Su Yumin

Hydrodynamic performance calculation and motion simulation of an AUV with appendages

Computational fluid dynamics (CFD) is considered as a possible effective tool to evaluate the performance of the autonomic underwater vehicle (in short, AUV) such as a body resistance, rudder force, motion in water. Focused on the hydrodynamic performance, the resistance and oblique sailing performance were simulated by CFD technique and planar motion mechanism test was also simulated by dynamic mesh technique. The major hydrodynamic coefficients were obtained, which were used to satisfy the need of a six-degree of freedom motion equation of the AUV with appendages. Based on this, the motion simulation platform of the AUV appendages was established. The maneuverability performance was simulated in the horizontal and vertical plane. In order to evaluate the influence of appendages on the motion performance of the AUV, simulation of the AUV with appendages and without appendages were compared.

Research on motion simulation system for underwater vehicle

The motion simulation system of underwater vehicle was developed based on dynamic model of the underwater vehicle and software platform - MultiGen Creator and Vega. The architecture of the simulation system was introduced. The coordinate system and 6-DOF dynamic equations of the underwater vehicle were constructed. The 3D modeling method based on Creator, the effect generation method of ocean environment and collision detecting method were discussed By using Vega to drive models, the visual simulation module was built. The simulation results show that this simulation system can realistically demonstrate the motion of underwater vehicle and satisfy the real time requirement. The system can also provide a platform for debugging and validating of the underwater vehiclepsilas intelligent control algorithm.

The experimental investigation of nominal wake of ice-going ship attached with ice based on SPIV technology

This paper is based on 76000DWT Panmax Bulker with Ice Class 1B, By using PIV measuring technology and towing DANTEC PIV system, the nominal wake field in open water is measured. Bilge vortex, propeller cap vortex and hook-shaped velocity contour are all observed precisely. The results show that the flow field characteristics are in accordance with stern flow field of U-huge ship, such as KVLCC and JBC. Then the stern nominal flow field is measured as the ship is attached to ice. Axial velocity distribution, velocity vector distribution and streamline are also analyzed. The results indicate that attachment of ice load makes the stern region produce dummy thickness which is equal to the thickness of ice. The dummy thickness destroys the fine linetype design and makes the stern become V-type which is not the best stern type. The attachment of ice in the bottom and side shell lead to the disturbtion stern nominal flow field has to bear when naked hull is sailing. Turbulent boundary layer around the shell is destroyed. Non-streamlined shape of ice produces complex vortex, and the disturbtion among vortexes results in the appearance of disordered vortex structure.

Structure design of an autonomous underwater vehicle made of composite material

Underwater vehicles are weight-sensitive structure for its balance requirement of buoyancy and gravity in water. Composite material which has an excellent specific strength and stiffness is stable against the chemical reaction. Besides, composite structure has excellent sound absorption properties. This paper studies the optimal calculation process that decreases the structure weight of an autonomous underwater vehicle which has a novel integral structure made of carbon fiber under the prescriptive working conditions. Based on the statistical techniques, a strategy of response surface model for AUV structure design is proposed. Genetic algorithm was used for the optimization using response surface model instead of the finite element analysis, and the number of carbon fiber layer in the different locations of the integrative structure is calculated finally.

Prediction of hydrodynamic performance of marine propellers by surface panel method

The potential based low order surface panel method is used to predict the hydrodynamic performance of marine propellers. In present method the hyperboloidal quadrilateral panels are employed to avoid the gap between the panels. The influence coefficients of panels are calculated by Morino’s analytical formulations for increasing numerically calculating speed. The pressure Kutta condition is satisfied on the trailing edge of propeller blade by Newton-Raphson iterative procedure. Therefore the pressure coefficients of the suction and pressure faces of blade are equal on trailing edge. The method developed by Yanagizawa is used to determine the velocities on propeller surface, and to avoid the singularity in the numerical differentiation. The predicted pressure distributions and open water performances of general propellers and highly skewed propellers have a good agreement with experimental dat and other calculation results.