Least-Squares Finite Element Analysis for Transient Radiative Transfer in Absorbing and Scattering Media

2005 ◽  
Vol 128 (5) ◽  
pp. 499-503 ◽  
Author(s):  
W. An ◽  
L. M. Ruan ◽  
H. P. Tan ◽  
H. Qi
Keyword(s):  
Finite Element ◽  
Radiative Transfer ◽  
Least Squares ◽  
Present Model ◽  
Element Model ◽  
Discrete Ordinates ◽  
Scattering Media ◽  
Element Analysis ◽  
Volume Method ◽  
Transfer Problems

In some radiative transfer processes, the time scales are usually on the order of 10−9-10−15s, so the transient effect of radiation should be considered. In present research, a finite element model, which is based on the discrete ordinates method and least-squares variational principle, is developed to simulate the transient radiative transfer in absorbing and scattering media. The numerical formulations and detailed steps are given. Moreover, two transient radiative transfer problems are investigated and the results are compared with those by integral method and finite volume method. It indicates that the present model can simulate the transient radiative transfer effectively and accurately.

Least-Squares Radial Point Interpolation Collocation Meshless Method for Radiative Heat Transfer

2006 ◽  
Vol 129 (5) ◽  
pp. 669-673 ◽  
Author(s):  
J. Y. Tan ◽  
L. H. Liu ◽  
B. X. Li
Keyword(s):  
Radiative Transfer ◽  
Least Squares ◽  
Meshless Method ◽  
Solution Method ◽  
Approximate Solutions ◽  
Discrete Ordinates ◽  
Scattering Media ◽  
Radial Point Interpolation ◽  
Point Interpolation ◽  
Transfer Problems

A least-squares radial point interpolation collocation meshless method based on the discrete ordinates equation is developed for solving the radiative transfer in absorbing, emitting, and scattering media, in which compact support radial basis functions augmented with polynomial basis are employed to construct the trial functions. In addition to the collocation nodes, a number of auxiliary points are also adopted to form the total residuals of the problem. The least-squares technique is used to obtain the solution of the problem by minimizing the summation of residuals of all collocation and auxiliary points. Three typical examples of radiative transfer in semitransparent media are examined to verify this new solution method. The numerical results are compared with other benchmark approximate solutions in references. By comparison, the results show that the least-squares radial point interpolation collocation meshless method has good accuracy in solving radiative transfer problems within absorbing, emitting, and scattering media.

Discontinuous Finite Element Approach for Transient Radiative Transfer Equation

2007 ◽  
Vol 129 (8) ◽  
pp. 1069-1074 ◽  
Author(s):  
L. H. Liu ◽  
L. J. Liu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Radiative Transfer ◽  
Scattering Media ◽  
Participating Media ◽  
Element Discretization ◽  
Discontinuous Finite Element ◽  
Transfer Problems ◽  
Discontinuous Finite Element Method ◽  
Element Method

A discontinuous finite element method based on the discrete ordinates equation is extended to solve transient radiative transfer problems in absorbing, emitting, and scattering media. The fully implicit scheme is used to discretize the transient term. Three numerical examples are studied to illustrate the performance of this discontinuous finite element method. The numerical results are compared to the other benchmark approximate solutions. By comparison, the results show that the discontinuous finite element method is efficient, accurate, and stable, and can be used for solving transient radiative transfer problems in participating media. Because the continuity at interelement boundaries is relaxed in discontinuous finite element discretization so that field variable is considered discontinuous across the element boundaries. This feature makes the discontinuous finite element method able to predict the correct propagation speed within medium and accurately capture the sharp drop in the incident radiation and the radiative heat flux at the penetration front.

