scholarly journals HEAD-ON COLLISIONS OF TWO SOLITARY WAVES WITH DIFFERENT AMPLITUDES USING IMAGING TECHNIQUES

2017 ◽  
pp. 34
Author(s):  
Motohiko Umeyama
Keyword(s):  
Phase Shift ◽  
Solitary Waves ◽  
Imaging Techniques ◽  
Surface Displacement ◽  
Correlation Method ◽  
Arbitrary Point ◽  
Technological Advantage ◽  
Image Velocimetry ◽  
Particle Tracer ◽  
Series Of Experiments

The behavior of two unequal solitary waves during head-on collision was experimentally studied by optical and particle-tracer methods. Spatial surface profiles were measured using the particle mask correlation method and the image thresholding method, which detects the air–water boundary as a set of locally extreme luminance values. The measured surface displacement of the colliding wave was compared with the corresponding shape of a third-order perturbation approximation. In addition, to estimate the phase shift from the crest at an arbitrary point, the instantaneous surface variations were measured by two wave gauges. The kinetic features of the target and the oncoming and colliding waves were measured by a particle image velocimetry method. To solve the phase shift, we acquired the velocity fields of the colliding waves in a series of experiments and could show our technological advantage over others.

Approaching Terahertz Holography Using the Free Electron Laser

2010 ◽  
Vol 5 (4) ◽  
pp. 98-102
Author(s):  
Yuliya Yu. Choporova ◽  
Maxim G. Vlasenko ◽  
Vasily V. Gerasimov ◽  
Boris A. Knyazev ◽  
Aleksandr A. Nikitin ◽  
...  
Keyword(s):  
Free Electron ◽  
Free Electron Laser ◽  
Quantum Cascade Lasers ◽  
Imaging Techniques ◽  
Reference Beam ◽  
Image Sensors ◽  
Terahertz Range ◽  
Terahertz Region ◽  
Series Of Experiments ◽  
Cascade Lasers

Many experiments in the terahertz region have been performed using low-power shot-pulse wideband sources. Appearance of more intense monochromatic terahertz sources (quantum cascade lasers, free electron lasers) and terahertz image sensors enables the implementation of classical variants of optical techniques in the terahertz range. In this paper we describe a series of experiments to demonstrate feasibility of classic holography at the terahertz range using the Novosibirsk free electron laser. Two imaging techniques have been applied for digital hologram recording. A modified MachZehnder interferometer has been fabricated for recording the reference-beam holograms. In-line holograms have been recorded and reconstructed

scholarly journals Forces and Flow Structures on a Simplified Car Model Exposed to an Unsteady Harmonic Crosswind

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Valérie Ferrand
Keyword(s):  
Phase Shift ◽  
Transient Flow ◽  
Measurement Techniques ◽  
Flow Topology ◽  
Average Force ◽  
Ground Vehicle ◽  
Vortical Structures ◽  
Car Model ◽  
Image Velocimetry ◽  
Evolution Phase

A ground vehicle traveling along a road is subject to unsteady crosswinds in a number of situations. In windy conditions, for example, the natural atmospheric wind can exhibit strong lateral gusts. Other situations, such as tunnel exits or overtaking induce sudden changes in crosswinds, as well. The interaction of this unsteady oncoming flow with the vehicle and the resulting aerodynamic forces and moments affect the vehicle stability and comfort. The objectives of the current study are to improve the understanding of flow physics of such transient flow and ultimately to develop measurement techniques to quantify the vehicle’s sensitivity to unsteady crosswind. A square back simplified car model is exposed to a forced oscillating yaw and results are compared to static measurements. Tests are conducted at Reynolds number Re = 3.7 × 105 and reduced frequencies ranging from 0.265 × 10−2 to 5.3 × 10−2. Unsteady side force and yawing moment measurements are associated with particle image velocimetry flow fields to interpret dynamic loads in link with flow topology evolution. Phase average force and moment measurements are found to exhibit a phase shift between static and dynamic tests that increases with oscillating frequency. Velocity fields reveal that the phase-shift seems to originate from the rear part of the car model. Moreover, lateral vortical structures appearing on the lee side from β = 15 deg increase this phase-shift and consequently appear to be favorable to the lateral stability of the vehicle.

Flow visualisation of the helicopter brown-out phenomenon

2009 ◽  
Vol 113 (1145) ◽  
pp. 467-478 ◽  
Author(s):  
N. D. Nathan ◽  
R. B. Green
Keyword(s):  
Particle Image ◽  
Dust Cloud ◽  
Ground Effect ◽  
Flow Visualisation ◽  
Forward Speed ◽  
Fine Dust ◽  
Dust Clouds ◽  
Image Velocimetry ◽  
Series Of Experiments ◽  
The Mean

Abstract Quantitative and qualitative results of a series of experiments conducted on a rotor in ground effect at low forward speeds are presented. The velocity over a wide area of the ground effect wake was measured using particle image velocimetry, and the evolution of the flow is described as the forward speed increases. The formation of a dust cloud leading to so-called helicopter brown-out was simulated through a series of flow visualisation experiments. The technique involved sprinkling a fine dust on the ground below and ahead of the rotor. Larger dust clouds were observed at lower forward speed, and the dust cloud penetrated into the areas of the flow including those where vorticity levels were of low magnitude and occasional velocity fluctuations from the mean were large.

