Investigation of turbulent flow through microchannels consisting of different micropost arrangementsKharati-Koopaee, Masoud; Rezaee, Mahsa
2017 Engineering Computations: International Journal for Computer-Aided Engineering and Software
doi: 10.1108/EC-02-2016-0069
PurposeThe purpose of the current research is to study the turbulent flow through microchannels having a micropost in aligned and staggered arrangements.Design/methodology/approachNumerical calculations are performed on the basis of the finite volume approach, which is based on the SIMPLEC algorithm. In this work, the slip velocity, flow velocity distribution and friction factor for the two micropost patterns are examined at friction Reynolds numbers of Reτ = 395 and 590, relative module widths of Wm = 0.1 and 1 and cavity fraction range of Fc = 0.1 to 0.9.FindingsResults reveal that for the two micropost patterns, as the friction Reynolds number, relative module width or cavity fraction increases, the slip velocity increases and friction factor decreases. It is found that the aligned micropost configuration leads to higher slip velocity and lower friction factor. Numerical findings indicate that the existence of the continuous cavity surface along the flow direction could be a significant criterion to realize if the velocity distribution deviates from that of the smooth channel. It is also shown that the turbulent flows are capable of producing more drag reduction than the laminar ones.Originality/valuePrevious studies have shown that microchannels consisting of a micropost pattern in aligned and staggered arrangements could be viewed as a promising alternative in the microscale flows for the heat removal purposes. Therefore, understanding the fluid flow through microchannels consisting of these configurations (which is a prerequisite to better understand thermal performance of such microchannels) is a significant issue, which is the subject of the present work.
A numerical investigation of transient MHD free convective flow of a nanofluid over a moving semi-infinite vertical cylinderRajesh, V.; Chamkha, A.J.; Sridevi, Ch.; Al-Mudhaf, A.F.
2017 Engineering Computations: International Journal for Computer-Aided Engineering and Software
doi: 10.1108/EC-03-2016-0090
PurposeThe purpose of this paper is to study numerically the influence of a magnetic field on the transient free convective boundary layer flow of a nanofluid over a moving semi-infinite vertical cylinder with heat transferDesign/methodology/approachThe problem is governed by the coupled non-linear partial differential equations with appropriate boundary conditions. The fluid is a water-based nanofluid containing nanoparticles of copper. The Brinkman model for dynamic viscosity and Maxwell–Garnett model for thermal conductivity are used. The governing boundary layer equations are written according to The Tiwari–Das nanofluid model. A robust, well-tested, implicit finite difference method of Crank–Nicolson type, which is unconditionally stable and convergent, is used to find the numerical solutions of the problem. The velocity and temperature profiles are studied for significant physical parameters such as the magnetic parameter, nanoparticles volume fraction and the thermal Grashof number Gr. The local skin-friction coefficient and the Nusselt number are also analysed and presented graphically.FindingsThe present computations have shown that an increase in the values of either magnetic parameter M or nanoparticle volume fraction decreases the local skin-friction coefficient, whereas the opposite effect is observed for thermal Grashof number Gr. The local Nusselt number increases with a rise in Gr and ϕ values. But an increase in M reduces the local Nusselt number.Originality/valueThis paper is relatively original and presents numerical investigation of transient two-dimensional laminar boundary layer free convective flow of a nanofluid over a moving semi-infinite vertical cylinder in the presence of an applied magnetic field. The present study is of immediate application to all those processes which are highly affected by heat enhancement concept and a magnetic field. Further the present study is relevant to nanofluid materials processing, chemical engineering coating operations exploiting nanomaterials and others.
