Flapping propulsion of low aspect-ratio wing with morphing trailing edge: Lattice Boltzmann simulation

Structural morphing introduces extra flexibility into flying machines by adding controllable degrees of freedom. Good morphing design requires robust transformable structures, vigorous actuators, and first of all, the strategy of transformation which effectively optimizes the performance. An example of how the morphing trailing edge helps to increase the flapping propulsion is presented in this numerical work. The lattice Boltzmann method is adopted for the incompressible airflow in Reynolds number (Re) of 200–1000. The immersed boundary method is utilized for the interaction of flapping structure and fluid. A three-dimensional model is established for the flapping wing with symmetric airfoil and an aspect ratio of two. The effects of chordwise bending on the propulsive performance including thrust, energy dissipation and efficiency are analyzed. Based on the parametric study, the best morphing scheme is achieved by adjusting the morphing deflection and phase lag in the maximization of either the thrust or the propulsive efficiency. The effects of in-service environment including flight speed, flapping frequency and flapping strength on the morphing scheme with maximum propulsive efficiency (MPE) are furtherly investigated. The simulating results present some design rules for the symmetric morphing wings with deflected camber, which helps the man-made flying robots achieving high performance as their natural counterparts.