COLLECTIVE MODES OF THREE COUPLED RELAXATION OSCILLATORS: THE INFLUENCE OF DETUNING

1999 ◽  
Vol 09 (10) ◽  
pp. 1969-1981 ◽  
Author(s):  
DIETMAR RUWISCH ◽  
MATHIAS BODE ◽  
DENIS VOLKOV ◽  
EVGENII VOLKOV
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Slow Variable ◽  
Phase Relations ◽  
Collective Modes ◽  
Large Set ◽  
Synchronous Oscillation ◽  
Relaxation Oscillators ◽  
Basic Set ◽  
Periodic Attractors

The dynamics of a ring of three relaxation oscillators symmetrically coupled in the slow variable is considered both experimentally and by means of numerical simulations. It is shown that apart from the synchronous oscillation the basic set of periodic attractors typical for identical oscillators is not essentially affected by a small detuning. However, detuning creates a large set of new collective modes which are characterized by larger system periods and a variety of phase relations between the oscillators. Comparisons of the experimental data with different oscillator models reveal that the results do not crucially depend on the specific features of the models and possible experimental uncertainties.

COMPARISON OF NUMERICAL SIMULATIONS WITH EXPERIMENTAL DATA FOR VERTICAL ANNULAR AND CHURN GAS-LIQUID FLOWS

2020 ◽  
Author(s):  
Larissa Steiger de Freitas ◽  
Marcus Vinícius Canhoto Alves ◽  
Rafael Rodrigues Francisco
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Liquid Flows

Effect of Interaction Modeling in AFM-Based Nanomanipulation

2008 ◽  
Author(s):  
Fakhreddine Landolsi ◽  
Fathi H. Ghorbel ◽  
James B. Dabney
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Interaction Model ◽  
Collision Process ◽  
Visual Sensing ◽  
Proposed Model ◽  
Interaction Modeling

AFM-based nanomanipulation is very challenging because of the complex mechanics in tip-sample interactions and the limitations in AFM visual sensing capabilities. In the present paper, we investigate the modeling of AFM-based nanomanipulation emphasizing the effects of the relevant interactions at the nanoscale. The major contribution of the present work is the use of a combined DMT-JKR interaction model in order to describe the complete collision process between the AFM tip and the sample. The coupling between the interactions and the friction at the nanoscale is emphasized. The efficacy of the proposed model to reproduce experimental data is demonstrated via numerical simulations.

The penetration and ricochet of ogive-nosed rigid projectiles obliquely impacting metallic targets

2021 ◽  
pp. 204141962110377
Author(s):  
Yaniv Vayig ◽  
Zvi Rosenberg
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Dynamic Pressure ◽  
Oblique Impacts ◽  
Simulation Results ◽  
The Impact ◽  
Penetration Depths ◽  
Resistance To Penetration ◽  
Good Agreement

A large number of 3D numerical simulations were performed in order to follow the trajectory changes of rigid CRH3 ogive-nosed projectiles, impacting semi-infinite metallic targets at various obliquities. These trajectory changes are shown to be related to the threshold ricochet angles of the projectile/target pairs. These threshold angles are the impact obliquities where the projectiles end up moving in a path parallel to the target’s face. They were found to depend on a non-dimensional entity which is equal to the ratio between the target’s resistance to penetration and the dynamic pressure exerted by the projectile upon impact. Good agreement was obtained by comparing simulation results for these trajectory changes with experimental data from several published works. In addition, numerically-based relations were derived for the penetration depths of these ogive-nosed projectiles at oblique impacts, which are shown to agree with the simulation results.

Control and measuring modernization systems of the “Soil Channel” stand and the development of a wheel motion mathematical model in stand conditions

Trudy NAMI ◽  
2021 ◽  
pp. 25-34
Author(s):  
B. B. Kositsyn ◽  
Kh. Chzhen ◽  
R. L. Gazizullin
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Thrust Force ◽  
Bench Test ◽  
Large Set ◽  
Virtual Experiments ◽  
Automatic Mode ◽  
Wheel Rolling ◽  
Adaptive Laws ◽  
Stand Conditions

