The Hydrodynamic Performance Examination of a New Floating Breakwater Configuration

International Journal of Advanced Engineering, Management and
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ISSN: 2454-1311 | Vol-9, Issue-1; Jan, 2023
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The Hydrodynamic Performance Examination of a New
Floating Breakwater Configuration
Yasser El Saie1
, Ayman El Sayed2
, Haitham Ehab3
, Ahmed Balah4
1
Associate professor, Head of Civil Department, The Higher Institute of Engineering, El Shorouk Academy, Egypt.
2
Professor of Harbor Engineering and Marine Structures, Irrigation and Hydraulics Department, Faculty of Engineering, Ain Shams
University, Egypt.
3
Instructor in civil engineering departement, The Higher Institute of Engineering, El Shorouk Academy, Egypt
Currently Pursuing M.SC Program in Civil Engineering, Irrigation and Hydraulics Department, Faculty of Engineering, Ain Shams
University, Egypt.
4
Lecturer, Irrigation and Hydraulics Department, Faculty of Engineering, Ain shams University, Egypt.
Received: 01 Dec 2022; Received in revised form: 30 Dec 2022; Accepted: 06 Jan 2023; Available online: 14 Jan 2023
Abstract— It is critical to protect coastal and offshore structures. Most current studies and scientific
investigations are centered on how to protect seashore with an efficient and cost-effective system. This study
involved the testing of a new floating breakwater configuration (FB). A series of experiments were carried out in
the lab of The Higher Institute of Engineering (El-shorouk City) on the new model and the traditional vertical
plane FB without a curved face to compare their behaviours and performance in wave attenuation. The incident,
reflected, and transmitted wave heights were measured, and the coefficients of reflection, transmission, and
energy dissipation were calculated using these measurements. In terms of hydrodynamic performance, the
curved-face floating breakwater outperformed the traditional vertical floating breakwater, according to the
study's highlights. The curved face model significantly reduced wave transmission values when compared to the
traditional vertical configuration. The greater the concavity of the curve, the better the model handles waves,
especially when the wave steepness is low.
Keywords— Curved face floating breakwater, Reflection Coefficient, Transmission coefficient, Energy
dissipation coefficient, shore protection.
I. INTRODUCTION
The parts of land that face the seas, oceans, marines, and
ports are known as coastlines. Breakwaters are wave
attenuators, which are used to dissipate wave energy and
protect coastlines from wave attacks. Breakwaters are
divided into two types: conventional and non-
conventional. The growth of offshore and maritime
activities increases the demand for larger ports, making
conventional bottom breakwater construction difficult.
Floating breakwaters have been widely used in the
protection of seashores, coastlines, ports, and marines over
the last few decades. Indeed, 90% of wave energy is
distributed along a depth three times the wave height
below the water's surface.
Various researchers and scientists worked on this issue
from (Fang He et al., 2012) to (S Rahman et al., 2022). [1]
Fang He et al. (2012) installed pneumatic chambers with
the original rectangular floating breakwater; the increased
mass and inertia of the model has a significant effect on
wave attenuation. Furthermore, the energy is dissipated
more effectively in the front chambers than in the back
chambers. [2] Chun-Yan Ji et al. (2016) investigated the
hydrodynamic performance of a new floating breakwater
configuration. The effect of beam and oblique waves on a
ten-cylinder floating breakwater with ten mesh cages and
eighteen connectors was investigated. Overall, the results
demonstrated the impact of this configuration on energy
dissipation and wave attenuation. [3] Chun-Yan et al.
(2017) studied the effect of wave attacks on a new
structure, A Cylindrical Dual Pontoon-Net floating

El- Saie et al. International Journal of Advanced Engineering, Management and Science, 7(3)-2021
breakwater (CDPNFB) attached to one or more rows of
plane net experimental model. This study discovered that
increasing net porosity lowers the reflection coefficient
and vice versa for the transmission coefficient.
Furthermore, the more cylinders used, the greater the wave
blocking achieved by the model. [4] Chun-Yan Ji et al.
(2019) investigated the hydrodynamic performance of a
double-row rectangular floating breakwater with porous
plates through a series of experiments. The experiments
were carried out in a wave flume measuring
40m*0.8m*1.4m. Overall, the results showed that porous
plates with small motion responses and mooring forces
have a significant effect on wave attenuation.
