Paper 7. Unsteady Flow around a Slender Fish-Like Body

1972 ◽  
Vol 14 (7) ◽  
pp. 43-52 ◽  
Author(s):  
Th. Y. Wu ◽  
J. N. Newman
Keyword(s):  
Unsteady Flow ◽  
Theoretical Calculations ◽  
Cross Flow ◽  
Vortex Sheet ◽  
The Body ◽  
Dynamic Force ◽  
Cross Sectional ◽  
Vortex Sheets ◽  
Flat Fish ◽  
The Cross

This paper attempts to extend some recent theoretical calculations on the unsteady flow generated by body movements of a slender ‘flat’ fish by further including the effect of finite body thickness in the consideration for various configurations of side and caudal fins as major appendages. Based on the slender-body approximation, the cross-flow is determined for different longitudinal body sections which are characterized by a variety of cross-sectional shapes and flow conditions (such as having smooth or fin-edged body contours, with or without vortex sheets alongside the body section). The effect of body thickness is found to arise primarily from its interaction with the vortex sheet already existing in the cross-flow. New results for the transverse hydro-dynamic force acting on the body are obtained, and their physical significances are discussed.

scholarly journals Cavity flow past a slender pointed hydrofoil

1961 ◽  
Vol 11 (2) ◽  
pp. 187-208 ◽  
Author(s):  
E. Cumberbatch ◽  
T. Y. Wu
Keyword(s):  
Angle Of Attack ◽  
Cross Flow ◽  
The Body ◽  
Two Dimensional ◽  
Cross Sectional ◽  
Slender Body Theory ◽  
Flow Past ◽  
Two Dimensional Flow ◽  
Cavity Boundary ◽  
The Cross

A slender-body theory for the flow past a slender, pointed hydrofoil held at a small angle of attack to the flow, with a cavity on the upper surface, has been worked out. The approximate solution valid near the body is seen to be the sum of two components. The first consists of a distribution of two-dimensional sources located along the centroid line of the cavity to represent the variation of the cross-sectional area of the cavity. The second component represents the cross-flow perpendicular to the centroid line. It is found that over the cavity boundary which envelops a constant pressure region, the magnitude of the cross-flow velocity is not constant, but varies to a moderate extent. With this variation neglected only in the neighbourhood of the hydrofoil, the cross-flow is solved by adopting the Riabouchinsky model for the two-dimensional flow. The lift is then calculated by intergrating the pressure along the chord; the dependence of the lift on cavitation number and angle of attack is shown for a specific case of the triangular plan form.

scholarly journals Petiole-Lamina Transition Zone: A Functionally Crucial but Often Overlooked Leaf Trait

Plants ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 774
Author(s):  
Max Langer ◽  
Thomas Speck ◽  
Olga Speck
Keyword(s):  
Transition Zone ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Body Plan ◽  
The Body ◽  
Vascular Bundles ◽  
Cross Sectional ◽  
Thin Sections ◽  
Transition Zones ◽  
The Cross

Although both the petiole and lamina of foliage leaves have been thoroughly studied, the transition zone between them has often been overlooked. We aimed to identify objectively measurable morphological and anatomical criteria for a generally valid definition of the petiole–lamina transition zone by comparing foliage leaves with various body plans (monocotyledons vs. dicotyledons) and spatial arrangements of petiole and lamina (two-dimensional vs. three-dimensional configurations). Cross-sectional geometry and tissue arrangement of petioles and transition zones were investigated via serial thin-sections and µCT. The changes in the cross-sectional geometries from the petiole to the transition zone and the course of the vascular bundles in the transition zone apparently depend on the spatial arrangement, while the arrangement of the vascular bundles in the petioles depends on the body plan. We found an exponential acropetal increase in the cross-sectional area and axial and polar second moments of area to be the defining characteristic of all transition zones studied, regardless of body plan or spatial arrangement. In conclusion, a variety of terms is used in the literature for describing the region between petiole and lamina. We prefer the term “petiole–lamina transition zone” to underline its three-dimensional nature and the integration of multiple gradients of geometry, shape, and size.

