Studying acting forces exerted on a fixed or free-moving body and its movement in a flow field,
Morison’ s equation is widely used. Since this equation includes quadratic drag force term, engineers
prefer to simplify it by linearization. This paper shows the error effect that should be tolerated by use of
the Fourier coefficients. Results are as follows:
1. In case, the velocity of the body is approximately expressed by first-order component with angular
velocity ω, exerted non-linear drag force is expressed by sum of the Fourier coefficients with angular
velocityω and its nth components, and it changes the non-linear equation of motion into the linear one.
2. The inertia force of Morison's equation is expressed as the first order component of the body motion
with angular velocityω and acts as the principle driving force of the body.
3. The first order component of the drag force acts as the frictional force and the higher order
components of that act as the driving forces. The latter's effect results in infinity at the point of
resonance（ nω=ω0） and substantially decreases when it apart from the point.
4. In case of the studied cases here, the simple harmonic action of motion with ω/ω0 is possible to
replicate the simple harmonic free-body motion under the estimated relative error of 10 percent by the
linearized equation of motion.
The ship roll motion has a significant impact on its safety. Therefore, it is imperative to estimate the
parameters in the equation of the ship roll motion. However, as the effect of the nonlinearity of the ship
roll motion becomes more prominent, estimating the parameters becomes more difficult. This research
proposes an estimation method that helps overcome this problem. The authors estimated the parameters
in the equation of motion using real-coded genetic algorithm, differential evolution （DE）, and particle
swarm optimization（ PSO） from roll decay data. The results confirmed that it is possible to estimate the
parameters with consistency and high accuracy.
In this study, visualization of water flow in a fish farming tank was conducted using computational
fluid dynamics（ CFD）. Here, a cylindrical tank with diameter of 0.5m, height of 0.5m, and surface height
of 0.4m was employed. A L-shaped pipe （internal diameter: 0.016m） was used for inlet. The angle
between direction of the inlet flow and x axis was defined as inlet flow direction θ, and set as 0 and 60° .
To validate the CFD results, flow velocity of the tank was measured using PIV experiment and
electromagnetic velocity meter, and CFD results showed good agreement with these experiments.
Regarding the velocity distribution, vertical circulating flow was confirmed when θ ＝ 0° , and horizontal
circulation was observed when θ ＝ 60° . As for the particle path line visualization, a half of particle sank
in the bottom when θ ＝ 0° . In contrast, when θ ＝ 60° , all particles were floated around the surface.
The air age was also visualized to evaluate the freshness of water. The air age of θ ＝ 0° was shorter
than θ ＝ 60° . From these results, it was considered that θ ＝ 60° was suitable to prevent particles from
sinking the bottom; however, θ ＝ 0° was better considered the freshness of water. Finally, we concluded
that we can comprehend the flow characteristics of fish farming tank using CFD analysis.
The large-mesh midwater trawl, bottom trawl with the knotless Dyneema netting, tuna longline,
squid jigging machine and drift net were equipped on the research and training vessel Shinyo Maru Ⅳ of
Tokyo University of Marine Science and Technology. In this paper, the composition and the performances
of these fishing equipment were explained. In addition, the outline of the sampling trawl with canvas
kites（ Larva Catcher） and autonomous multiple Codend Opening/Closing net（ COC-MOHT） equipped on
Shinyo Maru Ⅳ were also introduced. By using these fishing equipment and sampling gears in combination
with various hydroacoustic instruments, it is possible to conduct the effective fisheries resources surveys
and many different types of fishing practices for sustainable fisheries in the future.
We used UAV（Unmanned Aerial Vehicle） for the part of the investigation for the operation and
maintenance at the fishing port facilities. The decrepit degree diagnosis at the facilities which used UAV
can implement work correctly and safely. The settlement of the precast concrete armor unit and crack
width on the concrete structure were measured using UAV. The extraordinary acceptance standard of
the sinking of the precast concrete armor unit is defined as being 'the height which exceeds a block 1
layer'. The measurement accuracy which used UAV was judged enough. The threshold of the crack on
the breakwater was 10 mm wide but could measure a crack well of the degree from the image which
was photographed from the 20 m height.
We studied the image analysis technique of aerial photographs by drone for the large-scale survey of
spatial distribution of seaweed bed. The pixel of aerial photographs of coastal area of Bikuni and
Furubira, Hokkaido, were grouped to 7 elements （three species of seaweed, sand bottom, sandy shore,
rock bottom and rocky shore） by the supervised classification which used the field observation data of
seaweed distribution and bottom materials as teachers. It was possible to estimate the seaweed
distribution at the area shallower than 3 m in water depth. For estimation at the area deeper than 3 m in
water depth, it is necessary to correct the color tone of aerial photographs.
Recent rapid developments in UAV （unmanned aerial vehicle）, or drone, technology have made it
easier than ever to take aerial photographs. In this study, we tested the efficacy of using a consumer
drone as a tool for aerial photography studies of seagrass/seaweed vegetation, tidal flat topography
mapping, and epibenthic fauna research. By using the consumer drone（ DJI Phantom 3 Professional） and
an autonomous flight planning application （Pix4Dcapture） both seagrass/seaweed vegetation and tidal
flat topography were photographed from a vertical position at a height of 100 m. Oblique drone aerial
photographs were also taken at the tidal flat to map a wider area than that captured by the vertical
imagery. The orthomosaic maps were created by using PhotoScan Sfm software on both the vertical and
oblique photographs. Tidal flat epibenthic fauna was photographed from a height of 2 m and 10 m. In
general the equipment system used in this study was suitable for the seagrass/seaweed vegetation and
the tidal flat topography mapping, at least for objective areas that were relatively small （less than 1
km2）, but it was not suitable for the tidal flat epibenthic fauna study. Hence, improvements to the
equipment system, e.g., higher resolution of images, zoom control, and a mechanism to estimate the image
area would be valuable for future marine research applications.