The influence of gas jet velocity in laser heating—a moving workpiece case

2000 ◽  
Vol 214 (8) ◽  
pp. 1059-1078 ◽  
Author(s):  
S Z Shuja ◽  
B S Yilbas
Keyword(s):  
Laser Heating ◽  
Control Volume ◽  
Steel Substrate ◽  
Finite Thickness ◽  
Three Dimensional ◽  
Gas Jet ◽  
Maximum Temperature ◽  
Heating Process ◽  
Jet Velocity ◽  
Energy Equations

In the present study, gas jet-assisted laser heating of a moving steel substrate with finite thickness is considered. Three-dimensional flow and energy equations with variable properties of the gas are introduced in modelling the heating process. The low Reynolds number k-ε model is employed to account for the turbulence. A numerical scheme using a control volume approach is introduced to discretize the governing equations. The simulation is repeated for three assisting gas jet velocities (100, 10, 1 m/s) and a constant workpiece speed (0.3 m/s). It is found that the effect of assisting gas jet velocity on the surface temperature is more pronounced in the cooling cycle than in the heating cycle of the laser heating process. The workpiece movement affects the location of the maximum temperature at the surface, which moves away from the initially irradiated spot centre in the direction of motion of the workpiece.

Effect of Periodic Imposed Heat Flux on Three-Dimensional Natural Convection in a Partially Heated Cubical Enclosure

2016 ◽  
Vol 831 ◽  
pp. 83-91
Author(s):  
Lahoucine Belarche ◽  
Btissam Abourida
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Maximum Temperature ◽  
Cubical Enclosure ◽  
Simplec Algorithm ◽  
Volume Method

The three-dimensional numerical study of natural convection in a cubical enclosure, discretely heated, was carried out in this study. Two heating square sections, similar to the integrated electronic components, are placed on the vertical wall of the enclosure. The imposed heating fluxes vary sinusoidally with time, in phase and in opposition of phase. The temperature of the opposite vertical wall is maintained at a cold uniform temperature and the other walls are adiabatic. The governing equations are solved using Control volume method by SIMPLEC algorithm. The sections dimension ε = D / H and the Rayleigh number Ra were fixed respectively at 0,35 and 106. The average heat transfer and the maximum temperature on the active portions will be examined for a given set of the governing parameters, namely the amplitude of the variable temperatures a and their period τp. The obtained results show significant changes in terms of heat transfer, by proper choice of the heating mode and the governing parameters.

A Three-Dimensional Numerical Study of Tin Droplets Landing Sequentially on a Solid Surface

2002 ◽  
Author(s):  
R. Ghafouri-Azar ◽  
J. Mostaghimi ◽  
S. Chandra
Keyword(s):  
Surface Deformation ◽  
Numerical Study ◽  
Control Volume ◽  
Three Dimensional ◽  
Sequential Deposition ◽  
Free Surface Deformation ◽  
Energy Equations ◽  
Simulated Images ◽  
D Model ◽  
Shape And Size

A three-dimensional (3-D) model of spreading and solidification was used to investigate the sequential deposition of two tin droplets for different offset landing. Numerical simulations predicted the shape and size of the landing tin droplet as it spread over a previously landed splat. The model applies a fixed-grid Eulerian control volume to solve the fluid dynamics and energy equations. The Volume of Fluid (VOF) algorithm is used to track the free surface deformation. The comparison of the simulated images and experimental photographs validated the prediction of the model.

Three-Dimensional Temperature Distribution in EHD Lubrication: Part II—Point Contact and Numerical Formulation

1993 ◽  
Vol 115 (1) ◽  
pp. 36-45 ◽  
Author(s):  
Kyung-Hoon Kim ◽  
Farshid Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Numerical Study ◽  
Control Volume ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Numerical Formulation ◽  
Energy Equations

A numerical study of Newtonian thermal elastohydrodynamic lubrication (EHD) of rolling/sliding point contacts has been conducted. The two-dimensional Reynolds, elasticity and the three-dimensional energy equations were solved simultaneously to obtain the pressure, film thickness and temperature distribution within the lubricant film. The control volume approach was employed to discretize the differential equations and the multi-level multi-grid technique was used to simultaneously solve them. The discretized equations, as well as the nonorthogonal coordinate transformation used for the solution of the energy equation, are described. The pressure, film thickness and the temperature distributions, within the lubricant film at different loads, slip conditions and ellipticity parameters are presented.

