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Article

Frank Gardea, Daniel P. Cole, Bryan Glaz and Jaret C. Riddick

This study aims to discuss the effect of carbon nanotubes (CNTs) on the mechanical properties of acrylonitrile–butadiene–styrene (ABS) composites fabricated by additive…

Abstract

Purpose

This study aims to discuss the effect of carbon nanotubes (CNTs) on the mechanical properties of acrylonitrile–butadiene–styrene (ABS) composites fabricated by additive manufacturing (AM). Insight into the energy-dissipation mechanisms introduced and/or enhanced by the addition of CNTs is presented in this study.

Design/methodology/approach

ABS/CNT filaments were fabricated with different concentrations of CNTs. Using a fused deposition modeling approach, unidirectional specimens were printed using a MakerBot Replicator 2X (MakerBot Industries, Brooklyn, NY, USA). Specimens were tested under static and dynamic conditions, with the loading coinciding with the printing direction, to determine elastic modulus, strength and viscoelastic properties.

Findings

A CNT reinforcing effect is evident in a 37 per cent increase in elastic modulus. Likewise, the strength of the composite increases by up to 30 per cent with an increase in weight fraction of CNTs. At low dynamic strain amplitudes (0.05 per cent), a correlation between dissipated strain energy of the butadiene phase and strength of the composite is found such that less dissipation, from constraint of the butadiene particles by the CNTs, leads to higher strength of the composite. At higher dynamic strains, the presence of a high concentration of CNT leads to increased energy dissipation, with a maximum measured value of 24 per cent higher loss factor compared to baseline specimens. Because the trend of the composite behavior is similar (with a higher absolute value) to that of neat ABS, this study’s results indicate that well-established polymer/CNT dissipation mechanisms (such as stick-slip) are not significant, but that the CNTs amplify the dissipation of the ABS matrix by formation of crazes through stress concentrations.

Originality/value

This study provides knowledge of the dissipation behavior in additively manufactured ABS/CNT composites and provides insight into the expansion to new printable materials for dynamics applications.

Details

Rapid Prototyping Journal, vol. 26 no. 3
Type: Research Article
ISSN: 1355-2546

Keywords

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Article

Siddhartha Biswas and Soumen Shaw

The purpose of this paper is to analyze the thermal shock response on the deformation of circular hollow cylinder in a thermodynamically consistent manner.

Abstract

Purpose

The purpose of this paper is to analyze the thermal shock response on the deformation of circular hollow cylinder in a thermodynamically consistent manner.

Design/methodology/approach

The investigation is carried out under the light of generalized thermoelasticity theory with energy dissipation. In order to obtain the analytical expressions of the components of stress and strain fields, appropriate integral transform technique is adopted and the salient features are emphasized.

Findings

It has been observed that the existence of energy dissipation can minimize the development of the stress components into the cylindrical wall. Since more amount of heat is propagate into the medium in a short period of time consequently, the medium deformed in a high rate in presence of energy dissipation. Two special phenomena are also revealed in the particular cases.

Originality/value

The numerical simulated results are demonstrated through a numerous diagrams and some important observations are explained. This work may be helpful for those researchers who are devoted on several types of heat or fluid flow into the pipeline made with anisotropic solids.

Details

Multidiscipline Modeling in Materials and Structures, vol. 14 no. 3
Type: Research Article
ISSN: 1573-6105

Keywords

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Article

Seyi F. Olatoyinbo, Sarma L. Rani and Abdelkader Frendi

The purpose of this study is to investigate the accuracy and applicability of the Flowfield Dependent Variation (FDV) method for large-eddy simulations (LES) of decaying…

Abstract

Purpose

The purpose of this study is to investigate the accuracy and applicability of the Flowfield Dependent Variation (FDV) method for large-eddy simulations (LES) of decaying isotropic turbulence.

