Scour Controlling Effect of Hybrid Mono-Pile as a Substructure of Offshore Wind Turbine: A Numerical Study

Round 1

Reviewer 1 Report

1) The literature is rich of contributions about scouring problems related to offshore wind turbine. The Author is encouraged improving the literature review about the topic.

2) 50% of the article length is aimed at introducing the problem. The description of both the 'hybrid mono-pile with scour protection' and the numerical model used to verify the scouring control effect provided via the additional light turbine are dealt with too briefly. Please improve the paper structure.

3) What is the value of the D/L ratio in Kriebel's experiment? Is it possible improving the comparison between Kriebel's experiment and your numerical model? If I well understood your are comparing these experimental data with your numerical model even if your model is not 'equivalent'.

4) As the verification of the proposed method (light turbines mounted at the mono-pile toe) to control the scouring triggers is made only via a simplified numerical model, the reviewer recommends changing the paper title as follows: "Scour controlling effect of hybrid mono-pile as a substructure of offshore wind turbine: a numerical study" 

5) Line 119. "...purpose to protect the foundation was recently discovered." Some references are expected here.

6) Line 130. "...are recently emerging as new alternatives to hard structures such as rocks." Some references are expected here.

7) Line 153. "...the development of fluid mechanics over the last few decades." Please add some relevant references.

8) Line 208. "...achievements have been made." Please add some relevant references.

9) Please check the numbering of Figures. There are two figures #2 (Page 3).

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This paper studied the scour effect of offshore wind turbine (OWT) support structures. The authors should clarify the following points before it can be accepted for publication in the journal:

• Sections 2 and 3 contains a number of methods to protect the scour effect for OWTs. However, those topics were come from other researches. The contribution of the two sections should be addressed.
• Section 4 contains a numerical method to simulate the scour condition for OWTs, but the model was still used from a reference. The contribution of this section is still required to be mentioned.
• In Section 4, there are only basic continuous equations. Thus, how to simulation them using the iteration method (mentioned in the paper) is not clear.
• A number of parameters of equations in Section 4 used in Section 5 were not given values.
• Section 5 obtained a lot of results, but the numerical simulation was not clearly mentioned, such as time-domain of frequency-domain method, time step length, implicit or explicit method, and so on.
• The simulation results are highly dependent on the parameters used in the simulation, so the conclusion may only be used to this particular condition. The authors should discuss this issue.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The author solved most of my concerns. The paper can be accepted in present form.

Author Response

The author solved most of my concerns. The paper can be accepted in present form.

Thank you for your encouraging comments.

Reviewer 2 Report

(1) The numerical simulation of this paper was still not clear. For example, the time step length (dt) and the total simulation time should be listed.

(2) All the constants used in Section 4 for the numerical simulaion in Section should be given values, such as g, density, diffusion coefficient, ....

(3) Other answers are all right.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf