Slender Body Research Articles

Efficient convergent boundary integral methods for slender bodies

The interaction of fibers in a viscous (Stokes) fluid plays a crucial role in industrial and biological processes, such as sedimentation, rheology, transport, cell division, and locomotion. Numerical simulations generally rely on slender body theory (SBT), an asymptotic, nonconvergent approximation whose error blows up as fibers approach each other. Yet convergent boundary integral equation (BIE) methods which completely resolve the fiber surface have so far been impractical due to the prohibitive cost of layer-potential quadratures in such high aspect-ratio 3D geometries. We present a high-order Nyström quadrature scheme with aspect-ratio independent cost, making such BIEs practical. It combines centerline panels (each with a small number of poloidal Fourier modes), toroidal Green's functions, generalized Chebyshev quadratures, HPC parallel implementation, and FMM acceleration. We also present new BIE formulations for slender bodies that lead to well conditioned linear systems upon discretization. We test Laplace and Stokes Dirichlet problems, and Stokes mobility problems, for slender rigid closed fibers with (possibly varying) circular cross-section, at separations down to 1/20 of the slender radius, reporting convergence typically to at least 10 digits. We use this to quantify the breakdown of numerical SBT for close-to-touching rigid fibers. We also apply the methods to time-step the sedimentation of 512 loops with up to 1.65 million unknowns at around 7 digits of accuracy.

Analysis of the wake mechanism in external flow around tandem bluff bodies with different aspect ratios

The interaction mechanism of external flow with two inline rectangular cylinders having different aspect ratios under the impact of gap spacing (G) is the subject of this research. The gap spacing between the cylinders was varied from 0.25 to 20 times their size. Both cylinders were vertically mounted, with the first having a higher aspect ratio than the second. The results revealed five distinct flow patterns under the influence of G: single slender body, shear layer reattachment, intermittent shedding, binary vortex street, and single-row vortex street. The mean pressure on both cylinders was found to vary due to changes in flow patterns. Both cylinders bore the same shedding frequency but had different pressure variations. The second cylinder placed in the wake of first experienced negative average drag force for some spacing values, while the first cylinder had positive average drag values for all chosen G. Due to the change in flow pattern from shear layer reattachment to intermittent shedding flow, the negative drag force on the second cylinder jumped to a positive drag. It was also observed that the rms values of drag and lift force coefficients, as well as their amplitudes for the second cylinder, were mostly higher than corresponding values for the first cylinder at all selected G. This study revealed that G = 4 and 8 are the critical gap spacing values due to sudden changes in fluid force parameters.

Spin-leap performance by cetaceans is influenced by moment of inertia.

Cetaceans are capable of extraordinary locomotor behaviors in both water and air. Whales and dolphins can execute aerial leaps by swimming rapidly to the water surface to achieve an escape velocity. Previous research on spinner dolphins demonstrated the capability of leaping and completing multiple spins around their longitudinal axis with high angular velocities. This prior research suggested the slender body morphology of spinner dolphins together with the shapes and positions of their appendages allowed for rapid spins in the air. To test whether greater moments of inertia reduced spinning performance, videos and biologging data of cetaceans above and below the water surface were obtained. The principal factors affecting the number of aerial spins a cetacean can execute were moment of inertia and use of control surfaces for subsurface corkscrewing. For spinner dolphin, Pacific striped dolphin, bottlenose dolphin, minke whale and humpback whale, each with swim speeds of 6-7ms-1, our model predicted that the number of aerial spins executable was 7, 2, 2, 0.76 and 1, respectively, which was consistent with observations. These data implied that the rate of subsurface corkscrewing was limited to 14.0, 6.8, 6.2, 2.2 and 0.75 rad s-1 for spinner dolphins, striped dolphins, bottlenose dolphins, minke whales and humpback whales, respectively. In our study, the moment of inertia of the cetaceans spanned a 21,000-fold range. The greater moments of inertia for the last four species produced large torques on control surfaces that limited subsurface corkscrewing motion and aerial maneuvers compared with spinner dolphins.