Design/methodology/approach

In an earlier paper, the FDV method was successfully demonstrated for simulations of laminar flows with speeds varying from low subsonic to high supersonic Mach numbers. In the current study, the FDV method, implemented in a finite element framework, is used to perform LESs of decaying isotropic turbulence. The FDV method is fundamentally derived from the Lax–Wendroff Scheme (LWS) by replacing the explicit time derivatives in LWS with a weighted combination of explicit and implicit time derivatives. The increased implicitness and the inherent numerical dissipation of FDV contribute to the scheme’s numerical stability and monotonicity. Understanding the role of numerical dissipation that is inherent to the FDV method is essential for the maturation of FDV into a robust scheme for LES of turbulent flows. Accordingly, three types of LES of decaying isotropic turbulence were performed. The first two types of LES utilized explicit subgrid scale (SGS) models, namely, the constant-coefficient Smagorinsky and dynamic Smagorinsky models. In the third, no explicit SGS model was employed; instead, the numerical dissipation inherent to FDV was used to emulate the role played by explicit SGS models. Such an approach is commonly known as Implicit LES (ILES). A new formulation was also developed for quantifying the FDV numerical viscosity that principally arises from the convective terms of the filtered Navier–Stokes equations.

Findings

The temporal variation of the turbulent kinetic energy and enstrophy and the energy spectra are presented and analyzed. At all grid resolutions, the temporal profiles of kinetic energy showed good agreement with t(−1.43) theoretical scaling in the fully developed turbulent flow regime, where t represents time. The energy spectra also showed reasonable agreement with the Kolmogorov’s k(−5/3) power law in the inertial subrange, with the spectra moving closer to the Kolmogorov scaling at higher-grid resolutions. The intrinsic numerical viscosity and the dissipation rate of the FDV scheme are quantified, both in physical and spectral spaces, and compared with those of the two SGS LES runs. Furthermore, at a finite number of flow realizations, the numerical viscosities of FDV and of the Streamline Upwind/Petrov–Galerkin (SUPG) finite element method are compared. In the initial stages of turbulence development, all three LES cases have similar viscosities. But, once the turbulence is fully developed, implicit LES is less dissipative compared to the two SGS LES runs. It was also observed that the SUPG method is significantly more dissipative than the three LES approaches.

Research limitations/implications

Just as any computational method, the limitations are based on the available computational resources.

Practical implications

Solving problems involving turbulent flows is by far the biggest challenge facing engineers and scientists in the twenty-first century, this is the road that the authors have embarked upon in this paper and the road ahead of is very long.

Social implications

Understanding turbulence is a very lofty goal and a challenging one as well; however, if the authors succeed, the rewards are limitless.

Originality/value

The derivation of an explicit expression for the numerical viscosity tensor of FDV is an important contribution of this study, and is a crucial step forward in elucidating the fundamental properties of the FDV method. The comparison of viscosities for the three LES cases and the SUPG method has important implications for the application of ILES approach for turbulent flow simulations.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 1
Type: Research Article
ISSN: 0961-5539

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Article

Cheng Zhong and Alexandra Komrakova

This paper aims to demonstrate the capabilities of a diffuse interface free energy lattice Boltzmann method to perform direct numerical simulations of liquid–liquid…

Abstract

Purpose

This paper aims to demonstrate the capabilities of a diffuse interface free energy lattice Boltzmann method to perform direct numerical simulations of liquid–liquid dispersions in a well-controlled turbulent environment. The goal of this research study is to develop numerical techniques that can visualize and quantify drop interaction with the turbulent vortices. The obtained information will be used for the development of sub-models of drop breakup for multi-scale simulations.

Design/methodology/approach

A pure binary liquid system is considered that is subject to fully developed statistically stationary turbulent flow field in a cubic fully periodic box with the edge size of 300 lattice units. Three turbulent flow fields with varying energy input are examined and their coherent structures are visualized using a normalized Q-criterion. The evolution of the liquid–liquid interface is tracked as a function of time. The detailed explanation of the numerical method is provided with a highlight on a choice of the numerical parameters.

Findings

Drop breakup mechanisms differ depending on energy input. Drops break due to interaction with the vortices. Quantification of turbulent structures shows that the size of vortices increases with the decrease of energy input. Drop interacts simultaneously with multiple vortices of the size comparable to or smaller than the drop size. Vortices of the size smaller than the drop size disturb drop interface and pinch off the satellites. Vortices of the size comparable to the drop size tend to elongate the drop and tear it apart producing daughter drops and satellites. Addition of the second phase enhances turbulent dissipation at the high wavenumbers. To obtain physically realistic two-phase energy spectra, the multiple-relaxation-time collision operator should be used.

