Aeromechanical Analysis of a Smart Helicopter Rotor in Forward Flight
This paper deals with a smart system integrated into a helicopter blade aimed at giving an anhedral shape to the blade tip region to alleviate the blade-vortex interaction phenomenon that may cause reduced helicopter performance in terms of noise and vibrations. The blade tip morphing is obtained through the joint action of a magneto-rheological fluid (MRF) device, a shape-memory alloy ribbons- based (SMA) device and a set of concentrated masses properly distributed spanwise. The presence of this smart actuator (particularly the concentrated masses) inside the blades modifies the aeromechanical behaviour of the rotor and may be detrimental in terms of hub vibratory loads, pitch control effectiveness and aeroelastic stability. Following a previous literature work concerning with the effectiveness of the smart actuated rotor in hovering conditions, the present paper focuses on the aeromechanical effects due to the inclusion of the smart device in a four-bladed helicopter rotor in forward flight where blade morphing is not needed. Aim of this work is to investigate on the compatibility of the smart system with the required aeromechanical performance of the rotor, highlighting the feasibility of its application on helicopters.
Experimental results of the European HELINOISE aeroacoustic rotor test
In a cooperative research program between eight European partners, a 40% geometrically and dynamically scaled and highly instrumented model of the ECD (formerly MBB) BO 105 helicopter main rotor was tested in the open-jet anechoic test section of the German-Dutch Wind Tunnel (DNW) in the Netherlands. The primary objectives of this experimental study were 1) to improve the physical understanding of the impulsive rotor noise sources by correlating blade pressure and acoustic characteristics and 2) to provide an extensive airload and acoustic database for code validation purposes.Consequently, a comprehensive set of simultaneous acoustic and aerodynamic blade surface pressure data as well as blade dynamic and performance data were measured for the standard rotor with rectangular blade tips. In addition, initial quantitative information of the blade- vortecx miss distance during blade-vortex interaction (BVI) was obtained.
Boundary Integral Equation Methods for Aerodynamics
T HE objective of this chapter is to review the boundary-integral-equation methods in potential aerodynamics of airplanes and helicopter rotors, with emphasis on the "direct velocity-potential formulation," which was introduced by Morino' and further developed by him and his collaborators, in particular by Gennaretti. For the sake of clarity, the formulation is presented at levels of increasing complexity, starting with incompressible nonlifting problems and ending with the most recent developments: a boundary-integral-equation formulation for the velocity potential equation for compressible flows, in a frame of reference in arbitrary motion, and with applications to aerodynamics of airplanes and helicopter rotors. The formulation is given in terms of the velocity potential, for which an explicit treatment of the wake is required; special emphasis is given to the formulation for the wake transport. Recently obtained numerical results are included. Other methods, in particular those by Hess' and by Maskew, are also presented. In the remainder of this section we present an outline of this chapter. In Sec. n we present a review of the development of boundary-integral methods (in airplane and helicopter-rotor aerodynamics) with emphasis on the "direct velocity-potential formulation." Next, we present the mathematical aspects of the methodology. In order to introduce some fundamental concepts of the boundary-integral-equation methodology, we begin with incompressible potential flows (Sec. IE). Lifting flows require the introduction of potential wakes; this concept, which may not be familiar to the reader, is presented in Sec. IV, which includes a detailed discussion of the treatment of the wake, of the condition at the trailing edge, and of the numerical discretization of the problem. Then we extend the potential-flow formulation to compressible flows (Sec. V); the integral formulation for airplanes is treated in Sec. VI and its extension to