Gliding Performance Research Articles

Shape Optimization of Blended-Wing-Body Underwater Gliders Based on Free-Form Deformation

Currently developed underwater gliders can be roughly divided into the two types:traditional configuration and unconventional configuration. As a type of underwater gliders with unconventional configuration, a blended-wing-body (BWB) underwater glider has better fluid dynamic performances because of its unique shape. However, it is difficult to design the shape of the BWB underwater glider that has excellent hydrodynamic performances. Therefore, it is of great significance to optimize its shape, which this paper carries out by using the free-form deformation (FFD). The complete and automatic shape optimization framework is established by jointly using FFD parameterization method, CFD solver, optimization algorithm and mesh deformation method. The framework is used to optimize the shape of a BWB underwater glider. The average drag coefficient of the BWB underwater glider during its sinking and floating in one working period is used as the objective function to optimize its shape, with the volume constraints considered. The optimization results show that the gliding performance of the BWB underwater glider is remarkably enhanced.

Development of a Whale-Shark-Inspired Gliding Robotic Fish With High Maneuverability

In this article, we present the design and implementation of an innovative bioinspired gliding robotic fish and a gliding angle controller. Through mimicking a whale shark, the gliding robotic fish is designed with diversified control surfaces and a streamlined shape instead of the conventional wings with large wingspan aiming at both high maneuverability and distinguished gliding performance. The mechatronic design of the whale-shark-inspired gliding robotic fish is first provided. A dynamic model for gliding motion is established and the hydrodynamic analysis is performed via computational fluid dynamics simulation. The effects of both the deflection of the pectoral fins and the displacement of the movable mass on the gliding motion are analyzed. Then, based on the model and the analysis, a gliding angle control strategy is constructed via the backstepping methodology and the sliding mode methodology, aiming at the robustness of the control system to unknown perturbation. Afterward, a control allocation law is designed and solved by the Newton method. Simulations are conducted to evaluate the effectiveness of the proposed controller. Experiments are also executed to verify the dynamic model and illustrate the remarkable motion capability of the newly developed robot prototype. The results of this article supply clues to the improvement of the locomotive ability for the gliding robotic fish in both shape design and motion control.

Research on Gliding and Discharge Performance of Suspended Injection from Syringe —Effect of Diameter Ratio of Suspending Particle against Needle Hole on Needle Passageability—

Suspended injectable formulations such as sustained-release luteinizing hormone-releasing hormone (LH-RH) analogue loaded in polylactic acid-glycolic acid copolymer (PLGA) particles have been developed on market. Such formulations have potential issue of suspended particles blocking the injection needle. In this research, two types of injectability tests (gliding force, particles discharge) were developed to evaluate the needle passageability of suspended particles. The model suspension was newly designed using mono-dispersed polyethylene (PE) spheres and qualified dispersing fluid to enhance universality and validity of the test. The suspension-filled syringe, in which three sizes of spheres (L, M, S) were dispersed, was vertically fixed and pushed by auto-compression/tensile tester. The gliding force was continuously detected during testing time and all discharged PE spheres were collected and weighed. The combination of sphere (L, M, S) and injection needle were varied to evaluate the effect of the diameter ratio of sphere against needle hole (D/W) on passageability through needle. These injectability tests revealed that the blockage of a needle hole was occasionally observed when the D/W value increased up to 0.35-0.5, which was detected by jump-up of gliding force and drastic decrease of discharged sphere. In addition, the effect of the formulation properties (concentration of suspended spheres, viscosity of dispersing fluid) and operational factor (injection speed) on injectability was also investigated. The results from this study would be valuable in developing suspended injections and predicting injection trouble at the medical scene.

Tunas as a high-performance fish platform for inspiring the next generation of autonomous underwater vehicles

Tunas of the genus Thunnus are a group of high-performance pelagic fishes with many locomotor traits that are convergently shared with other high-performance fish groups. Because of their swimming abilities, tunas continue to be an inspiration for both comparative biomechanics and the design of biomimetic autonomous underwater vehicles (AUVs). Despite the strong history of studies in tuna physiology and current interest in tuna biomechanics and bio-inspired design, we lack quantitative data on the function of many features of tunas. Here we present data on the morphology, behavior, and function of tunas, focusing especially on experimentally examining the function of tuna lateral keels, finlets, and pectoral fins by using simple physical models. We find that both triangular lateral keels and flexible finlets decrease power requirements during swimming, likely by reducing lateral forces and yaw torques (compared to models either without keels or with rectangular keels, and models with stiff finlets or strip fins of equal area, respectively). However, both triangular keels and flexible finlets generate less thrust than other models either without these features or with modified keels or finlets, leading to a tradeoff between power consumption and thrust. In addition, we use micro computed tomography (µCT) to show that the flexible lateral keels possess a lateral line canal, suggesting these keels have a sensory function. The curved and fully-attached base of tuna pectoral fins provides high lift-to-drag ratio at low angles of attack, and generates the highest torques across speeds and angles of attack. Therefore, curved, fully-attached pectoral fins grant both better gliding and maneuvering performance compared to flat or curved, partially-attached designs. We provide both 3D models of tuna morphology derived from µCT scans and conclusions about the performance effects of tuna-like features as a resource for future biological and engineering work for next-generation tuna-inspired AUV designs.

