bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Prediction of Turbulent Wakes Behind a Square Cylinder
Authors: Hwang Robert R. , Jaw Sheng-Yuh 
Published: May 2011

ABSTRACTThis paper presents a numerical study on turbulent vortex shedding flows past a square cylinder. The 2D unsteady periodic shedding motion was resolved in the calculation and the superimposed turbulent fluctuations were simulated with a second-order Reynolds-stress closure model. The calculations were carried out by solving numerically the fully elliptic ensemble-averaged Navier-Stokes equations coupled with the turbulence model equations together with the two-layer approach in the treatment of the near-wall region. The performance of the computations was evaluated by comparing the numerical results with data from available experiments. Results indicate that the present study gives good agreement in the shedding frequency and mean drag as well as in some phase profiles of the mean velocity.
Optimal Shape/Topological Design of Plate/Shell Like Structures Subjected to Periodic Excitations
Authors: Cheng Hsien-Chie , Chiang Kuo-Ning 
Published: May 2011

ABSTRACTThis paper deals with the optimal shape/topological design of plate/shell like structures subjected to a harmonic, periodic excitation using an improved Homogenization Based Optimization Algorithm (HBOA), proposed by Cheng et al., [7]. The major goal of this work is to improve or control the frequency response of structures via the optimal distribution of a given amount of material in a fixed design space. Based upon the improved HBOA, two types of frequency response optimization problems are extensively explored: (1) structures subjected to a periodic excitation with a single excitation frequency, (2) structures subjected to a periodic excitation with excitation frequencies in a frequency domain. To this end, the basic mathematical formulation and a solution method are proposed as well as two numerical examples of obtaining the optimum layout of three-dimensional plate/shell structures. An interesting result is reported from the current optimization problems in comparison with static optimization problems.
EndoFEM Node-Released Strategy in the Simulations of Fatigue Crack Closure Phenomena
Authors: Hsiao L. T. , Lee C. F. 
Published: May 2011

AbstractApplications of the EndoFEM with node-released methods had been used successfully to simulate the plastic wakes left behind the advancing fatigue crack. In this paper, employing the plastic zone size estimated by LEFM as a guideline, four strategies with various plans of node-released rates and two plans of finite element discretization near crack tip, are proposed to generate various fatigue cracked lengths of A12024-T3 CCT specimen under all tensile-cyclic loading. Evaluations based on the mechanical responses near crack tip and the crack opened/closure behaviors, it can be concluded that the EndoFEM with the rc dominant node-released strategy can lead to not only economical but also reliable results.
Explicit Solutions of Plane Elastostatics Problems in Heterogeneous Solids
Authors: Chao C. K. , Gao B. 
Published: May 2011

AbstractThe problem of two circular inclusions of arbitrary radii and of different elastic moduli, which are perfectly bonded to an infinite matrix subjected to arbitrary loading, is solved by the heterogenization technique. This implies that the solution of the heterogeneous problem can be readily obtained from that of the corresponding homogeneous problem by a simple algebraic substitution. Based on the method of successive approximations and the technique of analytical continuation, the solution is formulated in a manner which leads to an approximate, but arbitrary accuracy, result. The present derived solution can be also applied to the problem with straight boundaries. Both the problem of two circular inclusions embedded in an infinite matrix and the problem of a circular inclusion embedded in a half-plane matrix are considered as our examples to demonstrate the use of the present approach.
Impulsive Motion of a Moving Circular Cylinder in a Viscous Flow by the Numerical Simulation
Authors: Young D. L. , Chang J. T. 
Published: May 2011