A new species of lamprey from Cretaceous semisaline environment in China

ABSTRACT A new fossil species of lamprey, Caeruleum gracilis sp. nov. is described from the Early Cretaceous Jiufotang Formation in China Hebei province, North China. Caeruleum gracilis sp. nov. is characterised by a slender body shape and a dorsal fin originating above the second branchial pouch. Given the intricate life history of lampreys, their presence in saltwater and freshwater, and their convoluted and ambiguous evolutionary trajectory, it is imperative to investigate whether the living environment of fossil lamprey species encompassed varying levels of salinity. This inquiry will facilitate our understanding and tracing of the earliest adaptations of lampreys to freshwater and saltwater environments. Based on salinity analysis, the environment of the Jiufotang Formation may be attributed to brackish conditions. Therefore, the lampreys Caeruleum gracilis sp. nov. and Caeruleum miraculum from the Jiufotang Formation may represent the one of earliest lampreys records that acquired adaptations to freshwater environments.

Non-uniform heat source or sink on the radiated and thermophoretic flow of slender body of paraboloid and cone revolutions in a saturated medium with Brownian motion

Heat and mass transfer acquired the attention of investigators and experts because of massive uses in the field of medicine, manufacturing of modern aircrafts, uses in advanced water filtration plants, distillation process of water, more efficient electronic instruments, more efficient batteries, textile industry, uses as manufacturer in cosmetics industry and modern defense equipment. By viewing this, we considered the numerical study of Fourier flux and buoyancy driven forces on the flow of thermal and diffusion transmission of body revolutions (Paraboloid and cone), situated in a water-logged Darcy medium by allowing the radiation, Brownian motion, time-space dependent heat source or sink, and thermopheretic. Later on, the governing system is solved via Runge–Kutta method. Properties of convoluted governing measures of the organisms on local Nusselt and Sherwood numbers along with velocity, thermal and diffusion shapes are described with the aid of graphically and tabular form. It is stimulating to declare that the non-uniform heat source or sink is highly dominated in cone form of revolution as associated to paraboloid form of flow due to more distribution of mass transfer. From this, one can draw the conclusion that wherever there are higher mass transportation phenomena, cone-shaped body of revolution can be used. It is found that the time- and space-dependent heat source or sink performs as a regulating factor of the transmission of flow phenomena.

A sharp MLS penalty immersed finite element method for fluid-structure interaction of highly deformable slender body in turbulent flow

This paper presents a new computational approach to simulate challenging fluid-structure interactions (FSI) between fluids and slender deformable structures. Key innovations address limitations of standard immersed boundary methods, including spurious forces, stability at low density ratios, and accuracy at high Reynolds numbers. The method couples a sharp interface immersed boundary technique with detached eddy simulation turbulence modelling to enable precise FSI for high Reynolds number flows. A strong coupling partitioned algorithm stabilized by Aitken relaxation significantly enhances stability for low density ratios down to 1. A moving least square compact support domain approximation reduces spurious oscillations from moving geometries while providing second-order accuracy. Adaptive mesh refinement imposes jump conditions on slim deformable bodies and minimizes grid leakage. The proposed method is evaluated on three conventional FSI benchmarks and four experimental cases, confirming its robustness, accuracy, and stability in low and significantly high Reynolds numbers. A more complex fluids engineering case is considered last to test the solution under challenging conditions with fast moving solid boundaries and fast flowing fluid. A thin deformable membrane is forced through a submersible centrifugal pump under standard operating conditions. The solution is shown to produce a stable solution with good collision handling ability.

Gastrointestinal helminths of the Australasian harrier (Circus approximans Peale, 1848) in New Zealand, and description of a new species of nematode, Procyrnea fraseri n. sp. (Habronematidae).

The Australasian harrier Circus approximans, a native of Australia, New Zealand and the South Pacific, is an opportunistic hunter of small prey, although a large part of its diet consists of carrion, mainly from roadkill. Besides a record of a single, unnamed species of capillariid nematode there have been no investigations into the parasites of Australasian harriers in New Zealand. In this study, a helminthological survey of sixty-five deceased harriers from southern New Zealand uncovered a gastrointestinal helminth fauna consisting of six parasite species. Porrocaecum circinum (Nematoda) was previously described only from fragmented females, and a redescription is presented here. Procyrnea fraseri n. sp. (Nematoda) is described, and distinguished from its congeners by its slender body shape and shorter spicules. Strigea falconis (Trematoda) is reported for the first time in New Zealand. Cladotaenia anomalis (Cestoda) and Polymorphus circi (Acanthocephala) were previously described as new species elsewhere. An unnamed species of capillariid appears to be mainly confined to North Island and is rare in South Island. Prevalence and intensity metrics are given, and DNA sequences provided to accompany new re/descriptions. Potential intermediate hosts are discussed, and the origins of the helminths and their potential for pathogenicity are considered.

