Simulation on Unsteady Crosswind Forces of a Moving Train in a Three-Dimensional Stochastic Wind Field

Round 1

Reviewer 1 Report

This paper is well written and useful for readers. I suggest to declare all variables and symbols. It is a veru important point for this reviewer. 

Maybe more information about the CFD setup would be useful. As for example please explain how the CFD domain was calibrated. Authors should be add in the introduction section a more general part to shortly discuss the CFD approach in civil engineering. Maybe they can discuss the paper below:

 

Computational study of a bluff body aerodynamics: Impact of the laminar-to-turbulent transition modelling.

Rizzo, F., D'Alessandro, V., Montelpare, S., Giammichele, L.

International Journal of Mechanical Sciences, 2020, 178, 105620

 

One of the most improtant part of this paper is the WT test. Please add more pictures and details about these crucial phase.

Figures 8 and 9 are significant and they have to be enlarged.

 

Overall this paper should be published in Applied Sciences after major revisions.

Author Response

Dear reviewer,

we would like to thank you for carefully reviewing our paper and giving us thoughtful comments. According to your valuable suggestions, we have made a large effort to conduct additional optimizations and try our best to revise the manuscript accordingly. The detailed responses to your comments are attached.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper discusses how to evaluate the effects of unsteady crosswinds on high-speed moving trains in a simplified manner, which is a meaningful topic for improving train safety. The simulation and experimental results are in very good agreement, and I believe that the basis for discussion has been established.

However, the discussion in this paper is based only on the difference of α, the angle between the cross wind and the traveling line, under one condition (U=20m/s, V=300kn/h), which is considered important in this paper. The results cannot be assumed to be universal for all conditions, and may mislead the reader.

 

In publishing the results, additional data should be provided to show that the proposed function can be adapted to different conditions, and that it can be universally applied. Or, it is necessary to clarify that there is a limitation on the evaluation target, saying that the ratio of train speed to wind speed can be evaluated in this way in cases where the ratio of train speed to wind speed is about 20%.

(1) Sector 3.1 Only the dependence on β is discussed and it is concluded that only β is important for aerodynamic forces. The data are organized in terms of Vr and β. In general, I believe that the presence or absence of a Reynolds number dependence of the force acting on an object is also important, thus a reference to the dependence on Vr is necessary.

(2)Equation(8) Although it is shown in the figures and other documents that this is an appropriate function in fitting the obtained results, neither the specific method for determining the coefficients, a, b, c, and d, nor the concrete numerical values are described, and the reader cannot make use of this number equation, so please describe it.

In other methods by Chiu and Squire and Baker, other βs can be predicted from the result of β=90 degrees and the shape can be theoretically derived from the force the object is subjected to, but there is no explanation of the physical background in Equation (8), which reads simply as an optimal fitting to fit each simulation result. If there is a meaning to such a function system, I would appreciate an explanation.

Furthermore, if these coefficients a, b, c, and d are not uniquely determined, but need to be determined by fitting from simulation results in each case, multiple simulations or experiments will first be required when considering actual use. In this case, it would not be possible to evaluate it equally with other methods that can be evaluated only by calculating one representative case, considering the total cost and other factors. I would like you to add a discussion on this issue.

(3)Fig. 23(a) In the previous section and (b), it is also mentioned that for α = 90 degrees, the lateral disturbance is parallel to the direction of travel and the lateral influence cannot be considered.

Therefore, in order to examine the effect of velocity, I believe that a comparative study is needed not only for the case of α=90, but also for angles where all components are affected, such as 15, 45, 135, and 165 degrees. I would appreciate it if you could add this to the discussion.

Minnor comment

Please list the resultant wind speed and yaw angle in each figure (Fig.7,8,9,11,12,13,14,15,18,20,21,22,23).

 

Author Response

Dear reviewer,

we would like to thank you for carefully reviewing our paper and giving us thoughtful comments. According to your valuable suggestions, we have made a large effort to conduct additional optimizations and try our best to revise the manuscript accordingly. The detailed responses to your comments are attached.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Authors have improved their manuscript. I suggest to publish the manuscript.

Author Response

Dear reviewer,

Thank you again for carefully reviewing and accepting our improvements in the revised manuscript. We are excited that the manuscript is suggested for publication in the journal.

Sincerely hope everything goes well with you.

Bset regards,

Authors