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The upcoming development of tidal turbine farms requires a great understanding of the environment in which they will be installed. The aim of this study is to better understand the effects of surface waves on the high-energy turbulence generated by the interaction between tidal currents and the bathymetry. To do so, specific conditions are reproduced in the IFREMER’s flume tank at Boulogne-sur-Mer. The bathymetry is represented by a square-based cylinder mounted on the tank floor perpendicularly to the current, in Froude similarity, at a scale of 1:20. The chosen wave conditions make it possible to study the wave frequency and wave amplitude effects on the obstacle wake development. From PIV measurements, the results show that, for a current speed of 0.8 m/s, low frequency waves (T p > 13 s at sea) are the most impactful. When the frequency is high, the surface wave amplitude must be greater (Hs > 3 m at sea) to modify the vortex shedding behind the obstacle. Whenever the cylinder wake is altered by the waves, the wake goes faster towards the surface. The vortex shedding, already present without waves, becomes more energetic and focuses on a sub-harmonic of the wave frequency.

The upcoming development of tidal turbine farms requires a great understanding of the environment in which they will be installed. The aim of this study is to better understand the effects of surface waves on the high-energy turbulence generated by the interaction between tidal currents and the bathymetry. To do so, specific conditions are reproduced in the IFREMER’s flume tank at Boulogne-sur-Mer. The bathymetry is represented by a square-based cylinder mounted on the tank floor perpendicularly to the current, in Froude similarity, at a scale of 1:20. The chosen wave conditions make it possible to study the wave frequency and wave amplitude effects on the obstacle wake development. From PIV measurements, the results show that, for a current speed of 0.8 m/s, low frequency waves (T p > 13 s at sea) are the most impactful. When the frequency is high, the surface wave amplitude must be greater (Hs > 3 m at sea) to modify the vortex shedding behind the obstacle. Whenever the cylinder wake is altered by the waves, the wake goes faster towards the surface. The vortex shedding, already present without waves, becomes more energetic and focuses on a sub-harmonic of the wave frequency.