AGE CHANGES IN THE BODY WEIGHT OF RAM LAMBS OBTAINED FROM EWES OF DIFFERENT BODY TYPES

The research was carried out in the production conditions of the private farm “AGRO-DIS” of the Podilsky district of the Odesa oblast with the population of crossbred F1 rams, obtained from the industrial crossing of ewes of the Askaniysky meat-wool breed with crossbred wool of the Odesa inbred type of different body types with Merinolandschaf rams. Changes in body weight of ram lambs from birth to 18 months old were studied according to generally accepted methods. It was established that the type of birth – singles or twins – affects the body weight of crossbred lambs. So, at birth, single lambs, offspring of ewes with a strong body type, had the largest body weight compared to peers of other body types. Their advantage compared to peers obtained from ewes of a slender body type was 1.3 kg or 26.42% (Р>0.999), and compared to rams of a corpulent body type, it was 0.59 kg or 10.48% (Р>0, 95). However, in later age periods of growth, peers of the corpulent body type dominated in terms of body weight. Crossbred rams (AMO x ME) in all age periods of growth had a high body weight regardless of the type of birth and the body type of the ewes. The difference in body weight of single rams, offspring from ewes of strong and corpulent body type was greater in favor of rams obtained from ewes of corpulent body type with a high degree of probability and amounted to: in 4 months. – 11.54 kg or 26.58% (Р>0.999), 8 months. – 9.29 kg or 18.8% (Р>0.999), 12 months. –14.26 kg or 23.2% (Р>0.999), 16 months. – 10.39 kg or 14.35% (Р>0.999), 18 months. – 11.15 kg or 13.93% (Р>0.999). Offspring born by ewes with a corpulent body type also prevailed over peers obtained from ewes of a slender body type at all age periods of growth. The obtained results of research indicate the expediency of industrial crossbreeding at farms with the aim of increasing the meat productivity of sheep.

Experimental investigation of flow characteristics around tandem arrangement of triangular and square cylinders

The paper presents an experimental investigation of the flow around two bluff bodies in a tandem arrangement. Two different configurations were investigated. The first one concerns two square cylinders (SS case) whereas in the second setup, a triangular cylinder was used as an upstream object (TS case). Particular attention was devoted to examining the effect of the gap space G between cylinders (from 1 to 6) on the flow structure and dynamics of vortices. The study also includes measurements conducted for single square and single triangular cylinders to show how the second object modifies the flow field. It was found that the wake behind each object is always wider for the SS case regardless of G. When G is less than or equal to 3 for the TS case, the slender body regime is seen in the flow field which for the SS case is normally present for G<1.5. Consequently, distinctive vortex shedding frequencies cannot be distinguished in the gap for the TS case when G≤3. When G≥4, twice as high values of the Strouhal number St are reported in the gap for the TS case compared to the SS case. Downstream the second object, St gradually decreases from ∼0.245 to ∼1.14 with increasing G from 1 to 4 for the TS case, whereas for 5≤G≤6 distinctive vortex shedding frequencies are no longer observed.

Aeroelastic reduced-order modeling for efficient static aeroelastic analysis considering geometric nonlinearity

The computational fluid dynamic/computational structural dynamic (CFD/CSD) coupling method plays an important role in static aeroelastic problems accounting for structural geometric nonlinearity. However, a huge computational burden comes from the CFD simulation, which also dominates the computational cost of the CFD/CSD coupling method. Therefore, this paper presents a reduced-order framework for steady aerodynamics to replace the CFD simulation, which is then coupled with the CSD solver for efficient static aeroelastic analysis considering geometric nonlinearity. Results first show that the proposed approach is capable of accurately predicting the surface pressure distribution of a high-aspect-ratio wing in its rigid undeformed shape at different Mach numbers and angles of attack, with at most a 2.5% relative error compared to CFD simulation. In addition, the geometrically nonlinear structure, a seminal benchmark without a tip slender body, is simulated by a three-dimensional open-source finite element solver coupled with either the CFD solver or the proposed reduced-order models (ROMs). The results demonstrate that the proposed ROM/CSD coupling approach can reflect the deformation and surface pressure distribution at static aeroelastic equilibrium with high accuracy and efficiency, thereby reducing the total computational cost at least five times while maintaining reasonable accuracy.