[5] Chun-Yan Ji et al. (2015) compared a new type of
floating breakwater with double pontoons and a box type,
and found that the new configuration, a cylindrical floating
breakwater with a flexible mesh cage, outperformed the
other two types in long and high waves. [6] Chun-Yan Ji et
al. (2016) conducted an experimental study of four types
of floating breakwaters; the results showed that the mesh
cage model was more effective than the other types. [7]
Zhiwen Yang et al. (2018) investigated the effectiveness of
a new floating breakwater against wave attacks. This
structure is made up of a water ballast double floating box
with a vertical plate. The findings of this study revealed
that water ballast attenuates the incident wave more than
dry ballast, and that the height of the vertical plate is
effective in reducing wave transmission. [8] Chun-Yan Ji
et al. (2019) conducted a series of experiments to compare
single and double-row floating breakwaters. In terms of
wave attenuation, the double-row performed better than
the single-row. [9] S Rahman et al. (2020) theoretically
and experimentally compared a modified pontoon type
with a pi-type breakwater. The study's findings revealed
that the developed pontoon type model has less
transmission coefficient than pi-type model also the peak
value of the heave motion is smaller than that of the pi-
type.
The curved face floating breakwater model was tested
against regular wave attacks in this study to determine the
effectiveness of the studied parameters on its efficiency.
The goal of this paper is to try a new configuration based
on previous studies. Experiments were performed on the
models under the influence of various wave conditions in
order to test the model's functionality before comparing the
results.
II. EXPERIMENTAL WORK
This part shows the experimental equipment and model
used in the experiments. Also, it states the steps that were
taken to carry out the experimental work.
2.1 Experimental Equipment
A series of experiments were conducted in two-
dimensional wave flume in the Hydraulics Laboratory of
the Higher Institute of engineering (El Shorouk City). The
flume is 12 m long, 0.5 m width and 0.6 m deep. The wave
maker used is fly wheel type connected by steel rod to
paddle. Two wave absorbers from sloped graded gravel
were used in the tests to prevent standing wave from
reflection. The absorbers were installed in the flume with
suitable slopes ranges from (2:1 to 5:1) and its size ranging
from (0.5 – 3 cm) in diameter. The mooring lines used
during the experiments were steel wires covered by a
plastic layer. Figures 1 and 2 show the wave flume and
schematic diagram for the flume.
Fig. 1: The Wave Flume
Fig. 2: Schematic Diagram of The Model in The Flume
An ultrasonic instrument (Wave Staff XB) used to
determine the wave motion showing the wave heights
versus time interval on a schematic diagram. The wave
staff XB was installed in three positions to indicate
incident, reflection, and transmission wave heights. The
instrument was mounted on a small steel frame moves on
the sides of the flume. The spacing between wave gauges
applied were based on ( [10] Mansard, and Funke, 1980)
suggestions to calculate the relative distances between
wave gauges. = L/10, L/6   L/3
Where L is the wavelength, is the distance between
the first two gauges positions and is the distance
between the first and third wave gauges in the line of wave
propagation.

Each pattern was examined under the effect of five
different wave heights, to complete this objective, about
135 runs were carried out and the wave heights were
measured to determine the reflection, transmission, and
energy dissipation coefficients, as the wavelength and
wave heights are constant in all runs, then the incident
wave heights were measured in the beginning of the
experimental work. The wave gauges (1),(2) and (3) were
used to determine the reflected wave height and wave
gauge (4) was used to determine transmitted wave height.
2.2 Experimental Model
The supposed models were examined due to the proposed
experimental program. The tested models were fixed to the
base of the flume by steel wires with anchors fixed in the
base. The parts of the model are two blocks (48 x 30 x 5
cm), one block (48 x 30 x 20 cm) and three curved parts
with apex angles ( , , ).
The experimental model used in this study is made of fiber
and out covered by a timber layer, the pattern used in
experimental work was to investigate the effect of each of
the following parameters: The floating breakwater width
(w), The floating breakwater draft (d) and the curvature of
breakwater face (). The studied parameters and the model
parts are shown in figure 3 and figure 4 respectively.
