Factors Controlling the Change of Shape of Certain Nemertean and Turbellarian Worms

1958 ◽  
Vol 35 (4) ◽  
pp. 731-748 ◽  
Author(s):  
R. B. CLARK ◽  
J. B. COWEY
Keyword(s):  
Water Conservation ◽  
Ecological Factors ◽  
Longitudinal Axis ◽  
The Body ◽  
Cross Sectional ◽  
Ciliary Action ◽  
Theoretical Predictions ◽  
Observed Behaviour ◽  
Body Wall Musculature ◽  
Sectional Shape

1. Nemerteans and turbellarians have an inextensible fibre system around them in the form of a lattice of left- and right-handed spirals. The effect of this system on the change of shape on these worms has been analysed theoretically and compared with the observed behaviour of nine species of turbellarian and nemertean from widely differing habitats. 2. The following theoretical relationships have been studied: (a) Variation of the angle between the geodesics and the longitudinal axis of the worm during changes in length, and the role of the fibre system in limiting changes in length of the animal. (b) The change in cross-sectional shape during changes in length. (c) The extension of the fibres and the extensibility of the worms, assuming the fibres of the lattice to be elastic. 3. The species investigated conform with the theoretical predictions to varying degrees and have been grouped accordingly: (a) Geonemertes dendyi and Rhynchodemus bilineatus have low extensibilities and fit the prediction well. They are nearly circular in cross-section at all lengths as a result of their low extensibility and this is related to their terrestrial habit and need for water conservation. (b) Amphiporus lactifloreus, Lineus gesserensis and L. longissimus are moderately flattened in the relaxed position and have extensibilities between 6 and 10. They are marine crawling forms using cilia for locomotion and so must present a fairly large ciliated surface to the substratum. The fibre system does not limit contraction; the compression of the epithelial cells causes the observed extensibilities to fall a little short of the theoretical values. (c) Cerebratulus lacteus, Malacobdella grossa, Polycelis nigra and Dendrocoelum lacteum are very flattened forms and have very high theoretical extensibilities, but very low observed ones. The factors causing this are the thickness of the body-wall musculature (Cerebratulus), the limiting effect of longitudinal and circular reticulin fibres in the muscle layers, and the presence of dorso-ventral and diagonal muscles. Their flattened form is correlated with ecological factors (with swimming in Cerebratulus, with its parasitic life in the mantle of bivalves in Melacobdella) or with physical ones in turbellarians where a permanently flattened form is necessary for these worms to move by ciliary action.

The Structure and Function of the Basement Membrane Muscle System in Amphiporus lactifloreus (Nemertea)

1952 ◽  
Vol s3-93 (21) ◽  
pp. 1-15
Author(s):  
J. B. COWEY
Keyword(s):  
Basement Membrane ◽  
Cross Section ◽  
Circular Cross Section ◽  
The Body ◽  
Minimum Length ◽  
Muscle Fibres ◽  
Body Volume ◽  
Cross Sectional ◽  
Elliptical Cross ◽  
Sectional Shape

The body wall of A. lactifloreus has the following structure from the outside inwards. (i) A basement membrane of five to six layers immediately underlying the epithelium. Each layer consists of right-hand and left-hand geodesic fibres making a lattice, whose constituent parallelograms have a side length of from 5 to 6µ. The fibres are attached to one another where they cross; so there can be no slipping relative to one another. (ii) A layer of circular muscle-fibres running round the animal containing two systems of argyrophil fibres--one of fibres at intervals of 10µ. running parallel to the muscle-fibres and the other of fibres running radially through the layer from the basement membrane to the myoseptum. (iii) A myoseptum which is identical in structure with a single layer of the basement membrane (iv) A layer of longitudinal muscle, whose fibres are arranged in layers on each side of a series of longitudinal radial membranes. Membranes identical in structure with the basement membrane invest the nerve cords, the gut, the gonads, and the proboscis. The interrelations of argyrophil and muscle-fibres in the muscle layers is described and their functioning discussed. The system of inextensible geodesic fibres is analysed from a functional standpoint. The maximum volume enclosed by a cylindrical element (cross-section circular), of such a length that the geodesic makes one complete turn round it, varies with the value of the angle θ between the fibres and the longitudinal axis. When θ is 0° the volume is zero; it increases to a maximum when θ is 54° 44' and decreases again to zero when θ is 90°. The length of the element under these conditions varies from zero when θ is 90° to a maximum (the length of one turn of the geodesic) when θ is 0°. The body-volume of the worm is constant. Thus it has a maximum and minimum length when its cross-section is circular, and at any length between these values its cross-section becomes more or less elliptical. It is maximally elliptical when θ is 54° 44', i.e. when the volume the system could contain, at circular cross-section, is maximal. From measurements of the ratio of major to minor axes of this maximally elliptical cross-section, the maximum and minimum lengths of the worm relative to the relaxed length and values of θ at maximum and minimum length are calculated. The worm is actually unable to contract till its cross-section is circular; but measurements of its cross-sectional shape at the minimum length it can attain, permit calculation of the theoretical length and value of θ for this cross-sectional shape. Calculated values of length and the angle 6 agree well with the directly observed values.

