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Title: Investigation of the dynamic wake of a model rotor
Author: Ellenrieder, Thomas Jochen
ISNI:       0000 0001 3444 322X
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 1995
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In this study the dynamic induced velocity field of a model helicopter rotor - excited in collective and cyclic pitch at frequencies extending to 1.5 times the nominal shaft speed - is investigated using mainly hot-wire and laser Doppler anemometry. The dynamic induced velocities are found to vary significantly with radial station and frequency. For cyclic excitations, azimuthal variations are also observed. The results point to the dynamic induced flow being influenced by the distribution of shed vorticity in the wake and cannot be explained using simple momentum theory. Vertical variations of the measured inflow response are also observed, with phase changes possibly partly due to transmission type delays. At frequencies above shaft speed a change in character of the induced flow is seen and around shaft speed an increase in the general level of turbulence is found. The available data on the dynamic induced velocity field of a rotor under controlled excitation, are substantially extended. The measured induced flow response was compared to that predicted using the Pitt and Peters dynamic inflow model. In the 'collective' case good agreement was found, suggesting that the primary inflow model parameters such as the inflow gain and apparent mass are correct with some evidence that a higher order inflow representation might be desirable. A novel method is used to infer the aerodynamic hub loading, which could not be directly measured, from the blade flapping data. This is used to isolate the inflow response using the Pitt and Peters dynamic inflow model and the results are compared with experimental measurements. The method shows the Pitt and Peters dynamic inflow representation to be adequate in the 'collective' case. In the 'cyclic' case, the inferred hub loads were very sensitive to the blade model and hence conclusions for this case are limited. A literature survey and review of the Pitt and Peters dynamic inflow model are also given
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Helicopter rotors ; Inflow ; Pitt and Peters model