Finite Element Simulation for Short Pulse Light Radiative Transfer in Homogeneous and Nonhomogeneous Media

2006 ◽  
Vol 129 (3) ◽  
pp. 353-362 ◽  
Author(s):  
W. An ◽  
L. M. Ruan ◽  
H. P. Tan ◽  
H. Qi ◽  
Y. M. Lew
Keyword(s):  
Finite Element ◽  
Optical Properties ◽  
Radiative Transfer ◽  
Short Pulse ◽  
Continuous Light ◽  
Ultrashort Pulses ◽  
Discrete Ordinates ◽  
Scattering Media ◽  
Nonhomogeneous Media ◽  
Pulse Light

With the rapid progress on ultrashort pulse laser, the transient radiative transfer in absorbing and scattering media has attracted increasing attention. The temporal radiative signals from a medium irradiated by ultrashort pulses offer more useful information which reflects the internal structure and properties of media than that by the continuous light sources. In the present research, a finite element model, which is based on the discrete ordinates method and least-squares variational principle, is developed to simulate short-pulse light radiative transfer in homogeneous and nonhomogeneous media. The numerical formulations and detailed steps are given. The present models are verified by two benchmark cases, and several transient radiative transfer cases in two-layer and three-layer nonhomogeneous media are investigated and analyzed. The results indicate that the reflected signals can imply the break of optical properties profile and their location. Moreover, the investigation for uniqueness of temporal reflected and transmitted signals indicate that neither of these two kinds of signals can be solely taken as experimental measurements to predict the optical properties of medium. They should be measured simultaneously in the optical imaging application. The ability of the present model to deal with multi-dimensional problems is proved by the two cases in the two-dimensional enclosure.

КОНСТРУКТИВНО-ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ХВОСТО-ВИХ БАЛОК СІТЧАСТОГО ТИПУ З ПОЛІМЕРНИХ КОМПО-ЗИЦІЙНИХ МАТЕРІАЛІВ ВЕРТОЛЬОТІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

2020 ◽  
pp. 15-30
Author(s):  
А. Г. Гребеников ◽  
И. В. Малков ◽  
В. А. Урбанович ◽  
Н. И. Москаленко ◽  
Д. С. Колодийчик
Keyword(s):  
Finite Element ◽  
Strain State ◽  
Layer Structure ◽  
Metal Structure ◽  
Element Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Mesh Structure ◽  
Stress Strain State ◽  
Mesh Structures

The analysis of the design and technological features of the tail boom (ТB) of a helicopter made of polymer composite materials (PCM) is carried out.Three structural and technological concepts are distinguished - semi-monocoque (reinforced metal structure), monocoque (three-layer structure) and mesh-type structure. The high weight and economic efficiency of mesh structures is shown, which allows them to be used in aerospace engineering. The physicomechanical characteristics of the network structures are estimated and their uniqueness is shown. The use of mesh structures can reduce the weight of the product by a factor of two or more.The stress-strain state (SSS) of the proposed tail boom design is determined. The analysis of methods for calculating the characteristics of the total SSS of conical mesh shells is carried out. The design of the tail boom is presented, the design diagram of the tail boom of the transport category rotorcraft is developed. A finite element model was created using the Siemens NX 7.5 system. The calculation of the stress-strain state (SSS) of the HC of the helicopter was carried out on the basis of the developed structural scheme using the Advanced Simulation module of the Siemens NX 7.5 system. The main zones of probable fatigue failure of tail booms are determined. Finite Element Analysis (FEA) provides a theoretical basis for design decisions.Shown is the effect of the type of technological process selected for the production of the tail boom on the strength of the HB structure. The stability of the characteristics of the PCM tail boom largely depends on the extent to which its design is suitable for the use of mechanized and automated production processes.A method for the manufacture of a helicopter tail boom from PCM by the automated winding method is proposed. A variant of computer modeling of the tail boom of a mesh structure made of PCM is shown.The automated winding technology can be recommended for implementation in the design of the composite tail boom of the Mi-2 and Mi-8 helicopters.

Torsional Analysis of a Steel Cord-Rubber Tire Belt Structure

1996 ◽  
Vol 24 (4) ◽  
pp. 339-348 ◽  
Author(s):  
R. M. V. Pidaparti
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Composite Structures ◽  
Three Dimensional ◽  
Element Model ◽  
Torsional Stiffness ◽  
Element Analysis ◽  
Rubber Belt ◽  
Steel Cord ◽  
Torsional Analysis

Abstract A three-dimensional (3D) beam finite element model was developed to investigate the torsional stiffness of a twisted steel-reinforced cord-rubber belt structure. The present 3D beam element takes into account the coupled extension, bending, and twisting deformations characteristic of the complex behavior of cord-rubber composite structures. The extension-twisting coupling due to the twisted nature of the cords was also considered in the finite element model. The results of torsional stiffness obtained from the finite element analysis for twisted cords and the two-ply steel cord-rubber belt structure are compared to the experimental data and other alternate solutions available in the literature. The effects of cord orientation, anisotropy, and rubber core surrounding the twisted cords on the torsional stiffness properties are presented and discussed.

