ABSTRACT

This paper presents the results from wind drag forces computational fluid dynamics (CFD) calculations performed on several single structures from the topside of a typical self-propelled wind turbine installation jack-up. From the topside structures, wind turbine towers with and without helical strakes and a truss-shaped leg were considered. The CFD model was constructed using the unsteady RANSE solver STAR-CCM+ from Siemens. The wind drag forces acting on the considered single structures were computed at model-scale as well as at full-scale by applying an atmospheric boundary layer profile. To validate the CFD model, the results of the CFD model-scale calculations were compared with wind tunnel measurements which were carried out at German-Dutch Wind Tunnels (DNW). It was found that the CFD results were in good agreement with the wind tunnel measurements and provided valuable insights into the physics of wind drag forces acting on the considered single structures from the jack-up. Based on the results of the CFD calculations this paper will discuss the uncertainties and scale effects of the drag forces acting on single wind turbine towers as well as on jack-up truss legs from a typical self-propelled wind turbine installation jack-up. The advantages and uncertainties of the applied approach will be highlighted.

INTRODUCTION

The typical topside structures of a self-propelled wind turbine installation jack-up consist of four truss-shaped legs, jacking structures, part of the ship, a large forward accommodation block, helideck, several cranes, large wind turbine towers, wind turbine nacelles, wind turbine blades, several structures and equipment on the deck. The wind turbine towers are usually partly fitted with helical strakes for suppressing the vortex-induced vibration of the towers. Fig. 1 shows the topside structures from a typical GustoMSC-designed self-propelled wind turbine installation jack-up.

Predicting wind loads on those large windage areas from the topside structures is a critical aspect in the design process of these types of jack-ups. An accurate prediction of the wind loads in an earlier stage of the design is, therefore, eminently important.

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