Nonlinear Numerical Analysis in Transient Cutting Tool Temperatures

2003 ◽  
Vol 125 (1) ◽  
pp. 48-56 ◽  
Author(s):  
Tien-Chien Jen ◽  
Sunil Eapen ◽  
Gustavo Gutierrez
Keyword(s):  
Heat Flux ◽  
Cutting Tool ◽  
Process Development ◽  
Control Volume ◽  
Computing Time ◽  
Three Dimensional ◽  
Nonlinear Effects ◽  
Transient Heat Conduction ◽  
Effect Of Temperature ◽  
Maximum Temperature

In any cutting processes, the temperature distribution in the cutting tool is intrinsically three-dimensional and very steep temperature gradient can be generated in the vicinity of the tool-chip interface. In this region, where the maximum temperature occurs, the effect of temperature dependent thermal properties may become important. The full three-dimensional nonlinear transient heat conduction equation is solved numerically using a control volume approach to study these nonlinear effects on cutting tool temperatures. The extremely small size of the heat input zone (tool-chip interface), relative to the tool insert rake surface area, requires the mesh to be dense enough in order to obtain accurate solutions. This usually requires very intensive computational efforts. Due to the size of the discretized domain, an optimized algorithm is used in the solution of the problem to significantly reduce the required computing time. This numerical model can be used for process development in an industrial setting. The effect of two different heat flux input profiles, a spatially uniform plane heat flux and a spatially nonuniform parabolic heat flux at the tool-chip interface, on the tool temperatures are also investigated in the present study. Some recommendations are given regarding the condition when these nonlinear effects cannot be ignored.

LASER HEATING AND THERMAL STRESSES TIME EXPONENTIALLY HEATING PULSE CASE

2006 ◽  
Vol 30 (1) ◽  
pp. 113-142 ◽  
Author(s):  
B.S. Yilbas ◽  
I. Z. Naqvi
Keyword(s):  
Laser Heating ◽  
Thermal Stresses ◽  
Control Volume ◽  
Equivalent Stress ◽  
Interaction Mechanism ◽  
Heating Process ◽  
Pulse Parameter ◽  
Heating Pulse ◽  
Model Studies ◽  
Laser Pulse Heating

Model studies of laser heating process minimize the experimental time and cost and give insight into the laser workpiece interaction mechanism. In the present study laser pulse heating is modelled and the governing equation of heat transfer, including phase change process, and thermal stresses are solved numerically using a control volume approach. In order to account for the time variation of the laser heating pulse, time exponentially varying pulse intensity is employed in the analysis. Since the heating conditions are considered to be axisymmetric, two dimensional case is introduced in the analysis. The temperature and stress fields are simulated for steel. It is found that temperature level attains considerably high values in the melt zone and pulse parameter (β/γ) with small values (1/2) results in large evaporated zones. Equivalent stress level increases rapidly in the region close to the melt surface and two stress peaks are developed in the radial direction. The location of stress peaks remains same with progressing heating period; however, the magnitude of second peak reduces with advancing heating periods.

Three-Dimensional Laser Heating Model and Entropy Generation Consideration

1999 ◽  
Vol 121 (3) ◽  
pp. 217-224 ◽  
Author(s):  
B. S. Yilbas
Keyword(s):  
Heat Treatment ◽  
Entropy Generation ◽  
Laser Heating ◽  
Energy Analysis ◽  
Three Dimensional ◽  
Heating Process ◽  
Theory Approach ◽  
Entropy Generation Number ◽  
Generation Number ◽  
Heating Model

Lasers find wide applications in heat treatment of engineering parts. The modeling and energy analysis of the heating process can reduce substantially the time required for process optimization and control. In the present study, three-dimensional laser heating model is introduced using an electron kinetic theory approach, the energy analysis is carried out to predict the first and second law efficiencies, and the entropy generation number is computed during the process. The equation derived for the heat conduction is in the form of an integro-differential equation, which does not yield an analytical solution. Therefore, a numerical method employing an explicit scheme is introduced to discretize the governing heat transfer equation. It is found that the electron lattice site atom collision is the determining process for the internal energy gain of the substrate in the surface vicinity. In addition, the overall entropy generation number computed in the heating cycle is less than what occurs in the cooling cycle of the heat treatment process.