Passive Drag in Young Swimmers: Effects of Body Composition, Morphology and Gliding Position.

The passive drag (Dp) during swimming is affected by the swimmer’s morphology, body density and body position. We evaluated the relative contribution of morphology, body composition, and body position adjustments in the prediction of a swimmer’s Dp. This observational study examined a sample of 60 competitive swimmers (31 male and 29 female) with a mean (±SD) age of 15.4 ± 3.1 years. The swimmer’s Dp was measured using an electro-mechanical towing device and the body composition was assessed using a bioelectrical impedance analyser. Body lengths and circumferences were measured in both the standing position and the simulated streamlined position. Partial correlation analysis with age as a control variable showed that Dp was largely correlated (p < 0.05) with body mass, biacromial- and bi-iliac-breadth, streamline chest circumference and breadth. Body mass, Body Mass Index, chest circumference and streamline chest circumference showed a significant and moderate to strong effect (η2 > 0.55) on Dp. Body mass was the best predictor of Dp explaining 69% of the variability. These results indicate that swimmers with lower Dp values were: (i) slimmer, with lower fat and fat-free mass, (ii) thinner, with lower shoulder breadth, chest circumference, and streamline trunk diameters (iii), shorter, with lower streamline height. These findings can be used for talent identification in swimming, with particular reference to the gliding performance.

Large Hind Wings Enhance Gliding Performance in Ground Effect in a Neotropical Butterfly (Lepidoptera: Nymphalidae)

AbstractNeotropical butterflies in the nymphalid genera Pierella Herrich-Schäffer, 1865 (Lepidoptera, Nymphalidae) and Cithaerias Hübner, 1819 (Lepidoptera, Nymphalidae) are known to glide near ground level, and have a high forewing aspect ratio. The hind wings of Pierella are proportionately larger than those of Cithaerias, suggesting a potential role in gliding flight. We show that Pierella helvina (Hewitson, 1860) (Lepidoptera, Nymphalidae) is capable of gliding for longer periods of time than Cithaerias pireta (Stoll, 1780) (Lepidoptera, Nymphalidae) both in the field and a laboratory setting. Experimental reduction of hind wing area in P. helvina led to a decrease in male gliding performance, and an increase in female wing-beat frequency. We also found that escape velocity decreased in both sexes after hind wing area reduction, but the effect was strongest in females. Although the increased drag associated with large hind wings could be detrimental to gliding flight, the large hind wing area of P. helvina effectively enhances gliding performance in ground effect. This study is the first to investigate the role of hind wings on butterfly gliding performance.

Numerical prediction of aerodynamic performance for a flying fish during gliding flight

Flying fish is a family of unique aerial–aquatic animals, which can both swim in the water and glide over the sea surface. Most previous studies on their aerodynamic characteristics were based on field observations or measurements of their morphometric parameters. In the present study, we consider three different flying fish models, of which the preliminary one mimics the Cypselurus hiraii in the pectoral fin morphology, following a previous wind tunnel experiment (Park and Choi 2010 J. Exp. Biol. 213 3269–79). Their aerodynamic performances are numerically studied by the computational fluid dynamics (CFD) method. The maximum lift force coefficient of 1.03 is reached at the angle of attack , and the maximum lift-to-drag ratio of 4.7 is achieved at . By choosing appropriately the center of gravity, the flying fish model is proved to be longitudinally stable, according to the negative slope of pitching moment profile. Furthermore, we build a three-degrees-of-freedom (3-DOF) dynamic model in the longitudinal plane based on the aerodynamic coefficients obtained in our simulations, to predict its gliding performance. The results show that the flying fish can achieve a distance up to 45.4 m, and reach a height of 13.2 m, indicating an extraordinary gliding performance. Our numerical simulations are consistent with previous experimental results and theoretical prediction, which can be taken as the basis of further research on robotic flying fish.