Explicit dynamic analysis of sheet metal forming processes using linear prismatic and hexahedral solid-shell elementsWang, Peng; Chalal, Hocine; Abed-Meraim, Farid
2017 Engineering Computations
doi: 10.1108/EC-04-2016-0150
PurposeThe purpose of this paper is to propose two linear solid-shell finite elements, a six-node prismatic element denoted SHB6-EXP and an eight-node hexahedral element denoted SHB8PS-EXP, for the three-dimensional modeling of thin structures in the context of explicit dynamic analysis.Design/methodology/approachThese two linear solid-shell elements are formulated based on a purely three-dimensional (3D) approach, with displacements as the only degrees of freedom. To prevent various locking phenomena, a reduced-integration scheme is used along with the assumed-strain method. The resulting formulations are computationally efficient, as only a single layer of elements with an arbitrary number of through-thickness integration points is required to model 3D thin structures.FindingsVia the VUEL user-element subroutines, the performance of these elements is assessed through a set of selective and representative dynamic elastoplastic benchmark tests, impact-type problems and deep drawing processes involving complex non-linear loading paths, anisotropic plasticity and double-sided contact. The obtained numerical results demonstrate good performance of the SHB-EXP elements in the modeling of 3D thin structures, with only a single element layer and few integration points in the thickness direction.Originality/valueThe extension of the SHB-EXP solid-shell formulations to large-strain anisotropic plasticity enlarges their application range to a wide variety of dynamic elastoplastic problems and sheet metal forming simulations. All simulation results reveal that the numerical strategy adopted in this paper can efficiently prevent the various locking phenomena that commonly occur in the 3D modeling of thin structural problems.
Solving the coupled Sylvester-like matrix equations via a new finite iterative algorithmHajarian, Masoud
2017 Engineering Computations: International Journal for Computer-Aided Engineering and Software
doi: 10.1108/EC-11-2015-0341
PurposeThe purpose of this paper is to obtain an iterative algorithm to find the solution of the coupled Sylvester-like matrix equations.Design/methodology/approachIn this work, the matrix form of the conjugate direction (CD) algorithm to find the solution X of the coupled Sylvester-like matrix equations: {A1XB1+M1f1(X)N1=F1,A2XB2+M2f2(X)N2=F2,with fi(X) = X, fi(X) = X¯, fi(X) = XT and fi(X) = XH for i = 1; 2 has been established.FindingsIt is proven that the algorithm converges to the solution within a finite number of iterations in the absence of round-off errors. Finally, four numerical examples were used to test the proficiency and convergence of the established algorithm.Originality/valueThe numerical examples have led the author to believe that the generalized CD (GCD) algorithm is efficient and it converges more rapidly in comparison with the CGNR and CGNE algorithms.
Adaptive response prediction for aerodynamic shape optimizationLeifsson, Leifur; Koziel, Slawomir
2017 Engineering Computations: International Journal for Computer-Aided Engineering and Software
doi: 10.1108/EC-02-2016-0070
PurposeThe purpose of this paper is to reduce the overall computational time of aerodynamic shape optimization that involves accurate high-fidelity simulation models.Design/methodology/approachThe proposed approach is based on the surrogate-based optimization paradigm. In particular, multi-fidelity surrogate models are used in the optimization process in place of the computationally expensive high-fidelity model. The multi-fidelity surrogate is constructed using physics-based low-fidelity models and a proper correction. This work introduces a novel correction methodology – referred to as the adaptive response prediction (ARP). The ARP technique corrects the low-fidelity model response, represented by the airfoil pressure distribution, through suitable horizontal and vertical adjustments.FindingsNumerical investigations show the feasibility of solving real-world problems involving optimization of transonic airfoil shapes and accurate computational fluid dynamics simulation models of such surfaces. The results show that the proposed approach outperforms traditional surrogate-based approaches.Originality/valueThe proposed aerodynamic design optimization algorithm is novel and holistic. In particular, the ARP correction technique is original. The algorithm is useful for fast design of aerodynamic surfaces using high-fidelity simulation data in moderately sized search spaces, which is challenging using conventional methods because of excessive computational costs.
