CFD prediction of aerodynamic pressures on silo surfaces to investigate wind induced ovalling vibrations

During a storm, wind induced ovalling vibrations were observed on several empty silos of a closely spaced group consisting of 8 by 5 thin-walled silos in the port of Antwerp (Belgium). To clarify the cause and location of these wind induced vibrations, the spatial distribution of the aerodynamic pressures on the silo surfaces is determined in both 2D and 3D CFD (computational fluid dynamics) simulations of the highly turbulent wind flow around the silo group. The influence of the angle of incidence of the wind flow on the dynamic wind pressures is investigated by performing 2D URANS (unsteady Reynolds averaged Navier-Stokes) simulations. Transformation of the transient wind pressure distributions on the silo surfaces to the frequency domain reveals strong narrow band frequency peaks in the turbulent pressure coefficient spectra near the lee side corners of the group that match the structural natural frequencies of the observed ovalling modes. The importance of 3D wake effects on the spatial distribution of aerodynamic pressures along the height of the silos is investigated with 3D DDES (delayed detached eddy simulations). An important issue in the 3D simulations is the application of the atmospheric boundary layer (ABL) at the inlet of the domain. The aerodynamic pressures on the silo surfaces are first investigated using a similar procedure as for the 2D results and afterwards by performing one-way coupling calculations; i.e. by applying the 3D aerodynamic pressures as transient external loads on a 3D finite element model of the silos. Determination of modal kinetic and deformation energy of the structural response shows that even for a single silo in ABL flow the ovalling mode shapes with 3 and 4 circumferential wavelengths are dynamically excited, corresponding to the observed ovalling vibrations during the storm in 2002.

ISBN:9783950353709

Publication year:2012

Accessibility:Open