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112 results on '"Feng, Dakui"'

12. Hydrodynamic analysis of the recovery of USV in regular waves

Author

FENG Dakui, ZHAN Jin, YAN Jun, SUN Yue, and WANG Xianzhou

Subjects
stern-slipway launch and retrieval system, unmanned surface vehicle(usv), cfd, overlapping grid technique, numerical wave tank, ship motion, Naval architecture. Shipbuilding. Marine engineering, VM1-989
Abstract

[Objectives] The recovery of the dinghy is a typical dynamic problem of multi-body interaction,and the stern-slipway launch and retrieval system is widely used in that process. When the dinghy moves rapidly towards the capture devices which are located in the aft of the mother ship,it may be affected by the wake of mother ship which may cause overturn.[Methods] Numerical wave tank,overlapping grid technique and 6-DOF are mainly used and the interference motion of Fridsma planing in approaching the mother ship is simulated. The motion characteristics of planing vessel in waves are calculated and analyzed while the grid independence is verified. Then the simulation of small craft's motion in regular waves in the wake of mother ship is carried out.[Results] Comparison of computational and experimental results indicates that the calculation method is reliable. And the simulation results show that the influence from the mother ship is obvious.[Conclusions] When the direction of motion of planing deviated from the center line of the wake of mother ship,the pitch and roll angle of it will be significantly affected,eventually leading to the occurrence of capsizing.

Published
2020
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16. Numerical Simulation of Submarine Surfacing Motion in Regular Waves

Author

Zhang, Zhiguo, Guo, Lixiang, Wei, Peng, Wang, Xianzhou, and Feng, Dakui

Abstract

Submarine surfacing in wave’s environments is fully three-dimensional unsteady motion and includes complex coupling with hydrodynamic force and dynamic motion of the rigid body. This paper uses in-house computational fluid dynamics (CFD) code HUST-SHIP to solve RANS equation coupled with six degrees-of-freedom (6DOF) solid body motion equations. RANS equations are solved by finite difference method and PISO algorithm. Level-set method is used to simulate the free surface flow. Computations are performed for the DARPA SUBOFF model. The structured dynamic overset grid is applied to the numerical simulation of submarine surfacing motion in calm water, transverse regular waves with different ratio of wave height over submarine length, wave length over submarine length and surfacing depth over submarine length. The asymmetric vortices in the process of submarine surfacing can be captured in this study. The existence of the vortex generated during the submarine surfacing could cause the destabilizing hydrodynamic rolling moment. Relations among maximum roll angle, surfacing velocity and wave parameters are concluded by comparison with variation trend of submarine motion attitude and velocities of surfacing in different wave conditions. Simulation results confirm that wave height and wave length lead to surfacing velocity and roll angle changes, significantly. Maximum roll angle also increases with the increase in wave height and wave length. Maximum roll angle with wave height (h/L= 0.04) can reach to 7.29°, while maximum roll angle with wave length (λ/L= 1.5) can reach to 5.79° by contrast with 0.85° in calm water. Surfacing depth has a great influence on the changes of submarine trim during surfacing. For rolling motion in the transverse wave, maximum roll angle with depth length ratio (d/L= 1.2) can reach to 2.46 times as much as that with depth length ratio (d/L= 0.6).

Published
2024
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