Unsteady Aerodynamics of Rotorcraft at Low Advance Ratios in Ground E?ect
The aerodynamic characteristics of rotorcraft flying at low speed close to the ground are investigated. This will help better understand and quantify the flowfield structures and unsteadiness associated with various in ground e?ect flight conditions. This study aims to separate out the various phenomena according to their causal factors.
Experimental investigations first involved flow visualization, which helped in identifying the various flight regimes and in getting an approximate estimate of the unsteadiness. The problem was divided into its unsteady and quasi-steady aspects. Hotwire measurements were performed and the unsteadiness in the flow structure was quanti?ed. It was found that there were long time scale ?uctuations in the upwind side of the rotor disk, with signi?cant changes in the in?ow.
On the quasi-steady side, the fuselage loads for two fuselage cross-sectional shapes were investigated both in and out of ground e?ect. The fuselage cross-section shape had a signi?cant e?ect on the loads felt by the fuselage in ground e?ect. The power required for the experimental con?guration was measured to provide a basis for comparison. Finally, the ?ow?eld around the ground vortex was quantified, and the structure of the ground vortex was investigated using Particle Image Velocimetry. It was found that tip vorticity was ingested by the ground vortex and that the strength of the ground vortex was considerably more than the tip vortex.
Advisor:Narayanan Komerath; Lakshmi Sankar; JVR Prasad; Mark Costello; A. Terrence Conlisk Jr.
School:Georgia Institute of Technology
School Location:USA - Georgia
Source Type:Master's Thesis
Date of Publication:04/05/2006