Investigations of Tip Vortex Mitigation By Using Roughness
Journal article, 2020

The application of artificial roughness to mitigate tip vortex cavitation inception is analyzed through numerical and experimental investigations carried out on an elliptical foil. Different roughness configurations and sizes are tested and effects on cavitation inception, drag, and lift, are studied. Implicit Large Eddy Simulation (ILES) is employed to conduct the simulation on a proper grid resolution having the tip vortex spatial resolution as fine as 0.062 mm. Two different approaches including using a rough wall function and resolving the flow around roughness elements are evaluated. New experiments, performed in the cavitation tunnel at Kongsberg Hydrodynamic Research Centre, for the rough foil are presented.
The vortical structures and vorticity magnitude distributions are employed to demonstrate how different roughness patterns and configurations contribute to the vortex roll-up and consequently on the tip vortex strength. It is found that the application of roughness on the leading edge, tip region and trailing edge of the suction side are acceptable to mitigate the tip vortex and also to limit the performance degradation. This is regarded to be in close relation with the way that the tip vortex forms in the studied operating condition. The analysis of boundary layer characteristics shows a separation line caused by roughness is the reason for a more even distribution of vorticity over the tip compared to the smooth foil condition leading to a reduction in vortex
strength. For the optimum roughness pattern, both the numerical results and experimental measurements show a decrease in the tip vortex cavitation inception as large as 33 % compared to the smooth foil condition with a drag force increase observed to be less than 2 %.

LES.

Roughness

Elliptical foil

Mitigation

Tip vortex

Author

Abolfazl Asnaghi

Chalmers, Mechanics and Maritime Sciences, Marine Technology

Urban Svennberg

Chalmers, Mechanics and Maritime Sciences, Marine Technology

Robert Gustafsson

Chalmers, Mechanics and Maritime Sciences, Marine Technology

Rickard Bensow

Chalmers, Mechanics and Maritime Sciences, Marine Technology

Physics of Fluids

0031-9171 (ISSN)

Vol. 32 6

RoughProp - reduced radiated noise to the oceans through surface roughness

VINNOVA, 2018-11-19 -- 2020-05-31.

Driving Forces

Sustainable development

Subject Categories

Applied Mechanics

Fluid Mechanics and Acoustics

Infrastructure

C3SE (Chalmers Centre for Computational Science and Engineering)

DOI

10.1063/5.0009622

More information

Latest update

6/23/2020