Large-scale experimental study on scour around monopile under the action of waves
[Objective]The development of offshore wind power technology is of great importance to China's dual carbon strategy,and the estimation of scour depths is a widely studied topic in the study of scour around offshore monopiles.The scale effect usually limits the applicability of the scour depth estimation equation obtained from traditional small-scale physical models.Thus,by analyzing the applicability of the existing scour depth prediction formulae under different scale conditions,this study aims to obtain a method to improve the estimation accuracy of scour depth formulae and derive a concise formula to calculate the scour hole volume according to the relationship between the scour hole volume and scour depth.[Methods]Large-scale(1∶13)experiments were conducted to study the maximum equilibrium scour depth and local scour volume around a monopile under irregular waves.The Keulegan-Carpenter(KC)numbers ranged from 4 to 9.According to the large-scale test data,the scour depth formulae under the actions of regular waves and irregular waves were compared in terms of applicability.The self-limitation of the formulae was analyzed,the influence of the KC number definition on the calculation of equilibrium scour depth was examined,and the different KC number definitions under irregular waves were compared in terms of applicability.Furthermore,through the analysis of the relationship between the scour hole volume and the scour depth,the factors affecting scour hole volume were determined,and according to this analysis,a formula for determining the scour hole volume was derived.[Results]The large-scale experimental results show that:1)The estimation of the scour depth by the existing formulae can be guaranteed to be within the deviation range of±50％under regular waves,whereas it fell below the deviation line of 50％under irregular waves.2)The depth of a backfilled scour hole for a given KC is different from the scour depth obtained with an initially flat bed and with the same KC.3)The maximum orbital velocity of the wave and peak wave period are used to redefine the KC number and applied to each formula.Moreover,the estimation accuracy is significantly improved,and predictions of the formulae were within the deviation range of±50％,except for some formulae with limited applicability.4)The KC number is an important factor affecting the scour hole volume.The formula for predicting the scour hole volume based on the existing equilibrium scour depth formula is within the deviation range of±25％.[Conclusions]Through the analysis of large-scale experimental data and previous data,the limitations of traditional scour depth formulae obtained using small-scale experiments are demonstrated under irregular waves.The estimation accuracy of the existing formula under irregular waves can be improved by improving the KC number calculation method.Additionally,according to the results of three-dimensional terrain scanning,the relationship between the local scour volume around a monopile and the existing equilibrium scour depth formulae is derived.Overall,this study provides a concise and convenient method for estimating the protection material amount around monopile.
NETL
NSTL
万方数据
维普