Fig. 3: The Studied Parameters
Fig. 4: Experimental Model Parts and its installation
2.3 Experimental Steps
A series of experiments were carried out in a 2D wave
flume to study the effectiveness of the curved face floating
breakwater. The new configuration was studied by testing
various widths (20, 25 and 30 cm), different draft values
(2, 10 and 20 cm) and three apex angles (30, 60 and 90
degrees). Each model was examined against five different
wave heights (16, 11, 6.25, 4.5 and 2.5 cm) with constant
wavelength approximately equals 248 cm and water depth
equals 30 cm. The incident reflected and transmitted wave
heights were calculated using the plot from the wave staff
XB illustrated in figure 5. Also, the wave staff XB used in
experiments is illustrated in figure 6. Both maximum and
minimum heights were recognized from the wave staff
plot, then the calculation of the wave heights was as
follows:
Incident wave height ( ) = (1)
Reflected wave height ( ) = (2)
Transmitted wave height ( ) = (3)
Reflection Coefficient ( ) = (4)
Transmission Coefficient ( ) = (5)
Energy Dissipation Coefficient ( ) = (6)
Fig. 5: The Wave Staff XB Plot
Fig. 6: The Wave Staff XB

2.4 Hydraulic Modeling
The water viscosity and surface tension are not the
dominant factors that affect the phenomenon. While the
gravity force and inertia are main parameters affecting the
phenomenon. Thus, the Froude law is used in simulating
the phenomenon.
= (7)
(model) = (prototype)
= (8)
= (9)
= = = (10)
= = = (11)
= = (12)
Considering Wave Characteristics, Wave Celerity (C):
C = (13)
= = (14)
= = (15)
Depending on the dimensions of the flume and the wave
conditions (length, height) that will be applied on the
models. A ratio of 1:20 was selected for the construction
of the curved face floating breakwater model.
III. EXPERIEMNTAL RESULTS
The hydrodynamic performance of the curved face floating
breakwater models was investigated by measuring wave
reflection and transmission heights then calculating
reflection, transmission and energy dissipation
coefficients. Finally, a comparison was held between the
tested apex angles of curved faces used in the experiments.
3.1 Effect of Apex angle on reflection coefficient
The applied experiments showed the role of the curvature
of the facing curve to wave attacks. The 30-, 60- and 90-
degree curves were tested with different widths, drafts and
five wave heights. The results proved that as the apex
angle decreases which leads to the increment of curvature
the reflection coefficient increases. this was highlighted as
the 30-degree curve with 30 cm width, 20 cm draft gives
the maximum values of reflection coefficients, on the other
hand, the 90-degree curve when fitted with the same width
and draft gives less values of reflection coefficients as
shown in figure 7.
Figure 7 shows that the 30-degree curve recorded better
results than the 60 degree and 90-degree curves, as it
resists the wave motion more than the other two curves.
These words could be more discussed with statistics that
showed that the 30-degree curve reflected the incident
wave with range from 88% to 97% for the five values of
wave steepness. Thus, the 90-degree curve gave results
from 84% to 92%. The 60-degree curve recorded values in
between the 30 degree and 90-degree curve. The reflection
coefficients produced from the tests of vertical face
floating breakwater range from 82% to 90%. These results
shows that the effectiveness of 30-degree curve in wave
attenuation when compared with other curves and vertical
face. also, it shows that the increment of the reflection
coefficient with decreasing value of wave steepness
attacking the curved face floating breakwater model. In
addition to that, the curved face behavior is more efficient
in low values of wave steepness than high values.
Fig. 7. Reflection Coefficient Vs Wave Steepness for
Different Examined Curvatures & Width = 30 cm
3.2 Effect of Apex angle on transmission coefficient
The hydrodynamic performance of the floating breakwater
is determined mainly by the transmission coefficient
resulted from experiments carried out on the model. The
highest values of transmission coefficients were resulted
from the 90-degree curve, but less values were
investigated from the tested 30-degree curve. The values
of transmission coefficients recorded by the 30-degree
curve illustrate the efficiency of this curvature in facing
wave when comparing the experimental results of the three

tested curves, the 30-degree curve showed the best
performance by decreasing the transmitting wave from the
coming incident wave, while the other two curves gave
more values of transmission coefficients than the 30-
degree curve as shown in figure 8.
