Low Wing Research Articles

Forest stratification shapes allometry and flight morphology of tropical butterflies

Studies of altitudinal and latitudinal gradients have identified links between the evolution of insect flight morphology, landscape structure and microclimate. Although lowland tropical rainforests offer steeper shifts in conditions between the canopy and the understorey, this vertical gradient has received far less attention. Butterflies, because of their great phenotypic plasticity, are excellent models to study selection pressures that mould flight morphology. We examined data collected over 5 years on 64 Nymphalidae butterflies in the Ecuadorian Chocó rainforest. We used phylogenetic methods to control for similarity resulting from common ancestry, and explore the relationships between species stratification and flight morphology. We hypothesized that species should show morphological adaptations related to differing micro-environments, associated with canopy and understorey. We found that butterfly species living in each stratum presented significantly different allometric slopes. Furthermore, a preference for the canopy was significantly associated with low wing area to thoracic volume ratios and high wing aspect ratios, but not with the relative distance to the wing centroid, consistent with extended use of fast flapping flight for canopy butterflies and slow gliding for the understorey. Our results suggest that microclimate differences in vertical gradients are a key factor in generating morphological diversity in flying insects.

Novel multi-zone self-heated composites tool for out-of-autoclave aerospace components manufacturing

Abstract In this paper, a multi-zone self-heating composite tool is developed to manufacture out-of-autoclave complex and high-quality business jet lower wing stiffened composite panel. Autoclave manufacturing is regarded as a benchmark for manufacturing aerospace-grade composite parts. However, high accruing operational costs limit production rates thereby not being practical for smaller-scale companies. Therefore, significant work towards developing out-of-autoclave manufacturing is underway. In this study, a production line tool is developed with embedded heating fabric that controls temperature at the desired zones, replacing the need for autoclave cure. It investigates and identifies the optimal design parameters of the self-heating setup namely the placement of the heating fabric, zones, thermal management system, temperature distribution, heating rate and thermal performance using a thermal FEA model. The associated thermal characterisation of the tooling material and the part are measured for accurate simulation results. The design developed in this study will be used as production guideline for the actual tool.

Predictive modelling of drop ejection from damped, dampened wings by machine learning.

The high frequency, low amplitude wing motion that mosquitoes employ to dry their wings inspires the study of drop release from millimetric, forced cantilevers. Our mimicking system, a 10-mm polytetrafluoroethylene cantilever driven through ±1 mm base amplitude at 85 Hz, displaces drops via three principal ejection modes: normal-to-cantilever ejection, sliding and pinch-off. The selection of system variables such as cantilever stiffness, drop location, drop size and wetting properties modulates the appearance of a particular ejection mode. However, the large number of system features complicate the prediction of modal occurrence, and the transition between complete and partial liquid removal. In this study, we build two predictive models based on ensemble learning that predict the ejection mode, a classification problem, and minimum inertial force required to eject a drop from the cantilever, a regression problem. For ejection mode prediction, we achieve an accuracy of 85% using a bagging classifier. For inertial force prediction, the lowest root mean squared error achieved is 0.037 using an ensemble learning regression model. Results also show that ejection time and cantilever wetting properties are the dominant features for predicting both ejection mode and the minimum inertial force required to eject a drop.

Taxonomic and Functional Diversity and Composition of Bats in a Regenerating Neotropical Dry Forest

This study evaluated the response of bat communities, from a taxonomic and functional perspective, to variation in the vegetation and landscape attributes produced by anthropogenic activities. We characterized the following: (1) the community of phyllostomid and mormoopid bats associated with the initial successional stages of a tropical dry forest, (2) the response of these communities to the variation in the attributes of the vegetation and the landscape, and (3) how the seasonality modulates such response. This allowed us to identify potential mechanisms underlying the response of bat communities to human disturbance. Our results showed that the species negatively affected by the anthropoghenic disturbance are those with greater body mass, larger nose-leaves, or a lower wing aspect ratio and relative wing loading, which perform low-speed flights and have high maneuverability and, potentially, a high directionality in their emissions. We also detected a greater sensitivity of bats to changes in the landscape attributes regarding the riparian than the dry forest, and that the effect of anthropic transformation on bats was intensified during the dry season. Then, the continued loss of the original vegetation can lead to a loss of certain groups of bat species in neotropical landscapes, reducing the resilience of the system.