scholarly journals Fluid Acoustic Properties of Improved Hydraulic Mufflers with Extended Necks

2019 ◽  
Vol 24 (4) ◽  
pp. 638-647
Author(s):  
Fan Yang ◽  
Bin Deng
Keyword(s):  
Plane Wave ◽  
Resonance Frequency ◽  
Insertion Loss ◽  
Acoustic Properties ◽  
Expansion Chamber ◽  
Cross Sectional ◽  
Conical Tube ◽  
Chamber Volume ◽  
Theoretical Predictions ◽  
Sectional Shape

The acoustic properties of three improved hydraulic mufflers with extended necks are investigated theoretically and experimentally. The effect of length and slope of the conical tube, and the perforations on the extended tube is studied on the resonance frequency and the insertion loss. The plane wave approach is used for the constant and the variable area tubes, while Sullivan and Peat's method is applied for the perforation tube unit. Theoretical predictions are compared with experiments for these three different hydraulic noise suppressors, which are fabricated. It is shown that the resonance frequency and the insertion loss characteristics may be controlled by the length and the slope of the conical tube and perforation porosity of the extended tube without changing the expansion chamber volume. Finally, the effect of the cross-sectional shape of the expansion chamber is investigated.

scholarly journals Pilot study about the micro hydropower generation by use of flow induced vibration phenomenon

2018 ◽  
Vol 180 ◽  
pp. 02122
Author(s):  
Yoshifumi Yokoi
Keyword(s):  
Power Generation ◽  
The Body ◽  
Flow Induced Vibration ◽  
Cross Sectional ◽  
Generation Characteristic ◽  
Micro Power ◽  
Power Generation System ◽  
Sectional Shape ◽  
Body Section ◽  
Piezo Electric

In order to construct a micro power generation system using a piezo-electric element, power generation was tried using excitation oscillation of the bluff cylinder by the vortex shedding from the bluff cylinder. The bluff cylinder consists of a board spring section in which the piezo-electric element was attached, and a body section. The bluff cylinder was inserted into the water flow, the shape and the submersion depth of the bluff cylinder, and the flow velocity were varied, and the power generation characteristic was investigated. As a result, it was found that it can generate electricity by vortex excitation. It was found that the length and the submersion depth of the body section influence power generation. It was shown that the power generation characteristic changes with cross-sectional shape of the bluff cylinder. The most suitable state was the case where the submersion depth was set to 140 mm with a circular cylinder with a span length of 250 mm. It is important to choose the power generation object which suited the use purpose.

Supersonic Flow Past Slender Bodies With Discontinuous Profile Slope

1955 ◽  
Vol 6 (2) ◽  
pp. 114-124 ◽  
Author(s):  
L. E. Fraenkel ◽  
H. Portnoy
Keyword(s):  
Internal Flow ◽  
Leading Edge ◽  
Rate Of Change ◽  
The Body ◽  
Cross Sectional ◽  
Slender Body Theory ◽  
Bodies Of Revolution ◽  
Slender Bodies ◽  
External Forces ◽  
Sectional Shape

