Subcritical Flow without Circulation past a Swept Semi-Infinite Elliptic Cylinder

1977 ◽  
Vol 28 (2) ◽  
pp. 142-148 ◽  
Author(s):  
G J Clapworthy
Keyword(s):  
Body Shape ◽  
Velocity Potential ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Elliptic Cylinder ◽  
The Body ◽  
Infinite Domain ◽  
Working Space ◽  
Mach Number Distribution ◽  
Grid Points

SummaryThe numerical calculation of the subcritical, steady, three-dimensional, potential flow past a semi-infinite swept elliptic cylinder attached to a plane wall is described. The full equations of motion are written in terms of the velocity potential and the exact body-surface conditions are applied. The equations are expressed in coordinates defined by the body shape and further transformations are necessary to reduce the infinite domain to a finite working space and to concentrate the grid points in regions of greatest variation of potential. The resulting equations are solved using a finite-difference scheme. The Mach number distribution for a typical case is presented.

A three-dimensional shoulder protector based on ergonomics for workers

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ran-i Eom ◽  
Yejin Lee
Keyword(s):  
Body Shape ◽  
Three Dimensional ◽  
Health And Safety ◽  
The Body ◽  
Construction Sites ◽  
Content Type ◽  
Three Dimensional Printing ◽  
Functional Studies ◽  
Work Posture ◽  
Dimensional Printing

PurposeThe use of shoulder protectors is strongly recommended when carrying objects on the shoulder to ensure the health and safety of workers. Thus, this study aimed to develop and verify an ergonomic shoulder protector that considers human body shape and carrying posture from an ergonomic perspective. Ultimately, this study will present a shoulder protector with enhanced fit and safety for carrying workers at construction sites.Design/methodology/approachThe shoulder protector was designed and printed using three-dimensional printing technology with variable side neck points and shoulder point heights to reflect the human body's shoulder line shape and to position the carried object stably on the shoulder. The developed shoulder protectors were evaluated in terms of their fit according to the work posture of the carrier, adherence upon motion and durability through structural analysis.FindingsThe design of the shoulder protector for carrying workers followed the shoulder line. It is best placed above the side neck point by 1.0 cm and above the shoulder point by 2.0 cm. Its length is slightly shorter than the human shoulder for superior fit and safety.Originality/valueThe final shoulder protector (FSP) for carrying workers reflects the body curvature while enhancing fit and safety by considering activity and protective factors. As functional studies and evaluations on the need for protectors are scarce, this study provides fundamental data in the evaluation of protective gears.

Mechanisms of helical swimming: asymmetries in the morphology, movement and mechanics of larvae of the ascidian Distaplia occidentalis

2001 ◽  
Vol 204 (17) ◽  
pp. 2959-2973 ◽  
Author(s):  
Matthew J. McHenry
Keyword(s):  
Body Shape ◽  
Three Dimensional ◽  
The Body ◽  
Hydrodynamic Theory ◽  
Helical Motion ◽  
Body Rotation ◽  
Oblique Angle ◽  
Free Swimming ◽  
Three Point Bending ◽  
And Control

SUMMARY A great diversity of unicellular and invertebrate organisms swim along a helical path, but it is not well understood how asymmetries in the body shape or the movement of propulsive structures affect a swimmer’s ability to perform the body rotation necessary to move helically. The present study found no significant asymmetries in the body shape of ascidian larvae (Distaplia occidentalis) that could operate to rotate the body during swimming. By recording the three-dimensional movement of free-swimming larvae, it was found that the tail possessed two bends, each with constant curvature along their length. As these bends traveled posteriorly, the amplitude of curvature changes was significantly greater in the concave-left direction than in the concave-right direction. In addition to this asymmetry, the tail oscillated at an oblique angle to the midline of the trunk. These asymmetries generated a yawing moment that rotated the body in the counterclockwise direction from a dorsal view, according to calculations from hydrodynamic theory. The tails of resting larvae were bent in the concave-left direction with a curvature statistically indistinguishable from the median value for tail curvature during swimming. The flexural stiffness of the tails of larvae, measured in three-point bending, may be great enough to allow the resting curvature of the tail to have an effect on the symmetry of kinematics. This work suggests that asymmetrical tail motion is an important mechanism for generating a yawing moment during swimming in ascidian larvae and that these asymmetries may be caused by the tail’s bent shape. Since helical motion requires that moments also be generated in the pitching or rolling directions, other mechanisms are required to explain fully how ascidian larvae generate and control helical swimming.