Elastic displacement of the surface due to a laser heating pulse

2001 ◽  
Vol 215 (10) ◽  
pp. 1271-1282 ◽  
Author(s):  
B S Yilbas ◽  
S Z Shuja ◽  
A F M Arif
Keyword(s):  
Thermal Expansion ◽  
Temperature Field ◽  
Temperature Rise ◽  
Laser Heating ◽  
Control Volume ◽  
Three Dimensional ◽  
Surface Displacement ◽  
Elastic Displacement ◽  
Heating Cycle ◽  
Heating Pulse

When the surface of a substrate material is heated by a laser pulse, the surface initially expands and then contracts after the laser heating pulse ends. This may allow the surface temperature to be measured by monitoring the surface displacement. In the present study, the elastic displacement of the surface due to the temperature field generated during a laser heating pulse is examined. Three-dimensional laser gas-assisted heating is considered and the governing equations of flow and energy are solved numerically using a control volume approach, while the elastic displacement of the surface due to the temperature field is modelled through the finite element method. The relationship between the temperature rise and the elastic thermal displacement is discussed in detail. It is found that the rate of thermal expansion of the surface in the heating cycle is not the same as the rate of thermal contraction in the cooling cycle. Moreover, in the heating cycle, the rate of temperature rise and the rate of thermal expansion are similar.

Computational Analysis of a Three-Dimensional Plasma Spray Jet

1997 ◽  
Author(s):  
B. Dussoubs ◽  
P. Fauchais ◽  
A. Vardelle ◽  
M. Vardelle ◽  
N.J. Themelis
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Control Volume ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Gas Flow Rate ◽  
Fluid Turbulence ◽  
Energy Equations ◽  
S Model ◽  
Carrier Gas Flow

Abstract An analysis of a d.c. plasma jet is presented using a three-dimensional commercial fluid dynamics code, ESTET. This code solves the coupled conservation equations of mass, species, momentum and thermal energy equations for a compressible and turbulent fluid in control volume and finite difference formulation. Computations take into account fluid turbulence using a standard k-s model with the Launder and Sharma correction for the laminar zones, e.g. the plasma core. Two series of spraying conditions differing in the total gas flow rate (30 and 60 slm) and the arc current (300 and 600 A, respectively) are computed. The process parameters are independently varied about the nominal operating conditions. The effect of the variation of primary and secondary gas flow rate, effective power and powder carrier gas flow rate on flow fields characteristics, is discussed.

THREE-DIMENSIONAL PLANNING OF BRACHYTHERAPY FOR LOCALLY ADVANCED CERVICAL CANCER BY CT/MRI IMAGES

2018 ◽  
Vol 64 (5) ◽  
pp. 645-650
Author(s):  
Olga Kravets ◽  
Yelena Romanova ◽  
Oleg Kozlov ◽  
Mikhail Nechushkin ◽  
A. Gavrilova ◽  
...  
Keyword(s):  
Cervical Cancer ◽  
Local Control ◽  
Control Volume ◽  
Locally Advanced ◽  
Three Dimensional ◽  
Advanced Cervical Cancer ◽  
3D Ct ◽  
Mri Imaging ◽  
Tumor Target ◽  
Locally Advanced Cervical Cancer

We present our results of 3D CT/MRI brachytherapy (BT) planning in 115 patients with locally advanced cervical cancer T2b-3bN0-1M0. The aim of this study was to assess the differences in the visualization of tumor target volumes and risk organs during the 3D CT/MRI BT. The results of the study revealed that the use of MRI imaging for dosimetric planning of dose distribution for a given volume of a cervical tumor target was the best method of visualization of the soft tissue component of the tumor process in comparison with CT images, it allowed to differentially visualize the cervix and uterine body, directly the tumor volume. Mean D90 HR-CTV for MRI was 32.9 cm3 versus 45.9 cm3 for CT at the time of first BT, p = 0.0002, which is important for local control of the tumor process. The contouring of the organs of risk (bladder and rectum) through MRI images allows for more clearly visualizing the contours, which statistically significantly reduces the dose load for individual dosimetric planning in the D2cc control volume, і.є. the minimum dose of 2 cm3 of the organ of risk: D2cc for the bladder was 24.3 Gy for MRI versus 34.8 Gy on CT (p = 0.045); D2cc for the rectum - 18.7 Gy for MRI versus 26.8 Gy for CT (p = 0.046). This is a prognostically important stage in promising local control, which allows preventing manifestation of radiation damage.

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