Two-dimensional computational fluid dynamics (CFD) is applied to better understand the effects of wing cross-sectional morphology on flow field and force production. This study investigates the influence of wing cross-section on insect scale flapping flight performance, for the first time, using a morphologically representative model of a bee (Bombus pensylvanicus) wing. The bee wing cross-section was determined using a micro-computed tomography scanner. The results of the bee wing are compared with flat and elliptical cross-sections, representative of those used in modern literature, to determine the impact of profile variation on aerodynamic performance. The flow field surrounding each cross-section and the resulting forces are resolved using CFD for a flight speed range of 1 to 5 m/s. A significant variation in vortex formation is found when comparing the ellipse and flat plate with the true bee wing. During the upstroke, the bee and approximate wing cross-sections have a much shorter wake structure than the flat plate or ellipse. During the downstroke, the flat plate and elliptical cross-sections generate a single leading edge vortex, while the approximate and bee wings generate numerous, smaller structures that are shed throughout the stroke. Comparing the instantaneous aerodynamic forces on the wing, the ellipse and flat plate sections deviate progressively with velocity from the true bee wing. Based on the present findings, a simplified cross-section of an insect wing can misrepresent the flow field and force production. We present the first aerodynamic study using a true insect wing cross-section and show that the wing corrugation increases the leading edge vortex formation frequency for a given set of kinematics.

Despite recent interests in complex fluid–structure interaction (FSI) problems, little work has been conducted to establish baseline multidisciplinary FSI modeling capabilities for research and commercial activities across computational platforms. The current work investigates the fluid modules of contemporary FSI methodologies by solving a purely fluid problem at low Reynolds numbers to improve understanding of the fluid dynamic capabilities of each solver. By incorporating both monolithic and partitioned solvers, a holistic comparison of computational accuracy and time-expense is presented between lattice-Boltzmann methods (LBM), coupled Lagrangian–Eulerian (CLE), and smoothed particle hydrodynamics (SPH). These explicit methodologies are assessed using the classical square lid-driven cavity for low Reynolds numbers (100–3200) and are validated against an implicit Navier–Stokes solution in addition to established literature. From an investigation of numerical error associated with grid resolution, the Navier–Stokes solution, LBM, and CLE were all relatively mesh independent. However, SPH displayed a significant dependence on grid resolution and required the greatest computational expense. Throughout the range of Reynolds numbers investigated, both LBM and CLE closely matched the Navier–Stokes solution and literature, with the average velocity profile error along the generated cavity centerlines at 1% and 4%, respectively, at Re = 3200. SPH did not provide accurate results whereby the average error for the centerline velocity profiles was 31% for Re = 3200, and the methodology was unable to represent vorticity in the cavity corners. Results indicate that while both LBM and CLE show promise for modeling complex fluid flows, commercial implementations of SPH demand further development.

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Insects, sustaining flight at low Reynolds numbers (500<Re<10,000), fly utilizing mechanically simple kinematics (3 degrees of freedom) at an extremely high flap frequency (150–200 Hz), resulting in a complicated vortical fluid field. These flight characteristics result in some of the most agile and maneuverable flight capabilities in the animal kingdom and are considered to be far superior to fixed wing flight, such as aircraft. Bees are of particular interest because of the utilization of humuli to attach their front and hind wings together during flight. A Cartesian-based adaptive meshing implementation of the Lattice-Boltzmann Method is utilized to resolve the complex flow field generated during insect flight and is verified against experimental and computational results present in the literature in two dimensions. The Lattice-Boltzmann Method was found to agree well in both qualitative and quantitative comparisons with both two-dimensional computational and three-dimensional experimental results.

Underwater fish of the class Batoidea, commonly known as rays and skates, use large cartilaginous wings to propel themselves through the water. This motion is of great interest in bioinspired robotics as an alternative propulsion mechanism. Prior research has focused primarily on the oscillating kinematics used by some species which resembles flapping; this study investigates undulatory motion induced by propagating sinusoidal waves along the fin. An analytical model of undulatory kinematics is presented and correlated with biological literature, and the model is then simulated via unsteady computational fluid dynamics and multiparticle collision dynamics. A bioinspired robot, Batoid Underwater Robotics Testbed (BURT), was developed to test the kinematics of the undulating propulsion system proposed. Finally, BURT was utilized as a platform to investigate engineering challenges in undulating Batoid robotics.