Body Dissatisfaction in Overweight Adolescents: The Role of Self Compassion and Gender

The body changes during adolescence, from puberty to adulthood. Late adolescents generally have completed physical development and grown to their full adult height. These changes make them pay great attention to their body. Females tend to regard a slender body shape as attractive, while males tend to perceive a more masculine muscular body shape as attractive. They might feel that their body is not as good as other people, especially adolescents who are overweight. Body dissatisfaction refers to holding negative thoughts or feelings about one’s body image. Those who are dissatisfied with their body will describe the difference between their subjective perception of their body and their ideal body image. Individuals’ attitude who are patient, kind, and understanding instead of judging themselves when facing shortcomings is known as self-compassion. The first purpose of this research was to find out the relationship between self-compassion with body dissatisfaction among overweight adolescents, and the second was how body dissatisfaction differs between males and females. The sample in this research used purposive sampling and obtained 103 late adolescent participants who had BMI &gt; 23kg/m². Measuring tools used in this study were the Indonesian version of Self-Compassion Scale and the Body Shape Questionnaire-34. Based on the correlation test results obtained a negative relationship between self-compassion with body dissatisfaction. So if overweight adolescents’ self-compassion is getting higher, their body dissatisfaction becomes lower and vice versa. The difference test showed that females were more dissatisfied with their bodies than males. In general, the level of both self-compassion and the level of body dissatisfaction of participants were at medium category.

System design study of a VLEO satellite platform using the IRS RF helicon-based plasma thruster

To achieve a feasible lifetime of several years, most satellites are deployed in orbits higher than 400 km. Drag of residual atmosphere causes a slow orbit decay, resulting in the deorbit of the spacecraft. However, e.g. optical instruments or communication devices would significantly benefit from lower altitudes in the range of 150–250 km. A solution to achieve this could be the application of atmosphere-breathing electric propulsion (ABEP), where the residual atmosphere is used to generate continuous thrust that compensates the drag.Within the EU-funded DISCOVERER project, the Institute of Space Systems (IRS) developed an electrode-less RF Helicon-based Plasma Thruster (IPT) suitable for such applications. Ignition and preliminary discharge characterizations of the IPT have been carried out at IRS facilities, using argon, nitrogen and oxygen. To further characterize the plasma plume, a torsional pendulum has been designed to determine the (local) momentum flux in the plasma jet, as well as a three-axis magnetic B-dot probe to carry out time-varying magnetic field measurements. Various intake designs were investigated, opening the possibility to conduct studies on potential satellite platforms within the frame of the ESA-funded project RAM-CLEP.A design study for an Earth Observation and Telecommunication satellite operating at 150–250 km with an extended mission lifetime is currently being carried out. The first system assessment focused on the comparison of different spacecraft configurations (“slender body” and “flat body”) and intake designs (specular or diffuse) with regard to overall drag and ABEP performance requirements.In this contribution, the design approaches for the current thruster and the diagnostic methods are depicted. Moreover, the current status of the system assessment is presented. Upcoming experimental studies of the ABEP system e.g. within the ESA-project RAM-CLEP and additional activities planned on system assessment are outlined.

Glyptothorax heokheei, a new species of catfish (Teleostei: Sisoridae) from the Brahmaputra River drainage, Arunachal Pradesh, Northeast India.

