Hull vibration is the vibration generated by the sailing ship due to various reasons. 90% of the vibration on the ship comes from the pulsating pressure of the propeller, which can generate the stern vibration, superstructure vibration and local vibration. Especially in the area above the propeller, the propeller pulsation pressure often causes local structural resonance or forced vibration, resulting in structural fatigue damage or reduced living comfort. It is therefore necessary to reduce the vibrations caused by the pulsating pressure of the propellers. However, in the early stage of the propeller design, it is not convenient to calculate the pulsating pressure of the propeller due to the complexity of the calculation method. It is important to design a software that can quickly estimate the pulsating pressure of the propeller. In the current study, a software for the rapid estimation of the pulsating pressure of propellers is developed by using the empirical formulas with a mixture of QT and MATLAB programming, to discuss the influencing factors and variations of the pulsating pressure. The results show that the shape parameters of the ship section, the type of the ship and the rotation speed of the propeller greatly affect the pulsation pressure of the propeller. It can provide references for the ship vibration and noise reduction.

Waterjet pumps generally use axial flow pumps or guide vane mixed flow pumps. A hump or even double-hump are often observed in the Capacity-Head (Q-H) curve for the high specific speed mixed flow pumps and axial flow pumps. When the pump is running in the hump region, the pump and the entire system may have problems of flow turbulence and increased vibration and noise. The waterjet pump may enter into the hump region during the rotation change of the waterjet pump corresponding to the ship speed change, which imposes hindrances to the efficient and low-noise operation of the ship, and affects the comfort of the crew and the stealthiness of the ship, even damages the propulsion system. The hydraulic performance curve of a test pump for a mixed-flow waterjet pump with guide vanes is obtained based on the standard test platform of axial (mixed) flow pumps and high-precision test method. It can be observed that there is a significant hump in the energy characteristic curve, accompanied with intensified vibration. A three-dimensional model of the fluid domain has been established according to the geometric model of the test pump for the waterjet pump, being divided by refined structured grids. The results show that under the trough condition, there are significant low-speed vortices in the impeller domain at a higher height in spanwise. The structure and scale of the low-speed vortices between different flow channels are different. In region A, though the flow rate is relatively slow, the flow still moves forward in a spiral. And in region B, the flow rate is even lower but with greater degree of rotation. Although the flow velocity in the A region is lower but still spirals forward. The flow rate in region C is slightly larger than those in region A and region B. However, under the crest condition, the flow in the impeller domain is more uniform and smooth, and the stable flow structure in the flow channel is significantly reduced.