bluuebunny/crossref_metadata_2025_split huggingface dataset:
A nonlinear numerical model for sloshing motion in tuned liquid dampers
Authors: Siddique M.R. , Hamed M.S. , El Damatty A.A. 
Published: January 2007

PurposeThis paper presents a new numerical model that, unlike most existing ones, can solve the whole liquid sloshing, nonlinear, moving boundary problem with free surface undergoing small to very large deformations without imposing any linearization assumptions.Design/methodology/approachThe time‐dependent, unknown, irregular physical domain is mapped onto a rectangular computational domain. The explicit form of the mapping function is unknown and is determined as part of the solution. Temporal discretization is based on one‐step implicit method. Second‐order, finite‐difference approximations are used for spatial discretizations.FindingsThe performance of the algorithm has been verified through convergence tests. Comparison between numerical and experimental results has indicated that the algorithm can accurately predict the sloshing motion of the liquid undergoing large interfacial deformations.Originality/valueThe ability to model liquid sloshing motion under conditions leading to large interfacial deformations utilizing the model presented in this paper improves our ability to understand the problem of sloshing motion in tuned liquid dampers (TLDs), which would eventually help in constructing more effective TLDs.
Process modeling of composites by resin transfer molding
Authors: Henz B.J. , Tamma K.K. , Mohan R.V. , Ngo N.D. 
Published: January 2007

PurposeThe purpose of the present paper is to describe the modeling, analysis and simulations for the resin transfer molding (RTM), manufacturing process with particular emphasis on the sensitivity analysis for non‐isothermal applications.Design/methodology/approachFor the manufacturing of advanced composites via RTM, besides the tracking of the resin flow fronts through a porous fiber perform, the heat transfer and the resin cure kinetics play an important role. The computational modeling is coupled multi‐disciplinary problem of flow‐thermal‐cure. The paper describes the so‐called continuous sensitivity formulation via the finite element method for this multi‐disciplinary problem for process modeling of composites manufactured by RTM to predict, analyze and optimize the manufacturing process.FindingsIllustrative numerical examples are presented for two sample problems which include examination of sensitivity parameters for the case of material and geometric properties, and boundary conditions including fill time sensitivity analysis. The results indicate that the proposed formulations serve a useful role for the design and optimization of the RTM manufacturing process, thereby, avoiding heuristic trial‐and‐error methods.Research limitations/implicationsThe paper restricts attention to constant properties and extensions to non‐linear thermophysical properties will serve as an added benefit.Practical implicationsThe present efforts significantly impact the design/optimization process in the process modeling of composites manufactured by RTM.Originality/valueTo the authors' knowledge, this is the first time that continuous sensitivity analysis is done for non‐isothermal considerations in RTM.
Steady mixed convection flow of a micropolar fluid near the stagnation point on a vertical surface
Authors: Lok Y.Y. , Amin N. , Campean D. , Pop I. 
Published: January 2007

PurposeTo study the steady mixed convection boundary‐layer flow of a micropolar fluid near the region of the stagnation point on a double‐infinite vertical flat plate is studied. The results of this paper are important for the researchers in the area of micropolar fluids.Design/methodology/approachFor the case considered the problem reduces to a system of ordinary differential equations, which is solved numerically using the Keller‐box method. This method is very efficient for solving boundary‐layer problems and it can easily be applied to other general situations than that presented in this paper. Any PhD student can learn and apply it very easily.FindingsRepresentative results for the velocity, microrotation and temperature profiles, as well as for the reduced skin friction coefficient and the local Nusselt number have been obtained for the case of strong concentration, Prandtl number of 0.7, some values of the material parameter K and the mixed convection parameter λ(≥0). Both assisting and opposing flow cases are considered. Results for the reduced skin friction coefficient and reduced local Nusselt number as well as for the reduced velocity, temperature and microrotation profiles are given in tables and figures. The obtained results are compared with ones from the open literature and it is found that they are in excellent agreement. The important conclusion is, we have been able to show that for opposing flow solutions are possible are possible only for a limited range of values of the mixed convection parameter λ.Research limitations/implicationsThe results of this paper are valid only in the small region around the stagnation point on a vertical surface and they are not applicable outside this region.Practical implicationsThe theory of micropolar fluids and also the results of the present paper can be used to explain the characteristics in certain fluids such as exotic lubricants, colloidal suspensions or polymeric fluids, liquid crystals, and animal blood.Originality/valueThe paper is very well prepared, presented and readable. We believe that the results are original and important from both theoretical and application point of views.
Stochastic perturbation‐based finite element approach to fluid flow problems
Authors: Kamiński Marcin , Carey Graham F. 
Published: January 2007