Glyptothorax heokheei, a new species of sisorid catfish is described from the Brahmaputra River drainage in India. It can be distinguished from all congeners, exceptG. dikrongensis,G. indicus,G. rugimentumandG. obliquimaculatus, in having the unculiferous striae of thoracic adhesive apparatus extending anteriorly onto gular region.Glyptothorax heokheeiis distinguished fromG. dikrongensisandG. obliquimaculatusin having a slender body at the anus, more serrations on posterior margin of pectoral-fin spine, greater number of branched anal fin rays, and the extremity of dorsoposterior margin of adipose fin uniformly convex (vs. sharply angular). It differs fromG. rugimentumin having a chevron-shaped (vs. rhomboidal) thoracic adhesive apparatus, more serrations on posterior margin of pectoral-fin spine, and lacking vertical bars on body.Glyptothorax heokheeidiffers fromG. indicusin having a shorter post-adipose distance, smaller interorbital width, more serrations on posterior margin of pectoral-fin spine and nasal barbel not reaching (vs. reaching) anterior margin of eye.Glyptothorax heokheeiis the fifth species ofthe genuspossessing unculiferous ridges of thoracic adhesive apparatus extending anteriorly onto the gular region.

The first articulated skeletons of enigmatic Late Cretaceous billfish-like actinopterygians.

Only few candidates of Mesozoic fishes with a similar body plan and ecological niche to the modern billfishes are suggested as their analogues. Several specimens were recovered from Cenomanian deposits in Germany and Lebanon and display a billfish-like fusiform body with elongated premaxillae. They are found close to the plethodids and show a unique combination of characters (rostrum pointed and extremely elongated, double articular head of the quadrate, anteroposteriorly elongated abdominal centra indicating a slender body and different types of scales on the body) allowing their inclusion in a new genus. Two 'Protosphyraena' species are also assigned to this new genus. This fish can be considered as an ecological analogue to the extant xiphioids sharing their feeding habits. This fish was abundant and roamed, as an apex predator, the Central Tethys and the Boreal realms during the Cenomanian.

A numerical model for simulation of two-phase flows interaction with flexible slender bodies

This paper introduces a fluid–structure interaction (FSI) model for simulation of the coupled dynamics between two-phase flows and elastic slender structures. This model is extended from the early FSI model for single-phase flows by Wang et al. [“A coupled flow and beam model for fluid–slender body interaction,” J. Fluids Struct. 115, 103781 (2022)] to two-phase flows with interfaces of two liquids or free surfaces between gas and liquid. To better capture the interface movement of the two-phase flows and the interaction with the deformable structure, a consistent mass and momentum flux scheme is developed to reduce the spurious oscillation of fluid velocities near the interface, especially in the lower density (e.g., air) region. The proposed model is validated by a series of two-dimensional laboratory experiments of flow impact on a deformable plate, demonstrating that the model has good capabilities of conserving mass and momentum during the process of plate deformation by impulsive flow forces. The model is also applied to the investigation of three-dimensional dam break flow impact on a column of elastic plates. The complex interaction between the plates and the flow is discussed based on the simulation results.

Record of the Amarsipa fish (Family Amarsipidae) from Pratas Island, South China Sea.

Two specimens of the rare Amarsipa fish, Amarsipus carlsbergi, were collected from Pratas Island in the northern South China Sea. They represent the first record of Taiwanese EEZ and fill the distribution gap in the northwestern Pacific Ocean between Japan (East China Sea) and Vietnam. The two specimens were identified based on their diagnostic characteristics, including no pharyngeal sacs, a pelvic fin well in front of the pectoral fin, a slender body and other morphology. Detailed data and descriptions of these two specimens, including a description of otolith morphology, are provided.

Rotation of a fibre in simple shear flow of a dilute polymer solution

The motion of a freely rotating prolate spheroid in a simple shear flow of a dilute polymeric solution is examined in the limit of large particle aspect ratio, $\kappa$ . A regular perturbation expansion in the polymer concentration, $c$ , a generalized reciprocal theorem, and slender body theory to represent the velocity field of a Newtonian fluid around the spheroid are used to obtain the $O(c)$ correction to the particle's orientational dynamics. The resulting dynamical system predicts a range of orientational behaviours qualitatively dependent upon $c\, De$ ( $De$ is the imposed shear rate times the polymer relaxation time) and $\kappa$ and quantitatively on $c$ . At a small but finite $c\, De$ , the particle spirals towards a limit cycle near the vorticity axis for all initial conditions. Upon increasing $\kappa$ , the limit cycle becomes smaller. Thus, ultimately the particle undergoes a periodic motion around and at a small angle from the vorticity axis. At moderate $c\, De$ , a particle starting near the flow–gradient plane departs it monotonically instead of spirally, as this plane (a limit cycle at smaller $c\, De$ ) obtains a saddle and an unstable node. The former is close to the flow direction. Upon further increasing $c\, De$ , the saddle node changes to a stable node. Therefore, depending upon the initial condition, a particle may either approach a periodic orbit near the vorticity axis or obtain a stable orientation near the flow direction. Upon further increasing $c\, De$ , the limit cycle near the vorticity axis vanishes, and the particle aligns with the flow direction for all starting orientations.

