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Article
Publication date: 15 June 2015

Wenchao Zhou, Drew Loney, Andrei G. Fedorov, F. Levent Degertekin and David W. Rosen

– The aim of this paper is to advance the understanding of the droplet deposition process to better predict and control the manufacturing results for ink-jet deposition.

Abstract

Purpose

The aim of this paper is to advance the understanding of the droplet deposition process to better predict and control the manufacturing results for ink-jet deposition.

Design/methodology/approach

As material interface has both geometric and physical significance to manufacturing, the approach the authors take is to study the interface evolution during the material joining process in ink-jet deposition using a novel shape metric and a previously developed powerful simulation tool. This tool is an experimentally validated numerical solver based on the combination of the lattice Boltzmann method and the phase-field model that enabled efficient simulation of multiple-droplet interactions in three dimensions.

Findings

The underlying physics of two-droplet interaction is carefully examined, which provides deep insights into the effects of the printing conditions on the interface evolution of multiple-droplet interaction. By studying line printing, it is found that increasing impact velocity or decreasing fluid viscosity can reduce manufacturing time. For array printing, the authors have found the issue of air bubble entrapment that can lead to voids in the manufactured parts.

Research limitations/implications

The array of droplets impinges simultaneously, in contrast to most ink-jet printers. Sequential impingement of lines of droplet needs to be studied. Also, impingement on non-planar surfaces has not been investigated yet, but is important for additive manufacturing. Finally, it is recognized that the droplet hardening mechanisms need to be incorporated in the simulation tool to predict and control the final shape and size of the arbitrary features and manufacturing time for ink-jet deposition.

Practical implications

The research findings in this paper imply opportunities for optimization of printing conditions and print head design. Furthermore, if precise droplet control can be achieved, it may be possible to eliminate the need for leveling roller in the current commercial printers to save machine and manufacturing cost.

Originality/value

This work represents one of the first attempts for a systematic study of the interface dynamics of multiple-droplet interaction in ink-jet deposition enabled by the novel shape metric proposed in the paper and a previously developed numerical solver. The findings in this paper advanced the understanding of the droplet deposition process. The physics-based approach of analyzing the simulation results of the interface dynamics provides deep insights into how to predict and control the manufacturing relevant outcomes, and optimization of the deposition parameters is made possible under the same framework.

Details

Rapid Prototyping Journal, vol. 21 no. 4
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 8 February 2016

Dawit Zenebe Segu and Pyung Hwang

– The purpose of this paper is to investigate and discuss the effect of multi-shape laser surface texturing (LST) steel surfaces on tribological performance.

Abstract

Purpose

The purpose of this paper is to investigate and discuss the effect of multi-shape laser surface texturing (LST) steel surfaces on tribological performance.

Design/methodology/approach

The textured surface with some specific formula arrays was fabricated by laser ablation process by combining patterns of circles and triangles, circles and squares and circles and ellipses. The tribological test was performed by a flat-on-flat tribometer under dry and lubrication conditions, and results were compared with that of untextured surface.

Findings

The results showed that the textured surface had better friction coefficient performance than the untextured surface due to hydrodynamic lubrication effect. Through an increase in sliding speed, the beneficial effect of LST performance was achieved under dry and lubrication conditions.

Originality/value

This paper develops multi-shape LST steel surfaces for improving the friction and wear performance under dry and lubrication conditions.

Details

Industrial Lubrication and Tribology, vol. 68 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 24 May 2013

Michiel H. Straathof, Giampietro Carpentieri and Michel J.L. van Tooren

An aerodynamic shape optimization algorithm is presented, which includes all aspects of the design process: parameterization, flow computation and optimization. The…

Abstract

Purpose

An aerodynamic shape optimization algorithm is presented, which includes all aspects of the design process: parameterization, flow computation and optimization. The purpose of this paper is to show that the Class‐Shape‐Refinement‐Transformation method in combination with an Euler/adjoint solver provides an efficient and intuitive way of optimizing aircraft shapes.

Design/methodology/approach

The Class‐Shape‐Transformation method was used to parameterize the aircraft shape and the flow was computed using an in‐house Euler code. An adjoint solver implemented into the Euler code was used to compute the required gradients and a trust‐region reflective algorithm was employed to perform the actual optimization.

Findings

The results of two aerodynamic shape optimization test cases are presented. Both cases used a blended‐wing‐body reference geometry as their initial input. It was shown that using a two‐step approach, a considerable improvement of the lift‐to‐drag ratio in the order of 20‐30 per cent could be achieved. The work presented in this paper proves that the CSRT method is a very intuitive and effective way of parameterizating aircraft shapes. It was also shown that using an adjoint algorithm provides the computational efficiency necessary to perform true three‐dimensional shape optimization.

Originality/value

The novelty of the algorithm lies in the use of the Class‐Shape‐Refinement‐Transformation method for parameterization and its coupling to the Euler and adjoint codes.