PurposeTo generalize the traditional 2nd order stochastic perturbation technique for input random variables and fields and to demonstrate for flow problems.Design/methodology/approachThe methodology is based on an n‐th order expansion (perturbation) for input random parameters and state functions around their expected value to recover probabilistic moments of the response. A finite element formulation permits stochastic simulations on irregular meshes for practical applications.FindingsThe methodology permits approximation of expected values and covariances of quantities such as the fluid pressure and flow velocity using both symbolic and discrete FEM computations. It is applied to inviscid irrotational flow, Poiseulle flow and viscous Couette flow with randomly perturbed boundary conditions, channel height and fluid viscosity to illustrate the scheme.Research limitations/implicationsThe focus of the present work is on the basic concepts as a foundation for extension to engineering applications. The formulation for the viscous incompressible problem can be implemented by extending a 3D viscous primitive variable finite element code as outlined in the paper. For the case where the physical parameters are temperature dependent this will necessitate solution of highly non‐linear stochastic differential equations.Practical implicationsTechniques presented here provide an efficient approach for numerical analyses of heat transfer and fluid flow problems, where input design parameters and/or physical quantities may have small random fluctuations. Such an analysis provides a basis for stochastic computational reliability analysis.Originality/valueThe mathematical formulation and computational implementation of the generalized perturbation‐based stochastic finite element method (SFEM) is the main contribution of the paper.
Metal matrix composite processing: numerical study of heat transfer between fibers and metal
Authors: Cantarel Arthur , Lacoste Eric , Danis Michel , Arquis Eric 
Published: January 2007

PurposeTo study heat transfer kinetics at the fiber scale in order to describe injection of liquid metal through a fibrous perform initially situated in a preheated mould, which is one of the various methods used in order to produce metal matrix composite materials (MMCs).Design/methodology/approachThe first part presents a preliminary study in a static case to describe heat transfer kinetics between a fiber and the matrix in the case of a sudden contact of both components initially set up at different temperatures. This model enables to study the influence of the various parameters of the problem on heat transfer kinetics with phase change. In the second part, we present a modeling which takes into account the metal convection within the pores of the preform.FindingsThe numerical results of these two models justify the instantaneous thermal equilibrium assumption classically admitted to describe MMCs manufacturing methods. The results of this dynamic microscopic model are compared with the results issued from a single temperature macroscopic model to justify the methodological approach and the choice of the microscopic domain geometry representative of the MMCs manufacturing process.Research limitations/implicationsThis first numerical model at the microscopic scale deals with the study of heat transfer between fibers and a pure metal. Next step will be the extension of this study to the preform infiltration by a metal alloy. Injection of matrix alloy implies the appearance of phenomena generated by segregation during phase changes.Originality/valueThe results of simulation tests, making use of the usual conditions of MMCs processing, show pretty good agreement with those of macroscopic models describing the anisothermal flow of a pure metal through a porous medium. From this coherence and from the results of the microscopic models as well, the hypothesis of instantaneous thermal equilibrium between fibers and metal (widely used in the literature to study the production of MMCs by infiltration of the liquid metal through the fibrous reinforcement) is justified. Moreover, it will be possible to extend it to the study of infiltration by an alloy, taking then into account thermal and solutal coupled transfers inside the study domain defined in the present work.
A hybrid differencing scheme for mass transport in electrochemical systems
Authors: Heppner Kevin L. , Evitts Richard W. 
Published: January 2007

PurposeTo present a new hybrid differencing scheme for the numerical solution of an electromigration‐diffusion equation. The value of this work is evidenced by demonstrated improvement in the simulation of the Fu and Chan experiment when using the hybrid scheme.Design/methodology/approachA hybrid differencing scheme is developed which is based upon the solution of the pseudo‐steady state electromigration‐diffusion equation. In this scheme, a weighting parameter is calculated that varies the relative influence of the upwind node (relative to the direction of electromigration). This scheme significantly enhances the accuracy of electrochemical system mass transport models.FindingsThe hybrid scheme was compared to the upwind scheme. Use of the new hybrid scheme improved the accuracy of the model predictions by as much as 87 percent compared to the upwind scheme. However, use of the new scheme also increased the simulation time by between 6 and 43 percent. Deviations from electroneutrality and the presence of an activity coefficient gradient were detrimental to the stability of the hybrid scheme.Research limitations/implicationsThis scheme is presented in the paper as an one‐dimensional (1D) scheme. However, it could be extended to more than 1D but some artificial viscosity may result.Practical implicationsThe hybrid scheme developed and demonstrated herein is useful for researchers developing mass transport models of electrochemical systems. It has been proven capable of improving the accuracy of electrolyte mass transport models.Originality/valueThis is the first hybrid differencing scheme designed for the special characteristics of electrochemical mass transport systems. It greatly improves the accuracy of simulation results. This work is useful to those who mathematically model electrochemical systems.
A two‐dimensional numerical procedure for a three dimensional internal flow through a complex passage with a small depth (its application to numerical analysis of fluidic oscillators)
Authors: Nakayama A. , Kuwahara F. , Kamiya Y. 
Published: January 2007