Fig. 8. Transmission Coefficient Vs Wave Steepness for
Different Examined Curvatures & Width = 30 cm
3.3 Effect of Apex angle on Energy dissipation
coefficient
The energy dissipation coefficient was calculated using the
values of reflection and transmission coefficients. Figure 9
shows that by increasing the apex angle of curved surface,
the energy dissipated from the incident wave increases. the
vertical face floating breakwater recorded the highest
energy dissipation coefficients values.
Fig. 9. Energy Dissipation Coefficient Vs Wave Steepness
for Different Examined Curvatures & Width = 30 cm
3.4 Effect of width relative to wavelength on the
hydrodynamic performance
The ratio of width relative to wavelength indicates the
energy dissipated from the floating breakwater. the
wavelength in the conducted experiments was 248 cm and
the three widths used were 20, 25 and 30 cm. Figures 10,
11 and 12 showed the reflection, transmission and energy
dissipation coefficients versus the width to wave length
ratio (W/L). The coefficients shown in the figures are
average values as for each width, the model was examined
by five different wave heights and draft values. The
increment of this ratio lowers the transmission coefficient
for floating breakwaters and adjust the hydrodynamic
performance against wave attacks.
Fig. 10. Reflection Coefficient Vs Width to
Wavelength ratio with different drafts
Fig. 11. Transmission Coefficient Vs Width to

Fig. 12. Energy Dissipation Coefficient Vs Width to
3.5 Effect of width and draft on curved face floating
breakwater performance
The results showed that the best performance recorded for
the examined model when the tested model was 30 cm
width, 20 cm draft and 30-degree curvature, while the least
hydrodynamic performance in wave attenuation and
damping when the 20 cm width, 2 cm draft and 90 degree
was used.
Figures 13 and 14 illustrated showed that the performance
of the 30-degree curve increases with the increment of
width and draft. The best performance was when the 30
cm width and 20 cm draft were used. On the other hand,
the 20 cm width and 2 cm draft gave the weakest results in
the tests.
Fig. 13. Reflection Coefficient Vs Wave Steepness for 30-
degree curvature with different widths and drafts
Fig. 14. Transmission Coefficient Vs Wave Steepness
for 30-degree curvature with different widths and
drafts
IV. ANALYSIS AND DISCUSSIONS
The experimental results demonstrate the effect of
increasing the width and draught of the floating breakwater
on the development of its performance. In addition to the
effect of curvature on wave reflection and transmission by
studying three different curvatures as previously discussed.
When the results of the three curved surfaces were
compared, it was discovered that the 30-degree curvature
performed better in wave attenuation than the others. As a
result, the curvature of the surface facing the wave attacks
has a significant impact on the performance of the floating
breakwater. The coefficients of reflection, transmission,
and energy dissipation were measured for a variety of
configurations with varying wave heights. These
coefficients, particularly transmission, indicate the
resistance of waves to the floating breakwater. The results
of the examined models were compared, and graphical
charts were created to determine the best coefficients.
Furthermore, studying the results of this paper and
comparing them to the performance of other floating
breakwaters will result in useful data and increased
knowledge in the field of floating breakwaters. Table 1
summarizes the experimental findings.
V. V. CONCLUSION
This study's findings concentrated on the effect of a curved
face floating breakwater against regular wave attacks in a
2D wave flume. To investigate the hydrodynamic
performance of a new configuration of floating breakwater
model, experiments were carried out. According to the
findings of this study, the greater the concavity of the
curved face floating breakwater, the better the performance
of the new type of floating breakwater when compared to
the original vertical face floating breakwater. As is well
known, the width and draft of floating breakwaters play an
important role in increasing the reflection coefficient and
decreasing the transmission coefficient. In this study, the

30 cm width and 20 cm draft produce the best results when
compared to the other widths and drafts used. The
reflection coefficient rises by around 25% and the
transmission coefficient falls by 28% compared to the
recorded values for 20 cm width and 2 cm draft, as shown
in figures 7 and 8. The effectiveness of the curved face is
directly proportional to the wave steepness decrement. The
curved face floating breakwater is better than the vertical
face floating breakwater in terms of hydrodynamic
performance. Curved faces have a higher reflection
coefficient than vertical faces. The average percentage
increase in reflection coefficient as values change from
low wave steepness to high wave steepness is around 7%
for 30-degree curvature, 4% for 60-degree curvature, and
2% for 90-degree curvature. While the transmission
coefficient decreases by 4.5%, 3%, and 2% for 30, 60, and
90-degree curvature, respectively as shown in table 1 for
all other investigated configurations.