Excitation-dependent enhancement and quenching of the 1.54 μm emission from Er3+ ions in dichroic Cu nanocomposite glass

The 1.54 μm emission of Er3+ ions embedded in a dichroic Cu nanocomposite glass is shown to be either quenched or enhanced depending on the excitation wavelength. The synthesized material consisted of an aluminphosphate matrix co-doped with Cu and Er as prepared by thermal processing, and characterized by optical absorption and photoluminescence (PL) spectroscopy including an assessment of decay dynamics. The extinction spectrum presented a broad surface plasmon resonance (SPR) band for Cu nanoparticles (NPs) around 588 nm, while the glass appeared to scatter red light but transmit blue, i.e. exhibiting dichroism. Interestingly, the PL obtained for the 4I13/2 → 4I15/2 emission around 1.54 μm was enhanced under the excitation of the 4I15/2 → 4F9/2 transition at 650 nm, which turned out to be located toward the low energy wing of the SPR of Cu NPs. About a 12% PL boost was estimated relative to a merely Er3+-doped reference. Conversely, a PL quenching effect was manifested for resonant Er3+ excitations (e.g. 4I15/2 → 2H11/2 transition at 520 nm) overlaid with the 3d → 4sp interband transitions absorption in copper. It is suggested that favorable conditions for the PL enhancement are achieved for when the excitation of Er3+ ions can benefit from light scattering by plasmonic Cu particles, while an excitation energy transfer from Er3+ to Cu NPs via interband transitions leads to the quenching.

Beak morphological and growth characteristic of Sthenoteuthis oualaniensis in the northwest Indian Ocean in winter and spring

Beak is one of the most important hard tissues of cephalopods, and thus is widely used in the study of cephalopod fisheries ecology and fishery resource assessment. With 1009 Sthenoteuthis oualaniensis samples collected by Chinese light falling-net fishery during February to May in the northwest Indian Ocean, we examined the morphologic and growth characteristics of beak. Results of the principal component analysis showed that the upper hood length (UHL), the upper crest length (UCL), the upper lateral wall length (ULWL), the lower crest length (LCL), the lower wing length (LWL) and the lower lateral wall length (LLWL) could be used as the morphological cha-racteristic parameters to examine the morphological changes of the beak. Results of the analysis of covariance (ANCOVA) showed that there were significant differences in the relationships between all of the morphological characteristic parameters and mantel length (ML) for males and females except UCL. There were significant differences in the relationships between all of the morphological characteristic parameters and body weight (BW) for males and females. The relationships between LCL, UCL and ML were optimally described by the linear functions. Power functions were best for UHL, LWL and linear functions were best for ULWL, LLWL for females. The relationships between ULWL and ML were optimally described by power functions, while the logarithm functions were best for UHL, LLWL and LWL for males. The relationships between all of the morphological characteristic parameters and BW were optimally described by the power functions for females, while the logarithm functions for males except the power function for ULWL. Our results provided scientific basis for the research of the fisheries ecology and stock assessment for S. oualaniensis.

Experimental analysis of aircraft directional control effectiveness

Aircraft directional control effectiveness is analyzed through experiments in wind tunnel. Control surfaces on low aspect ratio lifting surfaces exhibit different lifting capabilities compared to those with high aspect ratio. Such behavior must be carefully considered in the preliminary design phase to avoid any overestimation in size, weight, costs and emissions. Traditional sizing methodologies are based on coupling the effects of the wing planform (e.g. aspect ratio) at low angles of control surface deflection with the effects of wing section (e.g. chord ratio) evaluated on section data in the full range of control surface deflection, so that the non-linear aerodynamics is inherited from 2D data, completely neglecting the different aerodynamic behavior of a low aspect ratio wing at high angles of deflection. To fill this gap, an experimental wind tunnel test campaign on a generic regional turboprop aircraft model with a modular vertical tail with rudder has been performed. Results indicate that the aircraft design methodologies present in public literature underestimate the control surface effectiveness at high angle of deflections by 15% to 25%, leading to an average overestimation of control surface size.

