Original Article Hydrodynamic design of an advanced submerged propulsion Jing-Wei Jiang 1,2 and Wei-Xi Huang 1 Abstract A new kind of advanced submerged propulsion is automatically modeled and analyzed based on the hydrodynamic and cavitation performance. A mathematical algorithm is proposed to describe the fusion-duct, which is controlled by several design parameters, including section diameters, section lengths, and inlet shape and aspect ratio. The hydrodynamic performances of 13 cases with different parameter combinations are numerically simulated. The simulation is carried out by solving the Reynolds Average Navier-Stokes equations with STAR-CCMþ, and the SST k-x turbulence model is applied. The curves of rotor thrust and torque, stator thrust and duct resistance, along with efficiency and merit coefficient are obtained as functions of the advance coefficient and are compared for different cases. Meanwhile, the pressure distribution on both sides of the rotor and the flow field of intermediate section are systematically analyzed. To guide future designs, an impact factor is further defined and calculated to quantify the effects of different parameters. The results indicate that the section diameters have the most significant influence on hydrodynamic and cavitation performances. Keywords Submerged propulsion, automatic parametric modeling, hydrodynamic performance, cavitation performance Date received: 30 September 2018; accepted: 6 June 2019 Introduction Waterjet propulsion and pumpjet propulsion are cur- rently advanced and widely used surface/underwater propulsion types. Compared with traditional propel- lers, waterjet has lower radiated noise, less vibration, and the ability to delay cavitation, 1 while pumpjet enables a direct trade-off of cavitation performance with efficiency to be achieved. 2 Waterjet is usually installed inside the ship hull consisted of inlet duct, rotor, stator, and discharge nozzle, and pumpjet is installed after the submarine hull consisted of duct, rotor, and stator. Different installation patterns lead to different inflow wakes and flow channels of these two propulsions. Waterjet has only inner flow chan- nel, while pumpjet has both internal and external flow channels. In spite of this difference, the flow features are similar for both the waterjet and pumpjet, includ- ing complex flow at the inlet, axial flow acceleration by the rotor, and energy recovery by the stator, etc. Study on flow characteristics is the basis of design, which directly determines the performance of propul- sion. The hydrodynamic performance analysis for waterjet and pumpjet is a challenging work due to strong interactions among the flow fields of rotor, stator, and duct including inlet and outlet. The rotor is the component that generates thrust and the rear stator can absorb the rotational energy by reducing the radial velocity component in the rotor wake. Meanwhile, the function of duct is to guide water from inlet to outlet. With the rapid development of computational fluid dynamics (CFD), it has become an effective tool for studying the flow field. Park et al. 3 proposed a numerical method to study the complex flow features and the performance of the waterjet pro- pulsion system. The details of the flow field, such as the secondary flow inside of the intake duct, the recovery of axial flow by action of the stator, and the tip vortex, were well captured by numerical simulation. Then, they numerically analyzed the com- plicated flow near the intake duct of waterjet. 4 Strong suction flow through the inlet of the intake duct and the vortex induced by the flow separation along the corner of the inlet sidewall were shown to help 1 Department of Engineering Mechanics, Tsinghua University, Beijing, China 2 Advanced Propulsion Technology Research Department, China Marine Development and Research Centre, Beijing, China Corresponding author: Wei-Xi Huang, Tsinghua University, Room N717, Meng Minwei Science & Technology Building, Haidian District, Beijing 100084, China. Email: hwx@tsinghua.edu.cn Proc IMechE Part C: J Mechanical Engineering Science 0(0) 1–16 ! IMechE 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0954406219860166 journals.sagepub.com/home/pic