Large-Eddy Simulation, with an Immersed-Boundary method, is adopted to analyze the wake of a notional submarine propeller, using a cylindrical grid composed of about 840 million nodes. The accuracy of the overall approach is validated by comparisons with available measurements. Three different load conditions are investigated, allowing an assessment of the sensitivity to the rotational speed. Results demonstrate that tip and hub vortices are the main coherent structures. However, several additional vortices are produced across the span of the propeller blades. The evolution of turbulent kinetic energy in the propeller wake is substantially affected by coherent structures. The highest values occur at the axis and at outer radii, due to the hub and the tip vortices, respectively. In addition, downstream evolution of turbulence associated to the tip vortices is not monotonic. In contrast, fluctuations at the wake axis, originating mainly from instability of the hub vortex, keep decreasing starting from the near wake.
Analysis of the Wake Features of a Submarine Propeller via Large-Eddy Simulation
A Posa;R Broglia;M Felli;M Falchi;
2018
Abstract
Large-Eddy Simulation, with an Immersed-Boundary method, is adopted to analyze the wake of a notional submarine propeller, using a cylindrical grid composed of about 840 million nodes. The accuracy of the overall approach is validated by comparisons with available measurements. Three different load conditions are investigated, allowing an assessment of the sensitivity to the rotational speed. Results demonstrate that tip and hub vortices are the main coherent structures. However, several additional vortices are produced across the span of the propeller blades. The evolution of turbulent kinetic energy in the propeller wake is substantially affected by coherent structures. The highest values occur at the axis and at outer radii, due to the hub and the tip vortices, respectively. In addition, downstream evolution of turbulence associated to the tip vortices is not monotonic. In contrast, fluctuations at the wake axis, originating mainly from instability of the hub vortex, keep decreasing starting from the near wake.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