Orthodontic force prediction model of T-loop closing spring based on dynamic resistance model

2020 ◽  
Vol 234 (12) ◽  
pp. 1384-1396
Author(s):  
Jingang Jiang ◽  
Houjun Chen ◽  
Zhiyuan Huang ◽  
Xuefeng Ma ◽  
Yongde Zhang ◽  
...  
Keyword(s):  
Prediction Model ◽  
Orthodontic Treatment ◽  
Dynamic Resistance ◽  
Dynamic Force ◽  
Cross Sectional ◽  
Measuring Device ◽  
Orthodontic Force ◽  
Force Prediction ◽  
Resistance Model ◽  
The Cross

Malocclusion has been seriously endangering human oral function. The most effective and mature therapy is orthodontic treatment. But the relationship between the shape of the T-loop and the orthodontic force is unclear, and the precise mathematical model has not been established. In this article, the dynamic orthodontic force prediction model of the T-loop was established by analyzing the treatment process of the T-loop. The model was based on the dynamic resistance model of waxy dental jaw, the theory of beam deformation, and the deformation characteristics of the T-loop. In the experimental process, 11 kinds of orthodontic archwires were used as experimental samples, including 2 kinds of common archwire materials, 7 kinds of cross-sectional sizes, and 10 kinds of clearance distances. The T-loop was put into the extraction space and immersed in 75°C constant temperature water for 2 min. And the experimental data were measured and collected by the dynamic force measuring device. The experimental results show that the cross-sectional size and the clearance distance are positively correlated with the orthodontic force. The influence of the clearance distance on the orthodontic force is greater than that of the cross-section size. The deviation rates between the experimental values of orthodontic force and the theoretical values are between 1.10% and 9.09%, which verifies the accuracy of the dynamic orthodontic force prediction model. The model can predict the orthodontic force, improve the treatment effect, shorten the treatment cycle, and provide reference and guidance for orthodontists to carry out orthodontic treatment safely and effectively.

Interference in a three-dimensional array of jets

2015 ◽  
Vol 26 (5) ◽  
pp. 795-819
Author(s):  
P. E. WESTWOOD ◽  
F. T. SMITH
Keyword(s):  
Cross Sections ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Longitudinal Vortex ◽  
Cross Sectional ◽  
Dimensional Array ◽  
Unsteady Jets ◽  
The Cross ◽  
Jet Cross Sections

The theoretical investigation here of a three-dimensional array of jets of fluid (air guns) and their interference is motivated by applications to the food sorting industry especially. Three-dimensional motion without symmetry is addressed for arbitrary jet cross-sections and incident velocity profiles. Asymptotic analysis based on the comparatively long axial length scale of the configuration leads to a reduced longitudinal vortex system providing a slender flow model for the complete array response. Analytical and numerical studies, along with comparisons and asymptotic limits or checks, are presented for various cross-sectional shapes of nozzle and velocity inputs. The influences of swirl and of unsteady jets are examined. Substantial cross-flows are found to occur due to the interference. The flow solution is non-periodic in the cross-plane even if the nozzle array itself is periodic. The analysis shows that in general the bulk of the three-dimensional motion can be described simply in a cross-plane problem but the induced flow in the cross-plane is sensitively controlled by edge effects and incident conditions, a feature which applies to any of the array configurations examined. Interference readily alters the cross-flow direction and misdirects the jets. Design considerations centre on target positioning and jet swirling.

scholarly journals Ciało fortepianu – artykulacja doświadczenia cielesnego w korespondencji Fryderyka Chopina

2021 ◽  
pp. 15-38
Author(s):  
Aleksandra Świtka
Keyword(s):  
Physical Appearance ◽  
The Body ◽  
Cross Sectional ◽  
The Cross

The article focuses on the presentation and analysis of selected excerpts from Frédéric Chopin’s letters from the 1824-1849 period that illustrate their author’s attitude towards physical experiences. In contrast to the “disembodied” reception of the artist that reproduces the “soul of the piano” metaphor, the article describes a broad representation of the composer’s texts on physical appearance, the role of the body in the performance act, living through illness and the oncoming death. The cross-sectional and chronologically ordered study presented in the article shows the evolution of the subject’s attitude towards his own body along the progress of his illness. It is at the same time an illustration of the style and imagery used by the author of the letters while describing specific aspects of physical experience.

scholarly journals An Analytical Simulation of Boundary Roughness for Incompressible Viscous Flows

2021 ◽  
Vol 16 ◽  
pp. 9-15
Author(s):  
John Venetis
Keyword(s):  
Flow Direction ◽  
Deformable Body ◽  
Cross Sectional Area ◽  
The Body ◽  
Sectional Area ◽  
Cross Sectional ◽  
Random Roughness ◽  
Analytical Simulation ◽  
The Cross ◽  
Boundary Roughness

The intention of this paper is to investigate the boundary roughness of a mounted obstacle which is inserted into an incompressible, external and viscous flow field of a Newtonian fluid. In particular, the present study focuses on the cross – sectional area of the obstacle, which is assumed to be a non deformable body (rigid object) with a predefined shape of random roughness. For facility reasons and without violating the generality, one may select the cross – section of the body which contains its center of gravity and is perpendicular to the main flow direction. The boundary of this cross – sectional area is mathematically simulated as the polygonal path of the length of a single – valued continuous function. Evidently, this function should be of bounded variation. The novelty of this work is that the formulation of the random roughness of the boundary has been carried out in a deterministic manner.