The Body Design and Body Flow Passage Digital Simulation Analysis of the Solar Car

2013 ◽  
Vol 364 ◽  
pp. 14-18
Author(s):  
Xuan Zuo Liu ◽  
Hui Min Wang ◽  
Fei Zhang ◽  
Yu Long Zhang ◽  
Qian Cheng Liu
Keyword(s):  
Theoretical Basis ◽  
Body Shape ◽  
Simulation Analysis ◽  
Digital Simulation ◽  
Three Dimensional ◽  
The Body ◽  
Air Resistance ◽  
The World ◽  
Body Design ◽  
Design And Manufacture

This paper designs the three-dimensional body modelling of a solar car prototype mainly according to the World Solar Challenge rules, and carries on the flow field digital simulation analysis. This paper analyzes the air resistance of the car body and adjusts to the body shape, and ultimately gets a model well accorded with air dynamics. This paper provides scientific theoretical basis for the design and manufacture of the solar car prototype.

scholarly journals Motion of an infinite elliptic cylinder in fluids with constant vorticity

1937 ◽  
Vol 158 (895) ◽  
pp. 522-535 ◽  
Keyword(s):  
Equations Of Motion ◽  
Elliptic Cylinder ◽  
The Body ◽  
Uniform Rotation ◽  
Constant Vorticity ◽  
Uniform Shear ◽  
Potential Motion ◽  
Irrotational Motion ◽  
Shear Motion ◽  
Solid Bodies

An extension of Kirchoff’s theory of the motion of solid bodies in irrotationally moving liquids to the case of motion in liquids in which a vorticity is present does not exist. Only a few isolated cases of such motion are known. Bearing on the consideration of this paper, there is an important work by Taylor which expresses the additional pressure effect on a system of cylinders moving in a perfect liquid without rotation when the whole system is rotated uniformly about an axis. Taylor’s theory reduces the problem of such motion to one of irrotational motion. In the present paper the motion of a perfect liquid having constant vorticity, and in which a cylinder of any cross-section is moving in any manner, has been considered. The pressure integral can be obtained in a simple form, referred to axes fixed in the body, which is very suitable for calculation. It is shown, whenever the pure potential motion of the liquid for the rotation of the cylinder and the solution of a definite potential problem or the corresponding Green’s function can be found, the formula can be applied to calculate the motion of the cylinder in liquids with constant vorticity. Two important cases of constant vorticity are uniform shear motion along a direction and uniform rotation about an axis. In the present paper the former case is considered in detail for an elliptic cylinder. The case of uniform rotation being covered by Taylor’s result it is only verified that the present method gives the same result as Taylor’s formulae. There are some simple free motions of an elliptic cylinder in a liquid with uniform shear motion which have been discussed in the paper. 2—Equations of Motion Referred to Axes Fixed in the Body and the Pressure Integral It is first necessary to write down the equations of motion referred to a system of axes fixed in the body having both translation and rotation. These equations are obtained below following a method of Taylor.

Analysis on Structure and Morphological of Carton Packaging

2013 ◽  
Vol 442 ◽  
pp. 338-341
Author(s):  
A Qiang Sun
Keyword(s):  
Structural Design ◽  
Body Shape ◽  
Space Form ◽  
Dimensional Space ◽  
Three Dimensional ◽  
The Body ◽  
Packaging Materials ◽  
Paper Study ◽  
Structural Morphology ◽  
Three Dimensional Space

The package structure is a three-dimensional space form, so people know the products are in used in the packaging. In packaging materials for paper use is very extensive, paper products are easy to shape the body shape for easy printing and recyclable advantage. This paper study design of the paper packaging structural, combining paper packaging structural design applications to explore the paper packaging structural morphology and environmentalist design consciousness.

scholarly journals Countershading enhances camouflage by reducing prey contrast

2020 ◽  
Vol 287 (1927) ◽  
pp. 20200477
Author(s):  
Callum G. Donohue ◽  
Jan M. Hemmi ◽  
Jennifer L. Kelley
Keyword(s):  
Body Shape ◽  
Three Dimensional ◽  
Luminance Contrast ◽  
The Body ◽  
Body Parts ◽  
Live Fish ◽  
Average Luminance ◽  
Fish Predators ◽  
Dimensional Shape ◽  
Three Dimensional Shape

A three-dimensional body shape is problematic for camouflage because overhead lighting produces a luminance gradient across the body's surface. Countershading, a form of patterning where animals are darkest on their uppermost surface, is thought to counteract this luminance gradient and enhance concealment, but the mechanisms of protection remain unclear. Surprisingly, no study has examined how countershading alters prey contrast, or investigated how the presence of a dorsoventral luminance gradient affects detection under controlled viewing conditions. It has also been suggested that the direction of the dorsoventral luminance gradient (darkest or lightest on top) may interfere with predators' abilities to resolve prey's three-dimensional shape, yet this intriguing idea has never been tested. We used live fish predators (western rainbowfish, Melanotaenia australis ) and computer-generated prey images to compare the detectability of uniformly pigmented (i.e. non-countershaded) prey with that of optimally countershaded prey of varying contrasts against the background. Optimally countershaded prey were difficult for predators to detect, and the probability and speed of detection depended on prey luminance contrast with the background. In comparison, non-countershaded prey were always highly detectable, even though their average luminance closely matched the luminance of the background. Our findings suggest that uniformly pigmented three-dimensional prey are highly conspicuous to predators because overhead lighting increases luminance contrast between different body parts or between the body and the background. We found no evidence for the notion that countershading interferes with predator perception of three-dimensional form.