Gliding Motion Regulation of a Robotic Dolphin Based on a Controllable Fluke

This paper investigates a controllable fluke's regulation effect on the gliding motion of a self-propelled robotic dolphin in both theory and practice. In theory, based on a dynamic model, the gliding equilibria is first analyzed. Through deriving the explicit expressions of the pitch angle, gliding angle, and velocities, we explore how the deflection angle of the controllable fluke changes the gliding performance. Then, aided by these theoretical analyses, a pitch control strategy relying on the fluke is constructed. In simulations, the robotic dolphin is able to track a given pitch angle during gliding, directly through adopting this control strategy to regulate the fluke's deflection angle. Furthermore, extensive gliding experiments in different fluke's deflection angles are carried out. From the statistical data, we further explore the remarkable effects of the controllable fluke on the gliding performance in practice. Besides, the other pitch control experiment is also executed to validate the effectiveness of the proposed control approach. The results of this paper shed light on improving the gliding performance of the robotic dolphin in future mechanical design and gliding control.

Body density of humpback whales (Megaptera novaengliae) in feeding aggregations estimated from hydrodynamic gliding performance.

Many baleen whales undertake annual fasting and feeding cycles, resulting in substantial changes in their body condition, an important factor affecting fitness. As a measure of lipid-store body condition, tissue density of a few deep diving marine mammals has been estimated using a hydrodynamic glide model of drag and buoyancy forces. Here, we applied the method to shallow-diving humpback whales (Megaptera novaeangliae) in North Atlantic and Antarctic feeding aggregations. High-resolution 3-axis acceleration, depth and speed data were collected from 24 whales. Measured values of acceleration during 5 s glides were fitted to a hydrodynamic glide model to estimate unknown parameters (tissue density, drag term and diving gas volume) in a Bayesian framework. Estimated species-average tissue density (1031.6 ± 2.1 kg m-3, ±95% credible interval) indicates that humpback whale tissue is typically negatively buoyant although there was a large inter-individual variation ranging from 1025.2 to 1043.1 kg m-3. The precision of the individual estimates was substantially finer than the variation across different individual whales, demonstrating a progressive decrease in tissue density throughout the feeding season and comparably high lipid-store in pregnant females. The drag term (CDAm-1) was estimated to be relatively high, indicating a large effect of lift-related induced drag for humpback whales. Our results show that tissue density of shallow diving baleen whales can be estimated using the hydrodynamic gliding model, although cross-validation with other techniques is an essential next step. This method for estimating body condition is likely to be broadly applicable across a range of aquatic animals and environments.

Research on Gliding Aerodynamic Effect of Deformable Membrane Wing for a Robotic Flying Squirrel

Inspired by creatures with membrane to obtain ultra-high gliding ability, this paper presents a robotic flying squirrel (a novel gliding robot) characterized as membrane wing and active membrane deformation. For deep understanding of membrane wing and gliding mechanism from a robotic system perspective, a simplified blocking aerodynamic model of the deformable membrane wing and CFD simulation are finished. In addition, a physical prototype is developed and wind tunnel experiments are carried out. The results show that the proposed membrane wing is able to support the gliding action of the robot. Meanwhile, factors including geometry characteristics, material property and wind speed are considered in the experiments to investigate the aerodynamic effects of the deformable membrane wing deeply. As a typical characteristic of robotic flying squirrel, deformation modes of the membrane wing not only affect the gliding ability, but also directly determine the effects of the posture adjustment. Moreover, different deformation modes of membrane wing are illustrated to explore the possible effects of active membrane deformation on the gliding performance. The results indicate that the deformation modes have a significant impact on posture adjustment, which reinforces the rationality of flying squirrel’s gliding strategy and provides valuable information on prototype optimal design and control strategy in the actual gliding process.

Development of Injectable Sustained-Release PLGA Depot Formulation with Highly Dispersibility and Excellent Gliding Performance

Development of Injectable Sustained-Release PLGA Depot Formulation with Highly Dispersibility and Excellent Gliding Performance

Development of Injectable Sustained-Release PLGA Depot Formulation with Excellent Gliding Performance

Development of Injectable Sustained-Release PLGA Depot Formulation with Excellent Gliding Performance

Gliding performance of 3-D corrugated dragonfly wing with spanwise variation

Computational fluid dynamics (CFD) analyses are conducted to evaluate the gliding performance of a three-dimensional (3-D) corrugated wing while considering variations in the corrugation pattern across the wing span. Comparisons with the smoothly profiled counterpart assess the overall effect of wing corrugation on the gliding performance of the 3-D dragonfly wing, with primary focus on the effect of three-dimensionality as compared to the 2-D model.Earlier simulations of both 2-D and 3-D gliding corrugated wings showed oscillations on lift and drag, while in nature, such force fluctuation would be undesirable and unrealistic. In contrast, no non-realistic fluctuations are present in this simulation. The feature included here, which has been neglected in the earlier studies, namely the variation of leading edge orientation along the wing span, is the crucial detail for preventing such non-realistic oscillations.Furthermore, strong spanwise flow occurs in the 3-D corrugated wing used in this study, which earlier models have been incapable to capture.