PurposeTo introduce an efficient two‐dimensional numerical procedure for a three‐dimensional internal flow through a complex passage with a small depth, in which the viscous effects from upper and lower walls are significant.Design/methodology/approachA set of two‐dimensional governing equations has been derived by integrating the full three‐dimensional Navier‐Stokes equations over the depth. Then, this set of the governing equations has been discretized using a finite volume method. Simple algorithm and quick scheme are used to solve the resulting discretized equations.FindingsA numerical experiment conducted to investigate the oscillation mechanism of a feedback fluidic oscillator reveals that the feedback passage plays an important role of transmitting the pressure rise to the control port, which triggers the jet stream to deflect towards the opposite side wall in the reaction region. Comparison of the prediction and experiment substantiates the validity of the present numerical procedure.Originality/valueThe two‐dimensional numerical procedure, proposed in this study, will be used by researchers and practitioners to investigate various kinds of complex passages with a small depth. Especially, those who are interested in fluidic devices may find it extremely convenient to conduct numerical experiments.
Three‐dimensional numerical simulation of g‐jitter induced convection and solute transport in magnetic fields
Authors: Li K. , Li B.Q. , Handa J. , de Groh H.C. 
Published: January 2007

PurposeThe quality of crystals grown in space can be diversely affected by the melt flows induced by g‐jitter associated with a space vehicle. This paper presents a full three‐dimensional (3D) transient finite element analysis of the complex fluid flow and heat and mass transfer phenomena in a simplified Bridgman crystal growth configuration under the influence of g‐jitter perturbations and magnetic fields.Design/methodology/approachThe model development is based on the Galerkin finite element solution of the magnetohydrodynamic governing equations describing the thermal convection and heat and mass transfer in the melt. A physics‐based re‐numbering algorithm is used to make the formidable 3D simulations computationally feasible. Simulations are made using steady microgravity, synthetic and real g‐jitter data taken during a space flight.FindingsNumerical results show that g‐jitter drives a complex, 3D, time dependent thermal convection and that velocity spikes in response to real g‐jitter disturbances in space flights, resulting in irregular solute concentration distributions. An applied magnetic field provides an effective means to suppress the deleterious convection effects caused by g‐jitter. Based on the simulations with applied magnetic fields of various strengths and orientations, the magnetic field aligned with the thermal gradient provides an optimal damping effect, and the stronger magnetic field is more effective in suppressing the g‐jitter induced convection. While the convective flows and solute transport are complex and truly 3D, those in the symmetry plane parallel to the direction of g‐jitter are essentially two‐dimensional (2D), which may be approximated well by the widely used 2D models.Originality/valueThe physics‐based re‐numbering algorithm has made possible the large scale finite element computations for 3D g‐jitter flows in a magnetic field. The results indicate that an applied magnetic field can be effective in suppressing the g‐jitter driven flows and thus enhance the quality of crystals grown in space.
Quadratic Petrov‐Galerkin finite elements for advective‐reactive features in turbomachinery CFD
Authors: Corsini Alessandro , Rispoli Franco , Santoriello Andrea 
Published: January 2007

PurposeAn original finite element scheme for advection‐diffusion‐reaction problems is presented. The new method, called spotted Petrov‐Galerkin (SPG), is a quadratic Petrov‐Galerkin (PG) formulation developed for the solution of equations where either reaction (associated to zero‐order derivatives of the unknown) and/or advection (proportional to first‐order derivatives) dominates on diffusion (associated to second‐order derivatives). The addressed issues are turbulence and advective‐reactive features in modelling turbomachinery flows.Design/methodology/approachThe present work addresses the definition of a new PG stabilization scheme for the reactive flow limit, formulated on a quadratic finite element space of approximation. We advocate the use of a higher order stabilized formulation that guarantees the best compromise between solution stability and accuracy. The formulation is first presented for linear scalar one‐dimensional advective‐diffusive‐reactive problems and then extended to quadrangular Q2 elements.FindingsThe proposed advective‐diffusive‐reactive PG formulation improves the solution accuracy with respect to a standard streamline driven stabilization schemes, e.g. the streamline upwind or Galerkin, in that it properly accounts for the boundary layer region flow phenomena in presence of non‐equilibrium effects.Research limitations/implicationsThe numerical method here proposed has been designed for second‐order quadrangular finite‐elements. In particular, the Reynolds‐Averaged Navier‐Stokes equations with a non‐linear turbulence closure have been modelled using the stable mixed element pair Q2‐Q1.Originality/valueThis paper investigated the predicting capabilities of a finite element method stabilized formulation developed for the purpose of solving advection‐reaction‐diffusion problems. The new method, called SPG, demonstrates its suitability in solving the typical equations of turbulence eddy viscosity models.
Numerical study of forced convection in a 3D flow of a non‐Newtonian fluid through a porous duct
Authors: Nebbali R. , Bouhadef K. 
Published: January 2007

