scholarly journals A Basic Complete Numerical Toolbox for Picosecond Ultrasonics

Acoustics ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 137-155
Author(s):  
Philippe Babilotte
Keyword(s):  
Numerical Simulation ◽  
Laser Beam ◽  
Bulk Material ◽  
Optical Signal ◽  
Mechanical Wave ◽  
Acoustic Spectrum ◽  
Experimental Works ◽  
First Time ◽  
Measured Response ◽  
Pump Laser Beam

A complete numerical complete toolbox is proposed concerning the simulation of photo-induced propagative mechanical wave, and concerning the optical reflectometric measured response of the material, which is initially exposed to a first pump laser beam that photo-induces the acoustic wavefronts. The deformation field and its propagation into a bulk material are simulated. Based on this field expression, the complex transient reflectivity is given for a medium considered as homogeneous. The real part of this quantity permits afterwards to propose a numerical simulation of the transient reflectivity, which corresponds to the optical signal measured during experimental works. The frequency acoustic spectrum is simulated and successfully compared to the measured frequency spectrum. For the first time, numerical complete developments are explicitly proposed and fully-developed under the SciLab ® environment, related to the simulation of laser-induced picosecond acoustic wavefront photogenerated through an opto-acoustic transduction process (ultrasonics and pretersonics).

scholarly journals The Turbulent Flow over the BARC Rectangular Cylinder: A DNS Study

2021 ◽  
Author(s):  
Alessandro Chiarini ◽  
Maurizio Quadrio
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Finite Differences ◽  
Turbulence Models ◽  
Fine Tuning ◽  
Rectangular Cylinder ◽  
Budget Equation ◽  
Complete Set ◽  
First Time

AbstractA direct numerical simulation (DNS) of the incompressible flow around a rectangular cylinder with chord-to-thickness ratio 5:1 (also known as the BARC benchmark) is presented. The work replicates the first DNS of this kind recently presented by Cimarelli et al. (J Wind Eng Ind Aerodyn 174:39–495, 2018), and intends to contribute to a solid numerical benchmark, albeit at a relatively low value of the Reynolds number. The study differentiates from previous work by using an in-house finite-differences solver instead of the finite-volumes toolbox OpenFOAM, and by employing finer spatial discretization and longer temporal average. The main features of the flow are described, and quantitative differences with the existing results are highlighted. The complete set of terms appearing in the budget equation for the components of the Reynolds stress tensor is provided for the first time. The different regions of the flow where production, redistribution and dissipation of each component take place are identified, and the anisotropic and inhomogeneous nature of the flow is discussed. Such information is valuable for the verification and fine-tuning of turbulence models in this complex separating and reattaching flow.

Numerical Simulation on Temperature Field in Multi-Layers Inside-Beam Powder Feeding when Laser Cladding

2012 ◽  
Vol 499 ◽  
pp. 114-119 ◽  
Author(s):  
Ming Di Wang ◽  
Shi Hong Shi ◽  
X.B. Liu ◽  
Cheng Fa Song ◽  
Li Ning Sun
Keyword(s):  
Numerical Simulation ◽  
Heat Source ◽  
Laser Beam ◽  
Cooling Rate ◽  
Light Source ◽  
Laser Cladding ◽  
Laser Scanning ◽  
Initial Conditions ◽  
Cladding Layer ◽  
Powder Feeding

Numerical simulation of laser cladding is the main research topics for many universities and academes, but all researchers used the Gaussian laser light source. Due to using inside-beam powder feeding for laser cladding, the laser is dispersed by the cone-shaped mirror, and then be focused by the annular mirror, the laser can be assumed as the light source of uniform intensity.In this paper,the temperature of powder during landing selected as the initial conditions, and adopting the life-and-death unit method, the moving point heat source and the uniform heat source are realized. In the thickness direction, using the small melt layer stacking method, a finite element model has been established, and layer unit is acted layer by layer, then a virtual reality laser cladding manu-facturing process is simulated. Calculated results show that the surface temperature of the cladding layer depends on the laser scanning speed, powder feed rate, defocus distance. As cladding layers increases, due to the heat conduction into the base too late, bath temperature will gradually increase. The highest temperature is not at the laser beam, but at the later point of the laser beam. In the clad-ding process, the temperature cooling rate of the cladding layer in high temperature section is great, and in the low-temperature, cooling rate is relatively small. These conclusions are also similar with the normal laser cladding. Finally, some experiments validate the simulation results. The trends of simulating temperature are fit to the actual temperature, and the temperature gradient can also ex-plain the actual shape of cross-section.

Coupled electric fields in photorefractive driven liquid crystal hybrid cells – theory and numerical simulation

2016 ◽  
Vol 24 (4) ◽  
Author(s):  
P. Moszczyński ◽  
A. Walczak ◽  
P. Marciniak
Keyword(s):  
Numerical Simulation ◽  
Laser Beam ◽  
Electric Fields ◽  
Cell Response ◽  
Liquid Crystalline ◽  
Driving Field ◽  
Self Organized ◽  
Photosensitive Polymer ◽  
Photosensitive Layer ◽  
External Driving

