The Influence of Leading-edge Tubercles on the Hydrodynamic Performance and Propeller Wake Flow Development of a Ducted Propeller

Stark, C. and W. Shi

This study implements leading-edge (LE) tubercles on a benchmark 19A accelerating duct to investigate the impact on the hydrodynamic performance and propeller wake flow development at multiple operating conditions. The study was conducted using Computational Fluid Dynamics (CFD) where the sliding mesh technique was used to describe the propeller rotation and the hydrodynamic flow-field was solved using Improved Delayed Detached Eddy Simulations (IDDES). In summary, it was found that LE tubercles can enhance the thrust of the duct by a maximum of 7.15% and disrupt the coherent vortex structure of the benchmark ducted propeller which will likely influence the noise signature of the propulsor.

Hydrodynamic Characteristics of Remora’s Symbiotic Relationships

Xu, Y., Shi, W., & Arredondo Galeana, A

The remora fish attached to the body of a shark to compensate for their poor swimming ability.  To understand the remora's swimming strategy in the attachment state, a systematic study has been conducted using the commercial Computational Fluid Dynamics CFD software, STAR-CCM+ to analyse and compare the resistance characteristics of the remora in attached swimming conditions.  Two fundamental questions are addressed: what is the effect of the developed boundary layer flow and the effect of the adverse pressure gradient on the remora’s hydrodynamic characteristics?  By researching the hydrodynamic characteristics of the remora on varying attachment locations, the remora’s unique behaviours could be applied to autonomous underwater vehicles (AUVs), which currently cannot perform docking and recovery without asking the mother vehicle to come to a halt.

The Influence of Leading-edge Tubercles on the Sheet Cavitation Development of A Benchmark Marine Propeller

Stark, C. and W. Shi

This paper assesses the cavitation containment capability of the LE tubercles on a benchmark marine propeller in both heavy and light cavitating conditions using commercial code STAR-CCM+, unsteady incompressible Reynolds-averaged Navier Stokes (RANS) solver and the Schnerr-Sauer cavitation model to quantify the sheet cavitation present over a range of operating conditions. In summary, in heavy-cavitating conditions, a reduction in sheet cavitation with the inclusion of LE tubercles was observed to a maximum value of 2.75% in all operating conditions considered. A maximum improvement of 3.51% and 1.07% was predicted in propulsive thrust and hydrodynamic efficiency, respectively. In light cavitating conditions, although in some conditions a reduction in cavity volume was observed, this did not result in an improvement in hydrodynamic performance.

The Influence of Leading-Edge Tubercles on Wake Flow Dynamics of a Marine Rudder

Troll, M. M. F., W. Shi and C. Stark

The impact of two tubercle leading-edge (TLE) modifications on the turbulent wake of a representative marine rudder at Reynolds number 2.26×106 was analysed numerically using Detached-Eddy Simulations. TLE have been shown to alter the flow profile over aero/hydrofoils through the generation of streamwise counter-rotating vortex pairs behind the tubercles, which can enhance the lifting performance. This paper studies the formation of these vortex pairs and their impact on the wake structures behind the rudder to find out if vortex interaction can reduce the tip vortex.