Nadezhda Lapina

Bio: Nadezhda Lapina is an academic researcher from Moscow State University. The author has contributed to research in topics: Wing & Aerodynamic force. The author has an hindex of 1, co-authored 2 publications receiving 11 citations.

Aerodynamic performance of a bristled wing of a very small insect

Abstract: Aerodynamic force generation capacity of the wing of a miniature beetle Paratuposa placentis is evaluated using a combined experimental and numerical approach. The wing has a peculiar shape reminiscent of a bird feather, often found in the smallest insects. Aerodynamic force coefficients are determined from a dynamically scaled force measurement experiment with rotating bristled and membrane wing models in a glycerin tank. Subsequently, they are used as numerical validation data for computational fluid dynamics simulations using an adaptive Navier–Stokes solver. The latter provides access to important flow properties such as leakiness and permeability. It is found that, in the considered biologically relevant regimes, the bristled wing functions as a less than $$50\%$$ leaky paddle, and it produces between 66 and $$96\%$$ of the aerodynamic drag force of an equivalent membrane wing. The discrepancy increases with increasing Reynolds number. It is shown that about half of the aerodynamic normal force exerted on a bristled wing is due to viscous shear stress. The paddling effectiveness factor is proposed as a measure of aerodynamic efficiency.

A novel flight style allowing the smallest featherwing beetles to excel

Abstract: Flight speed generally correlates positively with animal body size [1]. Surprisingly, miniature featherwing beetles can fly at speeds and accelerations of insects three times as large [2]. We show here that this performance results from a previously unknown type of wing motion. Our experiment combines three-dimensional reconstructions of morphology and kinematics in one of the smallest insects, Paratuposa placentis (body length 395 μm). The flapping bristled wing follows a pronounced figure-eight loop that consists of subperpendicular up and down strokes followed by claps at stroke reversals, above and below the body. Computational analyses suggest a functional decomposition of the flapping cycle in two power half strokes producing a large upward force and two down-dragging recovery half strokes. In contrast to heavier membranous wings, the motion of bristled wings of the same size requires little inertial power. Muscle mechanical power requirements thus remain positive throughout the wing beat cycle, making elastic energy storage obsolete. This novel flight style evolved during miniaturization may compensate for costs associated with air viscosity and helps explain how extremely small insects preserved superb aerial performance during miniaturization. Incorporating this flight style in artificial flappers is a challenge for designers of micro aerial vehicles.

Novel flight style and light wings boost flight performance of tiny beetles

Abstract: Flight speed is positively correlated with body size in animals1. However, miniature featherwing beetles can fly at speeds and accelerations of insects three times their size2. Here we show that this performance results from a reduced wing mass and a previously unknown type of wing-motion cycle. Our experiment combines three-dimensional reconstructions of morphology and kinematics in one of the smallest insects, the beetle Paratuposa placentis (body length 395 μm). The flapping bristled wings follow a pronounced figure-of-eight loop that consists of subperpendicular up and down strokes followed by claps at stroke reversals above and below the body. The elytra act as inertial brakes that prevent excessive body oscillation. Computational analyses suggest functional decomposition of the wingbeat cycle into two power half strokes, which produce a large upward force, and two down-dragging recovery half strokes. In contrast to heavier membranous wings, the motion of bristled wings of the same size requires little inertial power. Muscle mechanical power requirements thus remain positive throughout the wingbeat cycle, making elastic energy storage obsolete. These adaptations help to explain how extremely small insects have preserved good aerial performance during miniaturization, one of the factors of their evolutionary success.

Aerodynamic interaction of bristled wing pairs in fling

Abstract: Tiny flying insects of body lengths under 2 mm use the “clap-and-fling” mechanism with bristled wings for lift augmentation and drag reduction at a chord-based Reynolds number (Re) on O ( 10 ). We examine the wing–wing interaction of bristled wings in fling at Re = 10 as a function of initial inter-wing spacing (δ) and degree of overlap between rotation and linear translation. A dynamically scaled robotic platform was used to drive physical models of bristled wing pairs with the following kinematics (all angles relative to vertical): (1) rotation about the trailing edge to angle θr, (2) linear translation at a fixed angle (θt), and (3) combined rotation and linear translation. The results show that (1) the cycle-averaged drag coefficient decreased with increasing θr and θt and (2) decreasing δ increased the lift coefficient owing to increased asymmetry in the circulation of leading and trailing edge vortices. A new dimensionless index, reverse flow capacity (RFC), was used to quantify the maximum possible ability of a bristled wing to leak the fluid through the bristles. The drag coefficients were larger for smaller δ and θr despite larger RFC, likely due to the blockage of inter-bristle flow by shear layers around the bristles. Smaller δ during early rotation resulted in the formation of strong positive pressure distribution between the wings, resulting in an increased drag force. The positive pressure region weakened with increasing θr, which in turn reduced the drag force. Tiny insects have been previously reported to use large rotational angles in fling, and our findings suggest that a plausible reason is to reduce drag forces.