Development of a Morphing Landing Gear Composite Door for High Speed Compound Rotorcraft

In the framework of fast rotorcraft, smoothness and flushness of external aerodynamic surfaces present challenges for high-speed conditions, where aerodynamics is the driver of helicopter performance. For AIRBUS-RACER helicopter the main landing gear trap doors are parts of the lower wing skins (in retracted configuration) affecting helicopter performance by minimizing the drag. Flushness requirements must not be in contrast with the functionally of the Landing gear system that must open and close the doors during the landing gear retraction-extension phases at moderately low velocity. To manage these goals, a novel design logic has been identified to support the trap doors development phase. The identified way to proceed needs of relevant numerical method and tool as well. This method is aimed at identifying the main landing gear composite compartment doors in pre-shaped configuration to match the smoothness and door-stopper engagements over each aerodynamic conditions. The authors propose a detailed non-linear Finite Element method, based on MSC Nastran (MSC Software, Newport Beach, US) SOL-400 solver in which the structure is modelled with deformable contact bodies in a multiple load step sequence, open door condition and pre-shaped, deformed under actuator pre-load, under flight load conditions. The method includes the entire pre-stressed field due to the preload and the actual door stiffness, considering the achieved large displacement to verify the most representative strain field during loads application. The paper defines a robust methodology to predict the deformation and ensure the most appropriate door “pre-bow” and pre-load, in order to achieve the desiderated structural shape that matches aerodynamic requirements. The main result is the identification of a pre-shaped doors configuration for the Airbus RACER Fast Rotorcraft.

Design, operation and analysis of wind-assisted cargo ships

This study presents a novel approach to analytically capture aero- and hydrodynamic interaction effects on wind-assisted ships. Low aspect ratio wing theory is applied and modified to be used for the prediction of lift and drag forces of hulls sailing at drift angles. Aerodynamic interaction effects are captured by analytically solving the Navier-Stokes equation for incompressible, potential flow. The developed methods are implemented to a 4 degrees-of-freedom performance prediction model called “ShipCLEAN”, including a newly developed method for rpm control of Flettner rotors on a ship to maximize fuel savings. The accuracy of the model is proven by model- and full-scale verification. To present the variability of the model, two case study ships, a tanker and a RoRo, are equipped with a total of 11 different arrangements of Flettner rotors. The fuel savings and payback times are assessed using realistic weather from ships traveling on a Pacific Ocean route (tanker) and Baltic Sea route (RoRo). The results verify the importance of using a 4 degrees-of-freedom ship performance model, aero- and hydrodynamic interaction and the importance of controlling the rpm of each rotor individually. Fuel savings of 30% are achieved for the tanker, and 14% are achieved for the RoRo.

Crack Detection Zones: Computation and Validation.

During the development of aerospace structures, typically many fatigue tests are conducted. During these tests, much effort is put into inspections in order to detect the onset of failure before complete failure. Strain sensor data may be used to reduce inspection effort. For this, a sufficient number of sensors need to be positioned appropriately to collect the relevant data. In order to minimize cost and effort associated with sensor positioning, the method proposed here aims at minimizing the number of necessary strain sensors while positioning them such that fatigue-induced damage can still be detected before complete failure. A suitable detection criterion is established as the relative change of strain amplitudes under cyclic loading. Then, the space of all possible crack lengths is explored. The regions where the detection criterion is satisfied before complete failure occurs are assembled into so-called detection zones. One sensor in this zone is sufficient to detect criticality. The applicability of the approach is demonstrated on a representative airplane structure that resembles a lower wing section. The method shows that four fatigue critical spots can be monitored using only one strain sensor in a non-intuitive position. Furthermore, we discuss two different strain measures for crack detection. The results of this paper can be used for reliable structural health monitoring using a minimum number of sensors.

