Flying animals possess flexible wings that deform during flight. The chordwise flexibility alters the wing shape, affecting the effective angle of attack and hence the surrounding aerodynamics. However, the effects of spanwise flexibility on the locomotion are inadequately understood. Here, we present a two-way coupled aeroelastic model of a plunging spanwise flexible wing. The aerodynamics is modelled with a two-dimensional, unsteady, incompressible potential flow model, evaluated at each spanwise location of the wing. The two-way coupling is realized by considering the transverse displacement as the effective plunge under the dynamic balance of wing inertia, elastic restoring force and aerodynamic force. The thrust is a result of the competition between the enhancement due to wing deformation and induced drag. The results for a purely plunging spanwise flexible wing agree well with experimental and high-fidelity numerical results from the literature. Our analysis suggests that the wing aspect ratio of the abstracted passerine and goose models corresponds to the optimal aeroelastic response, generating the highest thrust while minimizing the power required to flap the wings. At these optimal aspect ratios, the flapping frequency is near the first spanwise natural frequency of the wing, suggesting that these birds may benefit from the resonance to generate thrust.

No abstract

Fused deposition modeling (FDM), one among the most commonly used additive manufacturing (AM), techniques has been widely used in recent years to produce customized parts with intricate geometries, especially from thermoplastics. This method was limited in its ability to produce parts for industrial applications due to inferior properties and the poor quality of fabricated parts. Hence, researchers are being driven to discover novel materials that are viable for FDM in order to keep up with enormous demand for functional products. In the recent years, it is widely recognized that the emphasis was placed on the bio‐based polymer composite matrices rather than conventional thermoplastics due to its vital advantages that aid in the replacement of synthetic and perilous materials. On this context, this review focuses on the recent advancements in FDM printing with biomaterials. Specifically, attempts have been made to investigate and provide nutshell of 3D printing of current bio‐based nanocomposites which consist of either bio‐derived filler or polymer matrices in order to make 3D printing sustainable. The effect of fillers on the filaments and FDM based products, evolution of novel characteristics of bio nanocomposites, the printability of the developed composites and their development in leading applications were also investigated and summarized.

No abstract