scholarly journals Mobility of an axisymmetric particle near an elastic interface

2016 ◽  
Vol 811 ◽  
pp. 210-233 ◽  
Author(s):  
Abdallah Daddi-Moussa-Ider ◽  
Maciej Lisicki ◽  
Stephan Gekle
Keyword(s):  
Detailed Comparison ◽  
Boundary Integral ◽  
Particle Orientation ◽  
Spheroidal Particle ◽  
Analytical Approximations ◽  
Elastic Interface ◽  
General Relations ◽  
Independent Parameters ◽  
Membrane Particle ◽  
Good Agreement

Using a fully analytical theory, we compute the leading-order corrections to the translational, rotational and translation–rotation coupling mobilities of an arbitrary axisymmetric particle immersed in a Newtonian fluid moving near an elastic cell membrane that exhibits resistance towards stretching and bending. The frequency-dependent mobility corrections are expressed as general relations involving separately the particle’s shape-dependent bulk mobility and the shape-independent parameters such as the membrane–particle distance, the particle orientation and the characteristic frequencies associated with shearing and bending of the membrane. This makes the equations applicable to an arbitrary-shaped axisymmetric particle provided that its bulk mobilities are known, either analytically or numerically. For a spheroidal particle, these general relations reduce to simple expressions in terms of the particle’s eccentricity. We find that the corrections to the translation–rotation coupling mobility are primarily determined by bending, whereas shearing manifests itself in a more pronounced way in the rotational mobility. We demonstrate the validity of the analytical approximations by a detailed comparison with boundary integral simulations of a truly extended spheroidal particle. They are found to be in a good agreement over the whole range of applied frequencies.

scholarly journals Nonlinear two-dimensional free surface solutions of flow exiting a pipe and impacting a wedge

2021 ◽  
Vol 126 (1) ◽  
Author(s):  
Alex Doak ◽  
Jean-Marc Vanden-Broeck
Keyword(s):  
Surface Tension ◽  
Integral Equation ◽  
Free Surface ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Two Dimensional ◽  
Numerical Schemes ◽  
Additional Advantage ◽  
Infinite Wedge ◽  
Good Agreement

AbstractThis paper concerns the flow of fluid exiting a two-dimensional pipe and impacting an infinite wedge. Where the flow leaves the pipe there is a free surface between the fluid and a passive gas. The model is a generalisation of both plane bubbles and flow impacting a flat plate. In the absence of gravity and surface tension, an exact free streamline solution is derived. We also construct two numerical schemes to compute solutions with the inclusion of surface tension and gravity. The first method involves mapping the flow to the lower half-plane, where an integral equation concerning only boundary values is derived. This integral equation is solved numerically. The second method involves conformally mapping the flow domain onto a unit disc in the s-plane. The unknowns are then expressed as a power series in s. The series is truncated, and the coefficients are solved numerically. The boundary integral method has the additional advantage that it allows for solutions with waves in the far-field, as discussed later. Good agreement between the two numerical methods and the exact free streamline solution provides a check on the numerical schemes.

Rigid-Plastic Impact of Single Angular Particles

2021 ◽  
Author(s):  
Sandeep Dhar
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Orientation Dependence ◽  
Particle Orientation ◽  
Rigid Plastic ◽  
Plastic Model ◽  
Model Predictions ◽  
Good Agreement ◽  
Angular Particles

The trajectory of an angular particle as it cuts a ductile target is, in general, complicated because of its dependence not only on particle shape, but also on particle orientation at the initial instant of impact. This orientation dependence has also made experimental measurement of impact parameters of single angular particles very difficult, resulting in a relatively small amount of available experimental data in the literature. The current work is focused on obtaining measurements of particle kinematics for comparison to rigid plastic model developed by Papini and Spelt. Fundamental mechanisms of material removal are identified, and measurements of rebound parameters and corresponding crater dimensions of single hardened steel particles launched against flat aluminium alloy targets are presented. Also a 2-D finite element model is developed and a dynamic analysis is performed to predict the erosion mechanism. Overall, a good agreement was found among the experimental results, rigid-plastic model predictions and finite element model predictions.

scholarly journals In-Depth Verification of a Numerical Model for an Axisymmetric RC Dome

