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It is a technical difficulty to calculate the hydrodynamic parameters when autonomous underwater vehicle (AUV) carries some complex shape appendages (equipment). The general hydrodynamics simulation software CFX and the SST turbulence model were used to calculate the hydrodynamics of AUV with CTD and GPS/Beidou antennas, obtain the AUV hydrodynamic variation of three models and analyze the influence of different appendages on the hydrodynamics of AUV. The results show that the horizontal of AUV with appendages is asymmetric, the pressure and speed change rapidly at the appendages, resulting in the great change of AUV hydrodynamic parameters and the flow field. The numerical results pro- vide a reference frame for the engineering design of AUV. [ABSTRACT FROM AUTHOR]

A split Hopkinson pressure bar (SHPB) testing system was constructed to study the mechanical properties of sandstone at high temperature. The dynamic compression loading tests of sandstone with temperature rate varying from 25 °C to 1 000 °C were carried out to study the relationship among the dynamic mechanical properties, such as peak stress, failure strain, elastic modulus, and temperature. The experimental results show that the relationship of the mechanical properties of sandstone with the temperature changes sharply at 100 °C and 200 °C. With the increase of temperature, the peak stress and the elastic modulus all gradually decrease, while the failure strain increases when the temperature is over 200 °C. The mechanical properties deteriorate rapidly with the increase of temperature when the temperature is above 600 °C. In the sight of microstructure characteristics of sandstone, the mechanical properties of sandstone at high temperature were analyzed. It is found that the micro mechanism that the destruction of high temperature to the sandstone changes sharply with the increase of temperature. The research conclusions can provide references for analyzing the dynamic mechanical behavior of the country rock of underground projects at high temperature. [ABSTRACT FROM AUTHOR]

A finite element model of the rotating band engraving into the forcing cone section of gun tube is established to explore the mechanism of engraving process of rotating band of a large-caliber howitzer under launch conditions. The dynamic engraving process of the rotating band is studied through numerical simulation, and the maximum resistance, engraving pressure and projectile velocity at the corresponding time are obtained. The deformation and groove formation processes of the rotating band are analyzed. The dynamic engraving resistance of the rotating band, the engraving pressure and movement of projectile are also calculated. The calculated results show that the rotating band undergoes plastic deformation and material flow, and forms the grooves on it due to ductile fracture, where shear failure is dominant. The rotating band has a layered feature after engraving, and the plastic strain in the band is small. The heat generated by adiabatic deformation of the rotating band is not enough to melt it. The simulation results of the deformation of the rotating band show good agreement with the test data from the recovered projectile. [ABSTRACT FROM AUTHOR]

A multi-objective optimal method based on adaptive response surface is proposed for the multi-objective optimization of deep-sea AUV (automatic underwater vehicle) shell structure. The original samples are obtained by the experimental design, the response surface methodology is used to create an approximate model, and the Pareto solution set is obtained after optimization. A spatial sampling method is introduced to get the equally distributed samples from Pareto solution set. After the samples are checked using the finite-element analysis method, they are added into the original sample set. The approximate model can satisfy the accuracy requirements by using an asymptotic global strategy. At last, a grey relational analysis method is used to deal with the Pareto solution sets. A multilevel-scales evaluation method is presented to get the weight of every objective based on the shell structure design of AUV, and then get the satisfactory result. The optimal result is much better than the result got by the empirical formula. [ABSTRACT FROM AUTHOR]

In order to obtain the hydrodynamic characteristics of the unmanned underwater vehicle (UUV) parking on the seabed and the effect of vertical thrusters on it, two kinds of UUV, with and without vertical thrusters respectively, were modeled and meshed using the software ANSYS ICEM in different distances from the seabed and different seabed oblique angles, and the flow fields around these UUVs were simulated by using CFX. From the simulation, the lateral forces and lifts of these two UUVs under different conditions were obtained and the curves of lateral forces and lifts changing with distance from the seabed, oblique angle and water velocity were analyzed. Finally, the effect of vertical thrusters on the hydrodynamic characteristics was analyzed according to the simulation results. The results reveal that the effect of the distance from the seabed on the lateral forces is minor while that on lifts is great; both of the lateral forces and lifts increase rapidly with the increase of water velocity; the lateral forces decease slowly with the increase of the absolute value of seabed oblique angle while lifts increase rapidly; the lateral forces of UUV with vertical thrusters are 5% ~ 15% larger than that if UUV without vertical thrusters while lifts are several times larger. [ABSTRACT FROM AUTHOR]

Exothermic question of lithium/thionyl chloride battery will affect the efficiency of battery compartment of underwater vehicle, and may cause serious safety problems. Thus, the thermal process in battery compartment is analyzed by using CFD. Its mathematical and physical models are established by using coupled fluid-solid heat transfer method, and the temperature contours and temperature-time curves are simulated by adopting FLUENT 6.2 software. Also, they are tested experimentally. The test results indicate that the temperature contours and temperature-time curves inside the battery compartment are mainly relevant to the discharging current of ER48660 lithium/thionyl chloride battery and the heat conductivity of media. [ABSTRACT FROM AUTHOR]