Andres E. Rivero

Helicopters are still an indispensable addition to aviation in this day and age. They are characterized by their ability to master both forward flight and hover. These characteristics result in a wide range of possible operations. Key for the design of the rotor blades is a blade design that always represents a compromise between the different flight conditions, which enables safe and efficient flight in the various flight conditions. In order to operate the rotor blade even more efficiently in all flight conditions, a new morphing concept, the so-called linear variable chord extension, has been developed. Here, the blade chord length in the root area is changed with the help of an elastic skin to adapt it to the respective flight condition. The simulations performed for this concept showed a promising increase in overall helicopter performance. The fabrication of the resulting demonstrator as well as the tests in the whirl-tower and wind tunnel are presented in this paper. The results of the tests show that the concept of linear variable chord extension has a positive influence and a great potential for hovering flight.

Unlike hinged flaps (for example, ailerons, elevators, and rudders), camber morphing devices vary camber distribution in a smooth and continuous way, resulting in aerodynamic efficiency improvement...

Unlike hinged flaps (e.g. ailerons, elevator and rudder), camber morphing devices vary camber distribution in a smooth and continuous way, resulting on aerodynamic efficiency improvements due to the absence of surface discontinuities. One such camber morphing concept, the Fish Bone Active Camber (FishBAC) device, has shown significant aerodynamic benefits when compared to a flap. A 2D wind tunnel test was performed to further investigate the FishBAC's behavior in terms of its aerodynamic performance and the size and structure of the shed wake. To establish a direct comparison, a hinged flap was also tested under equivalent flow conditions. A combination of quasi-steady force balance and wake rake pressure measurements were used to determine aerodynamic force coefficients. Additionally, these measurements are complemented by a flow visualization study performed using Particle Image Velocimetry, where a visual comparison on the size and vortical structure of the near field wakes was conducted. Results show that the FishBAC achieves at least 16\% higher aerodynamic efficiency than the flap.

This paper presents a newly developed three-dimensional Fluid-Structure Interaction (FSI) routine for the Fish Bone Active Camber (FishBAC) concept that couples a three-dimensional Lifting-Line theory analysis to a two-dimensional viscous corrected panel method (XFOIL) to create a viscous corrected three-dimensional wing aerodynamic solver. This aerodynamic model is then coupled to a previously developed multi-component Mindlin-Reissner plate model based composite analysis routine for the FishBAC morphing device. The methodology is explained, and predictions are validated against existing modeling tools. The FSI model developed in this paper shows good agreement when compared against other structural, aerodynamic and FSI tools. Additionally, results show the FishBAC's ability to improve aerodynamic performance at a wide range of operating conditions

Camber morphing aerofoils have the potential to significantly improve the efficiency of fixed and rotary wing aircraft by providing significant lift control authority to a wing, at a lower drag penalty than traditional plain flaps. A rapid, mesh-independent and two-dimensional analytical model of the fish bone active camber concept is presented. Existing structural models of this concept are one-dimensional and isotropic and therefore unable to capture either material anisotropy or spanwise variations in loading/deformation. The proposed model addresses these shortcomings by being able to analyse composite laminates and solve for static two-dimensional displacement fields. Kirchhoff–Love plate theory, along with the Rayleigh–Ritz method, are used to capture the complex and variable stiffness nature of the fish bone active camber concept in a single system of linear equations. Results show errors between 0.5% and 8% for static deflections under representative uniform pressure loadings and applied actuation moments (except when transverse shear exists), compared to finite element method. The robustness, mesh-independence and analytical nature of this model, combined with a modular, parameter-driven geometry definition, facilitate a fast and automated analysis of a wide range of fish bone active camber concept configurations. This analytical model is therefore a powerful tool for use in trade studies, fluid–structure interaction and design optimisation.