Effects of Nonlinearity of Restoring Springs on Propulsion Performance of Wave Glider

Abstract Wave glider is an unmanned surface vehicle which can directly convert wave energy into forward propulsion and fulfill long-term marine monitoring. Previous study suggested that the wave motion and stiffness of restoring springs mounted on the hydrofoil are main factors affecting the propulsion performance of wave glider. In this paper, the dynamic responses and nonlinear characteristics of underwater propulsion mechanism considering the nonlinear stiffness of restoring springs are investigated based on a fluid-rigid body coupled model. Firstly, the models of propulsion mechanism with different kind of restoring spring are proposed, and the linear and nonlinear characteristics of restoring spring are considered. Then, a fluid-rigid body coupled model of wave glider is developed by coupling the rigid body dynamics model and hydrodynamic model. Dynamic responses are simulated by numerical analysis method and the nonlinear characteristics with different restoring springs are illustrated by time/frequency domain motion response and phase diagram analysis. The effects of wave excitation frequency and wave heights on the propulsion performance of wave glider are analyzed. The results show that, multi-frequency responses occurred in propulsion system. And the study suggests that the nonlinear restoring spring on the hydrofoil can be suitable for different sea condition and better propulsion performance can obtained than linear stiffness spring, which provides a reference for developing propulsion mechanism with high performance in complex marine environment.

Download Full-text

Analysis of propulsion performance of wave-propelled mechanism based on fluid-rigid body coupled model

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/14750902211062069 ◽

2021 ◽

pp. 147509022110620

Author(s):

Zongyu Chang ◽

Zhanxia Feng ◽

Chao Deng ◽

Lin Zhao ◽

Jiakun Zhang ◽

...

Keyword(s):

Rigid Body ◽

Dynamic Model ◽

Coupled Model ◽

Rigid Body Dynamics ◽

Design And Optimization ◽

Marine Vehicles ◽

Propulsion Performance ◽

Operation Conditions ◽

Propulsion Force ◽

Cfd Method

Wave-propelled mechanisms are applied to propel unmanned marine vehicles such as Wave Glider and wave-powered boats, which can convert wave energy directly into propulsion. In this paper, a fluid-rigid body coupled dynamic model is utilized to investigate the propulsion performance of the wave-propelled mechanism. Firstly, the coupled dynamic model of the wave-propelled mechanism is developed based on relative motion principle by combining rigid body dynamics model and CFD method. Then, the motion responses of wave-propelled mechanism are calculated. The relationship between the propulsion force, heave and pitch motion of hydrofoil are analyzed by using phase diagrams and the actual operation conditions of propulsion mechanism are obtained. Besides, the effects of restoring spring stiffness and wave heights on the propulsion performance are also investigated, and the vortex evolution is illustrated at different moments of movement and different restoring stiffness. These works can be helpful for the design and optimization of different kinds of wave-propelled vehicles.

Download Full-text

Simulation on the Vehicle Frontal Collision Based on the PC-Crash

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.940.103 ◽

2014 ◽

Vol 940 ◽

pp. 103-107

Author(s):

Chang Li Zhao

Keyword(s):

Rigid Body ◽

Rigid Body Dynamics ◽

Dynamic Responses ◽

Response Characteristics ◽

Vehicle Collision ◽

Frontal Collision ◽

Body Dynamics ◽

Rigid Body Model ◽

Basic Parameters ◽

Vehicle Movement

The probability of frontal collision is the highest in the vehicle collision accidents, and crew injury mechanism of frontal collision is an attractive research subject. Based on the multi-rigid-body dynamics, a “vehicle-crew-belt” dynamics model is introduced, and software Pc-crash is used to simulate dynamic responses of this multi-rigid-body model by referencing basic parameters of FMVSS law. Dynamic response characteristics between the vehicle and the crew body are analyzed so as to expound the link between the vehicle movement and human-body injury. The result shows that a reliable evaluation of frontal collision is achieved, which provides a theory basic and practical reference for the research of accident injury.

Download Full-text

Slipping–rolling transitions of a body with two contact points

Nonlinear Dynamics ◽

10.1007/s11071-021-06538-5 ◽

2021 ◽

Author(s):

Mate Antali ◽

Gabor Stepan

Keyword(s):

Rigid Body ◽

Contact Point ◽

Static Friction ◽

Rigid Body Dynamics ◽

Contact Forces ◽

Friction Forces ◽

Contact Points ◽

Body Dynamics ◽

Coulomb Model ◽

Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

Download Full-text