Effect of non-extensivity during the collision between inward and outward ion acoustic solitary waves in cylindrical and spherical geometry

2013 ◽  
Vol 79 (5) ◽  
pp. 789-795 ◽  
Author(s):  
UDAY NARAYAN GHOSH ◽  
PRASANTA CHATTERJEE
Keyword(s):  
Phase Shift ◽  
Perturbation Method ◽  
Solitary Waves ◽  
Spherical Geometry ◽  
Planar Geometry ◽  
Extended Version ◽  
Electrons And Positrons ◽  
Ion Acoustic Solitary Waves ◽  
Ion Acoustic ◽  
Analytical Phase

AbstractThe head-on collision between two cylindrical/spherical ion acoustic solitary waves (IASWs) in un-magnetized plasmas comprising inertial ions and q-non-extensive electrons and positrons is investigated using the extended version of the Poincaré–Lighthill–Kuo perturbation method. How the interactions are taking place in cylindrical and spherical geometry are studied, and the collision is shown at different times. The non-planar geometry can modify analytical phase shifts following the head-on collision are derived. The effects of q-non-extensive electrons and positrons on the phase shift are studied. It is shown that the properties of the interaction of IASWs in cylindrical and spherical geometry are very different.

Vision-Based Measurement of Part Deformation and Misalignment for Deformable Cylindrical Peg-in-Hole Tasks

2005 ◽  
Vol 219 (6) ◽  
pp. 589-606 ◽  
Author(s):  
J. Y. Kim
Keyword(s):  
Success Rate ◽  
Measurement Accuracy ◽  
Arbitrary Point ◽  
Image Plane ◽  
Experimental Results ◽  
Sensing System ◽  
Visual Sensing ◽  
Standard Resolution ◽  
Series Of Experiments ◽  
Assembly Operations

For successful assembly of deformable parts, information about their deformation and possible misalignments between the holes and their respective mating parts is essential. Such information can be mainly acquired from visual sensors. In this paper, part deformation and misalignment in cylindrical peg-in-hole tasks are measured by using a visual sensing system. First, the configuration and the specifications of the system, such as resolution, are described. Next, a series of experiments to measure the position of an arbitrary point are performed and its measurement accuracy is investigated. Then, an algorithm to estimate the centre-line and deformation of a cylindrical peg and an algorithm to divide and recognize a peg and a hole separately in an image are presented. On the basis of these algorithms, a series of experiments to measure part shape as part deformation are performed. Finally, an algorithm to select two views from the four on the image plane and an algorithm to estimate the centre of an occluded hole are presented. On the basis of these algorithms, a series of experiments to measure misalignment are performed. Experimental results show that the errors in measuring part deformation are approximately less than five or seven times the standard resolution of the system, and the errors in measuring misalignment are less than three or four times the standard resolution. Thereby, the system and the proposed algorithms are effective in measuring part deformation and misalignment and will dramatically increase the success rate in deformable assembly operations.

scholarly journals Volumetric Flow Rate Measurement using Surface Imaging Techniques

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Julio Enrique Chavez Dorado ◽  
, Blair Anne Johnson
Keyword(s):  
Flow Rate ◽  
Open Channel ◽  
Imaging Techniques ◽  
Volumetric Flow Rate ◽  
Flow Rate Measurement ◽  
Natural Systems ◽  
Image Velocimetry ◽  
Layer Analysis ◽  
Volumetric Discharge ◽  
Surface Particle

The purpose of our research is to validate an experimental method developed by Johnson and Cowen (2016) aimed at measuring volumetric discharge in an open channel using Surface particle image velocimetry (SPIV) combined with turbulent boundary layer analysis to infer the bathymetry and calculate volumetric flow rate, ultimately extending this work to natural systems (Hendrickson, 2020).

scholarly journals An application of Nwogu’s Boussinesq model to analyze the head-on collision process between hydroelastic solitary waves

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 177-191 ◽  
Author(s):  
Muhammad Mubashir Bhatti ◽  
Dong-Qiang Lu
Keyword(s):  
Phase Shift ◽  
Solitary Waves ◽  
Free Parameter ◽  
Wave Speed ◽  
Physical Parameters ◽  
Beam Model ◽  
Boussinesq Model ◽  
Highly Nonlinear ◽  
Run Up ◽  
The Impact

AbstractThis article deals with the nonlinear head-on collision between two hydroelastic solitary waves in plate–covered water with Nwogou’s Boussinesq model for the nonlinear fluid motion. This model contains a parameter α that is associated with horizontal velocities according to the chosen level of horizontal velocity variables. A thin elastic cover is considered as the Euler–Bernoulli beam model. To derive the series solution, we apply the Poincaré–Lighthill–Kuo (PLK) method to solve analytically the highly nonlinear coupled partial differential equations. The impact of all the physical parameters is discussed with the help of the asymptotic solutions and graphic representations. In particular, the authors address the behavior of plate deflection, maximum run-up during a collision, phase shift, distortion profile, and wave speed. It is found that the variation of the free parameter α and plate terms dramatically change the amplitude of a solitary wave. It is noticed that a very small tilting occurs due to the distortion in wave profile. The maximum run-up amplitude and the wave speed rise due to a greater influence of the free parameter. The phase shift tends to diminish due to an increment in the free parameter and plate terms. The novelty of the present methodology is compared with previously published results.

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