As an economical and easy deployment wave energy converter (WEC), oscillating bodies WEC is gained more and more attention, and it has great significance of research, especially on supplying power for buoy observation and underwater sensor network. Hybrid wave energy converter, it also named combined mode wave energy converter, can capture the kinetic energy of multiple degrees of freedom of an oscillating body. This paper presents a design of hybrid wave energy converter equipped with a hydraulic power take-off (PTO) unit, and builds the mathematical model of the hydraulic PTO circuit. According to the result of the numerical simulation of the hydraulic circuit, a steady system pressure and an essentially constant motor speed can be obtained with the help of accumulators. More cylinders than one are applied in the hydraulic circuit, and the relative spatial positions of the cylinders will affect the stability of the system pressure. Additionally, the stability of hydraulic system pressure is influenced also by the size of the accumulator and the number of the cylinders.

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An underwater wireless sensor network (UWSN) has multiple functions in ocean survey. A kind of UWSN has been proposed by Zhejiang University. In this paper the CFD method is utilized to verify the ability of a node to adjust its posture in deploying and recovering process. The minimum depth and the minimum time for a node to adjust itself to vertical were obtained in different initial inclined angles and different ocean current velocities. The different initial inclined angles were chosen as 45 degree, 60 degree and 90 degree. The different ocean current velocities were chosen as 0.5m/s and 1m/s according to the actual sea conditions around the Zhoushan Island. The minimum rising height and the minimum time for the retrievable cabin to turn 180 degree were obtained in still water. The purpose of the retrievable cabin to turn 180 degree is to keep antenna upright on the ocean surface. Because the antenna was installed on the bottom of the retrievable cabin. These results show that the design of the UWSN node is reliable as to the scheme of the node to deployment and recovery.