Numerical simulation of the wake dynamics of the pumpjet propulsor in oblique inflow

Abstract

A numerical analysis based on detached eddy simulations is conducted to investigate vortex dynamics of a pre-swirl pumpjet propulsor (PJP) in oblique inflow. In this paper, the working conditions of PJP operating in axisymmetric flow and drift with two angles (10° and 20°) are considered. The effects of incidence α and propeller loading on the wake dynamics of PJP as well as the mechanism leading to its destabilization are discussed. The results show that high hydrodynamic efficiency loss is found for PJP operating in drift. In addition, a different “secondary vortex structure” caused by the duct is found for PJP in both axisymmetric and oblique flow conditions. The instability mechanism of tip vortices shows obvious asymmetry. On the leeward side, it is dominated by the interaction caused by the duct-induced vortex, while it is dominated by the secondary vortices on the windward side. Furthermore, the fluctuation frequency of tip vortex for PJP is characterized by the rotor blade-passing frequency and the stator blade-passing frequency. In addition, the hub rotation frequency is important in oblique flow conditions.

Effects of a nozzle on the propeller wake in an oblique flow using modal analysis

“…Rotor devices (e.g. propellers, wind and tidal turbines) that are initially designed to operate under uniform and axisymmetric flow are sometimes required to work in off-design conditions for manoeuvring (Felli & Falchi 2018; Huang, Qin & Pan 2022) or optimal energy extraction (Li & Yang 2021; Borg et al. 2022).…”

“…For yawed DPs, vortex shedding is generated at the leeward nozzle leading edge due to the yaw misalignment, and the interaction between the vortex shedding and the helixes accelerates wake destabilization in the leeward region (Huang et al. 2022; Li et al. 2022).…”

“…2014; Felli & Falchi 2018; Huang et al. 2022; Li et al. 2022), but a comprehensive comparison of the wake characteristics of a propeller with and without a nozzle over a wide range of inflow angles is rare.…”

“…Rotor devices (e.g. propellers, wind and tidal turbines) that are initially designed to operate under uniform and axisymmetric flow are sometimes required to work in off-design conditions for manoeuvring (Felli & Falchi 2018;Huang, Qin & Pan 2022) or optimal energy extraction (Li & Yang 2021;Borg et al 2022). For instance, when a ship changes its direction, the lateral flow can strongly modify the propeller propulsive loads, thus affecting the ship dynamic response and inducing the thruster-hull interaction (Viviani et al 2007;Dubbioso, Muscari & Di Mascio 2013Zhang, Ma & Liu 2018;Qiu et al 2020).…”

“…Under yawed conditions, asymmetric evolution, instability and breakdown of helixes were observed on the windward and leeward sides of the NP and DP (Dubbioso et al 2013(Dubbioso et al , 2014Di Mascio et al 2014;Felli & Falchi 2018;Huang et al 2022;Li et al 2022). For an NP operating in an oblique flow, a significant difference compared with the NP in an axisymmetric flow is the generation of the time-dependent shed vortices that induce the secondary vortex systems at the slipstream boundary via shear (Di Mascio et al 2014;Felli & Falchi 2018).…”