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Journal of Physics: Conference Series
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Comparative Analysis of Hydrodynamic
Performance of Small Wave Buoys
To cite this article: Shanshan Zheng
et al
2023
J. Phys.: Conf. Ser.
2660 012018
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ICMMAP-2023
Journal of Physics: Conference Series 2660 (2023) 012018
IOP Publishing
doi:10.1088/1742-6596/2660/1/012018
1
Comparative Analysis of Hydrodynamic Performance of
Small Wave Buoys
Shanshan Zheng *1, 2, 3, Xingkui Yan 1 ,2, 3 , Zhuo Lei 1, 2, 3, Jiming Zhang 1, 2, 3 ,
Saiyu Gao 1, Chengyu Kai 1, Haihui Song 1, Jiuzhang Huang 1
1 Institute of Oceanographic Instrumentation, Qilu University of Technology
(Shandong Academy of Sciences), Qingdao 266061, China;
2 School of Ocean Technology Sciences, Qilu University of Technology (Shandong
Academy of Sciences), Qingdao 266061, China;
3 National Engineering and Technological Research Center of Marine Monitoring
Equipment, Qingdao 266061, China;
* Corresponding author: 18153250813@163.com
Abstract: The hydrodynamic performance of the floating body in seawater is very important.
The wave buoy is a small buoy that measures wave parameters such as wave height and wave
direction, for the non-powered wave buoy, the hydrodynamic performance mainly refers to the
seaworthiness of the buoy body. Seakeeping refers to the motion law of the floating body in the
wave. For the wave buoy, the seakeeping of the floating body has an important impact on the
measurement of wave data. Therefore, the analysis of the hydrodynamic performance of the
wave measurement float is an important reference for evaluating the performance of the wave
buoy. In this paper, the hydrodynamic performance of cylindrical and spherical wave-finding
buoys is compared and analyzed, and the influence of different structural forms on their
hydrodynamic performance is analyzed, which provides a reference for optimizing the
hydrodynamic performance of wave-measuring buoys.
1. Introduction
If the floating body is regarded as a rigid body, this rocking motion can be decomposed into three angular
movements and three translational movements, which are called horizontal rocking, pitching, bow
rocking, and longitudinal, sideways, and hanging [1]. Spherical and cylindrical buoys are two common
small buoy structures. For spherical and cylindrical buoys with the same outer size, how are their
hydrodynamic performance, whether there is a difference, and how much influence the form of the
structure has on hydrodynamic performance, these problems will be the main content of this study. For
cylindrical and spherical wave-buoys, because it is an axisymmetric structure, it is important to analyze
their role and droop characteristics [2].
2. Build NUMERICAL MODELS
In the Inventor 3D modeling software, a 3D stereogram of a cylindrical wave buoy is created at a 1:1
scale [3-4], as shown in Figure 1.
ICMMAP-2023
Journal of Physics: Conference Series 2660 (2023) 012018
IOP Publishing
doi:10.1088/1742-6596/2660/1/012018
2
Figure 1. 3D renderings.
The overall appearance of the cylindrical type wave buoy is cylindrical type, diameter of 900 mm,
total height of 900 mm, the material is 316 stainless steel, the draft is located in the middle of the standard
body, the top is installed with the anchor lights, antennas, and the bottom has a tethered eyeboard, which
can follow the swivel and anchor chain.
The overall appearance of the spherical wave buoy is spherical. For easy analysis, the diameter is
also set to 900 mm, the material is the same, and the draft is also located in the middle of the standard
[5-6].
3. COMPARATIVE Hydrodynamic analysis
Hydrodynamic analysis software enables analysis of the response of motion under environmental loads
on floating bodies. HydroSTAR is a 3D hydrodynamic analysis software launched by the French Bureau
of Shipping (BV), which is a software for hydrodynamic analysis based on the boundary element method
(BEM) of potential flow theory, which is suitable for the hydrodynamic calculation of first- and second-
order wave loads of various marine structures. Therefore, this paper uses HydroSTAR software to
perform hydrodynamic analysis of the buoy body, first constructs the standard boundary element model
through meshing, then calculates the relevant parameters of the structure properties of the buoy model
with the help of Inventor, and finally obtains the response curve of the model in both vertical and
horizontal directions [7-9].