Based on previous research ( [11] Koutandos et al., 2005;
[12] Tolba et al., 1998) and various studies applied to
floating breakwater (box type...).................etc., the studied
new configuration is similar to the ordinary box type
floating breakwater, i.e. it is a curved part attached to a
box. As a result, the study's findings recommend designing
and employing this new configuration when the water
depth to wavelength ratio is 0.12, the floating breakwater
depth to wave length ratio is 1, and the draught to water
depth ratio is 0.67. These ratios are similar to those of the
box type.
Table 1: Studied Parameters and Ranges of Coefficients
Studying Parameters Ranges (%)
Curvature Width Draft
20 cm 2 cm 62.5 to 72 32 to 38.13 61.56 to 68.12
25 cm 2 cm 64 to 74 28.8 to 37.19 60.78 to 67.18
30 cm 2 cm 65 to 76 26 to 36.25 59.57 to 66.79
20 cm 10 cm 75 to 90 16 to 21.88 40.55 to 62.42
25 cm 10 cm 76.88 to 92 12 to 20.94 37.31 to 60.43
30 cm 10 cm 77.81 to 96 6 to 20 27.35 to 59.54
20 cm 20 cm 84.06 to 92 10 to 15.63 37.89 to 51.86
25 cm 20 cm 86.13 to 94 6.8 to 14.38 33.43 to 48.74
30 cm 20 cm 87.5 to 96.8 4 to 13.25 24.77 to 46.56
20 cm 2 cm 58.75 to 66 33.2 to 39.38 22.71 to 24.99
25 cm 2 cm 61.56 to 70 31.2 to 38.13 64.24 to 68.97
30 cm 2 cm 63.75 to 74 28 to 37.19 61.16 to 67.48
20 cm 10 cm 72.50 to 84 18 to 22.81 51.19 to 64.99
25 cm 10 cm 74.38 to 88 15.2 to 21.88 45 to 63.17
30 cm 10 cm 75.94 to 92 10 to 20.94 37.89 to 61.60
20 cm 20 cm 82.5 to 88 12 to 16.56 45.96 to 54.03
25 cm 20 cm 84.38 to 92 8.8 to 15.31 38.19 to 51.44
30 cm 20 cm 85.94 to 94 6 to 14.06 33.59 to 49.16
20 cm 2 cm 58.13 to 64 37.2 to 40.63 67.23 to 70.51

25 cm 2 cm 59.06 to 68 34 to 39.38 64.96 to 70.44
30 cm 2 cm 60.94 to 72 30 to 38.13 62.58 to 69.52
20 cm 10 cm 70.63 to 80 22 to 23.75 55.82 to 66.70
25 cm 10 cm 72.5 to 82 20 to 22.81 53.63 to 64.99
30 cm 10 cm 74.38 to 88 18 to 21.88 43.95 to 63.17
20 cm 20 cm 81.56 to 86.4 14 to 17.5 48.36 to 55.15
25 cm 20 cm 82.5 to 88.8 11.2 to 15.94 44.60 to 54.22
30 cm 20 cm 84.38 to 92 8 to 15 38.37 to 51.54
Vertical 20 cm 2 cm 55.94 to 62 39.2 to 42.81 67.97 to 70.98
Vertical 30 cm 2 cm 58.75 to 69.2 32.8 to 39.69 64.31 to 70.52
Vertical 25 cm 10 cm 70.88 to 79.6 22 to 24.88 56.39 to 66.01
Vertical 20 cm 20 cm 79.69 to 84 16 to 20.13 51.85 to 56.96
ACKNOWLEDGEMENTS
The authors are grateful for El- Shorouk Academy for
funding and lab facilities.
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