AbstractIn cyclic articles previously published we described and analysed self-organized light fibres inside a liquid crystalline (LC) cell contained photosensitive polymer (PP) layer. Such asymmetric LC cell we call a hybrid LC cell. Light fibre arises along a laser beam path directed in plane of an LC cell. It means that a laser beam is parallel to photosensitive layer. We observed the asymmetric LC cell response on an external driving field polarization. Observation has been done for an AC field first. It is the reason we decided to carry out a detailed research for a DC driving field to obtain an LC cell response step by step. The properly prepared LC cell has been built with an isolating layer and garbage ions deletion. We proved by means of a physical model, as well as a numerical simulation that LC asymmetric response strongly depends on junction barriers between PP and LC layers. New parametric model for a junction barrier on PP/LC boundary has been proposed. Such model is very useful because of lack of proper conductivity and charge carriers of band structure data on LC material.

scholarly journals Performance Evaluation of a Nanomaterial-Based Thermoelectric Generator with Tapered Legs

2020 ◽  
Vol 7 ◽  
pp. 48-54
Author(s):  
Marilyn A. Ebiringa ◽  
John Paul Adimonyemma ◽  
Chika Maduabuchi
Keyword(s):  
Cross Sections ◽  
Thermoelectric Generator ◽  
Bulk Material ◽  
Electrical Energy ◽  
Ansys Software ◽  
Thermoelectric Effects ◽  
Trapezoidal Shape ◽  
Solar Radiation Intensity ◽  
Geometry Configuration ◽  
First Time

A thermoelectric generator (TEG) converts thermal energy to electricity using thermoelectric effects. The amount of electrical energy produced is dependent on the thermoelectric material properties. Researchers have applied nanomaterials to TEG systems to further improve the device’s efficiency. Furthermore, the geometry of the thermoelectric legs has been varied from rectangular to trapezoidal and even X-cross sections to improve TEG’s performance further. However, up to date, a nanomaterial TEG that uses tapered thermoelectric legs has not been developed before. The most efficient nanomaterial TEGs still make use of the conventional rectangular leg geometry. Hence, for the first time since the conception of nanostructured thermoelectrics, we introduce a trapezoidal shape configuration in the device design. The leg geometries were simulated using ANSYS software and the results were post-processed in the MATLAB environment. The results show that the power density of the nanoparticle X-leg TEG was 10 times greater than that of the traditional bulk material semiconductor X-leg TEG. In addition, the optimum leg geometry configuration in a nanomaterial-based TEG is dependent on the operating solar radiation intensity.

Automated heat source calibration for the numerical simulation of laser beam welded components

2016 ◽  
Vol 10 (2) ◽  
pp. 129-136 ◽  
Author(s):  
A. Belitzki ◽  
C. Marder ◽  
A. Huissel ◽  
M. F. Zaeh
Keyword(s):  
Numerical Simulation ◽  
Heat Source ◽  
Laser Beam

scholarly journals Steel Sheets Laser Lap Joint Welding—Process Analysis

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2258 ◽  
Author(s):  
Hubert Danielewski ◽  
Andrzej Skrzypczyk
Keyword(s):  
Numerical Simulation ◽  
Laser Beam ◽  
Steel Sheet ◽  
Process Analysis ◽  
Welding Process ◽  
Parameters Estimation ◽  
Welding Parameters ◽  
Lap Joint ◽  
Beam Radiation ◽  
Keyhole Effect

This article presents the results of steel-sheet lap-joint-welding using laser beam radiation. The use of a laser beam and keyhole effect for deep material penetration in lap joint welding was presented. Thermodynamic mechanism of laser welding is related to material properties and process parameters. Estimation of welding parameters and joint properties’ analysis was performed through numerical simulation. The article presents a possibility of modeling laser lap-joint welding by using Simufact Welding software based on Marc solver and thermo-mechanical solution. Numerical calculation was performed for surface and conical volumetric heat sources simulating laser absorption and keyhole effect during steel sheet welding. Thermo-mechanical results of fusion zone (FZ), heat-affected zone (HAZ) and phase transformations calculated in numerical simulation were analyzed. The welding parameters for partial sealed joint penetration dedicated for gas piping installations were estimated from the numerical analysis. Low-carbon constructional steel was used for numerical and experimental analyses. A trial joint based on the estimated parameters was prepared by using a CO2 laser. Numerical and experimental results in the form of hardness distributions and weld geometry were compared. Metallographic analysis of the obtained weld was presented, including crystallographic structures and inclusions in the cross section of the joint.

scholarly journals One-Step Femtosecond Laser Stealth Dicing of Quartz

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 327 ◽  
Author(s):  
Caterina Gaudiuso ◽  
Annalisa Volpe ◽  
Antonio Ancona
Keyword(s):  
Laser Beam ◽  
Bulk Material ◽  
Laser Pulses ◽  
Ultrashort Laser Pulses ◽  
Focal Volume ◽  
Step Method ◽  
Compressive Stresses ◽  
Scan Speed ◽  
One Step ◽  
Ultrashort Laser

We report on a one-step method for cutting 250-µm-thick quartz plates using highly focused ultrashort laser pulses with a duration of 200 fs and a wavelength of 1030 nm. We show that the repetition rate, the scan speed, the pulse overlap and the pulse energy directly influence the cutting process and quality. Therefore, a suitable choice of these parameters was necessary to get single-pass stealth dicing with neat and flat cut edges. The mechanism behind the stealth dicing process was ascribed to tensile stresses generated by the relaxation of the compressive stresses originated in the laser beam focal volume during irradiation in the bulk material. Such stresses produced micro-fractures whose controlled propagation along the laser beam path led to cutting of the samples.

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