Sun, P.; Pan, L.; Liu, W.; Zhou, J., and Zhao, T., 2022. Wake characteristic analysis of a marine propeller under different loading conditions in coastal environments. Journal of Coastal Research, 38(3), 613–623. Coconut Creek (Florida), ISSN 0749-0208. The propeller wake field is closely related to the cavitation and noise performance of the propeller. The propeller wake fields under light and heavy loading conditions were numerically studied based on the delayed detached eddy simulation method. The characteristics of propeller wake dynamics under different loading conditions were analyzed to reveal the flow physics during the propeller wake evolution. The results showed that the pitch of the helicoidal vortex behind the propeller is large and the wake is relatively stable under light loading conditions with a high advance coefficient. In the heavy loading condition with a low advance coefficient, the pitch of the helicoidal vortex is smaller; the vortex system tends to be unstable and break down earlier. The downstream alternate strong- and weak-tip vortices indicate that the tip vortex evolution is accompanied by a dissipation process, which plays an important role in the interaction between adjacent tip vortices and the inception of propeller wake instability. The present work can provide a reference for the design and optimization of propellers used by ships sailing in coastal environments and zones farther out to sea.

Zhou, J.; Sun, P., and Pan, L., 2022. Modal analysis of the wake instabilities of a propeller operating in coastal environments. Journal of Coastal Research, 38(6), 1163–1171. Coconut Creek (Florida), ISSN 0749-0208. The dynamic characteristics of propeller wakes are a function of hydrodynamics, noise propagation, and structural vibration, among other factors. The evolution of propeller wake flow mechanisms from the near field to the far field has always been a significant topic of turbulence research. Numerical simulations of propeller wakes under different loading conditions were conducted using the improved delayed-detached eddy simulation (IDDES) method. Based on the mode decomposition technique, the results of numerical simulations were used as the input data to perform a reduced-order analysis of propeller wake fields. The results showed that there is a considerable difference between the morphology characteristics of propeller wakes under high and low loading conditions, where the former tends to be unstable earlier in the evolution. According to the mode decomposition results, with decreasing mode frequency, there is strong circumferential diffusion in the tip vortices, which is more pronounced under the high loading condition and at locations further downstream. Circumferential diffusion is a key factor triggering the propeller wake to change from the stable to the unstable state. The present work can provide a significant reference for the design and optimization of next-generation marine propellers operating behind vessels sailing in both coastal and offshore environments.

Sun, P.; Zhou, J.; Liu, Y., and Wang, Y., 2022. Lattice Boltzmann method for simulations of nozzle flows in coastal environments. Journal of Coastal Research, 38(1), 204–217. Coconut Creek (Florida), ISSN 0749-0208. A better understanding of flow in pipes is considered to be critical for marine equipment because it helps to improve pipe performance related to vibration and structure problems. In this study, flow simulations were conducted using a large–eddy-simulation lattice Boltzmann method (LES-LBM) in a nozzle under various Reynolds numbers (Re) and the effect of the three-dimensional cubic lattice models D3Q15, D3Q19, and D3Q27 was examined. The results show that when Re < 200 (i.e. the asymmetry of the results calculated using lattice models D3Q15 and D3Q19 is below 5%) or when the lattice model D3Q27 is adopted, computational results can satisfy the requirement of rotational invariance. When 250 < Re < 300 or the flow suddenly traverses an abrupt expansion, the isotropy of lattice models D3Q15 and D3Q19 experience “collapse”. Defective planes cannot be used to completely solve complex flows and accurately transfer flow information. The resultant problems in the computational results include preference in the circumferential distribution of axial velocity and contraction effects of the phase portrait of axial and radial velocities. More complex flows (e.g., for situations with large Re or fluid traversing abrupt expansion) universally cause more significant lattice model effects, where nonlinear flow phenomena become dominant. Therefore, it is necessary to ensure that solutions in the entire computational domain are independent of lattice orientation during flow simulation using LBM. Overall, the results in this paper have important potential applications in predicting flow characteristics for pipe flows in marine structures such as marine risers in coastal environments and zones farther out to sea.