ABSTRACTAn innovative computation procedure is developed to solve the external flow problems for viscous fluids. The method is able to handle the infinite domain so that it is convenient for the external flows. The code is based on the projection method of the Navier-Stokes equations. We use the three-step explicit finite element method to solve the momentum equation by extracting the boundary effects from the finite computation domain. The pressure Poisson equation for the external field is treated by the boundary element method. The arbitrary Lagrangian-Eulerian (ALE) scheme is employed to incorporate the present algorithm to deal with the moving boundary, such as the motion of an impulsively moving circular cylinder in a viscous fluid. The model demonstrates that drag force is well predicted for a circular cylinder moving in a still viscous fluid starting from rest, to a constant acceleration, and then maintaining at a uniform velocity. In the constant acceleration phase, the drag force is closed to the added mass effect from the ideal flow theory. On the other hand, the drag force is equal to viscous flow theory in the constant velocity phase.
Parallel Computation of Turbulent Flows Using Equation Decomposition Scheme
Authors: Jaw Shenq-Yuh , Wang Alpha Y. 
Published: May 2011

ABSTRACTA problem independent, equation decomposition scheme of parallel computation is adopted and tested using a two-dimensional turbulent channel flow. The incompressible Navier-Stokes equations, incorporated with the SIMPLEC algorithm and a two-layer turbulence model, were distributed to four nodes of IBM SP2 parallel machine using the PVM software and solved simultaneously. The computation domain and the interior iteration loop for the solution of every transport equation is the same, load balancing among different machines is automatically satisfied. Since all the transport equations and the flow field was solved and updated simultaneously, the solutions obtained from the equation decomposition scheme at each time step were more accurate than those obtained from a unit process code, which in turn sharply reduced the required convergence time steps. Without modifying any of the solution algorithm, or tuning the computer code, the rate of convergence speeds up more than four times by invoking four nodes of parallel machines using the equation decomposition scheme.
Numerical Investigation of Flow Around Bluff Bodies
Authors: Tsai Chou-Jiu , Chen Ger-Jyh 
Published: May 2011

ABSTRACTIn this study, fluid flow around bluff bodies are studied to examine the vortex shedding phenomenon in conjuction with the geometrical shapes of these vortex shedders. These flow phenomena are numerically simulated. A finite volume method is employed to solve the incompressible two-dimensional Navier-Stokes equations. Thus, quantitative descriptions of the vortex shedding phenomenon in the near wake were made, which lead to a detailed description of the vortex shedding mechanism. Streamline contours, figures of lift coefficent, and figures of drag coefficent in various time, are presented, respectively, for a physical description.
Dynamic Green's Function for SH-Wave in Multi-Dipping Layers Embedded in a Half-Space
Authors: Teng Tsung-Jen , Chai Juin-Fu , Yeh Chau-Shioung 
Published: May 2011

ABSTRACTIn this paper, the recursive T-matrix formalism is developed to determine the dynamic Green's function for SH-wave in the multi-dipping layers with arbitrary shape embedded in a half-space. In each layer, the wave field generated by a harmonic line load can be separated into two parts: the source term and the complementary part. The source term is exactly the Green's function for SH-wave in two-dimensional half-space, and the complementary part which causes the SH-wave to satisfy the boundary conditions at the interface is determined by the wave function expansion method. Using the polar coordinates, the basis functions are constructed by Bessel typed cylindrical functions, and their orthogonality conditions at the corresponding interfaces can be derived by means of Betti's third identity. Applying the conditions of continuity at the interface, the recursive T-matrix formalism is developed for determining the expansion coefficients of the complementary part from the associated source dependent constants.
Chaotic Behavior of an Inelastic Beam
Authors: Yeh Jiin-Po 
Published: May 2011

ABSTRACTThe dynamical system considered in this paper is an inelastic beam whose supports are subjected to a harmonic excitation. This paper first explores whether the system has chaotic motion. The appearance of the irregular time history, strange attractor on the Poincaré map as well as period-doubling bifurcation phenomenon strongly indicates that chaos indeed exist in this system. After finding the chaos phenomenon, this paper continues to investigate the relationship between the decay time of the autocorrelation function and the largest Lyapunov exponent. The Poincaré mapping points are chosen to be the sampled function of the discrete autocorrelation function. It's found that a power model of regression analysis can fit with good accuracy the data points, which are composed of the mapping times for the autocorrelation to decay into the square of the mean of the Poincaré points and the corresponding largest Lyapunov exponent.
Blowing/Suction Effect on Combined Convection in Stagnation Flow Over a Vertical Plate Embedded in a Porous Medium
Authors: Yih K.A. 
Published: May 2011

