Among the various transient operations, the startup process of a centrifugal pump brings attention to a number of practical issues. A representative application of the startup process is the underwater launch, which requires transient high pressure and high flowrate during a very short time. Due to the rotational inertia of the pump and motor, the dynamic response of the pump is slow, so the rotational speed cannot reach the design point rapidly. To get a high response of the starting process, a throttle valve is installed in the downstream of the pump. The valve keeps closed before the rotational speed of the pump reaches a certain point. It is important to investigate the transient behavior of pump during such transient operations. In this paper, experiment and numerical simulation are implemented to study the external transient hydrodynamic performance and the internal flow of the pump during the transient process. Different operating schemes of the pump and valve are designed to find the best coordinated modes. The contents and conclusions of the current work can provide references for the performance prediction, design optimization and fluid control of the pump and valve during the transient process.

The quality of centrifugal pump inlet flow field is an important factor that affecting the performance of pump. Studies have proved that the vortex in the inlet area can also bring an extra flow instability to pump, which results in a hydro-induced vibration. This phenomenon is more common and significant in the pumps with an elbow tube, which is often applied to minimize installation size, before pump inlet. Therefore, it is necessary to look into the influence of inlet flow field instability on pump performance especially the vibration performance. The methods of adjusting pump inlet flow field is also worthy of being studied in the meantime. In this study, the influence of inlet vortex on the performance of centrifugal pump with an elbow inlet tube is investigated by means of CFD analysis. The flow is significantly affected when going through the elbow tube inlet and then turbulence is generated as a result, which enters the impeller at the next moment. The turbulence brings an asymmetrical flow condition at the impeller suction area, which can intensify pressure pulsation and hydro-induced vibration. In order to reduce the turbulence, two modifications on the elbow inlet tube are investigated in this study. A specially designed vane is deployed inside the inlet tube in the MOD1, and the MOD2 is added with two splitter vanes on the basis of the MOD1. The turbulent flow in the elbow inlet tube can be reordered as it is controlled by the vanes. The difference on pump performances that the inlet vane has made is specifically simulated and compared. The flow fields of the inlet tube influenced by the vane is also investigated on the vortex distribution and velocity vector distribution. The MOD1 has a generally smaller pressure fluctuation amplitude than the prototype in the impeller inlet area while the pressure fluctuation amplitude of the MOD2 in the impeller inlet area is stronger than the prototype. It is considered as a consequence of multiple effects, which are, the rise of velocity because of flow area replacement by the vanes making the flow field less stable as well as the wake flow induced by the vanes increasing the instability of the flow field. Therefore, although the flat vanes can help adjusting the flow field, their negative influences also act in the opposite way. It is worthwhile to find the balance between the benefits and the costs in flow field stability of installing adjusting vanes. The selection of parameter, number and installation position needs to be further investigated. The numerical results of the MOD1 are also validated through experimental investigations.

Based on actual working conditions and parameters of the rudder system, the purpose is optimizing the connection of rudder system by keyless coupling technology. Analysis on the keyless coupling of rudder system is done by the finite element method under impact loads in different directions. It can improve the performance of keyless coupling in the specific operation conditions of rudder system to be excellent. According to the test requirements of the torque and impact, the results of the completion of the finite element analysis are verified by establishing the experimental platform of keyless coupling. Experiments and analysis of the results show that the preload is formed by the hydraulic nut in the keyless coupling and the static frictions is formed between the rudder and tiller. In the meantime, it is formed between rudder and the rudder blade which can make the working state of the rudder system stable under the required torque and impact loads.

Numerical simulation on groundwater is critical for water resources management. Much research has been conducted in the past using different techniques. Groundwater and surface water should not be treated as isolated components, but rather as interconnected constituents. The interaction between surface and ground water is complex and has never been fully understood. A clear understanding of fundamentals between surface and ground water is essential to conduct groundwater simulation. A

The coupled influence between structure and internal flow field will make the pressure oscillation during working process of the solid rocket motor. This coupled effect will bring the dynamic press on the payload and extremely destroyed the payload. For researching the influence of internal flow field by the deformation of inhibitor, the parallel fluid structure interaction method with the large eddy simulation model was used to analyze the solid rocket motor with segments. The results show that the deformation of inhibitor will influence the internal flow field parameter’s distribution and enhance the pressure frequency and amplitude remarkably. The partitioned method could solution the fluid structure interaction problems in the segmented solid rocket motor properly.