Tip vortex structure and aerodynamic loading on rotating wings in confined spaces

• Published in: Experiments in fluids 2014-09, Vol.55 (9), Article 1815
• Main Authors: Manar, Field, Medina, Albert, Jones, Anya R.
• Format: Article
• Language: English
• Subjects: Aerodynamics; Applied fluid mechanics; Engineering; Engineering Fluid Dynamics; Engineering Thermodynamics; Exact sciences and technology; Fluid dynamics; Fluid- and Aerodynamics; Fundamental areas of phenomenology (including applications); Heat and Mass Transfer; Instrumentation for fluid dynamics; Physics; Research Article
• ISSN: 0723-4864; 1432-1114
• DOI: 10.1007/s00348-014-1815-4

Experiments on a rotating wing in a liquid-filled tank were conducted to determine the minimum required tip clearance to produce data free from wall effects. A rotating wing fixed at an angle of attack of 45° was revolved for two revolutions at Reynolds numbers between 120 and 10,000. Tip clearance was varied from 0.5 to 5 chords by varying wing size, while also varying wing speed to hold Reynolds number constant. Force measurements on the wing, as well as dye flow visualization and particle image velocimetry of the entire tank, were conducted. Tip clearances of 0.5–7 chords were also tested computationally. Results of all measurements show large tip effects for 0.5 chords of tip clearance, and no wall effects for 5 chords of tip clearance at all Reynolds numbers tested. The 3 chord clearance case showed negligible wall effects in both the particle image velocimetry and dye flow visualization for all Reynolds numbers observed. The forces on the 3 chord tip clearance wing indicate wall effects appearing in the second revolution for Reynolds numbers of >1,000. A tip clearance of 5 chords is deemed to be free of wall effects for experiments limited to two wing revolutions within the range of tested Reynolds numbers.