ABSTRACTBlowing/suction effect on steady two-dimensional laminar combined convection owing to the stagnation flow against a vertical flat plate with linear wall temperature with distance in a saturated porous medium is numerically analyzed. The nonlinear coupled boundary-layer equations were transformed and the resulting ordinary differential equations were solved by Keller box method. Numerical results for the local friction coefficient and the local Nusselt number are presented for various parameters. In general, it is observed that in the buoyancy assisting (opposing) flow both the local friction coefficient and the local Nusselt number increase (decrease) because of the increase of buoyancy parameter, blowing/suction parameter and permeability parameter. The local Nusselt number becomes nearly constant when Ω is very small (pure fluid flow) and Ω is very large (pure Darcy flow).
On the Viscous Models for Wave Propagation in Solid Loaded with Viscous Liquid
Authors: Chang M.-P. , Wu T.T. 
Published: May 2011

AbstractRecently, in the fields of biosensing and nondestructive of materials, there are increasing interests on the investigations of the surface wave propagation in fluid loaded layered medium. Several different models for the elastic coefficients of viscous liquids are usually adopted in the investigations. The purpose of this paper is to study the variations of choosing different viscous liquid models on the dispersion and attenuation of waves in liquid loaded solids. In the paper, a derivation of the elastic coefficients of a viscous liquid based on the Stokes' assumption is given first. Then, for the hypothetical solid assumption of a viscous liquid, the associated wave equations and expressions of the stress components for different viscous liquid models utilized in the literatures are given. Finally, dispersion and attenuation of waves in a viscous liquid loaded A1 half space and a SiC plate immersed in a viscous liquid are calculated and utilized to discuss the differences among these four different models.
Evaluation of Interlaminar Shear Stress by Strain Measurements on Laminate Surfaces
Authors: Lee C.Y. , Huang C.C. 
Published: May 2011

AbstractFor most composite structures, because of the uncertainty in some design variables, it is not possible to predict precisely the stresses during design stage. Therefore, monitoring the structural responses in service becomes crucial for structure with concerns, e.g., the composite panels on an airplane, etc. In this study, the strains at neighboring points of the interested location on surfaces of the laminate, along with the classical laminate theory and the higher-order shear deformation theory, are used to predict the interlaminar shear stresses in the cross-ply laminate. Several numerical examples using the simulated surface strains are employed to evaluate the accuracy of the proposed technique. It is found that the approach using the higher-order shear deformation theory has improved accuracy for the analysis of thick symmetric laminate over the approach using the classical laminate theory.
Some Nonlinear Features of the Squeeze-Film Problem
Authors: Lei U. , Chen Chia-Han 
Published: May 2011

AbstractThe nonlinear features of the squeeze-film problem between two parallel long strips driven by the relative harmonic oscillation of the strips is studied via the regular perturbation and numerical calculation for ∈ < 1 and σ = O(1)- O(103), where ∈ is the dimensionless amplitude of the oscillation, and σ is the squeeze number. The fluid film behaves as a (nonlinear) spring for large σ and as a (nonlinear) damper for small σ, which are qualitatively similar to the linear analysis. However, a steady state force is generated even though the driving mechanism is purely oscillatory due to the nonlinear effect. Furthermore, the dimensionless quasi-steady rate of energy dissipation within one cycle of the plate oscillation, E, is not zero (zero for linear analysis), and is maximized at σ ≈ 10. Also the rate of increase of E with ∈ is greater than ∈2. The present study may be helpful for the design of some accelerometers and vibration absorbers.
Optimal Allocation of Heat Transfer Area for a Heat Engine
Authors: Hsieh Y. C. , Chiou J. S. 
Published: May 2011