Does ‘gliding while gravid’ explain Rensch's rule in flying lizards?

Among species with sexual size dimorphism (SSD), taxa in which males are the larger sex have increasing SSD with increasing body size, whereas in taxa in which females are the larger sex, SSD decreases with body size: Rensch's rule. We show in flying lizards, a clade of mostly female-larger species, that SSD increases with body size, a pattern similar to that in clades with male-biased SSD or more evenly mixed SSD. The observed pattern in Draco appears due to SSD increasing with evolutionary changes in male body size; specifically divergence in body size among species that are in sympatric congeneric assemblages. We suggest that increasing body size, resulting in decreased gliding performance, reduces the relative gliding cost of gravidity in females, and switches sexual selection in males away from a small-male, gliding advantage and toward selection on large size and fighting ability as seen in many other lizards. Thus, selection for large females is likely greater than selection for large males at the smaller end of the body size continuum, whereas this relationship reverses for species at the larger end of the continuum. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 270–282.

Miniature Underwater Glider: Design and Experimental Results

The concept of gliding robotic fish combines gliding and fin-actuation mechanisms to realize energy-efficient locomotion and high maneuverability. Such robots hold strong promise for mobile sensing in versatile aquatic environments. In this paper, we present the design and implementation of a miniature glider, a key enabling component for gliding robotic fish. The steady-state glide equation is first presented and then solved numerically for given net-buoyancy and movable mass displacement. Scaling analysis is conducted to understand the tradeoff between the glide performance and energy cost. Comprehensive design for the glider is provided. Experimentation and modeling analysis are further conducted to investigate the impacts of movable mass displacement, net buoyancy, and wing size on the gliding performance.

UFO cross-section gives snakes a lift

If you're afraid of snakes, you're really not going to like the next bit: some snakes can fly. It sounds like a frightful nightmare, but for Jake Socha, the discovery was the start of a fascinating odyssey to learn how an animal that looks as unaerodynamic as a snake can glide as much as 30 m from a tall tree. Socha describes the snakes as ‘slithering’ in an S-shape through the air as they descend through the Southeast Asian rainforest: ‘They look like they are swimming’, he adds. But what keeps the reptiles aloft? ‘They turn their whole body into one aerodynamic surface’, explains Socha – who has spent much of his career unpicking details of the snake's flying style – and has now turned his attention to the animal's intriguing body shape to find out how they generate the lift they require to remain airborne (p. 382).According to Socha, the snakes flex their ribs as they launch to stretch and flatten the body to change their profile from a circle into an arched semi-circle: ‘It looks like someone's version of a UFO’, laughs Socha, adding that as aerofoils go it's an unconventional shape. To get to grips with the aerodynamic forces generated by the snake's body, Socha and his colleagues, Daniel Holden, Nicholas Cardwell and Pavlos Vlachos, used a 3D printer to produce a rod with the same UFO cross-section as the snake's body before placing it across a tank filled with water that flowed over the snake-shaped bar. Socha explains that although water is much denser and stickier than air, you can precisely recreate the air conditions experienced as the snakes fly by flowing the water over the model at a specific range of speeds.Tilting the snake model at angles (of attack) ranging from −10 to 60 deg as the water flowed over it at speeds ranging from 20 to 50 cm s−1, the team measured the lift and drag forces pulling on the model and saw that at most angles the animal's unusual body shape generated sufficient lift to account for some of the snake's impressive gliding performance. But when the team tilted the model at 35 deg, there was a massive spike in the lift generated by water flowing at higher speeds. More surprisingly, when the model was held level with the flow, instead of generating upward lift, the fluid pushed the rod down. And when the team visualised the turbulent water flowing around the model with microscopic reflective beads, they could clearly see a spinning vortex sitting beneath the untilted snake shape, sucking it down: which may not be that crazy, according to Socha. He says, ‘Maybe the snake does hold part of its body flat at some point, using it as a mechanism for control’, explaining that twisting the body while airborne could allow the snakes to fine tune the forces on their bodies for precise flight control.But Socha adds that there is much more to the snake's impressive glide than just its unusual body shape. ‘If you make a rough estimate of the lift to drag ratio for the real animal, it appears to do better than what we got from this study. So even though this shape produced more lift than we were expecting, it doesn't get us the glide performance that snakes can attain, giving us a hint that there is something in what the animal is doing aerodynamically that is not captured by the cross-sectional shape alone’ – which is the next part of the problem that Socha and his team hope to crack.