First explorations: ontogeny of central place foraging directions in two tropical seabirds

Abstract A widespread hypothesis for the ontogeny of behavior and decision-making is the early-exploration-later-canalization hypothesis. It postulates that juveniles are more exploratory and adults more consistent in their behavior. In addition, it is often assumed that naïve juveniles could overcome the costs of individual experience building by copying more the decisions of others than adults (early-conformism-later-self-defining hypothesis). Here, we compare the central place foraging movements of adults and postfledging juveniles in their first flights around the colony before dispersal and migration in two sympatric species of tropical seabirds: red-footed boobies and great frigatebirds. Using GPS records of individual movements, we analyzed the foraging directions of seabirds from the colony across successive trips. Juveniles of both species showed significant within-individual consistency in foraging direction but at lower levels than adults. Juveniles leaving the colony within the same time window showed significant but low between-individual resemblance in foraging direction at levels similar to adults. In both species, homing efficiency was lower in juveniles than in adults. Juvenile foraging directions were initially influenced by wind conditions, particularly in low wing loading frigatebirds. Wind conditions progressively lost influence on juvenile foraging directions during their first weeks of flights. In contrast, within-individual consistency, between-individual resemblance, and homing efficiency did not show signs of progression in juveniles. Our results support the early-exploration-later-canalization hypothesis but not the early-conformism-later-self-defining hypothesis. Relaxed constraints on self-feeding efficiency could favor high variability in postfledging tropical seabirds. Our simple approach could be applied to further test these hypotheses by comparing strategies across a wide range of central place foragers.

How Comparable are 2D and 3D Methods for Measuring Bone Laminarity in Developing Pigeons?

The cortical bone of birds contains microscopic tunnels called vascular canals, which can be classified based on orientation as: longitudinal, radial, oblique, or circumferential. Circumferential canals are hypothesized to reflect adaptation to flapping flight. This hypothesis is supported by histological surveys of birds that show the proportion of circumferential canals (laminarity) is elevated in bones thought to experience habitual torsional loads. However, the most detailed data on torsional loading during avian flight is from the pigeon, a species in which the adults show low wing bone laminarity. Nevertheless, there may still be support for biomechanical adaptation if the laminarity is greater in adults than in juveniles incapable of flight. Alternatively, if the pattern is reversed, laminar bone may simply be a juvenile trait.Laminarity has largely been analyzed using 2D histological sections, which may not accurately represent complex 3D structure. High‐resolution micro‐CT is an imaging technique that allows 3D reconstruction, providing greater accuracy and objectivity in the measurement of canal orientation. Here, we compare 2D and 3D methods to clarify how wing bone laminarity develops in pigeons.We sampled a growth series of four pigeons that were collected from a previous study. A cortical strip (1 × 3 mm) was cut from the right humerus, ulna, and radius of each bird. The strips were scanned with high resolution microCT. 3D analysis involved segmentation, autoskeletonization, and measurement of 3D canal orientation using Avizo. For 2D analysis, five evenly spaced orthoslices were digitally extracted from each strip. Canals were fitted with ellipses and trigonometric equations were used to approximate orientation. In both 2D and 3D methods, canals were categorized and laminarity was calculated. Principal components analysis was performed to convert highly correlated variables (i.e., mass, bone length, and section modulus) into principal components (PCs). The relationship between principal components and laminarity was assessed using beta regression modeling.2D analysis overestimates laminarity among juvenile specimens. Therefore caution is warranted when applying 2D analysis to complex canal networks. Nevertheless, both methods show that the laminarity of each element significantly decreases with maturity (PC 1). Therefore, torsionally loaded bone is not necessarily more laminar. It seems laminarity is influenced by additional factors that warrant further investigation.Support or Funding InformationCollege of Graduate Studies Intramural Funding (Erin L. R. Simons & Andrew H. Lee); Kenneth A. Suarez AZCOM Summer Research Fellowship (Alexandra Brown, Kittaporn Jonglertjanya, Rylee S. McGuire)

