Experimental Study on Local Scour at the Monopile Foundation of an Offshore Wind Turbine under the Combined Action of Wave–Current–Vibration

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript “Experimental study on local scour at monopile foundation of offshore wind turbine under the combined action of wave-current-vibration” report an interesting study on the role of the vibration in the evolution and characterization of scour in the surrounding of an offshore monopile. The study is of interest, but the article has several important issues to solve. Many partes are not clear or not understandable. For this reason I suggest a major revision of the manuscript.

The methodological part is not clear enough. In particular the measurement devices and measurement procedure should be more detailed, emphasizing the location where the measurement are taken, and their accuracy.

The language is clear enough, even if some language check is required to make the text completely understandable. Additionally, not all the symbols are defined, this making some part of the manuscript difficult to understand

How do you chose the location where the characteristics of the wave are measured? Keep in mind that the wave can change by interacting with the bottom and the pile.

Many figures are not clear: In Fig 1 some geometrical information are missing; legends in figs from 2 to 20 should be improved. Some of them are not readable

Several test have been conducted, but their description and classification should be better described.

Many assessment are not based on the results. All the physical interpretation reported in the manuscript should be supported by literature (with reference) or by results

Fig 18: take care: the results with vibration are not clearly identifiable and they all fall in the range of the data use to built the curves, so the assessments about their comparison is not supported by these results

Comments on the Quality of English Language

The language is clear enough, even if some language check is required to make the text completely understandable.

Author Response

对审稿人 #1 评论的回应

非常感谢您抽出宝贵时间审阅本手稿。请在下面找到详细的回复，并在重新提交的文件中找到突出显示/跟踪更改的相应修订/更正。

评论1-方法论部分不够清楚。特别是测量设备和测量程序应更加详细，强调测量的位置及其准确性。
回应 1：感谢您指出这一点。我们同意这一评论。因此，在2.3实验方案（第212-219行）中增加了测量程序的相关内容，以强调测量的位置和精度。相关附加内容如下：

在测试过程中，通过读取砂堆周围的刻度和砂床的临界刻度来记录冲刷深度的发展。量表在开始前10 min每1 min读取一次，10 min~30 min每5 min读取一次，30 min~120 min每10 min读取一次量表，120 min~210 min每20 min读取量表，210 min后每30 min读取量表。测试完成和特征时间点后，用遮阳布覆盖处理，然后用水下地形扫描仪扫描采集沙床地形。每个扫描位置都保持在同一位置，以确定它不会影响扫描结果。最后，通过加工获得所需的地形。

评论 2- 语言足够清晰，即使需要一些语言检查才能使文本完全理解。此外，并非所有符号都已定义，这使得手稿的某些部分难以理解。
回应 2：感谢您指出这一点。我们同意这一评论。因此，我们检查了本文中使用的符号，并在它们首次出现时对其进行了定义。

 

评论 3- 您如何选择测量波特性的位置？请记住，波浪可以通过与底部和桩相互作用来改变。
回应 3：感谢您指出这一点。波浪特性的测量位置如图1（第173行）所示。本文在测试开始前通过波高计对造波系统进行校准，以确保计算机在测试过程中产生的波与要求一致，便于在测试过程中收集波高数据。在测试过程中，共布置了6个波高计，以收集入射波高和桩周围的波高变化。相关内容已在文件第2.1部分（第168-172行）中补充。

 

注释 4- 许多数字不清楚：在图 1 中缺少一些几何信息; 图 2 到 20 中的图例应改进。其中一些是不可读的。
回应 4：感谢您指出这一点。我们同意这一评论。因此，在图1中增加了一些几何信息，并对图2至图20中的图例进行了适当的检查和修改。修改后的图片内容和图例更清晰直观。

 

评论 5- 已经进行了几次测试，但应该更好地描述它们的描述和分类。
回应5：感谢您的评论。在本文中，第2.3.1章详细介绍了相关的工作条件。本文主要将工况分为波流工况和波流振动试验工况两大类。波电流条件是无振动的控制组。根据您的建议，检查测试条件部分的内容。所有结果分析的标题部分都给出了研究的工作条件类型，并在正文部分补充了所选工作条件的具体数字。

评论 6- 许多评估不是基于结果。手稿中报告的所有物理解释都应有文献（有参考）或结果的支持。
回复 6：感谢您的评论。 本文的所有分析均基于实验结果。本文在一些相关解释中增加了一些参考资料，主要立场是第3.2章（第371行第381行）和第4章（第583行）。对振动引起的一些物理现象的解释主要基于同一研究小组的另一篇相关文献。主要内容是研究单桩在振动作用下的泥沙运动规律。文献如下：

程彦;谢旭东;郑彦;振动作用下单桩周围沉积物运动的实验研究. 海洋工程 2023， 288， 116206， doi：10.1016/j.oceaneng.2023.116206.

注释 7- 图 18：注意：振动结果无法清晰识别，它们都落在用于构建曲线的数据范围内，因此这些结果不支持对它们进行比较的评估。
回复 7：感谢您的评论。图18（第588行）是本文相关实验数据与其他现有相关研究实验数据对比示意图。立体点数据为本文的实验数据，空心点数据为其他文献的实验数据，曲线为相对冲刷深度S/D随其他实验数据拟合的KC数变化的拟合曲线。该图的主要意义在于分析本文获得的结果与其他相关类型的测试结果之间的异同。

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

In this manuscript, local scouring under waves, currents, and vibration was examined and discussed experimentally. It is a very useful contribution to researchers and engineers related to this kind of problem and I recommend the manuscript be acceptable as it is, except for the incident wave conditions. The relatively small wave heights were chosen as shown in Figures 2 and 3, which show linear water surface fluctuations and flow velocities, but local scour problems are predominant under high wave conditions such as typhoons. The reviewer suggests that the authors should explain why the relatively small wave conditions were used.

Author Response

Response for Reviewer #2 Comments

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments 1- In this manuscript, local scouring under waves, currents, and vibration was examined and discussed experimentally. It is a very useful contribution to researchers and engineers related to this kind of problem and I recommend the manuscript be acceptable as it is, except for the incident wave conditions. The relatively small wave heights were chosen as shown in Figures 2 and 3, which show linear water surface fluctuations and flow velocities, but local scour problems are predominant under high wave conditions such as typhoons. The reviewer suggests that the authors should explain why the relatively small wave conditions were used.

Response 1: Thanks for the comment. The test is carried out in a wave-current flume with a length × width × height of 60 m × 1.5 m × 1.8 m. The normal working depth of the flume is 0.2 m ~ 1.5 m. Because the construction environment of the offshore wind turbine is offshore area, the water depth is much larger than the pile diameter of the offshore wind turbine, so the test depth is selected as the fixed value h = 0.5 m, which is greater than 4 times the pile diameter D. The incident waves in the test are regular waves. In order to prevent breaking during wave propagation, all wave parameters meet the following requirements.Please see the attachment.

In the formula: H is the wave height; d is the water depth; L is the wavelength; k is the wave number.

Therefore, in this paper, after considering the working water depth of the flume, the test water depth, the ratio of wave height to water depth, and the wave stability, the higher wavelet height is selected. The explanation of wave height selection is added to chapters 2.2.(line192, line197-199)

Author Response File: Author Response.docx