Large-scale experimental study on scour around both slender and large monopiles under irregular waves

Abstract The offshore wind power is of great significance in the energy strategy. The experimental results simulated by traditional small-scale physical model may become unreliable when extrapolated to strong field scales. This work conducts large scale (1:13) experiments to study the scour hole pattern and equilibrium scour depth around both slender and large monopiles under irregular waves. The Keulegan-Carpenter (KC) number ranges from 1.01 to 8.89, and the diffraction parameter (D/L) number ranges from 0.016 to 0.056. The large-scale experiment indicates changes of maximum scour location and scour hole shape around slender monopile are associated with KC number, and the changes are different in irregular and regular waves. The accuracy of existing scour formulae under irregular waves is improved by improving the calculation of KC number. The maximum scour location around large monopile is always located on both sides, regardless of the KC and D/L numbers, but the topography of the scour hole is related to both. The scour range is at least as large as the diameter of the large monopile.