WIND TUNNEL CALIBRATION, CORRECTIONS AND EXPERIMENTAL VALIDATION FOR FIXED-WING MICRO AIR VEHICLES MEASUREMENTS

The increase in the number of Unmanned Aerial Vehicles (UAVs) and Micro Air Vehicles (MAVs), which are used in a variety of applications has led to a surge in low Reynolds number aerodynamics research. Flow around fixedwing MAVs has an unusual behavior due to its low aspect ratio and operates at low Reynolds number, which demanded to upgrade the used wind tunnel for this study. This upgrade enables measuring the small aerodynamics forces and moment of fixed-wing MAVs. The wind tunnel used in this work is upgraded with a state of art data acquisition system to deal with the different sensors signals in the wind tunnel. For accurate measurements, the sting balance, angle sensor, and airspeed sensor are calibrated. For validation purposes, an experiment is made on a low aspect ratio flat plate wing at low Reynolds number, and the measured data are corrected and compared with published results. The procedure presented in this paper for the first time gave a detailed and complete guide for upgrading and calibrating old wind tunnel, all the required corrections to correct the measured data was presented, the turbulence level correction new technique presented in this paper could be used to estimate the flow turbulence effect on the measured data and correct the measured data against published data.

Low Reynolds Number Flow over Low Aspect Ratio Corrugated Wing

Voluminous research exists on the effect of combination of low Reynolds number flow over low aspect ratio flat plate wings for usage in micro-aerial vehicles and UAVs, as they also fly under similar conditions and combination of low aspect ratio and low Reynolds number. It has been well established by many researchers (Torres and Mueller in AIAA 42(5):865–873, 2004; Okamoto and Azuma in AIAA 49(6):1135–1150, 2011; Mizoguchi and Itoh in AIAA 51(7):7–52, 2013; Shields and Mohseni in AIAA 50(1):85–99, 2012; Mizoguchi and Kajikawa in Trans Jpn Soc Aero Sp Sci 59(2):56–63, 2016; Pelletier and Mueller in J Aircr 37(5):825–832, 2000; Liu and Hsiao in J Mech 28(01):77–89, 2012; Taira and Colonius in J Fluid Mech 623:187–207, 2009) that low aspect ratio wings in low Reynolds number flow gives a higher lift coefficient and stall angle is also increased which is quite different from the high aspect ratio wing. Also, it is a well-established fact in the existing literature that linear theories cannot be applied as in case of high aspect ratio wings because of non-linear increase in lift coefficient. The reason for such increase in lift and stall angle has been attributed to wingtip vortices that become prominent in low aspect ratio wings called the vortical lift which keeps on increasing up to a certain high angle of attack till it interacts with the separation bubble. In the past, very limited work has been done to study the vortices and their contribution in enhancement of aerodynamic characteristics. In the present work, flat plate model with corrugations at an aspect ratio (AR) of 1.0 are studied and compared with flat plate wing of AR 1.0; also flow visualization in water tunnel has been carried out at Reynolds number of 102 to ascertain the flow physics involved.

Nanoindentation analysis comparing dragonfly-inspired biomimetic micro-aerial vehicle (BMAV) wings

Biomimetic micro-aerial vehicle (BMAV) are micro-scaled, unmanned aircraft based on flying biological organisms, generating thrust and lift by flapping their wings. This study investigates and compares the nano mechanical mechanical properties of four sets of fabricated, dragonfly inspired BMAV wings and compares them to actual dragonfly wings used as a baseline reference. The BMAV wings were fabricated using a 3D printer, based on these simplified models. Different 3D printer filament materials were used for each of the four wing sets: acrylonitrile butadiene styrene (or ABS), polylactic acid (or PLA), high impact polystyrene (or HIPS) as well as Ultrat. Nanoindentation tests of the actual dragonfly wings and the BMAV wings were conducted to measure their hardness and Young's modulus. The test result demonstrates the feasibility solution in the development of strong, practical and low cost BMAV wings, this work is a stepping-stone on the path to flying robotic dragonfly.