AbstractFor an endoreversible heat engine operates steadily between two fixed temperatures, Bejan found the engine's best performance can be obtained if the total thermal conductance is evenly divided for hot-end and cold-end heat exchangers. In this study, a heat by-pass model is used to represent the losses due to internal irreversibilities, and the more general formulations are derived for both the optimal area allocation and the maximum thermal efficiency. The results calculated from the present formulations when there is no internal irreversibility(a special case) are consistant with that obtained by Bejan.
Heat Conduction in Dissimilar Anisotropic Media with Bonding Defects/Interface Cracks
Authors: Shiah Y. C. , Yang R.-B. , Hwang P.-W. 
Published: May 2011

AbstractAs an essential foundation for the associated thermoelasticity analysis in the boundary element method (BEM), this article proposes an expedient, yet powerful, approach to analyze the heat conduction in multiply jointed anisotropic media with bonding defects/interface cracks. The direct domain mapping technique (DDM) is applied to treat a domain consisting of dissimilar anisotropic sub-regions in the potential theory of BEM. The heat transfer across a crack is modeled with a gap conductance equation specially formulated for the BEM analysis. Two numerical examples are provided as illustrations of the validity and the applicability of this proposed scheme.
Method of Fundamental Solutions for Stokes' First and Second Problems
Authors: Hu S. P. , Fan C. M. , Chen C. W. , Young D. L. 
Published: May 2011

AbstractThis paper describes the applications of the method of fundamental solutions (MFS) as a mesh-free numerical method for the Stokes' first and second problems which prevail in the semi-infinite domain with constant and oscillatory velocity at the boundary in the fluid-mechanics benchmark problems. The time-dependent fundamental solutions for the semi-infinite problems are used directly to obtain the solution as a linear combination of the unsteady fundamental solution of the diffusion operator. The proposed numerical scheme is free from the conventional Laplace transform or the finite difference scheme to deal with the time derivative term of the governing equation. By properly placing the field points and the source points at a given time level, the solution is advanced in time until steady state solutions are reached. It is not necessary to locate and specify the condition at the infinite domain such as other numerical methods. Since the present method does not need mesh discretization and nodal connectivity, the computational effort and memory storage required are minimal as compared to the domain-oriented numerical schemes. Test results obtained for the Stokes' first and second problems show good comparisons with the analytical solutions. Thus the present numerical scheme has provided a promising mesh-free numerical tool to solve the unsteady semi-infinite problems with the space-time unification for the time-dependent fundamental solution.
Extraction of Frequency Dependent Macromodels for Mems Squeezed-Film Damping Effects
Authors: Joseph Yang Yao-Joe , Chien Chih-Ming , Kamon Mattan , Rabinovich Vladimir L. , Gilbert John R. 
Published: May 2011

AbstractIn this paper, an efficient macromodel extraction technique for dynamical MEMS gas damping effects is presented. The technique applies an Arnoldi-based model-order-reduction algorithm to generate low-order macromodels from a FEM approximation of the governing equation of the squeeze-film fluidic damping effect, the Reynolds equation. We demonstrate that this approach is more than 100 times efficient than previous approaches, which solve the Reynolds equation using transient finite-element/finite-difference methods. The generated gas-damping macromodels can be easily inserted into system-level modeling packages, such as SPICE, Saber and Simulink, for transient and frequency coupled-domain analysis. We also demonstrated that the simulated results are in good agreement with experimental results for various MEMS devices.
The Stationary Values of Young's Modulus For Monoclinic and Triclinic Materials
Authors: Ting T. C. T. 
Published: May 2011

AbstractThe stationary values (maximum, minimum, saddle point) of Young modulusE(n) for a general anisotropic elastic materials is studied. The general results are then spcialized for monoclinic materials. Equations that provide the directionnfor a stationary value are given. Some have an explicit solution. Other may require a numerical computation. The equations that required numerical solutions are two coupled polynomials of degree no more than four.
Clarifying Low-Frequency Variatoions Phenomenon Using a Novel Mode Decomposition Method
Authors: Wang C.-T. 
Published: May 2011

