Comparison of Velocity Deficit Distribution Between Semi-Submersible and Monopile Designs

Hello,
I conducted a comparison of the velocity deficit distribution between semi-submersible and monopile designs using the IEA 15MW wind turbine.The analysis was performed using FAST.Farm under the following conditions:


Analysis Conditions

  • Wind speed: Constant wind speed of 9 m/s
  • Water surface conditions: Still water

Graph Details

  • Measurement location: 6D (1440 m) downstream from the wind turbine
  • Measurement height: 150 m
  • Data format: Horizontal plane velocity deficit distribution
  • Figure layout:
    • Top figure: Nacelle yaw angle set to 0°
    • Bottom figure: Nacelle yaw angle set to 10°

Summary of Results

  • The velocity deficit of the monopile design was observed to be larger than that of the semi-submersible design.

Data Used

  • The same fstf file was used for both designs.
  • It was also confirmed that changes in the value of f_c had no impact on the results.

Question

Why does such a difference in velocity deficit occur between the semi-submersible and monopile designs?

Are there any points in the settings of the fstf file that need to be modified to better understand this difference?


Dear @Rikuto.Nitta,

The semisubmersible will tilt backward as a result of rotor thrust, effectively increasing the shaft tilt relative to the monopile design and causing additional vertical deflection of the wake, which would reduce the wake deficit at hub height. This will be more clearly illustrated if you visualize the wake deficit in the XZ plane.

Best regards,

Apologies for the delayed response.

After checking the wake deficit in the XZ plane, the issue has been resolved.

Thank you.