Introduction (problem statement and relevance). A promising direction for reducing a vehicle moving energy is the application of adaptive laws for controlling the power supplied to the propeller based on neural networks. To create a training array of the latter, a large set of experimental data is required, the collection of which, as a rule, is carried out by using research stands, such as the “Soil Channel”. But the fi eld studies require a lot of resources.The purpose of the study was to create a wheel rolling mathematical model in the conditions of the stand, with the help of which it would be possible to organize the collection of needed statistical data on the wheel rolling modes by calculation them in an automatic mode.Methodology and research methods. The paper describes the “Soil Channel” bench test, held by the Department of “Multipurpose tracked vehicles and mobile robots” of Bauman Moscow State Technical University. A list of the control and measuring systems components used in the process of its modernization in order to automate the collection of experimental data was considered. The “Soil Channel” stand mathematical model was presented which was based on the use of experimentally obtained dependences of the specifi c longitudinal thrust force on sliding and the specifi c longitudinal thrust force on the specifi c circumferential force.Scientifi c novelty and results. The developed mathematical model has been verifi ed on the basis of the data obtained in the course of fi eld studies. Conclusions were made about the suitability of the developed mathematical model of wheel motion under the stand conditions for conducting virtual experiments.Practical signifi cance. The data obtained by applying the developed mathematical model can be used to create a training array of a neural network to provide the implementation of adaptive laws for controlling the power supplied to the propeller.

Numerical Simulations as a Reliable Alternative for Landmine Explosion Studies: The AUTODYN Approach

2010 ◽  
Author(s):  
Stephanie Follett ◽  
Amer Hameed ◽  
S. Darina ◽  
John G. Hetherington
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Reasonable Agreement ◽  
Specific Impulse ◽  
Numerical Procedure ◽  
Ground Surface ◽  
Time Of Arrival ◽  
Linear Dynamics ◽  
Non Linear

In order to validate the numerical procedure, the explosion of a mine was recreated within the non-linear dynamics software, AUTODYN. Two models were created and analysed for the purposes of this study — buried and flush HE charge in sand. The explosion parameters — time of arrival, maximum overpressure and specific impulse were recorded at two stand-off distances above the ground surface. These parameters are then compared with LS-DYNA models and published experimental data. The results, presented in table format, are in reasonable agreement.

Rounded Fin Edge and Step Position Effects on Discharge Coefficient in Rotating Labyrinth Seals

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Andrea Rapisarda ◽  
Alessio Desando ◽  
Elena Campagnoli ◽  
Roberto Taurino
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Leading Edge ◽  
Experimental Tests ◽  
Velocity Profiles ◽  
Pollutant Emission ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Position Effects ◽  
Impact Reduction

The design of modern aircrafts propulsion systems is strongly influenced by the important objective of environmental impact reduction. Through a great number of researches carried out in the last decades, significant improvements have been obtained in terms of lower fuel consumption and pollutant emission. Experimental tests are a necessary step to achieve new solutions that are more efficient than the current designs, even if during the preliminary design phase, a valid alternative to expensive experimental tests is the implementation of numerical models. The processing power of modern computers allows indeed the simulation of more complex and detailed phenomena than the past years. The present work focuses on the implementation of a numerical model for rotating stepped labyrinth seals installed in low-pressure turbines. These components are widely employed in sealing turbomachinery to reduce the leakage flow between rotating components. The numerical simulations were performed by using computational fluid dynamics (CFD) methodology, focusing on the leakage performances at different rotating speeds and inlet preswirl ratios. Investigations on velocity profiles into seal cavities were also carried out. To begin with, a smooth labyrinth seal model was validated by using the experimental data found in the literature. The numerical simulations were extended to the honeycomb labyrinth seals, with the validation performed on the velocity profiles. Then, the effects of two geometrical parameters, the rounded fin tip leading edge, and the step position were numerically investigated for both smooth and honeycomb labyrinth seals. The obtained results are generally in good agreement with the experimental data. The main effect found when the fin tip leading edge was rounded was a large increase in leakage flow, while the step position contribution to the flow path behavior is nonmonotone.

scholarly journals Influence of Induction Hardening on Wear Resistance in Case of Rolling Contact

2016 ◽  
Vol 66 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Michal Šofer ◽  
Rostislav Fajkoš ◽  
Radim Halama
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Induction Hardening ◽  
Rolling Contact ◽  
Isotropic Hardening ◽  
Wear Model ◽  
Wear Rates ◽  
C Programming Language ◽  
Hardening Rule ◽  
C Programming

AbstractThe main aim of the presented paper is to show how heat treatment, in our case the induction hardening, will affect the wear rates as well as the ratcheting evolution process beneath the contact surface in the field of line rolling contact. Used wear model is based on shear band cracking mechanism [1] and non-linear kinematic and isotropic hardening rule of Chaboche and Lemaitre. The entire numerical simulations have been realized in the C# programming language. Results from numerical simulations are subsequently compared with experimental data.

scholarly journals Differential and integral cross sections for electron elastic scattering by ammonia for incident energies ranging from 10 eV to 20 keV

