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The process of concrete breaking by a high-speed water jet was simulated in this study based on the coupled method of smoothed particle hydrodynamics and the finite element method. The Riedel–Hiermaier–Thoma constitutive model was adopted to describe the mechanical characteristics of the concrete material. Various impact velocities (250–800 m/s) and jet diameters (1.0–3.0 mm) were simulated to investigate the effect of incident parameters on the dynamic responses and damage behaviors of the concrete material. The simulation results were also verified by water-jet impact experiments. The results show that the model can reproduce the nonlinear behaviors of concrete due to the impact of the water jet, including crack propagation, large deformation of the crushing crater, and penetration. For the constant jet diameter, a critical velocity of water-jet flow is identified. Lateral cracks can be generated inside concrete when the impact velocity exceeds the critical velocity, which can enhance the water-jet capability significantly to damage the concrete. The evolution process of the concrete crushing crater is also obtained. The initial shape of the crushing crater is “ω-shaped” and then gradually transforms into “V-shaped” until being penetrated by the water jet. The section shape of the concrete crushing hole is trapezoidal after penetration. For impact velocity v ranging from 250 to 500 m/s, the size of the concrete crushing hole increases with the increase in v, and the section shape tends to be rectangular. If v exceeds 500 m/s, the size and section shape no longer change significantly. It was also found that the greater the diameter of the water jet, the more the sensitivity of crushing hole size on water-jet velocity.

In this paper, considering the heat exchange between the ends of stator&rotor and lubricating oil, the internal flow field model is established to analyse the flow state. The variation law of the pressure drops in the internal flow field and the friction loss of the rotor surface are specified. The operation characteristic of the motor and the variation law of the magnetic field loss are obtained through the analysis of motor magnetic field. Based on the results of internal flow field and magnetic field, the temperature distribution law of motor is obtained. Compared with the result of the temperature simulation in which only air gap path is considered, the stator temperature shows totally different distribution law, and the stator temperature increases from 32°C to 42°C. Compared with the result of the temperature simulation without considering heat source loss change, the maximum temperature of the motor decreases from 71°C to 49°C. The results show that the ends of stator&rotor and the variation of heat source loss can influence the temperature simulation results.

The reliability of submersible motor is the key to determining the stability of the middle and deep sea exploration and development equipment. In this paper, in view of different equivalent modes of convective heat transfer of housing surface, two temperature field models are established in the finite volume method (FVM). The unidirectional and bidirectional coupling mode between loss and temperature of motor are analyzed, and the temperature calculation results are compared when the oil friction loss and copper loss are constant and variable. Then, the bidirectional coupling mode between radiator temperature field and cooling system internal flow field is determined based on the structural parameters of radiator and cooling circulation impeller. The circulation flow is simulated and the influence of different loss unidirectional coupling modes on the temperature field is compared. Finally, the cooling system design procedure is proposed to obtain the matching relationship of the same cooling system structure parameters of the two temperature field models. Experimental validation is presented, and a more reasonable temperature field model is obtained under the coupling mode proposed. It provides the necessary theoretical basis for the research on the submersible motor cooling system.