A Substructure Synthesis Method with Nonlinear ROM Including Geometric Nonlinearities

Large flexible aircraft are often accompanied by large deformations during flight leading to obvious geometric nonlinearities in response. Geometric nonlinear dynamic response simulations based on full-order models often carry unbearable computing burden. Meanwhile, geometric nonlinearities are caused by large flexible wings in most cases and the deformation of fuselages is small. Analyzing the whole aircraft as a nonlinear structure will greatly increase the analysis complexity and cost. The analysis of complicated aircraft structures can be more efficient and simplified if subcomponents can be divided and treated. This paper aims to develop a hybrid interface substructure synthesis method by expanding the nonlinear reduced-order model (ROM) with the implicit condensation and expansion (ICE) approach, to estimate the dynamic transient response for aircraft structures including geometric nonlinearities. A small number of linear modes are used to construct a nonlinear ROM for substructures with large deformation, and linear substructures with small deformation can also be assembled comprehensively. The method proposed is compatible with finite element method (FEM), allowing for realistic engineering model analysis. Numerical examples with large flexible aircraft models are calculated to validate the accuracy and efficiency of this method contrasted with nonlinear FEM.

Experimental analysis of fluid-structure interaction in flexible wings at low Reynolds number flows

Purpose The purpose of this exhaustive experimental study is to investigate the fluid-structure interaction in the flexible membrane wings over a range of angles of attack for various Reynolds numbers. Design/methodology/approach In this paper, an experimental study on fluid-structure interaction of flexible membrane wings was presented at Reynolds numbers of 2.5 × 104, 5 × 104 and 7.5 × 104. In the experimental studies, flow visualization, velocity and deformation measurements for flexible membrane wings were performed by the smoke-wire technique, multichannel constant temperature anemometer and digital image correlation system, respectively. All experimental results were combined and fluid-structure interaction was discussed. Findings In the flexible wings with the higher aspect ratio, higher vibration modes were noticed because the leading-edge separation was dominant at lower angles of attack. As both Reynolds number and the aspect ratio increased, the maximum membrane deformations increased and the vibrations became visible, secondary vibration modes were observed with growing the leading-edge vortices at moderate angles of attack. Moreover, in the graphs of the spectral analysis of the membrane displacement and the velocity; the dominant frequencies coincided because of the interaction of the flow over the wings and the membrane deformations. Originality/value Unlike available literature, obtained results were presented comparatively using the sketches of the smoke-wire photographs with deformation measurement or turbulence statistics from the velocity measurements. In this study, fluid-structure interaction and leading-edge vortices of membrane wings were investigated in detail with increasing both Reynolds number and the aspect ratio.

The experimental study of aerodynamic characteristics with wing flexibility for hawkmoth-like wings in hovering flight

An experimental study on flapping wing flexibility in hovering flight has been conducted to investigate the wing flexibility for insect-inspired flapping Micro Aerial Vehicles (MAVs). Hawkmoth-like wing models, derived from Manduca sexta, were made of Polycarbonate (PC) sheet with a spanwise length of 200 mm and an aspect ratio of 6.18. For the distributions of wing flexibility, the wing thickness was selected as the design variable: rigid wing (3 mm-thick) and flexible wings (2, 1, 0.8, 0.5, 0.35, 0.2, and 0.1 mm-thick). In the experiment, the wing models were constrained to the symmetrical and sinusoidal flapping motions with sweeping and rotating amplitudes of 120° and 90° in water tank with size of 3.5 m×1.0 m×1.1 m. Aerodynamic force and flow structures for flapping the wing were measured using a six-axis force/torque sensor and a high speed camera with a laser using Digital Particle Image Velocimetry (DPIV). To compare the flow structures of flexible wings with rigid wing, they were captured at the same chordwise cross-section as the rigid wing, 50% of wing length. Based on the experimental results, vortices and aerodynamic force. Consequently, the wing with thickness of 0.8 mm has better aerodynamic characteristics than other wings in hovering flight. This finding will be instrumental in identifying the range of wing flexibilities that improves the aerodynamic efficiency for the development of insect-inspired flapping MAVs.

The experimental study of aerodynamic characteristics with wing flexibility for hawkmoth-like wings in hovering flight

An experimental study on flapping wing flexibility in hovering flight has been conducted to investigate the wing flexibility for insect-inspired flapping Micro Aerial Vehicles (MAVs). Hawkmoth-like wing models, derived from Manduca sexta, were made of Polycarbonate (PC) sheet with a spanwise length of 200 mm and an aspect ratio of 6.18. For the distributions of wing flexibility, the wing thickness was selected as the design variable: rigid wing (3 mm-thick) and flexible wings (2, 1, 0.8, 0.5, 0.35, 0.2, and 0.1 mm-thick). In the experiment, the wing models were constrained to the symmetrical and sinusoidal flapping motions with sweeping and rotating amplitudes of 120° and 90° in water tank with size of 3.5 m×1.0 m×1.1 m. Aerodynamic force and flow structures for flapping the wing were measured using a six-axis force/torque sensor and a high speed camera with a laser using Digital Particle Image Velocimetry (DPIV). To compare the flow structures of flexible wings with rigid wing, they were captured at the same chordwise cross-section as the rigid wing, 50% of wing length. Based on the experimental results, vortices and aerodynamic force. Consequently, the wing with thickness of 0.8 mm has better aerodynamic characteristics than other wings in hovering flight. This finding will be instrumental in identifying the range of wing flexibilities that improves the aerodynamic efficiency for the development of insect-inspired flapping MAVs.