scholarly journals ¿Y si toda la innovación no es positiva en Educación Física? Reflexiones y consideraciones prácticas (Is innovation always positive in Physical Education? Reflections and practical considerations)

Retos ◽  
2019 ◽  
pp. 579-587
Author(s):  
Ángel Pérez Pueyo ◽  
David Hortigüela Alcalá
Keyword(s):  
Physical Education ◽  
Cooperative Learning ◽  
Scientific Evidence ◽  
The Body ◽  
Cross Sectional ◽  
Positive Effects ◽  
Current Trends ◽  
True Purpose ◽  
The Cross ◽  
Aprendizaje Cooperativo

En la actualidad la innovación parece querer inundarlo todo, pero que algo sea nuevo no implica que tenga efectos positivos en el aula. Este artículo surge de la necesidad de pararse a pensar y reflexionar sobre las tendencias actuales de Educación Física que no parece estar permitiéndole avanzar e, incluso, ir en contra de sus verdaderos fines y esencia. A partir de las evidencias científicas que los sustentan, se han planteado cinco aspectos de práctica habitual en nuestra área sobre los que reflexionar: (1) La gamificación mal entendida; (2) la utilización indiscriminada de las APPs: (3) el aprendizaje cooperativo mal enfocado; (4) la verdadera motivación; (5) las evidencias en el aprendizaje del alumnado. Ante esto, se dan diferentes soluciones prácticas basadas en el uso de la evaluación formativa y compartida y el uso transversal de lo corporal. Finalmente se plantean consideraciones a modo de conclusión, no con la intención de ofrecer recetas, sino reflexiones con base científica con el fin de contribuir a una mejor Educación Física. Abstract. Currently, innovation seems to be spreading uncontrollably everywhere; however, just because something is new it does not necessarily imply that it also has positive effects in the classroom. This article arises from the need to stop, think, and reflect on current trends in Physical Education, which at times seem to be more an obstacle to its progress to the extent that they may even work against its true purpose and essence. Based on scientific evidence, five common practice aspects to reflect upon in our field have been proposed: (1) Misunderstood gamification; (2) indiscriminate use of APPs: (3) poorly focused cooperative learning; (4) true motivation; and (5) evidences of students’ learnings. Different practical solutions based on the use of formative and shared evaluation and the cross-sectional use of the body were proposed. Finally, considerations were presented as a conclusion; however, they are intended to offer any formulae, but rather scientifically supported reflections aiming at contributing to the enhancement of Physical Education.

Analysis of Cross-Reactivity and Allergic Symptoms of 19 Allergens: Results from NHANES 2005–2006

2021 ◽  
pp. 1-10
Author(s):  
Zhi-Ling Zhu ◽  
Ying-Xing Wu ◽  
Zhu-Ping Zhang ◽  
Song Li
Keyword(s):  
Respiratory Health ◽  
Specific Ige ◽  
Cross Reactivity ◽  
The Body ◽  
Cross Sectional ◽  
Allergic Symptoms ◽  
Allergen Sources ◽  
The Usa ◽  
The Cross ◽  
Using Data

<b><i>Introduction:</i></b> We explored the cross-reactivity among 19 common allergen sources and evaluated the influence of serum IgE concentrations and the number of sensitized allergens on the incidence of allergic symptoms. <b><i>Methods:</i></b> We conducted this cross-sectional analysis using data from the National Health and Nutrition Examination Survey (NHANES) 2005–2006 which is a program of studies designed to assess the health and nutritional status of adults and children in the USA. After excluding participants with missing data from the allergen IgE test, allergy questionnaire, and respiratory health questionnaire, a total of 7,224 participants aged 6 years and older were included, as children younger than 6 years old did not complete all 19 allergen-specific IgE tests. Spearman correlation analysis was used to analyze the cross-reactivity between allergen sources. An independent sample Kruskal-Wallis test was performed to investigate the relationship between the serum-specific IgE levels of 19 allergens and the incidence of allergic symptoms. <b><i>Results:</i></b> The cross-reactivity between <i>D. farinae</i> and <i>D. pteronyssinus</i> was the strongest (ρ = 0.88), and cross-reactivity of cross-species was universal. With the increase in serum-specific IgE levels of <i>D. farinae</i>, <i>D. pteronyssinus</i>, oak, and birch, the incidence of sneezing increased (<i>p</i> &#x3c; 0.05). With the increase in serum-specific IgE levels of cats, dogs, peanuts, <i>Aspergillus</i>, and <i>Alternaria</i>, the incidence of wheezing increased (<i>p</i> &#x3c; 0.05). The incidence of rash was positively correlated with serum-specific IgE levels of <i>D. farinae</i>, <i>D. pteronyssinus</i>, shrimp, and peanut (<i>p</i> &#x3c; 0.05). The incidence of wheezing continued to increase with an increase in sensitized allergens. When participants were sensitized to &#x3c;10 allergens, the incidence of sneezing continued to increase as the number of sensitized allergens increased, whereas the incidence of rash did not have a clear association with the number of sensitized allergens. <b><i>Conclusion:</i></b> Species that are biologically close are more likely to have antigen cross-reactivity, while cross-reactivity among different species is common. Different allergens tend to cause different allergic symptoms. Different allergic sites in the body have inconsistent responses to the number of sensitized allergens.