2018 ◽  
Vol 64 (5) ◽  
pp. 498
Author(s):  
Hocine Aouchiche
Keyword(s):  
Experimental Data ◽  
Elastic Scattering ◽  
Cross Sections ◽  
Optical Potential ◽  
Large Set ◽  
Quantum Calculation ◽  
Hartree Fock ◽  
Spherical Complex ◽  
Static Part ◽  
Model Point

Differential and integral cross sections for elastic scattering of electron by NH3 molecule are investigated for the energy ranging from 10 eV to 20 keV.  The calculations are carried out in the framework of partial wave formalism describing the target molecule by means of one center molecular Hartree-Fock functions.  A spherical complex optical potential used includes a static part – obtained here numerically from quantum calculation – and fine effects like correlation, polarization and exchange potentials. The results obtained in this model point out clearly the role played by the exchange and the correlation-polarization contributions in particular at lower scattering angles and lower incident energies. Both differential and integral cross sections obtained are compared with a large set of experimental data available in the literature and well agreement is found throughout the scattering angles and whole energy range investigated here.

scholarly journals Quantitative Assessment of the Influence of Tensile Softening of Concrete in Beams under Bending by Numerical Simulations with XFEM and Cohesive Cracks

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 626
Author(s):  
Ireneusz Marzec ◽  
Jerzy Bobiński
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Extended Finite Element ◽  
Three Point Bending ◽  
Material Parameters ◽  
Error Measures ◽  
Rational Bézier Curve ◽  
Initial Fracture ◽  
Experimental Values ◽  
Tensile Softening

Results of the numerical simulations of the size effect phenomenon for concrete in comparison with experimental data are presented. In-plane geometrically similar notched and unnotched beams under three-point bending are analyzed. EXtended Finite Element Method (XFEM) with a cohesive softening law is used. Comprehensive parametric study with the respect to the tensile strength and the initial fracture energy is performed. Sensitivity of the results with respect to the material parameters and the specimen geometry is investigated. Three different softening laws are examined. First, a bilinear softening definition is utilized. Then, an exponential curve is taken. Finally, a rational Bezier curve is tested. An ambiguity in choosing material parameters and softening curve definitions is discussed. Numerical results are compared with experimental outcomes recently reported in the literature. Two error measures are defined and used to quantitatively assess calculated maximum forces (nominal strengths) in comparison with experimental values as a primary criterion. In addition, the force—displacement curves are also analyzed. It is shown that all softening curves produce results consistent with the experimental data. Moreover, with different softening laws assumed, different initial fracture energies should be taken to obtain proper results.

scholarly journals Static stability predicts the continuum of interleg coordination patterns in Drosophila

2018 ◽  
Author(s):  
Nicholas S. Szczecinski ◽  
Till Bockemühl ◽  
Alexander S. Chockley ◽  
Ansgar Büschges
Keyword(s):  
Experimental Data ◽  
Static Stability ◽  
Fruit Flies ◽  
Coordination Pattern ◽  
Large Set ◽  
Summary Statement ◽  
Walking Speeds ◽  
Coordination Patterns ◽  
Phase Relationships ◽  
The Continuum

AbstractDuring walking, insects must coordinate the movements of their six legs for efficient locomotion. This interleg coordination is speed-dependent; fast walking in insects is associated with tripod coordination patterns, while slow walking is associated with more variable, tetrapod-like patterns. To date, however, there has been no comprehensive explanation as to why these speed-dependent shifts in interleg coordination should occur in insects. Tripod coordination would be sufficient at low walking speeds. The fact that insects use a different interleg coordination pattern at lower speeds suggests that it is more optimal or advantageous at these speeds. Furthermore, previous studies focused on discrete tripod and tetrapod coordination patterns. Experimental data, however, suggest that changes observed in interleg coordination are part of a speed-dependent spectrum. Here, we explore these issues in relation to static stability as an important aspect of interleg coordination in Drosophila. We created a model that uses basic experimentally measured parameters in fruit flies to find the interleg phase relationships that maximize stability for a given walking speed. Based on this measure, the model predicted a continuum of interleg coordination patterns spanning the complete range of walking speeds. Furthermore, for low walking speeds the model predicted tetrapod-like patterns to be most stable, while at high walking speeds tripod coordination emerged as most optimal. Finally, we validated the basic assumption of a continuum of interleg coordination patterns in a large set of experimental data from walking fruit flies and compared these data with the model-based predictions.Summary statementA simple stability-based modelling approach can explain why walking insects use different leg coordination patterns in a speed-dependent way.

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