Two types of buoy underwater part meshing models were established, as shown in Figure 2. Each
element’s normal face is outward, and the buoy can be translated along 3 coordinates or rotated around
an axis.
Figure 2. Boundary element model of buoy based on HydroSTAR.
Table 1. Structure parameters of two buoy bodies.
PARAMETER VALUE/Cylindrical VALUE/Spherical
Diameter/m 0.9 0.9
Total mass/Kg 172 175.3
X-axis Mass moment of inertia/
𝐾𝑔 ∙ 𝑚
14.3412
15.4432
Y-axis Mass moment of inertia
/𝐾𝑔∙𝑚
14.2973
15.1457
Z-axis Mass moment of inertia /
𝐾𝑔 ∙ 𝑚
18.0732
19.0852
ICMMAP-2023
Journal of Physics: Conference Series 2660 (2023) 012018
IOP Publishing
doi:10.1088/1742-6596/2660/1/012018
3
Table 1 shows the main structural property parameters of the buoy model. The relationship between
the radius of moment of inertia r and the mass moment of inertia I is:
𝑟
(1)
By substituting the above values, the radius of the traversal moment of inertia of the model can be
obtained. We set other parameters as shown in Table 2:
Table 2. Parameter-setting of hydrodynamic calculation.
PARAMETER VALUE
Calculate the frequency
domain (ω)
WMIN 0.5 (
𝑟𝑎𝑑 𝑠
⁄
)
WMAX 3.14 (
𝑟𝑎𝑑 𝑠
⁄
)
WSTP 0.1 (
𝑟𝑎𝑑 𝑠
⁄
)
Calculate the wave direction
HMIN 0.0
HMAX 360.0
HSTP 90.0
WATER DEPTH 100
SPEEDS TYPE 0
Additional damping value The damping matrix element value is 8% of the
critical damping
The software calculates the RAO response curves of the model in both the vertical and horizontal
directions, as shown in Figures 3 and 4.
(a) (b)
Figure 3. The hydrodynamic response curve of cylindrical buoy body.
ICMMAP-2023
Journal of Physics: Conference Series 2660 (2023) 012018
IOP Publishing
doi:10.1088/1742-6596/2660/1/012018
4
(a) (b)
Figure 4. Hydrodynamic response curve of spherical buoy body.
From Figures 3 (b) and 4 (b), it can be seen that at relatively small wave periods (two seconds), the
amplitude operators of the unit wave amplitude heave response of both types of floating bodies are close
to 1, but the spherical buoy is closer. From Figures 3 (a) and 4 (a), it can be seen that when the amplitude
operator of the wave amplitude roll response reaches its maximum peak, the wave period of the
cylindrical buoy is 3.34 seconds, while the spherical buoy reaches its maximum peak at a wave period
of 3.14 seconds. In theory, it can be considered that the natural periods of the two types of buoys swaying
in waves are 3.34 seconds and 3.14 seconds, both of which are less than 4 seconds and are not within
the range of the main energy period of the waves, which is 4 s to 12 s. However, the natural period of
the spherical buoy is smaller, indicating a lower probability of resonance in waves [10-11].
4. Conclusion
In summary, it can be seen that in the range of the main energy period of the wave, the amplitude
operators of the vertical direction of the two structures float are close to 1, the wave performance is good,
the inherent period of the roll direction is not within the range of the main energy period of the wave,
the swing amplitude is small, and the overall wave performance of the spherical buoy is better than that
of the column buoy. Therefore, under the condition of the same shape and size, the buoy with a spherical
structure is preferred, which is more conducive to the measurement of wave buoy.
Acknowledgments
Qingdao Natural Science Foundation (23-2-1-159-zyyd-jch)
Key R&D Program of Shandong Province, China (2023ZLYS01)
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Journal of Physics: Conference Series 2660 (2023) 012018
IOP Publishing
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