Educational Activities

Graduate school: Ocean Observation Technology, Experimental Methodology of Ocean Technology, Policy, and Environment

Research Activities

The sea surface is constantly changing. Sea surface winds, atmospheric pressure, seawater density, seafloor topography, and other factors drive these changes. The main changes in the state of the sea surface include waves, ocean currents, and tidal currents. Everything on the ocean surface either drifts or is disturbed by the effects of currents and waves. Ocean engineering starts from understanding the changing ocean and assesses the impacts of those changes.
The Rheem Laboratory is developing monitoring systems using a microwave pulse Doppler radar for observing the physical environment of the sea surface including waves, ocean surface winds, tsunamis, and tidal level; developing systems for using the renewable ocean energy of waves and tidal currents; and investigating the impacts of waves and current flow on floating and underwater structures including linear structures. Our research contributes to mitigating climate change (development of energy resources that don?ft emit GHGs) and adapting to climate change (environmental change due to extreme meteorological events and disaster response).
Field testing of sea surface monitoring systems and renewable ocean energy generation systems is being conducted in Hiratsuka City on Sagami Bay; on Sabusawa Island in Shiogama City, Miyagi Prefecture; in Kuji City, Iwate Prefecture; and in Mombetsu City, Hokkaido.


Research Field

Sea surface measurement by active microwave remote sensing
Technology for monitoring the changing sea surface is an important technology for utilizing the ocean space. From the strength and Doppler velocity of backscattering microwaves on the sea surface, the information on sea surface wave height, frequency, and direction; speed and direction of surface current; speed and direction of surface winds; changes in sea surface height (tidal level and tsunamis); and distribution and approach speed of sea ice can be obtained. Our objective is to build systems that monitor the sea surface from the land, sea, air, and space.


Sea surface measurement by radar

Development of renewable ocean energy
Among those nations that are developing and deploying sustainable energy resources, there are high expectations for renewable energy that does not emit greenhouse gases. The most important factor for expanding the use of renewable ocean energy is the capital cost of deployment, which is strongly impacted by system efficiency. Generation systems using wave power or tidal currents convert natural energy into mechanical energy and then convert that mechanical energy into electric power. It is necessary to increase the overall conversion efficiency of electric power generation using renewable ocean energy. Research is being conducted to develop high-efficiency generation suitable for the relatively low energy density of renewable ocean energy using hydraulic systems. Field testing is being conducted with a 5 kW vertical rotor tidal current power generation system in the Sabusawa Channel in the Urato District of Shiogama City, Miyagi Prefecture, while a 43 kW wave power generation system is being tested in the ocean in the Tamanowaki area of Kuji Harbor, Kuji City, Iwate Prefecture.



Development of renewable ocean energy

Investigation of the behavior of underwater linear structures
Although ocean drilling pipes are relatively simple structures, the hydrodynamic forces acting on drilling pipes and their response characteristics are generally non-linear. Also, in ocean regions where there are currents and other flows, the oscillations related to flows interacting with the oscillations caused by the rotation of drill pipes result in more complicated responses. As the relative strength of pipes declines with increasing ocean depth, changes in flow velocity with each depth become important issues from the perspectives of design strength and safety.

Literature

1) Chen W. and Rheem: Experimental investigation of rotating cylinders in flow, J Mar Sci Technol, https://doi.org/10.1007/s00773-018-0535-5 (2018).
2) Kobayashi, Rheem, and Maruyama: Field Demonstration of Pendulum Type Wave Power Generation System (Wave Rudder), J.JSCE Ser.B2 Coastal engineering, Vol.73(2), pp. I_1453-I_1458 (2017).
3) Mustapa, Yaakob, Ahmed, Rheem, Koh, and Adnan: Wave energy device and breakwater integration: A review, Renewable and Sustainable Energy Reviews, 77 (2017), pp. 43-58 (2017).
4) Yoshida and Rheem: Time-Domain Simulation of Along-Track Interferometric SAR for Moving Ocean Surfaces, Sensors 15(6), pp. 13644-13659 (2015).
5) Ikoma, Masuda, Nakazawa, Rheem, and Eto: Effect of Pitch Angle and Rotor Solidity of a Vertical Axis Turbine with Variable Pitch Blade on a Turbine Efficiency, J.JSCE Ser.B3 Ocean Engineering, Vol. 70(2), pp. I_91-I_96 (2014).
6) Yoshida and Rheem: SAR Image Simulation in the Time Domain for Moving Ocean Surfaces, Sensors 13(4), 4450-4467 (2013).
7) Ikoma, Masuda, Rheem, and Maeda: Hydroelastic Behaviors of VLFS Supported by Many Aircushions with the Three-Dimensional Linear Theory, J. Offshore Mech. Arct. Eng., Vol. 134(1), 011104 (8 pages), doi:10.1115/1.4003697 (2012).
8) Chen C.-Y. and Rheem: A Study on Sea Surface Wave Observation and Progress at off Hiratsuka of Sagami-bay by a Microwave Pulse Doppler Radar, J.JSCE Ser.B2 Coastal Engineering, Vol. 67(2), pp. I_1376-I_1380 (2011).

Other Activities

The Japan Society of Naval Architects and Ocean Engineers (JASNAOE)
Japanese Association for Coastal Zone Studies (JACZS)
Institute of Electrical and Electronics Engineers (IEEE/OES)

Future Plan

We are advancing social implementation of research results by constructing an ocean observation system, constructing an observation information utilization system, and spreading power generation systems using renewable ocean energy.

Messages to Students

I expect freewheeling thinking.

URL

http://seasat.iis.u-tokyo.ac.jp/rheem/