Originality/value

Detailed information of drop breakup in the turbulent flow field is crucial for the development of drop breakup sub-models that are necessary for multi-scale numerical simulations. The improvement of numerical methods that can provide these data and produce reliable results is important. This work made one step towards a better understanding of how drops interact with the turbulent vortices.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

Zijing Wang

Special shaped columns composed of concrete-filled square steel tubes have broad application prospects in steel structure residential buildings. The paper aims to discuss…

Abstract

Purpose

Special shaped columns composed of concrete-filled square steel tubes have broad application prospects in steel structure residential buildings. The paper aims to discuss this issue.

Design/methodology/approach

In this paper, the thermal bridge problem of special-shaped column structures is studied, T-shaped column composed of concrete-filled square steel tubes is taken as an example, the finite element thermal bridge model is established by ANSYS software, the heat treatment is calculated by the software and the results are output.

Findings

According to the finite element results, it can be found that in the thermal bridge model, the temperature distribution is uniform, the heat flux density is small and the heat dissipation where the steel plate locates is serious. The lowest temperature of the thermal bridge is greater than the air condensation temperature, and the affected area is about 0.2 m, which is larger than the thickness of the wall and will not cause too much impact on the wall. It will help to suppress heat dissipation and achieve energy-saving and heat preservation inside the buildings.

Originality/value

The experimental results prove the effectiveness of the special-shaped column structure for building energy-saving buildings. This study provides some theoretical basis for further application of special-shaped column structures in architecture.

Details

International Journal of Building Pathology and Adaptation, vol. 38 no. 3
Type: Research Article
ISSN: 2398-4708

Keywords

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Article

Chao‐Lieh Chen, Kuan‐Rong Lee and Yau‐Hwang Kuo

The purpose of this paper is to propose an energy‐proportional routing (EPR) algorithm, which effectively extends the lifetimes of sensor networks.

Abstract

Purpose

The purpose of this paper is to propose an energy‐proportional routing (EPR) algorithm, which effectively extends the lifetimes of sensor networks.

Design/methodology/approach

The algorithm makes no specific assumption on network topology and hence is suitable for improving sensor networks with clustering. To optimally utilize energy, light‐load units – nodes or clusters that conserve energy are ideal candidates as intermediate units for forwarding data from others. To balance the load, first, the proposed algorithm predicts energy consumption of each node in each round. Then the algorithm controls the energy consumption of each unit as close as possible to the threshold representing the energy utilization mean value among clusters. Finally the algorithm checks satisfaction of the energy constraints in terms of distances and predicted data amounts. The proposed algorithm performs routing by determining whether a cluster head or a node should either undertake forwarding tasks or transmit data to intermediate hops. In this way, energy dissipation is evenly distributed to all units and the lifetime of the whole wireless sensor network is ultimately extended.

Findings

The algorithm applies hierarchically to different levels of network topology. In addition to experiments, the mathematical proofs of lifetime extension by the proposed routing algorithm are given in accordance with three widely accepted criteria – total energy dissipation, the number of live nodes in each round and the throughput (data amount per round).

Originality/value

A new routing algorithm is proposed.

Details

International Journal of Pervasive Computing and Communications, vol. 3 no. 3
Type: Research Article
ISSN: 1742-7371

Keywords

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Article

Shutian Liu, Xueshan Ding and Zeqi Tong

This paper aims to study the energy absorption properties of the thin-walled square tube with lateral piecewise variable thickness under axial crashing and the influence…

Abstract

Purpose

This paper aims to study the energy absorption properties of the thin-walled square tube with lateral piecewise variable thickness under axial crashing and the influence of the tube parameters on energy absorption.

Design/methodology/approach

In this work, the energy absorption properties of the thin-walled square tube were analyzed by theoretical, numerical and experimental approach. The numerical results are obtained based on the finite element method. The explicit formulation for predicting the mean crushing force of the tube with lateral piecewise variable thickness was derived based on Super Folding Element method. The limitation of the prediction formulation was analyzed by numerical calculation. The numerical calculation was also used to compare the energy absorption between the tube with lateral piecewise variable thickness and other tubes, and to carry out the parametric analysis.

Findings

Results indicate that the thin-walled tube with lateral piecewise variable thickness has higher energy absorption properties than the uniform thickness tubes and the tubes with lateral linear variable thickness. The thickness of the corner is the key factor for the energy absorption of the tubes. The thickness of the non-corner region is the secondary factor. Increasing the corner thickness and decreasing the non-corner thickness can make the energy absorption improved. It is also found that the prediction formulation of the mean crushing force given in this paper can quickly and accurately predict the energy absorption of the square tube.