PurposeTo investigate the forced convection heat transfer to hydrodynamically and thermally fully developed laminar steady flow of power‐law non‐Newtonian fluid in a partially porous square duct.Design/methodology/approachThe modified Brinkmann‐Forchheimer extended Darcy model for power‐law fluids is used in the porous layer. The solutions for the velocity and temperature fields are obtained numerically using the finite volume method. Computations are performed over a range of Darcy number, power‐law indices, porous insert thickness and thermal conductivity ratio.FindingsThe average Nusselt number and the Fanning factor, so obtained are found to be in good agreement with the literature. It is highlighted that a heat transfer improvement is obtained when the channel is entirely porous and this enhancement is maximized at low permeability. While depending on the working conditions, heat transfer enhancement can also be obtained by filling partially the duct with the porous insert, even if the conductivity ratio is equal to 1. The results indicate also that the conductivity ratio has a strong impact on the heat transfer enhancement at high permeability, while this impact is significant beyond a critical thickness of the porous layer at low permeability. It is found that both shear‐thinning (n<1) and shear‐thickening (n>1) fluids allow obtaining the highest Nusselt number according to the properties of the porous insert. The presence of the porous insert causes a significant increase in pressure drop. This added pressure drop is found to be more important with shear thickening fluids (n>1).Research limitations/implicationsThe results of this paper are valid for square ducts and H1 thermal boundary condition, corresponding to an axially uniform heat flux and peripherally uniform temperature. The inertial effects are neglected in the porous region.Practical implicationsThe obtained results can be used in the design of heat exchangers and in the cooling of electronic equipments.Originality/valueThis work investigates some interesting ways to enhance heat transfer in three‐dimensional square ducts by using porous substrates and non‐Newtonian fluids. It is believed that the case studied in this paper has not previously been investigated.
Fin angle effect on turbulent heat transfer in parallel‐plate channel with flow‐inclining fins
Authors: Yuan Z.X. , Zhao L.H. , Zhang B.D. 
Published: January 2007

PurposeThis paper aims to develop enhanced surfaces that possess improved heat transfer rate with moderate flow pressure‐drop.Design/methodology/approachThe characteristics of the heat transfer and flow resistance in a parallel‐plate channel with flow‐inclining fins have been numerically and experimentally studied. In the turbulent flow range, the effect of the fin angle from 0 to 23.2° in addition to three channel heights, has been investigated.FindingsThe friction factor and the Nusselt number of the experimented 3D finned ducts are both lower than those of the numerical 2D channel at the same Reynolds number. The assessment under the constraint of the same pump power consumption shows that the enhancement ratio, Num/Nu0, is in between 1.6 ∼ 3.3. Showing different priority, the fin of β=23.2° is the most profitable for the 2D channel, while the case of β=16.0° is superior to the other fin angles for thicker 3D ducts.Research limitations/implicationsFor wide flat channels the 3D fins rather than the 2D fins are profitable. The deployment of the 3D fin, which is unchangeable in the current study, should be further optimized. The fin dimension and configuration in other duct forms are also challenging subjects.Practical implicationsThe results can be referenced by those who engage in design of plate‐fin heat exchangers. Attention should be paid to the optimum fin angle for different aspect ratios of the duct.Originality/valueThe study provides a practical fulfillment of the effective enhancement of the convective heat transfer with properly designed inserts that the field synergy principle predicted.
Response surface‐based shape optimization of a Francis draft tube
Authors: Marjavaara Daniel , Lundström Staffan 
Published: January 2007

PurposeThis paper aims to develop an efficient and accurate numerical method that can be used in the design process of the waterways in a hydropower plant.Design/methodology/approachA range of recently published (2002‐2006) works, which aim to form the basis of a shape optimization tool for flow design and to increase the knowledge within the field of computational fluid dynamics (CFD) and surrogate‐based optimization techniques.FindingsProvides information about how crude the optimization method can be regarding, for example, the design variables, the numerical noise and the multi objectives, etc.Research limitations/implicationsIt does not give a detailed interpretation of the flow behaviour due to the lack of validation data.Practical implicationsA very useful flow design methodology that can be used in both academy and industry.Originality/valueShape optimization of hydraulic turbine draft tubes with aid of CFD and numerical optimization techniques has not been performed until recently due to the high CPU requirements on CFD simulations. The paper investigates the possibilities of using the global optimization algorithm response surface methodology in the design process of a full scale hydraulic turbine draft tube.