Finite Element Analysis of Nonuniformity of Tires with Imperfections5

2007 ◽  
Vol 35 (3) ◽  
pp. 226-238 ◽  
Author(s):  
K. M. Jeong ◽  
K. W. Kim ◽  
H. G. Beom ◽  
J. U. Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Radial Force ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Dimensional Finite Element ◽  
Force Variation ◽  
Three Dimensional Finite Element

Abstract The effects of variations in stiffness and geometry on the nonuniformity of tires are investigated by using the finite element analysis. In order to evaluate tire uniformity, a three-dimensional finite element model of the tire with imperfections is developed. This paper considers how imperfections, such as variations in stiffness or geometry and run-out, contribute to detrimental effects on tire nonuniformity. It is found that the radial force variation of a tire with imperfections depends strongly on the geometrical variations of the tire.

Finite Element Analysis of Tire/Rim Interface Forces Under Braking and Cornering Loads

1992 ◽  
Vol 20 (2) ◽  
pp. 83-105 ◽  
Author(s):  
J. P. Jeusette ◽  
M. Theves
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Contact Pressure ◽  
Element Model ◽  
Shear Stresses ◽  
Detailed Knowledge ◽  
Stress Distributions ◽  
Element Analysis ◽  
Plane Shear ◽  
Normal Contact

Abstract During vehicle braking and cornering, the tire's footprint region may see high normal contact pressures and in-plane shear stresses. The corresponding resultant forces and moments are transferred to the wheel. The optimal design of the tire bead area and the wheel requires a detailed knowledge of the contact pressure and shear stress distributions at the tire/rim interface. In this study, the forces and moments obtained from the simulation of a vehicle in stationary braking/cornering conditions are applied to a quasi-static braking/cornering tire finite element model. Detailed contact pressure and shear stress distributions at the tire/rim interface are computed for heavy braking and cornering maneuvers.

Redrawing Operation a Star Shape from Cylindrical Shape Using Experimental and FE Analysis

2020 ◽  
Vol 38 (1A) ◽  
pp. 25-32
Author(s):  
Waleed Kh. Jawad ◽  
Ali T. Ikal
Keyword(s):  
Finite Element ◽  
Effective Strain ◽  
Element Model ◽  
Cylindrical Shape ◽  
Element Analysis ◽  
Punch Force ◽  
Maximum Value ◽  
Element Simulation ◽  
Blank Sheet ◽  
The Finite Element Model

The aim of this paper is to design and fabricate a star die and a cylindrical die to produce a star shape by redrawing the cylindrical shape and comparing it to the conventional method of producing a star cup drawn from the circular blank sheet using experimental (EXP) and finite element simulation (FES). The redrawing and drawing process was done to produce a star cup with the dimension of (41.5 × 34.69mm), and (30 mm). The finite element model is performed via mechanical APDL ANSYS18.0 to modulate the redrawing and drawing operation. The results of finite element analysis were compared with the experimental results and it is found that the maximum punch force (39.12KN) recorded with the production of a star shape drawn from the circular blank sheet when comparing the punch force (32.33 KN) recorded when redrawing the cylindrical shape into a star shape. This is due to the exposure of the cup produced drawn from the blank to the highest tensile stress. The highest value of the effective stress (709MPa) and effective strain (0.751) recorded with the star shape drawn from a circular blank sheet. The maximum value of lamination (8.707%) is recorded at the cup curling (the concave area) with the first method compared to the maximum value of lamination (5.822%) recorded at the cup curling (the concave area) with the second method because of this exposure to the highest concentration of stresses. The best distribution of thickness, strains, and stresses when producing a star shape by

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