Experimental Study of Flow Kinematics and Impacting Pressures on a Suspended Horizontal Plate by Extreme Waves

Round 1

Reviewer 1 Report

In this manuscript, the authors present an experimental study on the flow evolution process and slamming force characteristics of a suspended plate, considering the different impact positions of plunging waves and structures. The experimental results show that under different impact conditions, flow patterns differ significantly, and the velocity distribution in aeration areas is more discrete. During the slamming process, air acts as a buffer layer, resulting in a prolonged slamming time and reduced force.

Generally, this work is valuable and is of interest to the reader of the Water. The reviewer supports its acceptance if the following comments can be addressed.

1. A definition of time zero (t = 0) is missing from this article. Does time zero correspond to the predefined focusing time? Is the time zero the same in different impact conditions?

2. The instantaneous moment of the flow field is missing in Figure 5, Figure 6, and Figure 7. The authors need to further explain the chronological order in the figure or title.

3. In Table 1, the authors defined different plunging phases as ‘unbreaking, incipient breaking, and broken wave’. However, these interaction conditions are called ‘unbroken wave, breaking wave, and broken wave’ in Figure 3, Figure 4, Figure 8, and Figure 9. These definitions need to be unified by the authors.

4. On page 12, Line 292, ‘due to the addition of gas, there is a significant oscillation phenomenon’. The oscillation phenomenon of pressure is significant in Figure 8, the oscillation occurs at different times but with high frequencies. Is this oscillation caused by structural vibration or bubble vibration? During the experiment, a high-speed camera was used for recording. Are these oscillations reflected in the captured images?

Author Response

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Reviewer 2 Report

This manuscript presents the results of a laboratory experiment conducted to understand how extreme waves cause a green water effect on a fixed deck. Their experimental results demonstrate the effect of slamming position on fluid aeration and slamming force. 

It is certainly an interesting subject, yet, there are still some issues that need to be addressed in the article. After the following suggestions have been addressed, I willcommend the publication of this paper.

1. In the process of wave breaking, complex phenomena of aeration, turbulence, and dissipation will occur in the water body, leading to flow instability. The incident wave in this article is the breaking wave, and the authors need to explain the repeatability of the incident waves.

2. Many complex flow phenomena are described in the article, like the generation of water tongue, jet flow, water splashing, water collision, and flow separation. From the snapshots, it is difficult for readers to identify these phenomena accurately. The authors need to markand explain these phenomena in Figure 3 and Figure 4.

3. The splashing height of water in the broken case is much higher than in un-breaking and incipient breakingcases. In the author's description, wave breaking has already consumed some kinetic energy of the water body, but why has this resulted in higher water splash levels?

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors’ Manuscript.

In this manuscript, the 2D kinematic characteristics and impact pressures are experimentally investigated during the interaction of plunging waves with a plate (deck) fixed in a tank above the still-water level. Using snapshots of the aerated flow around the deck and measurements of the velocity field, the author compared the evolution of the flow field under different types of wave breaking (un-breaking, incipient breaking, and broken). They also showed how wave breaking affects slamming pressures by aerating the water.

I recommend the publication of this paper if the following comments/suggestions are well addressed.

1. There's a lot of confusion about incident wave parameters in the text. Does the spectral period T in Table 1 represent the peak period of the wave spectrum? It is necessary for the article to provide the effective wave height of the wave spectrum or the amplitude of the focusing-wave peak.

2. On page 4, Line 138, the amplitudes of corresponding components were determined by the constant-steepness approach. What is the specific meaning of the ‘constant-steepness approach’? The authors need to provide a specific expression for the wave spectrum.

3. To measure aerated flow velocity, the authors used Bubble Image Velocimetry (BIV), a technique proposed by Ryu et al. (2005). According to Ryu, BIV uses bubbles as the tracer and measures the bubble velocity by correlating the ‘texture’ of the bubble images. No laser light sheet was needed and the depth of field (DOF) was limited to minimize the error. Ryu introduced the calculation method of measurement error, ε = D/2L, in which D is the depth of field, and L is the distance between the camera and the focal plane. The author needs to provide a detailed introduction to the measurement errors of BIV used in the experiment.

4. On page 9, Line 252, ‘In this paper, C₀ is the maximum flow velocity of the incident plunging wave’. How is the wave velocity C₀ estimated in the experiments? Was it obtained through experimental measurements?

5. Although the author measured the flow field under different types of wave breaking and provided detailed flow field vector maps, I found it strange that the author did not provide a quantitative comparison under different wave conditions. Consequently, we are unable to accurately assess the magnitude of flow fields.

Reference:

Ryu, Y., Chang, K.A. and Lim, H.J., 2005. Use of bubble image velocimetry for measurement of plunging wave impinging on structure and associated greenwater. Measurement Science and Technology, 16(10): 1945-1953.

Author Response

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