Aerodynamics of the flying snake Chrysopelea paradisi: how a bluff body cross-sectional shape contributes to gliding performance

A prominent feature of gliding flight in snakes of the genus Chrysopelea is the unique cross-sectional shape of the body, which acts as the lifting surface in the absence of wings. When gliding, the flying snake Chrysopelea paradisi morphs its circular cross-section into a triangular shape by splaying its ribs and flattening its body in the dorsoventral axis, forming a geometry with fore-aft symmetry and a thick profile. Here, we aimed to understand the aerodynamic properties of the snake's cross-sectional shape to determine its contribution to gliding at low Reynolds numbers. We used a straight physical model in a water tunnel to isolate the effects of 2D shape, analogously to studying the profile of an airfoil of a more typical flyer. Force measurements and time-resolved (TR) digital particle image velocimetry (DPIV) were used to determine lift and drag coefficients, wake dynamics and vortex-shedding characteristics of the shape across a behaviorally relevant range of Reynolds numbers and angles of attack. The snake's cross-sectional shape produced a maximum lift coefficient of 1.9 and maximum lift-to-drag ratio of 2.7, maintained increases in lift up to 35 deg, and exhibited two distinctly different vortex-shedding modes. Within the measured Reynolds number regime (Re=3000-15,000), this geometry generated significantly larger maximum lift coefficients than many other shapes including bluff bodies, thick airfoils, symmetric airfoils and circular arc airfoils. In addition, the snake's shape exhibited a gentle stall region that maintained relatively high lift production even up to the highest angle of attack tested (60 deg). Overall, the cross-sectional geometry of the flying snake demonstrated robust aerodynamic behavior by maintaining significant lift production and near-maximum lift-to-drag ratios over a wide range of parameters. These aerodynamic characteristics help to explain how the snake can glide at steep angles and over a wide range of angles of attack, but more complex models that account for 3D effects and the dynamic movements of aerial undulation are required to fully understand the gliding performance of flying snakes.

Gliding performance in the yellow-bellied glider in low-canopy forest

Knowledge of the gliding performance of gliding mammals is fundamental to understanding how these species have adapted to their environment and is of increasing relevance to their conservation. I describe aspects of the glide performance of the yellow-bellied glider (Petaurus australis) based on 22 glides of 17 individuals within 20–30-m-high open forest in western Victoria. Gliders launched into a glide from a horizontal branch that was, on average, 2.8 m below the top of a tree, 5.2 m out from the main trunk and 18.5 m above the ground. Gliders landed on the trunks of trees 5.8 m above the ground. The mean horizontal glide distance was 25.2 ± 1.5 m (s.e.) (range = 19–45 m), producing a glide ratio (horizontal distance/height dropped) of 2.0 and a glide angle of 27.3°. These values are similar to those reported for other gliding petaurids in low-canopy forest. This knowledge should be used to guide the management of habitat connectivity for yellow-bellied gliders.

Gliding-induced Ski Vibrations: Approaching Proper Modeling

Phenomena of the ski and snow boards vibrations generated in gliding are known for years. In the cross country and jumping skis such vibrations are not very obvious but can play quite positive role reducing the effective gliding friction. The research into the nature of friction-induced vibrations and the factors influencing their frequencies and magnitudes is driven by the desire to control them for improving ski gliding performance. Significant amount of experimental data acquired in the field and laboratory studies is already available making it possible to formulate certain qualitative conclusions. But so far it did not bring comprehensive understanding of the phenomenon and specifically of the mechanisms controlling such vibrations. Modeling is one of the potent tools allowing to deeper understand experimentally studied phenomena and it can provide much stronger quantitative prediction capacity. Present paper discusses possible approaches to modeling of the phenomenon and first results of constructing simplified models.

공대지 폭탄용 유도키트 시험

Tests and evaluations following the U.S. MIL-HDBK/STANDARD were successfully conducted to assure the performance of the air-to-surface guidance kit which was developed first in Korea. Various ground tests confirmed the operation capability and reliability of the guidance kit, and flight tests proved very good mid-range gliding performance and accuracy of the gliding bomb which was a general purpose bomb with the guidance kit.