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2152
Author(s):  
Przemysław Czumaj ◽  
Sławomir Dudziak ◽  
Zbigniew Kacprzyk
Keyword(s):  
Three Dimensional ◽  
Spatial Models ◽  
Detailed Comparison ◽  
The Finite Element Method ◽  
Robot System ◽  
Engineering Structures ◽  
Computational Analyses ◽  
Computational Systems ◽  
Good Agreement ◽  
Made In

The designers of civil engineering structures often have to face the problem of the reliability of complex computational analyses performed most often with the Finite Element Method (FEM). Any assessment of reliability of such analyses is difficult and can only be approximate. The present paper puts forward a new method of verification and validation of the structural analyses upon an illustrative example of a dome strengthened by circumferential ribs along the upper and lower edges. Four computational systems were used, namely Abaqus, Autodesk Robot, Dlubal RFEM, and FEAS. Different models were also analyzed—two-dimensional (2D) and three-dimensional (3D) ones using continuum, bar, and shell finite elements. The results of the static (with two kinds of load—self-weight and load distributed along the upper ring) and modal analyses are presented. A detailed comparison between the systems’ and models’ predictions was made. In general, the spatial models predicted a less stiff behavior of the analyzed dome than the planar models. The good agreement between different models and systems was obtained for the first natural frequency with axisymmetric eigenmodes (except from the Autodesk Robot system). The presented approach to the verification of complex shell–bar models can be effectively applied by structural designers.

Longitudinal characterization of the wake and electron bunch in a laser wakefield accelerator

2019 ◽  
Vol 85 (1) ◽  
Author(s):  
Zhijun Zhang ◽  
Wentao Wang ◽  
Jiansheng Liu ◽  
Ming Fang ◽  
Wentao Li ◽  
...  
Keyword(s):  
Electron Bunch ◽  
Detailed Comparison ◽  
Beam Loading ◽  
Space Rotation ◽  
Laser Wakefield ◽  
Chirp Compensation ◽  
Wakefield Accelerator ◽  
Good Agreement ◽  
Laser Wakefield Accelerator

Energy chirp compensation of the electron bunch (e-bunch) in a laser wakefield accelerator, which is caused by the phase space rotation in the gradient wakefield, has been applied in many schemes for low energy spread e-bunch generation. We report the experimental observation of energy chirp compensation of the e-bunch in a nonlinear laser wakefield accelerator with a negligible beam loading effect. By adjusting the acceleration length using a wedge-roof block, the chirp compensation of the accelerated e-bunch was observed via an electron spectrometer. Apart from this, some significant parameters for the compensation process, such as the longitudinal dispersion and wakefield slope at the bunch position, were also estimated. A detailed comparison between experiment and simulation shows good agreement of the wakefield and bunch parameters. These results give a clear demonstration of the longitudinal characteristics of the wakefield in a plasma and the bunch dynamics, which are important for better control of a compact laser wakefield accelerator.

Analytical and Numerical Study of Nearshore Multiple Oscillating Water Columns

2013 ◽  
Author(s):  
Kourosh Rezanejad ◽  
Joydip Bhattacharjee ◽  
C. Guedes Soares
Keyword(s):  
Water Depth ◽  
Numerical Study ◽  
Integral Equation Method ◽  
Wave Theory ◽  
Boundary Integral ◽  
Water Columns ◽  
Finite Water Depth ◽  
Cartesian Coordinate ◽  
Oscillating Water Columns ◽  
Good Agreement

In the present study, the performance of two chamber nearshore oscillating water columns (OWCs) in finite water depth is analyzed based on the linearized water wave theory in the two dimensional Cartesian coordinate systems. The barriers are assumed to be fixed and the turbine characteristics are assumed linear with respect to the fluctuations of volume flux and pressure inside the chamber. The free surface inside the chambers is modeled as a non-plane wave surface. Two different mathematical models are employed to solve the hydrodynamic problem; the semi-analytic method of matched eigenfunction expansion and the numerical scheme of Boundary Integral Equation Method (BIEM). The numerical results are compared with the semi-analytic results and show good agreement. The effects of the distance between the barriers and the length of the barriers on the efficiency of the OWC device are investigated. The results of two chambers OWC are also compared with the results for an equivalent single OWC chamber. Further, the effect of the water depth on the capacity of the wave power absorption is discussed.