Partitioning the Parameter Space According to Different Behaviors During Three-Dimensional Impacts

1995 ◽  
Vol 62 (3) ◽  
pp. 740-746 ◽  
Author(s):  
V. Bhatt ◽  
J. Koechling
Keyword(s):  
Parameter Space ◽  
Initial Conditions ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Flow Patterns ◽  
The Body ◽  
Qualitative Behavior ◽  
Sliding Velocity ◽  
Physical Behavior ◽  
Rule Out

The equations of motion that define three-dimensional rigid-body impact with finite friction and restitution cannot be solved in a closed form. Previous work has shown that for general shapes and initial conditions, the direction of sliding velocity keeps changing continuously throughout the duration of impact. The flow patterns defined by the trace of the sliding velocity can be classified into a finite number of qualitatively distinct physical behavior. We identify three dimensionless parameters that completely specify the sliding behavior, and determine regions in this parameter space that correspond to each of the different flow patterns. The qualitative behavior during impact can now be determined based on the region which contains the parameters for a given impact configuration. The analysis is also used to study the sensitivity of the sliding behavior to changes in shape or configuration of the body and to rule out the occurrence of certain ambiguities in the post-sticking behavior during impact.

scholarly journals Experiments on the motion of solid bodies in rotating fluids

1923 ◽  
Vol 104 (725) ◽  
pp. 213-218 ◽  
Keyword(s):  
Equations Of Motion ◽  
Three Dimensional ◽  
Steady Motion ◽  
The Body ◽  
Two Dimensional ◽  
Experimental Conditions ◽  
Axis Of Rotation ◽  
Rotating Liquid ◽  
Steady Motions ◽  
Solid Bodies

Some years ago it was pointed out by Prof. Proudman that all slow steady motions of a rotating liquid must be two-dimensional. If the motion is produced by moving a cylindrical object slowly through the liquid in such a way that its axis remains parallel to the axis of rotation, or if a two-dimensional motion is conceived as already existing, it seems clear that it will remain two-dimensional. If a slow three-dimensional motion is produced, then it cannot be a steady one. On the other hand, if an attempt is made to produce a slow steady motion by moving a three-dimensional body with a small uniform velocity (relative to axes which rotate with the fluid) three possibilities present themselves:— ( a ) The motion in the liquid may never become steady, however long the body goes on moving. ( b ) The motion may be steady but it may not be small in the neighbourhood of the body. ( c ) The motion may be steady and two-dimensional. In considering these three possibilities it seems very unlikely that ( a ) will be the true one. In an infinite rotating fluid the disturbance produced by starting the motion of the body might go on spreading out for ever and steady motion might never be attained, but if the body were moved steadily in a direction at right angles to the axis of rotation, and if the fluid were contained between parallel planes also perpendicular to the axis of rotation, it seems very improbable that no steady motion satisfying the equations of motion could be attained. There is more chance that ( b ) may be true. A class of mathematical expressions representing the steady motion of a sphere along the axis of a rotating liquid has been obtained. This solution of the problem breaks down when the velocity of the sphere becomes indefinitely small, in the sense that it represents a motion which does not decrease as the velocity of the sphere decreases. It seems unlikely that such a motion would be produced under experimental conditions.

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.

Classification of body shape characteristics of women's torsos using angles

2010 ◽  
Vol 22 (4) ◽  
pp. 297-311 ◽  
Author(s):  
Wookyung Lee ◽  
Haruki Imaoka
Keyword(s):  
Body Shape ◽  
Three Dimensional ◽  
The Body ◽  
Data Set ◽  
Content Type ◽  
Body Sizes ◽  
Body Shapes ◽  
Three Body ◽  
Shape Characteristics

PurposeThe purpose of this paper is to classify body shapes using angular defects instead of sizes.Design/methodology/approachA large amount of dimensional data from a national anthropometry survey was analysed, and a basic pattern and its polyhedron were also used to create a three‐dimensional body shape from three body sizes. Using this method, the sizes were converted into nine angular defects.FindingsThe authors could define the factors explaining body shape characteristics and classify the body shapes into four groups. The four groups could be characterised by two pattern making difficulties of the upper and lower parts of the body as well as by two proportions, of waist girth to bust girth and bust girth to back length. Furthermore, depending on the age, the authors could understand body shape by the angle made.Originality/valueUsing a polyhedron model, the angles could be calculated using an enormous existing data set of sizes. An angular defect serves as an index to indicate the degree of difficulty for developing a flat pattern. If an angular defect of the bust is large, it is difficult to make a paper pattern of a bust dart. On the other hand, if an angular defect of the waist is large, it is easy to make a paper pattern of a waist dart. Thus, each body shape could be simultaneously characterized by two difficulty indices and two proportions of sizes.

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