The mechanical and acoustic properties of two-dimensional pentamode metamaterials with different structural parameters

2016 ◽  
Vol 109 (13) ◽  
pp. 131904 ◽  
Author(s):  
Xuan Cai ◽  
Lei Wang ◽  
Zhigao Zhao ◽  
Aiguo Zhao ◽  
Xiangdong Zhang ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Acoustic Properties ◽  
Two Dimensional

The response of a turbulent boundary layer to lateral divergence

1979 ◽  
Vol 94 (2) ◽  
pp. 243-268 ◽  
Author(s):  
A. J. Smits ◽  
J. A. Eaton ◽  
P. Bradshaw
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Turbulent Boundary Layer ◽  
Structural Parameters ◽  
Axial Flow ◽  
Turbulence Structure ◽  
Two Dimensional ◽  
Transition Section ◽  
Two Dimensional Flow ◽  
Made In

Measurements have been made in the flow over an axisymmetric cylinder-flare body, in which the boundary layer developed in axial flow over a circular cylinder before diverging over a conical flare. The lateral divergence, and the concave curvature in the transition section between the cylinder and the flare, both tend to destabilize the turbulence. Well downstream of the transition section, the changes in turbulence structure are still significant and can be attributed to lateral divergence alone. The results confirm that lateral divergence alters the structural parameters in much the same way as longitudinal curvature, and can be allowed for by similar empirical formulae. The interaction between curvature and divergence effects in the transition section leads to qualitative differences between the behaviour of the present flow, in which the turbulence intensity is increased everywhere, and the results of Smits, Young & Bradshaw (1979) for a two-dimensional flow with the same curvature but no divergence, in which an unexpected collapse of the turbulence occurred downstream of the curved region.

SAXS of self-assembled nanocomposite films with oriented two-dimensional cylinder arrays: an advanced method of evaluation

2005 ◽  
Vol 38 (1) ◽  
pp. 78-86 ◽  
Author(s):  
Wilhelm Ruland ◽  
Bernd Smarsly
Keyword(s):  
Structural Parameters ◽  
Hexagonal Lattice ◽  
Preferred Orientation ◽  
Nanocomposite Films ◽  
Two Dimensional ◽  
Advanced Method ◽  
Cylinder Arrays ◽  
X Ray Scattering ◽  
Comparable Method ◽  
Method Of Evaluation

In a recent paper [Ruland & Smarsly (2002).J. Appl. Cryst.35, 624–633], an advanced method for the evaluation of the small-angle X-ray scattering (SAXS) from oriented lamellar systems was presented. In the present work, a comparable method is developed for the study of oriented cylinder arrays. Basic differences between the two methods are found in the way in which the preferred orientation affects the intensity distribution. The method is applied to the SAXS of SiO2-surfactant nanocomposite films which contain highly oriented arrays of cylinders. It is shown that up to eight structural parameters can be obtained by this method which characterize size, imperfection and preferred orientation of the two-dimensional hexagonal lattice formed by the cylinders, the radius and the polydispersity of the cylinders, and the interface boundary.

An Investigation Into the Characteristics of a Two Dimensional “2D” Flow Control Valve

2001 ◽  
Vol 124 (1) ◽  
pp. 214-220 ◽  
Author(s):  
J. Ruan ◽  
R. Burton ◽  
P. Ukrainetz
Keyword(s):  
Flow Control ◽  
Flow Rate ◽  
Structural Parameters ◽  
Control Valve ◽  
Favorable Effect ◽  
Flow Control Valve ◽  
Two Dimensional ◽  
System Pressure ◽  
Hydrostatic Force ◽  
2D Flow