Shrinking body size of European anchovy in the Bay of Biscay.

Decreased body size is often cited as a major response to ocean warming. Available evidence, however, questions the actual emergence of shrinking trends and the prevalence of temperature-driven changes in size over alternative drivers. In marine fish, changes in food availability or fluctuations in abundance, including those due to size-selective fishing, provide compelling mechanisms to explain changes in body size. Here, based on three decades of scientific survey data (1990-2021), we report a decline in the average body size-length and weight-of anchovy, Engraulis encrasicolus L., in the Bay of Biscay. Shrinking was evident in all age classes, from juveniles to adults. Allometric adjustment indicated slightly more pronounced declines in weight than in total length, which is consistent with a change toward a slender body shape. Trends in adult weight were nonlinear, with rates accelerating to an average decline of up to 25% decade-1 during the last two decades. We found a strong association between higher anchovy abundance and reduced juvenile size. The effect of density dependence was less clear later in life, and temperature became the best predictor of declines in adult size. Theoretical analyses based on a strategic model further suggested that observed patterns are consistent with a simultaneous, opposing effect of rising temperatures on accelerating early growth and decreasing adult size as predicted by the temperature-size rule. Macroecological assessment of ecogeographical-Bergmann's and James'-rules in anchovy size suggested that the observed decline largely exceeds intraspecific variation and might be the result of selection. Limitations inherent in the observational nature of the study recommend caution and a continued assessment and exploration of alternative drivers. Additional evidence of a climate-driven regime shift in the region suggests, however, that shrinking anchovy sizes may signal a long-lasting change in the structure and functioning of the Bay of Biscay ecosystem.

New details of the enigmatic 100 million years old antlion-like larvae of Ankyloleon (Myrmeleontiformia, Neuroptera)

Lacewing larvae in the Cretaceous were more diverse in appearance than they are today, best documented by numerous fossils preserved in amber. One morphotype of an unusual larva from about 100 Ma old Kachin amber (Myanmar) was formally recognised as a distinct group called Ankyloleon. The original description erected a single formal species, Ankyloleon caudatus. Yet, it was indicated that among the five original specimens, more species were represented. We here report five new specimens. Among these is the so far largest as well as the so far smallest specimen. Based on this expanded material we can estimate certain aspects of the ontogenetic sequence and are able to recognise a second discrete species, Ankyloleon caroluspetrus sp. nov. We discuss aspects of the biology of Ankyloleon based on newly observed details such as serrations on the mandibles. Long and slender mouthparts, legs and body together with a weakly expressed outer trunk segmentation provide indications for a lifestyle hunting for prey in more confined spaces. Still many aspects of the biology of these larvae must remain unclear due to a lack of a well comparable modern counterpart, emphasising how different the fauna of the Cretaceous was.

Karakteristik Morfologi dan Organ Reproduksi pada Bebek Betina

This research aims to determine the morphology of female ducks from two different feeds andalso determine the reproductive organs in female ducks. The data collection technique was carried out directly by observing the development of the morphological characteristics of the ducks every week. In this study, two female ducks were used with two different feeds, namely 1 duck eating bran and the other duck eating pellets as the main feed. Based on the observations made, it can be concluded that ducks that eat bran (natural feed) and pellets (artificial feed) have a morphology that is not much different from each other, namely they have a slender body shape and a relatively long neck. The main difference lies only in the diet. and the nutritional quality obtained from the food. The reproductive organs of female ducks are located inside their bodies. The main reproductive organs in female ducks consist of the ovaries, oviducts (egg tubes), and cloaca. The ovaries of female ducks generally have an oval shape like small eggs at the end of the cloaca.