent analysis of the fluctuating wind pressures on the silo surfaces shows that ovalling oscillations of the eigenmodes with three and four circumferential wavelengths will be induced at the lee side of the silo group, corresponding to the lowest structural eigenfrequencies of the silos and the pattern of the visually detected vibrations during the 2002 storm.status: publishe

Healing efficiency of polystyrene electrospun nanofibers with Grubbs' catalyst in thermosetting composite

The study presents a novel method for the protection of Grubbs' catalyst, by incorporation in polystyrene fibres via electrospinning technique. Epoxy-glass fibre composite with embedded self-healing agents (polystyrene fibres with Grubbs' and microcapsules with dicyclopentadiene) was processed. Fibres retained pale purple colour during processing, revealing that fibres provided good protection of the catalyst from the amine hardener. The influence of self-healing agents' content and thermal treatment on self-healing efficiency was investigated. Fourier transform infrared spectroscopy revealed that a polydicyclopentadiene formed at the healed interface. Thermal analysis revealed that bleed' at the healing sites from different samples had similar concentration of polydicyclopentadiene, indicating that the same amount of the catalyst has been provided to dicyclopentadiene for polymerization. This finding lead to assumption that electrospun polymer fibres enabled good dispersion of the catalyst in the composites. The low energy impact tests of the samples showed a recovery of 90% after 24h at room temperature and up to 111% after repeated heating cycles