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In this paper, the natural supercavitys are studied both experimentally and numerically. A series of supercavitating vehicle water-entry test are carried out at different speeds, where it is found that the minimum pressure in the cavity gradually reduced with the increase of water-entry speed. The cause for the evolution progress of natural supercavitation is difficult to get from the experiment,...
The statistics of extreme wave heights is of great importance in many ocean and coastal engineering applications and is an important part of physical oceanography. For example, in the design and operation of marine structures one needs to take the influence of extreme ocean environments into account and estimates of very large return values of wave heights are often needed. However, due to the limited...
St. George Island, part of the Pribilof Islands, is located in the Bering Sea, more than 320 kilometers (200 miles) north of the nearest Aleutian Island and equally distant to the mainland of Alaska. For nearly two centuries, St. George's primary economy was based on commercial fur seal harvesting. In the early 1980s when commercial fur seal harvesting halted, the community turned to a fishing economy...
During the launching of the AUV especially in air-launching, the water entry problem is inevitable. The AUV will stir the flow field of surrounding fluid during the moving into water, while the fluid will act a strong force on the AUV in return, which may cause trajectory deflection problems or damage to their structure and inner components in severe cases. The water entry experiment of full-size...
This paper aims at investigating the effects of the ocean current in the thrusters closed-loop performance. In particular, the intervention case, and thus the vehicle slowly moving, is of interest. Vehicle controllers are commonly designed without taking into account both the thruster dynamics and the presence of ocean current which, however, influence the closed loop. A fixed gains PID and an adaptive...
Refraction of light underwater is a major source of error for 3D reconstruction. Use of a physically correct camera model taking into account properties of the optical system is essential for understanding the reasons why errors occur and obtaining quantitative estimates of errors. It was proven that use of the single viewpoint model of the camera leads to significant distortions in reconstruction...
In this paper, we employ a dynamics modeling method for investigating a multi-body dynamics system consisting of an unmanned surface vehicle (USV), an umbilical cable (UC), and an autonomous underwater vehicle (ROV). The ROV, which is towed by a UC for the purposes of exploration or mine hunting, is modeled with a Six-Degree-of-Freedom (6-DOF) equation of motion that reflects its hydrodynamics characteristics...
It is known that a dysoxic water mass threatens oyster farming in Dangdong bay. A density current generator is planned to be installed to solve this problem. In this study, we reconstructed the tide level, physical field and dysoxic water mass in Dangdong bay by using numerical simulation and comparing with field measurements and investigated the effect of density current generator by installing it...
In this study, numerical investigations of flow characteristics of a pumpjet propulsor based on Computational Fluid Dynamics (CFD) method have been presented. The Zwart-Gerber-Belamri (Z-G-B) cavitation model based on the Reynolds Averaged Navier-Stokes (RANS) method is employed. The structured gird is applied. A four-blade skewed E779A propeller has been used to verify the numerical method. The comparison...
A Complex Conjugate (CC) control is implemented with a Proportional-Derivative (PD) controller for WEC devices to improve and optimize power absorbed. Traditionally, CC control has not been realizable due to actual implementation that requires acceleration feedback or exact term cancellation. For the PD implementation, only the stiffness term is employed to modify the impedance and achieve resonance...
The underwater vehicles are always being disturbed by ocean current when they work under the sea. In this paper, the Magnus force of a new type autonomous underwater vehicle (AUV) named “autonomous underwater helicopter (AUH)”, a disk-shaped deep-sea underwater vehicle, was analyzed to help it move away from a deep-sea region with temporary ocean current. The simulation technique of the ANSYS-CFX...
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