Evaluation of body geometry and symmetry for adolescent idiopathic scoliosis with 3D body scanning system

2017 ◽  
Vol 21 (4) ◽  
pp. 276-292
Author(s):  
Lu Lu ◽  
Kit-Lun Yick ◽  
Sun Pui Ng ◽  
Joanne Yip ◽  
Chi Yung Tse
Keyword(s):  
Adolescent Idiopathic Scoliosis ◽  
Idiopathic Scoliosis ◽  
Three Dimensional ◽  
The Body ◽  
Scanning System ◽  
X Rays ◽  
Cross Sectional ◽  
Content Type ◽  
Body Scanning ◽  
The Cross

Purpose The purpose of this paper is to quantitatively assess the three-dimensional (3D) geometry and symmetry of the torso for spinal deformity and the use of orthotic bracewear by using non-invasive 3D body scanning technology. Design/methodology/approach In pursuing greater accuracy of body anthropometric measurements to improve the fit and design of apparel, 3D body scanning technology and image analysis provide many more advantages over the traditional manual methods that use contact measurements. To measure the changes in the torso geometry and profile symmetry of patients with adolescent idiopathic scoliosis, five individuals are recruited to undergo body scanning both with and without wearing a rigid brace during a period of six months. The cross-sectional areas and profiles of the reconstructed 3D torso models are examined to evaluate the level of body symmetry. Findings Significant changes in the cross-sectional profile are found amongst four of the patients over the different visits for measurements (p < 0.05), which are consistent with the X-rays results. The 3D body scanning system can reliably evaluate changes in the body geometry of patients with scoliosis. Nevertheless, improvements in the symmetry of the torso are found to be somewhat inconsistent among the patients and across different visits. Originality/value This pilot study demonstrates a practical and safe means to measure and analyse the torso geometry and symmetry so as to allow for more frequent evaluations, which would result in effective and optimal treatment of spinal deformation.

scholarly journals Three-dimensional extension of Lighthill's large-amplitude elongated-body theory of fish locomotion

2011 ◽  
Vol 674 ◽  
pp. 196-226 ◽  
Author(s):  
FABIEN CANDELIER ◽  
FREDERIC BOYER ◽  
ALBAN LEROYER
Keyword(s):  
Cross Sections ◽  
Velocity Potential ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Neumann Boundary ◽  
The Body ◽  
Navier Stokes ◽  
Cross Sectional ◽  
Curvature Effects ◽  
The Cross

The goal of this paper is to derive expressions for the pressure forces and moments acting on an elongated body swimming in a quiescent fluid. The body is modelled as an inextensible and unshearable (Kirchhoff) beam, whose cross-sections are elliptic, undergoing prescribed deformations, consisting of yaw and pitch bending. The surrounding fluid is assumed to be inviscid, and irrotational everywhere, except in a thin vortical wake. The Laplace equation and the corresponding Neumann boundary conditions are first written in terms of the body coordinates of a beam treating the body as a fixed surface. They are then simplified according to the slenderness of the body and its kinematics. Because the equations are linear, the velocity potential is sought as a sum of two terms which are linked respectively to the axial movements of the beam and to its lateral movements. The lateral component of the velocity potential is decomposed further into two sub-components, in order to exhibit explicitly the role of the two-dimensional potential flow produced by the lateral motion of the cross-section, and the role played by the curvature effects of the beam on the cross-sectional flow. The pressure, which is given by Bernoulli's equation, is integrated along the body surface, and the expressions for the resultant and the moment are derived analytically. Thereafter, the validity of the force and moment obtained analytically is checked by comparisons with Navier–Stokes simulations (using Reynolds-averaged Navier–Stokes equations), and relatively good agreements are observed.

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