Determining the orientation of marine CSEM receivers using orthogonal Procrustes rotation analysis

Geophysics ◽  
2010 ◽  
Vol 75 (3) ◽  
pp. F63-F70 ◽  
Author(s):  
Kerry Key ◽  
Andrew Lockwood
Keyword(s):  
Field Vector ◽  
Northwest Coast ◽  
Gas Field ◽  
Procrustes Rotation ◽  
Data Application ◽  
Orientation Method ◽  
Marine Csem ◽  
2D Data ◽  
Independent Parameters ◽  
Good Agreement

Electromagnetic receivers deployed to the seafloor for CSEM surveys can have unknown orientations because of the unavailability of compass and tilt recordings. In such situations, only the orientation-independent parameters derived from the measured CSEM field vector can be interpreted, and this may result in less structural resolution than possible when the sensor orientations are known. An orthogonal Procrustes rotation analysis (OPRA) technique can be used to estimate the full 3D receiver orientation for inline and off-line CSEM receivers. The generality of this method allows it to be easily embedded into nonlinear CSEM inversion routines so that they iteratively search for both the receiver orientation and a seafloor electrical-conductivity model compatible with the data. Synthetic tests using the OPRA method jointly with a 1D inversion demonstrate that it can recover the rotation and tilt angles to about one degree accuracy for 1D data and to within a few degrees for 2D data. Application of this method to real survey data shows good agreement with a previous orientation method that is suitable only for determining the horizontal rotation of inline receivers. CSEM data collected over the Pluto gas field offshore the northwest coast of Australia were used to demonstrate how the OPRA method can be used to orient CSEM receivers prior to inversion of only the inline electric- and crossline magnetic-field components.

Contributions to the theory of heterogeneous barrier layer rectifiers

1951 ◽  
Vol 206 (1087) ◽  
pp. 477-488 ◽  
Keyword(s):  
Schottky Barrier ◽  
Barrier Layer ◽  
Diffusion Theory ◽  
Arbitrary Distribution ◽  
Voltage Curve ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
General Relations ◽  
And Diffusion ◽  
Good Agreement

Assuming an arbitrary distribution of space charge in the barrier layer of a rectifier, the general form of the current-voltage relation has been derived on both diode and diffusion theory. A connexion, valid for most barriers, between this characteristic and the capacitance-voltage curve has been pointed out, and it has been shown that the Sachs breakdown voltage can be deduced from the latter characteristic. The general relations have been applied to a barrier whose distribution of impurity centres is assumed to establish itself by a diffusion process. Its properties have been investigated, and it has been found that the shapes of the experimental d. c. characteristics, considered in a previous paper (Landsberg 1951 b ), are in the same good agreement with the hypothesis of this barrier as they are with the hypothesis of a Schottky barrier. The difficulties regarding the constants of the rectifiers , as obtained from the experimental curves, are, however, greatly alleviated if the present barriers rather than Schottky’s barrier is assumed. It has been shown that both barriers belong to a whole class of barrier layers whose d. c. and capacitance-voltage curves have the same shape as the corresponding curves for a Schottky barrier.

Elastic Constants of Nematic Liquid Crystals

1972 ◽  
Vol 27 (6) ◽  
pp. 966-976 ◽  
Author(s):  
Hans Gruler ◽  
Terry J. Scheffer ◽  
Gerhard Meier
Keyword(s):  
Magnetic Fields ◽  
Electric Fields ◽  
Detailed Comparison ◽  
Theoretical Treatment ◽  
Electrical Capacitance ◽  
Normal Deformation ◽  
Electric And Magnetic Fields ◽  
The Magnetic Field ◽  
Dynamic Phenomena ◽  
Good Agreement

Abstract We present a theoretical treatment and give experimental observations of the deformation that occurs in a nematic liquid crystal when electric or magnetic fields are applied. We consider only normal deformations in the nematic material where fluid flow and other dynamic phenomena play no role. Three important sample geometries are considered in the magnetic field, and the experimentally observed deformations are in good agreement with theory. The normal deformation induced by electric fields is of interest from a device standpoint, and we give a solution for the deformation that is valid even for large dielectric anisotropics. This solution has been experimentally verified. We give a detailed comparison of the distortions produced by electric and magnetic fields and show that the deformations are of a similar form even though the field is nonuniform in the electric case. The change in birefringence and electrical capacitance as a function of distortion is discussed as a means of observing the deformation.