Nanoindentation analysis comparing dragonfly-inspired biomimetic micro-aerial vehicle (BMAV) wings

Biomimetic micro-aerial vehicle (BMAV) are micro-scaled, unmanned aircraft based on flying biological organisms, generating thrust and lift by flapping their wings. This study investigates and compares the nano mechanical mechanical properties of four sets of fabricated, dragonfly inspired BMAV wings and compares them to actual dragonfly wings used as a baseline reference. The BMAV wings were fabricated using a 3D printer, based on these simplified models. Different 3D printer filament materials were used for each of the four wing sets: acrylonitrile butadiene styrene (or ABS), polylactic acid (or PLA), high impact polystyrene (or HIPS) as well as Ultrat. Nanoindentation tests of the actual dragonfly wings and the BMAV wings were conducted to measure their hardness and Young's modulus. The test result demonstrates the feasibility solution in the development of strong, practical and low cost BMAV wings, this work is a stepping-stone on the path to flying robotic dragonfly.

Chromophor Inhomogeneity Indication by Diffuse Vibronic Spectra

Determination of gap between optically combining states (0-0- transition) from diffuse vibronic absorption or emission spectra is possible now for homogeneous ensembles of chromophores. If the observed spectra present composite polymorphic chromophores or different species they are formed by partial spectra and differing electronic transitions. For these conditions the indicating pure-electronic transition frequency attribute is distorted, smeared or even absent. That behavior is qualitative indication of the chromophore inhomogeneity. The same would be because of impurities. It is shown that the approach of inhomogeneity qualitative indication by spectra is adaptable to different structural forms of chromophor and at polymorphic sites of containing the chromophore media. The experimental data show that the approach is applicable to see the chromophore inhomogeneity by linear and circular vibronic spectra even of molecular dye-labels. The examples of observed distortions for the spectra of different composite species in different media as manifestation of their inhomogeneity are given. As the region of indication 0-0-transition is situated at low intensity antistokes wings of spectra the sensitivity to inhomogeneity is high as to hindrance by impurities and measurement precision.

Intrinsic infrared absorption for carbon–fluorine bonding in fluorinated nanodiamond

IR spectroscopy of fluorinated detonation nanodiamond demonstrates that an intense absorption band at ∼1344 cm–1 and two smaller ones at ∼1324 and ∼1258 cm–1 form the extended low wave-number wing of the observed consolidated spectrum in the range of 1100–1400 cm–1. The intrinsic infrared absorption of CFx bonding at the nanodiamond surface sites has been determined after subtraction of the contribution from remaining C–O and C–O–C groups inside the aggregates of tightly-bonded fundamental nanodiamond particles, which had not been subjected to fluorine attack and to their replacement by fluorine containing groups.

PIV Flow Visualization around Low Aspect Ratio Wing at Low Reynolds Numbers

PIV Flow Visualization around Low Aspect Ratio Wing at Low Reynolds Numbers

Bistable permanent magnet actuator based on double wing magnetic flux

This letter presents a bistable permanent magnet actuator, based on double wing magnetic flux (DWMF) formed by the structure of welding sleeve and slotted armature. The double wing magnetic flux consist of high wing magnetic flux (HWMF) and low wing magnetic flux (LWMF), resulting in bistable performance under differentiating control. Parameters improvement around DWMF is analyzed based on modeling, and optimized results for a prototype actuator are obtained. The experimental and simulation results agree well, and show that the prototype actuator can realize bistable performance under the DC step voltage drive, with the holding force of 8.2 N (without current) and the restoring force of −31.7 N (with negative current), the dynamic results show that the displacement response time within 8 mm is 28 ms, of which the actuation time is 16.5 ms, the transient maximum power consumption of the restoring period is 18 W.