Icing of wind turbines happens occasionally at different latitudes and locations in the world and consequently affects the wind turbine fatigue loads. Large ice accretion may cause wind turbine vibration due to uneven ice shedding, which could lead to structural failures in addition to hazardous issues accompanied with ice being shed off wind turbine blades. In this paper, a review study of the effects of ice accretion on the structural behavior of the wind turbines is presented.
Wind energy is a promising way in the middle of growing demand for clean energy in high north, where atmospheric icing is a hazard for safe operations of wind turbines. In this research work, the vibrational effects due to atmospheric ice accretion on a multi megawatt large wind turbine are numerically investigated using a finite element based approach. Three different icing scenarios were addressed and accreted on-blade ice mass was calculated analytically based upon ISO 95214 standards. Special attentions are given to the first natural frequency of the wind turbine blade and its interaction when the exciting frequency approaches the natural frequency of the wind turbine tower. Results show variations of natural frequencies due to different accreted icing loads scenarios, which may have different implications to the integrity of the structure.
Continuous structures such as beams, rods and plates can be modelled by discrete mass and stiffness parameters and analysed as multi-degree-of-freedom systems. The analysis of structural vibration is necessary to obtain the natural frequencies of a structure and the response to the external excitation. In this way, it can be determined whether a particular structure will fulfil its intended function and, in addition, the results of the dynamic loadings acting on a structure can be predicted. The lack of a sober analytical research about the vibrational behaviour of the 5-MW wind turbine blade pushed us to investigate about this crucial issue, however, most of the discreet researches are concerned with the aerodynamic effects rather than structural analysis. In this article, Rayleigh–Ritz method was implemented for a typical 5-MW wind turbine blade. MATLAB codes were developed and natural frequencies were obtained for both flapwise and edgewise vibrational behaviour. A good agreement was observed between the analytical results and the manufacturer results.
This study was conducted to mathematically evaluate the impact of forced convection of viscous dissipation on a porous media filled with Williamson fluid and exposed to fixed surface heat flux. The technique of Darcy_Forchheimer_Brinkman was employed, then the non-dimensional equations were solved numerically over a flat plate by using bvp4c through the MATLAB package. Different parameters were examined including the profiles of velocity, temperature and shear_stress in addition to Nusselt Number. Furthermore, the study evaluated the effects of several essential parameters, including Forchheimer, Darcy, porous media, Williamson, and viscous dissipation, on the temperature and velocity profiles, heat transfer and friction coefficients. The numerical solution results showed that, under high Forchheimer_parameter values, all, shear_stress, Nusselt_number parameter and temperature showed an increase in their values. Also, as Williamson_parameter increased, the shear_stress and boundary layer velocity were improved, while a decrease in Nusselt_number caused an increased in values of temperature profile. Finally, the boundary layer of velocity and shear_stress showed an increase in their values when Darcy parameter increased. On the other hand, a decrease in the temperature profile and Nusselt_number were observed.
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