In hydraulic servo systems, a pilot stage is often used to reduce the influence of Bernoulli’s forces and frictional forces when trying to accurately position a spool. A unique pilot controlled valve (defined as a two dimensional or “2D” flow control valve), which utilizes both rotary and linear motions of a single spool, is presented. The rotary motion uses a spiral groove in the sleeve combined with high and low pressure holes on the spool land to control the pressure in the spool chamber, while the linear motion of the spool is actuated by a hydrostatic force. Both linear theory and numerical simulation are adopted in the investigation of the characteristics of the valve. A criterion for stability is established from a linearized model of the valve. The analysis establishes the effects that certain structural parameters have on the valve’s static and dynamic characteristics. Special experimental procedures were designed to obtain properties such as mechanical stiffness, leakage flow rate, and dynamic response under different structural parameters and system pressure. It was shown that the leakage through the spool-sleeve clearance had a favorable effect on the valve stability. Theoretical and experimental results show that it is necessary to establish a balance between the static and dynamic performance in establishing appropriate structural parameters. It is also shown that the 2D flow control valve can demonstrate a high speed of response, while maintaining the pilot flow rate at a low level.

COMBINATION OF FUZZY ARITHMETIC AND A FAST BOUNDARY ELEMENT METHOD FOR ACOUSTIC SIMULATION WITH UNCERTAINTIES

2009 ◽  
Vol 17 (01) ◽  
pp. 45-69 ◽  
Author(s):  
M. JUNGE ◽  
D. BRUNNER ◽  
J. BECKER ◽  
M. MAESS ◽  
J. ROSEIRA ◽  
...  
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Sound Velocity ◽  
Fuzzy Numbers ◽  
Structural Parameters ◽  
Acoustic Properties ◽  
Fuzzy Arithmetic ◽  
Driving Frequency ◽  
Radiated Sound ◽  
Element Method

A so-called FuzzBEM methodology for analyzing the influence of uncertain acoustic and structural parameters on the radiated sound field of vibrating structures combining fuzzy arithmetic and fast multipole boundary element method is introduced. Uncertainties in acoustic properties may result from uncertain parameters of the vibrating mechanical structures, e.g. material density or geometry, as well as from uncertainties in the acoustic domain, e.g. sound velocity. The use of the transformation method in the proposed approach allows to employ simulation tools based on the crisp number arithmetic by appropriate preprocessing of the fuzzy numbers modeling the uncertain input parameters and postprocessing of the simulation results to determine the fuzzy numbers for the considered output quantities. In this contribution, the proposed FuzzBEM procedure is applied to a sound radiating, vibrating stiffened cylindrical shell where the investigated uncertainties include the shell wall thickness and the driving frequency of a monofrequency point load and the air density and sound velocity. As exemplary output quantities of acoustic performance, the acoustic pressure at multiple field points and the radiated sound power are evaluated. The proposed coupling of fuzzy arithmetic and acoustic boundary elements yields run times two orders of magnitudes or more longer than a single BEM calculation. Nevertheless, the systematic parameterization obtained by the proposed fuzzy analysis has the potential to reveal input–output relationships difficult to identify with individual conventional BEM simulation runs.

scholarly journals Automatic reconstruction of polycrystalline ice microstructure from image analysis: application to the EPICA ice core at Dome Concordia, Antarctica

1999 ◽  
Vol 45 (151) ◽  
pp. 547-554 ◽  
Author(s):  
Michel Gay ◽  
Jerome Weiss
Keyword(s):  
Preliminary Analysis ◽  
Structural Parameters ◽  
Ice Core ◽  
Grain Morphology ◽  
Two Dimensional ◽  
Cross Sectional ◽  
Thin Sections ◽  
Polycrystalline Ice ◽  
Analysis Application ◽  
The Mean

AbstractA digital image-processing approach is proposed which allows the extraction of two-dimensional polycrystalline ice microstructure (grain boundaries) from thin sections observed between cross-polarisers. It is based on image segmentation of colour images. The method is applied to the preliminary analysis of the shallow ( Holocene) ice of the European Project for Ice Coring in Antarctica (EPICA) ice core at Dome Concordia. Structural parameters, such as the mean cross-sectional area, shape anisotropy and grain morphology, are obtained. The interest and limitations of this automatic procedure are discussed.

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