AbstractLow-frequency variations in wake flow are complex and many aspects of its behavior remain poorly understood. A mode decomposition method developed by Huang et al is utilized herein because it can decompose any complicated data set into a finite number of intrinsic modes without distorting their original characteristics. The results of decomposition analysis of the measured base pressure signals reveal that a finite number of various kinds of flow structure modes, with their own characteristic time scales, coexist with the residue that exhibits most of the low-frequency variations in flow at Re = 11760 and 31600, respectively. As the Reynolds number increases, the decomposition method yields more components. Results also show exactly the vortex shedding structure in an intrinsic mode and the low-frequency variations that appear in the residue during vortex shedding process.
A Study of Duct Flow Passing in a Horizontal Channel with a Cylinder Source Adjacent to Planar Boundary
Authors: Wang L. W. , Kung Y. C. , Lin K. H. , Sung S. H. , Wu C. Y. 
Published: May 2011

AbstractThe purpose of the present study is to investigate laminar fully developed flow in a horizontal rectangular channel with a cylinder solutal source adjacent to planar boundary. The boundaries in this experiment include four cases:(A) Cylinder is cathode and top plate is anode;(B) Cylinder is anode and top plate is cathode;(C) Cylinder is cathode and bottom plate is anode;(D) Cylinder is anode and bottom plate is cathode.The influences of the mass transfer rate and the boundary types between the sources have also been investigated. An experimental investigation of mixed convection mass transfer between a cylinder and a plate mass source with an electrochemical system is carried in a horizontal rectangular channel. The working fluid here is CuSO4 + H2SO4 + H2O. The shadowgraph technique is used to visualize the flow and to determine the nature and effect of solutal driven secondary flows in a horizontal channel. The ranges of the parameters in the work are Pr = 7, Ar = 1, Sc = 1700 ∼ 2400, Re = 50 ∼ 200 (Red= 12.5 ∼50), Grm = 9.45 × 105, d/H = 0.25, h/d=0, 3.
Hygrothermal Effect on Deformations of QFN Electronic Packaging
Authors: Tsai M. Y. , Huang C. H. , Huang C. Y. 
Published: May 2011

AbstractThe hygrothermal-mechanical behavior of a quad flat non-lead (QFN) package without a chip inside is investigated experimentally and numerically. The present study is focused on understanding the effect of the inherent hygrothermal behaviors of epoxy molding compound (EMC) on the deformations of QFN package. Prior to studying the package, the coefficient of moisture expansion for the EMC is measured experimentally. Full-field moiré and Twyman-Green interferometries are used for measuring the real-time in-plane and out-of-plane deformations of the specimen, respectively, under thermal and moisture loading. In addition, the finite element and theoretical analyses are adopted for validating the experimental observations and further understanding the hygrothermal mechanics of the specimen. The coefficient of moisture expansion of the EMC was experimentally obtained to be about 0.2. The experimental results of the full-field deformations of the specimen, due to temperature, moisture and a combination of both, are presented. The experimental observations are validated by the finite element and theoretical analyses. It was observed that the maximum moisture-induced deformation (strain) can be up to as large as 50% of the thermal deformation (strain) caused by ΔT = 50°C for the specimen. As a result, neglecting moisture-induced deformations (strains) would cause the significant amount of error in thermal deformation (strain) measurement of plastic packages. Furthermore, the present study has laid down the fundamental mechanics and approaches for the QFN packaging structural design and analysis in terms of hygrothermal effects.
Deflection Form Factors of Worm and Worm Gear
Authors: Chung M. Y. , Shaw D. 
Published: May 2011

AbstractIn this study, a simplified method for evaluating amount of deflection for the tooth of worm and worm gear under loading is proposed. In a previous study, the plate theory was used for the approximation. However, it was found that the deflection of gear tooth using the plate theory was far from the actual value, and that the values from 3D FE analyses were closer to the actual value than from the plate theory. However, the FE analysis process starting from the CAD model to the final analysis results is complicated and too time-consuming. Therefore, the form factors are needed to facilitate simple but accurate results for the design purpose. In this study, the equations of form factors obtained from the results of plate theory and the 3D FEM, are developed. Since the worm gear assembly has various tooth geometries, the moment of inertia and the deflection of tooth geometry are different. Therefore, tooth geometries with trapezoid and involute forms are investigated.