Software tool for simulation of vehicle – road interactionDuarte, Francisco; Ferreira, Adelino; Fael, Paulo
2017 Engineering Computations: International Journal for Computer-Aided Engineering and Software
doi: 10.1108/EC-07-2016-0273
PurposeThis paper aims to deal with the development of a software tool to simulate and study vehicle – road interaction (VRI) to quantify the forces induced and energy released from vehicles to the road pavement, in different vehicle motion scenarios, and the energy absorbed by the road surface, speed reducers or a specific energy harvester surface or device. The software tool also enables users to quantify the energetic efficiency of the process.Design/methodology/approachExisting software tools were analysed and its limitations were identified in terms of performing energetic analysis on the interaction between the vehicle and the road pavement elements, such as speed reducers or energy harvest devices. The software tool presented in this paper intends to overcome those limitations and precisely quantify the energy transfer.FindingsDifferent vehicle models and VRI models were evaluated, allowing to conclude about each model precision: bicycle car model has a 60 per cent higher precision when compared with quarter-car model, and contact patch analysis model has a 67 per cent higher precision than single force analysis model. Also, a technical study was performed for different equipment surface shapes and displacements, concluding that these variables have a great influence on the energy released by the vehicle and on the energy harvested by the equipment surface.Originality/valueThe developed software tool allows to study VRI with a higher precision than existing tools, especially when energetic analyses are performed and when speed reduction or energy harvesting devices are applied on the pavement.
Degenerate-scale problem of the boundary integral equation method/boundary element method for the bending plate analysisChen, Jeng-Tzong; Kuo, Shyh-Rong; Chang, Yu-Lung; Kao, Shing-Kai
2017 Engineering Computations: International Journal for Computer-Aided Engineering and Software
doi: 10.1108/EC-06-2016-0187
PurposeThe purpose of this paper is to detect the degenerate scale of a 2D bending plate analytically and numerically.Design/methodology/approachTo avoid the time-consuming scheme, the influence matrix of the boundary element method (BEM) is reformulated to an eigenproblem of the 4 by 4 matrix by using the scaling transform instead of the direct-searching scheme to find degenerate scales. Analytical degenerate scales are derived from the boundary integral equation (BIE) by using the degenerate kernel only for the circular case. Numerical results of the direct-searching scheme and the eigen system for the arbitrary shape are also considered.FindingsResults using three methods, namely, analytical derivation, the direct-searching scheme and the 4 by 4 eigen system, are also given for the circular case and arbitrary shapes. Finally, addition of a constant for the kernel function makes original eigenvalues (2 real roots and 2 complex roots) of the 4 by 4 matrix to be all real. This indicates that a degenerate scale depends on the kernel function.Originality/valueThe analytical derivation for the degenerate scale of a 2D bending plate in the BIE is first studied by using the degenerate kernel. Through the reformed eigenproblem of a 4 by 4 matrix, the numerical solution for the plate of an arbitrary shape can be used in the plate analysis using the BEM.
Thermo-mechanical coupling particle simulation of three-dimensional large-scale non-isothermal problemsXia, Ming
2017 Engineering Computations: International Journal for Computer-Aided Engineering and Software
doi: 10.1108/EC-04-2016-0135
PurposeThe main purpose of this paper is to present a comprehensive upscale theory of the thermo-mechanical coupling particle simulation for three-dimensional (3D) large-scale non-isothermal problems, so that a small 3D length-scale particle model can exactly reproduce the same mechanical and thermal results with that of a large 3D length-scale one.Design/methodology/approachThe objective is achieved by following the scaling methodology proposed by Feng and Owen (2014).FindingsAfter four basic physical quantities and their similarity-ratios are chosen, the derived quantities and its similarity-ratios can be derived from its dimensions. As the proposed comprehensive 3D upscale theory contains five similarity criteria, it reveals the intrinsic relationship between the particle-simulation solution obtained from a small 3D length-scale (e.g. a laboratory length-scale) model and that obtained from a large 3D length-scale (e.g. a geological length-scale) one. The scale invariance of the 3D interaction law in the thermo-mechanical coupled particle model is examined. The proposed 3D upscale theory is tested through two typical examples. Finally, a practical application example of 3D transient heat flow in a solid with constant heat flux is given to illustrate the performance of the proposed 3D upscale theory in the thermo-mechanical coupling particle simulation of 3D large-scale non-isothermal problems. Both the benchmark tests and application example are provided to demonstrate the correctness and usefulness of the proposed 3D upscale theory for simulating 3D non-isothermal problems using the particle simulation method.Originality/valueThe paper provides some important theoretical guidance to modeling 3D large-scale non-isothermal problems at both the engineering length-scale (i.e. the meter-scale) and the geological length-scale (i.e. the kilometer-scale) using the particle simulation method directly.