SummaryWard’s slender-body theory is extended to derive first approximations to the external forces on slender bodies of general cross section with discontinuous profile slope. Two classes of body are considered: bodies whose profile (typified by the local radius) is continuous between the nose and base, and certain bodies whose profile is discontinuous, such as bodies with annular or side air intakes and wing-bodies on which the wing has an unswept leading edge. (Where air intakes are concerned, it is assumed that they are sharp-edged and that there is no “ spillage ” of the internal flow).The following conclusions apply to the former class of bodies. The variation of drag with Mach number is found to depend only on the discontinuities in the longitudinal rate of change of the cross-sectional area, and is thus independent of cross-sectional shape. The drag itself is unchanged if the direction of the flow is reversed. The expressions for lift and moment assume the same forms as for smooth pointed bodies, the lift depending only on conditions at the base of the body.The general theory is applied to winged bodies of revolution with an unswept wing leading edge: the results bear a marked resemblance to those obtained by Ward. The results for wings alone are seen to be applicable, with one modification, to subsonic as well as to supersonic speeds.

Wave Propagation of Water Hammer in Compound Tube

2014 ◽  
Author(s):  
Kengo Takeda ◽  
Kazuaki Inaba ◽  
Kosuke Takahashi
Keyword(s):  
Wave Propagation ◽  
Water Hammer ◽  
Junction Conditions ◽  
Strain Gages ◽  
Cross Sectional ◽  
Wave Speeds ◽  
Pressure Transducers ◽  
Simply Supported ◽  
Theoretical Predictions ◽  
Sectional Shape

There are pipes with square or rectangular cross sectional shape rather than more common circular shape. Moreover, a part of the walls can be made of different materials or have different wall thicknesses. To estimate pressure wave propagation in such a channel, we examined water hammer phenomenon and measured wave speeds in rectangular tubes assembled with different wall materials and thicknesses by strain gages and pressure transducers. We newly proposed theoretical wave speeds based on the classical theory and the junction conditions of two walls: fixed, simply supported, and mixed supported. Circumferential strains on the wall can be estimated from the different forms derived by the different junction conditions. We confirmed that theoretical predictions with the simply supported conditions agreed with experimental wave speed in compound tubes, while wave speeds in ready-made square tubes with the same wall-thickness were close to those by the fixed conditions.

Structural Mechanics of Radial Tires

1981 ◽  
Vol 54 (3) ◽  
pp. 461-492 ◽  
Author(s):  
T. Akasaka
Keyword(s):  
Closed Form Solution ◽  
Structural Mechanics ◽  
Form Solution ◽  
The Body ◽  
Theoretical Studies ◽  
Bending Rigidity ◽  
Cross Sectional ◽  
Analytical Studies ◽  
The Cross ◽  
Sectional Shape

Abstract This review has included only theoretical studies of cross-sectional tire shape, structural properties of the belt, and certain topics on structural mechanics of radial tires. Many other papers on these subjects have been omitted because of the space limitation and because of the objective to describe only broad trends and prospects rather than to present an exhaustive review. Many different but interesting problems remain regarding stresses, deformations, and failure of radial tires under various loading conditions, for example: ( 1 ) physico-chemical and mechanical studies of the viscous flow and vulcanization of rubber during tire formation, in order to determine the setting mechanism and residual stresses in the cord-rubber array; (2) theoretical studies of both in-plane and interply loads and deformations in laminates of more than three layers, by developing a three dimensional lamination theory; (3) accurate determinations of spring bed coefficients in equations based on a shell model (e.g. for use in a ring model, which could yield a closed form solution for various tire performance parameters); (4) experimental and analytical studies of elastic properties and strengths of twisted tire cords under various conditions of extension, compression, bending, and torsion; (5) experimental and analytical studies of the distribution of contact pressure between a radial carcass and a belt (which pressure strongly affects the cross-sectional shape of a tire, especially near the belt edges); and (6) theoretical studies of the cross-sectional shape of the inflated radial tire by relating the bending rigidity of the body, particularly near the bead, to the mold shape.