The vorticity versus the scalar criterion for the detection of the turbulent/non-turbulent interface

2014 ◽  
Vol 750 ◽  
pp. 578-596 ◽  
Author(s):  
Markus Gampert ◽  
Jonas Boschung ◽  
Fabian Hennig ◽  
Michael Gauding ◽  
Norbert Peters
Keyword(s):  
Mixing Layer ◽  
Detailed Comparison ◽  
Passive Scalar ◽  
Normal Vector ◽  
Interface Position ◽  
Conditional Mean ◽  
Vortex Lines ◽  
The Mean ◽  
Conditional Statistics ◽  
Good Agreement

AbstractBased on a direct numerical simulation (DNS) of a temporally evolving mixing layer, we present a detailed study of the turbulent/non-turbulent (T/NT) interface that is defined using the two most common procedures in the literature, namely either a vorticity or a scalar criterion. The different detection approaches are examined qualitatively and quantitatively in terms of the interface position, conditional statistics and orientation of streamlines and vortex lines at the interface. Computing the probability density function (p.d.f.) of the mean location of the T/NT interface from vorticity and scalar allows a detailed comparison of the two methods, where we observe a very good agreement. Furthermore, conditional mean profiles of various quantities are evaluated. In particular, the position p.d.f.s for both criteria coincide and are found to follow a Gaussian distribution. The terms of the governing equations for vorticity and passive scalar are conditioned on the distance to the interface and analysed. At the interface, vortex stretching is negligible and the displacement of the vorticity interface is found to be determined by diffusion, analogous to the scalar interface. In addition, the orientation of vortex lines at the vorticity and the scalar based T/NT interface are analyzed. For both interfaces, vorticity lines are perpendicular to the normal vector of the interface, i.e. parallel to the interface isosurface.

scholarly journals Direct Fiber Simulation of a Compression Molded Ribbed Structure Made of a Sheet Molding Compound with Randomly Oriented Carbon/Epoxy Prepreg Strands—A Comparison of Predicted Fiber Orientations with Computed Tomography Analyses

2020 ◽  
Vol 4 (4) ◽  
pp. 164
Author(s):  
Jan Teuwsen ◽  
Stephan K. Hohn ◽  
Tim A. Osswald
Keyword(s):  
Computed Tomography ◽  
Detailed Comparison ◽  
Micro Computed Tomography ◽  
Molding Compound ◽  
Sheet Molding Compound ◽  
Discontinuous Fiber ◽  
Orientation Tensors ◽  
Fiber Sheet ◽  
Local Fiber ◽  
Good Agreement

Discontinuous fiber composites (DFC) such as carbon fiber sheet molding compounds (CF-SMC) are increasingly used in the automotive industry for manufacturing lightweight parts. Due to the flow conditions during compression molding of complex geometries, a locally varying fiber orientation evolves. Knowing these process-induced fiber orientations is key to a proper part design since the mechanical properties of the final part highly depend on its local microstructure. Local fiber orientations can be measured and analyzed by means of micro-computed tomography (µCT) and digital image processing, or predicted by process simulation. This paper presents a detailed comparison of numerical and experimental analyses of compression molded ribbed hat profile parts made of CF-SMC with 50 mm long randomly oriented strands (ROS) of chopped unidirectional (UD) carbon/epoxy prepreg tape. X-ray µCT scans of three entire CF-SMC parts are analyzed to compare determined orientation tensors with those coming from a direct fiber simulation (DFS) tool featuring a novel strand generation approach, realistically mimicking the initial ROS charge mesostructure. The DFS results show an overall good agreement of predicted local fiber orientations with µCT measurements, and are therefore precious information that can be used in subsequent integrative simulations to determine the part’s mesostructure-related anisotropic behavior under mechanical loads.

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