Abstract

The temporal evolution of seabed scour was investigated to prevent damage around a monopile foundation for Darrieus-type tidal current turbine. Temporal scour depths and profiles at various turbine radius and tip clearances were studied by using the experimental measurements. Experiments were carried out in a purpose-built recirculating water flume associated with 3D printed turbines. The scour hole was developed rapidly in the initial process and grew gradually. The ultimate equilibrium of scour hole was reached after 180 min. The scour speed increased with the existence of a rotating turbine on top of the monopile. The findings suggested that monopile foundation and the rotating turbine are two significant considerations for the temporal evolution of scour. The scour depth is inversely correlated to the tip-bed clearance between the turbine and seabed. Empirical equations were proposed to predict the temporal scour depth around turbine. These equations were in good agreement with the experimental data.

Highlights

  • Tidal current energy is a proven type of ocean renewable energy gaining more attention after the successful installation of the first grid-connected tidal turbine in Strangford Loch, Belfast [1]

  • For the investigation of scour induced by tidal current turbine, Neill et al [18] found the energy extraction from tidal current turbine reduced the overall bed level change; the asymmetry tidal region had a greater (20%) increase in sediment transport level compared to the tidal symmetry region

  • Dimensionless analysis produces the empirical equation to predict the temporal evolution of scour hole depth around monopile foundation of Darrieus tidal current turbine in Equations (15)–(19): a

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Summary

Introduction

Tidal current energy is a proven type of ocean renewable energy gaining more attention after the successful installation of the first grid-connected tidal turbine in Strangford Loch, Belfast [1]. The development of scour hole induced by tidal current turbine amplifies the flow speed compared to the bridge pier scour due to flow suppression in the narrow area between rotor tip and seabed. This phenomenon has been proved in paper [6]. Chen and Lam [4] found that tip clearance between the turbine and seabed is the important parameter to determine its impact to the scour by CFD simulation using OpenFOAM They found the presence of turbine rotor changed the boundary layer profile and results in the altering of horseshoe vortex formation. The temporal evolution of scour around foundation of Darrieus-type tidal current turbine

Experimental Set Up
Experimental
Physical Similarity Relationships
Scaling Effects of Experimental Setup
Temporal Variations of Scour Profiles
Temporal Seabed Scours at Various Tip Clearance
Maximum Scour Depth
Position of Maximum Scour Depth
Deposition
Temporal Seabed Scours at Various Rotor Radius
Size of Scour Hole
Overall Temporal Evolution of Scour Depth
Equations to Predict Temporal Evolution of Scour Depth
Comparison of the Proposed Model with the Previous Works
Comparison with Bridge
12. Comparison
Comparison with the Equations of Ship Propeller Induced Scour
Comparison with Published Data of Turbine Scour
Findings
Conclusions

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