Stimulated Brillouin scattering in a sub-wavelength anisotropic waveguide with slightly-misaligned material and structural axes: Misalignment-sensitive behaviors and underlying physics

2021 ◽  
Author(s):  
Xiao-Xing Su ◽  
D zi long ◽  
Heow Pueh Lee
Keyword(s):  
Brillouin Scattering ◽  
Circular Waveguide ◽  
Longitudinal Axis ◽  
Cross Sectional ◽  
Symmetry Properties ◽  
Brillouin Gain ◽  
Sectional Shape ◽  
Stimulated Brillouin ◽  
Micro Structures ◽  
Sub Wavelength

Abstract The stimulated Brillouin scatterings (SBSs) in the sub-wavelength rutile waveguides with slightly misaligned material and structural axes are numerically studied. The misalignment is introduced between the extraordinary material axis and longitudinal axis of the waveguide only. Four nanowire waveguides with different cross-sectional geometries are considered. They consist of a circular waveguide, two elliptical waveguides with different cross-sectional orientation angles, and a trapezoidal waveguide with a completely unsymmetrical cross-sectional shape. As reported earlier, the resonant peaks emerging rapidly in response to the introduced small misalignment angle can also be observed in the calculated Brillouin gain spectra of the considered waveguides. But these misalignment-sensitive resonant peaks further exhibit some extraordinary behaviors, which may not be intuitively understandable. For instance, despite a plausible absence of symmetry breaking, many misalignment-sensitive resonant peaks can still be observed in the forward SBS gain spectrum of the trapezoidal waveguide. Based on the symmetry properties of the considered waveguides, the physics underlying the observed extraordinary phenomena are revealed. The obtained results highlight the effectiveness of introducing symmetry breakings for activating/harnessing opto-mechanical couplings in photonic-phononic micro structures, which would enable us to gain some deeper insights into the sub-wavelength opto-mechanics in anisotropic media.

Note on the Numerical Evaluation of the Wave Drag of Smooth Slender Bodies Using Optimum Area Distributions for Minimum Wave Drag

1956 ◽  
Vol 60 (541) ◽  
pp. 61-63 ◽  
Author(s):  
E. Eminton ◽  
W. T. Lord
Keyword(s):  
Numerical Evaluation ◽  
Practical Method ◽  
Wave Drag ◽  
The Body ◽  
Cross Sectional ◽  
Area Distribution ◽  
Slender Bodies ◽  
Kinetic Pressure ◽  
Image Position ◽  
Sectional Shape

The linearised theory value of the wave drag D at zero lift of a smooth slender body of arbitrary cross-sectional shape was shown by Ward to be given bywhere S (x), 0 ⩽ x ⩽ 1, is the cross-sectional area distribution of the body and q is the kinetic pressure. The development of this result has aroused interest in two problems: the derivation of the optimum area distribution for minimum wave drag under certain specified conditions and the numerical evaluation of the wave drag of a specified area distribution. These apparently distinct problems have hitherto been treated separately, but it is shown here how an attempt to solve the first problem has led to a practical method of solving the second.

Flow Structure Near the Bow of a Two-Dimensional Body

1989 ◽  
Vol 33 (04) ◽  
pp. 269-283
Author(s):  
Mark A. Grosenbaugh ◽  
Ronald W. Yeung
Keyword(s):  
Free Surface ◽  
Power Spectra ◽  
Leading Edge ◽  
Two Dimensional ◽  
Cross Sectional ◽  
Bow Wave ◽  
Wave Elevation ◽  
Characteristic Oscillation ◽  
Theoretical Predictions ◽  
Sectional Shape

Flow near a blunt ship's bow is experimentally investigated by studying the flow in front of horizontal, surface-piercing cylinders. A bore-like structure develops at the bow of a cylinder when it is immersed in a uniform stream. Observations indicate that the leading edge of this bow wave coincides with a point at which the main flow separates from the free surface. Experimental measurements of the location of the wavefront and the slope of the free surface at the wavefront are in fair agreement with existing theoretical predictions. Power spectra of the time records of the bow-wave elevation show a characteristic oscillation frequency at Froude numbers above a critical value. The bow-wave oscillation is a function of the cross-sectional shape of the two-dimensional body, the draft, and, to a lesser extent, the flow velocity. The inception of the oscillation depends on the Reynolds number, but the characteristic frequency is governed by inertial and gravitational forces.

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