Originality/value

The outcome of the present research provides a design idea to improve the energy absorption of thin-walled tube by designing cross-section thickness and gives an explicit formulation for predicting the mean crushing force quickly and accurately.

Details

Engineering Computations, vol. 36 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

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Article

Stefan May, Julien Vignollet and René de Borst

– The purpose of this paper is to introduce a new arc-length control method for physically non-linear problems based on the rates of the internal and the dissipated energy.

Abstract

Purpose

The purpose of this paper is to introduce a new arc-length control method for physically non-linear problems based on the rates of the internal and the dissipated energy.

Design/methodology/approach

In this paper, the authors derive from the second law of thermodynamics the arc-length method based on the rate of the dissipated energy and from the time derivative of the energy density the arc-length method based on the rate of the internal energy.

Findings

The method requires only two parameters and can automatically trace equilibrium paths which display multiple snap-through and/or snap-back phenomena.

Originality/value

A fully energy-based control procedure is developed, which facilitates switching between dissipative and non-dissipative arc-length control equations in a natural way. The method is applied to a plate with an eccentric hole using the phase field model for brittle fracture and to a perforated beam using interface elements with decohesion.

Details

Engineering Computations, vol. 33 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

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Article

Michał T. Lewandowski, Paweł Płuszka and Jacek Pozorski

This paper aims to assess the sensitivity of numerical simulation results of turbulent reactive flow to the formulation of inlet boundary conditions. The analysis concerns…

Abstract

Purpose

This paper aims to assess the sensitivity of numerical simulation results of turbulent reactive flow to the formulation of inlet boundary conditions. The analysis concerns the profiles of the mean velocity the turbulence kinetic energy k and its dissipation rate ϵ. It is intended to provide guidance to the determination of inlet conditions when only global flow data are available. This situation can be met both in simple laboratory experiments and in industrial full-scale applications, when measurements are either incomplete or infeasible, resulting in lack of detailed inlet data.

Design/methodology/approach

Two turbulence–chemistry interaction models were studied: eddy dissipation concept and partially stirred reactor. Three different velocity profiles and related turbulence statistics were applied to present feasible scenarios and their consequences. Simulations with the most appropriate inlet data were accompanied with profiles of turbulent quantities obtained with a proposed method. This method was contrasted to other approaches popular in the literature: the pre-inlet pipe and the separate cold flow simulations of a burner. The methodology was validated on two laboratory-scale jet flames: Delft Jet-in-Hot-Coflow and Sandia CHN B. The simulations were carried out with open source code OpenFOAM.

Findings

The proposed relations for turbulence kinetic energy and its dissipation rate at the inlet are found to provide results comparable to those obtained with the use of experimental data as inlet boundary conditions. Moreover, from a certain location downstream the jet, weakly dependent on the Reynolds number, the influence of inlet conditions on flow statistics was found to be negligible.

Originality/value

This work reveals the consequences of the use of rather crude assumptions made for inlet boundary conditions. Proposed formulas for the profiles for k and epsilon are attractive alternatives to other approaches aiming to determine the inlet boundary conditions for turbulent jet flows.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

A. Caignot, P. Ladevèze, D. Néron and J.‐F. Durand

The purpose of this paper is to propose a virtual testing strategy in order to predict damping due to the joints which are present in the ARIANE 5 launcher.

Abstract

Purpose

The purpose of this paper is to propose a virtual testing strategy in order to predict damping due to the joints which are present in the ARIANE 5 launcher.

Design/methodology/approach

Since engineering finite element codes do not give satisfactory results, either because they are too slow or because they cannot calculate dissipation accurately, a new computational tool is introduced based on the LArge Time INcrement (LATIN) method in its multiscale version.

Findings

The capabilities of the new strategy are illustrated on one of the joints of ARIANE 5. The damping predicted virtually is compared to experimental results, and the approach appears promising.

Originality/value

The tool which has been developed gives access to calculations which were previously unaffordable with standard computational codes, which may improve the design process of launchers. The code is transferred into ASTRIUM‐ST, where it is being used to build a database of dissipations in the joints of the ARIANE 5 launcher.

Details

Engineering Computations, vol. 27 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

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