Extraordinary flight performance of the smallest beetles.

Abstract: Size is a key to locomotion. In insects, miniaturization leads to fundamental changes in wing structure and kinematics, making the study of flight in the smallest species important for basic biology and physics, and, potentially, for applied disciplines. However, the flight efficiency of miniature insects has never been studied, and their speed and maneuverability have remained unknown. We report a comparative study of speeds and accelerations in the smallest free-living insects, featherwing beetles (Coleoptera: Ptiliidae), and in larger representatives of related groups of Staphylinoidea. Our results show that the average and maximum flight speeds of larger ptiliids are extraordinarily high and comparable to those of staphylinids that have bodies 3 times as long. This is one of the few known exceptions to the "Great Flight Diagram," according to which the flight speed of smaller organisms is generally lower than that of larger ones. The horizontal acceleration values recorded in Ptiliidae are almost twice as high as even in Silphidae, which are more than an order of magnitude larger. High absolute and record-breaking relative flight characteristics suggest that the unique morphology and kinematics of the ptiliid wings are effective adaptations to flight at low Reynolds numbers. These results are important for understanding the evolution of body size and flight in insects and pose a challenge to designers of miniature biomorphic aircraft.

Aerodynamic interaction of bristled wing pairs in fling

Abstract: Tiny flying insects of body lengths under 2 mm use the `clap-and-fling' mechanism with bristled wings for lift augmentation and drag reduction at chord-based Reynolds number ($Re$) on $\mathcal{O}$(10). We examine wing-wing interaction of bristled wings in fling at $Re$=10, as a function of initial inter-wing spacing ($\delta$) and degree of overlap between rotation and linear translation. A dynamically scaled robotic platform was used to drive physical models of bristled wing pairs with the following kinematics (all angles relative to vertical): 1) rotation about the trailing edge to angle $\theta_\text{r}$; 2) linear translation at a fixed angle ($\theta_\text{t}$); and 3) combined rotation and linear translation. The results show that: 1) cycle-averaged drag coefficient decreased with increasing $\theta_\text{r}$ and $\theta_\text{t}$; and 2) decreasing $\delta$ increased the lift coefficient owing to increased asymmetry in circulation of leading and trailing edge vortices. A new dimensionless index, reverse flow capacity (RFC), was used to quantify the maximum possible ability of a bristled wing to leak fluid through the bristles. Drag coefficients were larger for smaller $\delta$ and $\theta_\text{r}$ despite larger RFC, likely due to blockage of inter-bristle flow by shear layers around the bristles. Smaller $\delta$ during early rotation resulted in formation of strong positive pressure distribution between the wings, resulting in increased drag force. The positive pressure region weakened with increasing $\theta_\text{r}$, which in turn reduced drag force. Tiny insects have been reported to use large rotational angles in fling, and our findings suggest that a plausible reason is to reduce drag forces.

Flight efficiency is a key to diverse wing morphologies in small insects.

Abstract: Insect wings are hybrid structures that are typically composed of veins and solid membranes. In some of the smallest flying insects, however, the wing membrane is replaced by hair-like bristles attached to a solid root. Bristles and membranous wing surfaces coexist in small but not in large insect species. There is no satisfying explanation for this finding as aerodynamic force production is always smaller in bristled than solid wings. This computational study suggests that the diversity of wing structure in small insects results from aerodynamic efficiency rather than from the requirements to produce elevated forces for flight. The tested wings vary from fully membranous to sparsely bristled and were flapped around a wing root with lift- and drag-based wing kinematic patterns and at different Reynolds numbers (Re). The results show that the decrease in aerodynamic efficiency with decreasing surface solidity is significantly smaller at Re = 4 than Re = 57. A replacement of wing membrane by bristles thus causes less change in energetic costs for flight in small compared to large insects. As a consequence, small insects may fly with bristled and solid wing surfaces at similar efficacy, while larger insects must use membranous wings for an efficient production of flight forces. The above findings are significant for the biological fitness and dispersal of insects that fly at elevated energy expenditures.