The study of acoustic noise generated by helicopter main rotors is the object of many theoretical and experimental investigations because of the complexity of the related physical phenomena and its strong influence on the vehicle performance. One of the main targets of the FriendCopter European Project is to define technical solutions aimed at improving the helicopter acoustic performance. In this work some related activities are described. The extremely complex operating environment of a helicopter rotor contributes to noise generation through several distinct mechanisms: among them, blade vortex interaction noise (BVI) results extremely annoying when it occurs. One method for BVI alleviation is to increase the separation of the tip vortex from the rotor plane using an adaptive blade tip (anhedral configuration) to diffuse the tip vortex or to displace it. In this work, as a first step of the investigation, a feasibility study on blade tip morphing will be addressed, neglecting any aeroacoustic estimation; a specific flight condition will be considered to evaluate the efficiency of a particular smart system based on the coupled action of shape memory alloys (SMAs) and magneto-rheological fluids (MRFs). Such a kind of actuation system has to realise an on-off mechanism through which the tip blade displacement is maximised: the properties of the MR fluid will be exploited to selectively reduce the bending stiffness spanwise so that the SMA actuation is increased. A theoretical model and numerical investigations will be shown to evaluate the reliability and the effectiveness of the integrated system.
[1]
J. David Carlson,et al.
What Makes a Good MR Fluid?
,
2002
.
[2]
Magnus Nilsson,et al.
Mechanical and Electrical Properties of an Electrorheological Fluid
,
2000
.
[3]
A. V. Srinivasan,et al.
Smart Structures: Analysis and Design
,
2000
.
[4]
Lionel Tauszig,et al.
NUMERICAL DETECTION AND CHARACTERIZATION OF BLADE VORTEX INTERACTIONS USING A FREE WAKE ANALYSIS
,
1998
.
[5]
H. Andrä,et al.
A Constitutive Model of Shape Memory Alloys Based on Viscoplastic like Evolution Equations
,
2000
.
[6]
Dewey H. Hodges,et al.
Linear Flap-Lag Dynamics of Hingeless Helicopter Rotor Blades in Hover
,
1972
.