Details

Engineering Computations, vol. 30 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 2 October 2017

Hongxing Han, Wei Chen, Bin Huang and Xudong Fu

This paper aims to propose a shape factor for granular materials based on particle shape. The scientific goal is to investigate the influence of particle shape on the…

Abstract

Purpose

This paper aims to propose a shape factor for granular materials based on particle shape. The scientific goal is to investigate the influence of particle shape on the mechanical properties of rockfill materials.

Design/methodology/approach

The method of generating four regular-shaped particles is based on the observation that most rockfill grains are regarded as like-triangle, like-rhombus, like-square and like-hexagon. A shape factor F that is developed using the Blaschke coefficient and a concave–convex degree is proposed. A biaxial compression test on rockfill materials under stress path is numerically simulated by discrete element method. The evolution of the shape factor F under the simulated stress paths is analyzed, and particle breakage rate, peak intensity and peak-related internal friction angle for rockfill materials are derived. A method of determining the shape factor F involved in the two functions is proposed.

Findings

A new micro-parameter is calibrated using the test data of one rockfill material. Particle shape greatly affects the particle breakage rate, peak intensity and peak-related internal friction angle for rockfill materials. The final experimental grading curves all approach the particle breakage grading curve proposed by Einav (the fractal dimension is 2.7).

Originality/value

This study proposes a shape factor F, which describes the geometric features of natural rockfill particles. The proposed shape factor F has a simple structure, and its parameters are easy to determine. The method provides an opportunity for a quantitative study on the particle shape of granular materials, and this study helps to better understand the influence of particle shape on the mechanical characteristics of rockfill materials.

Details

Engineering Computations, vol. 34 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 29 November 2018

Aparna Prasad Bhat

The purpose of this paper is to ascertain the pattern of the implied volatility function for currency options traded on the National Stock Exchange of India (NSE)…

Abstract

Purpose

The purpose of this paper is to ascertain the pattern of the implied volatility function for currency options traded on the National Stock Exchange of India (NSE), identify its potential determinants and to investigate any seasonality in the pattern.

Design/methodology/approach

The paper examines four different specifications for the implied volatility smile of exchange-traded dollar-rupee options. These specifications are tested by running Ordinary Least Squares (OLS) regressions on a daily basis for all options over the entire sample period. Seven potential determinants for the shape of the volatility function are identified. Contemporaneous and lead-lag relationships between these determinants and the shape of the volatility function are examined using OLS and multivariate VAR. Impulse response functions are employed to test the strength and persistence of the lead-lag relations. Seasonality of the smile pattern is tested using OLS.

Findings

The study shows that the implied volatility function for dollar-rupee options is asymmetric and varies with the time to maturity of the option. Historical volatility, momentum and jumps in the exchange rate, time to maturity, traded volume of options and volatility in the stock market appear to Granger-cause the shape of the volatility smile. Feedback causality is observed from the shape of the smile to the volatility, momentum and jumps in the exchange rate and trading volume of currency options. A weak day-of-the-week effect is observed in the pattern of the volatility smile.

Practical implications

The study sheds light on the potential determinants of the smile and highlights the predictive power of the smile which findings can be useful to market practitioners for pricing and hedging of dollar-rupee options. The study has strong practical implications during a period of increased volatility in the dollar-rupee pair.

Originality/value

Most of the existing literature regarding implied volatility smiles has focused either on the volatility smile of US equity index options or that of major liquid currencies. There is a need for such studies in the context of options on emerging market currencies such as the Indian rupee which are characterized by thin trading and frequent central bank intervention and signaling. To the best of the author’s knowledge this study is the first to focus on the volatility smile of exchange-traded options on the US dollar–Indian rupee.

Details

International Journal of Emerging Markets, vol. 13 no. 6
Type: Research Article
ISSN: 1746-8809

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Article
Publication date: 1 September 2016

Qiquan Chen, Ji Weng, Stephen Corcoran and Chenhao Fan

The performance of the building envelope of a large-scale public building significantly influences the energy consumption of such a building. This study aims to determine…

Abstract

The performance of the building envelope of a large-scale public building significantly influences the energy consumption of such a building. This study aims to determine the best strategy for the envelope by examining the engineering design of the building in Nanchang University. The building shape coefficient, sun-shading strategies, window–wall ratio, roof, and walls were studied through a method involving multilayer feed-forward neural network model simulations. Results show that the optimum shape coefficient value is 0.32. The combination of interior and exterior blinds and electrochromic glass is the ideal option to reduce the increase in the energy consumption of the architecture caused by solar radiation. Maintaining the window–wall ratio at 0.4 is ideal. A green roof exerts a minimal effect on building energy consumption decrease (only 0.4%). Applying the strategy of vertical greening to the external wall can reduce cooling energy consumption by as much as 5.4%. Adopting the best envelope strategy combination can further decrease energy consumption by 20.8%. This strategy is also applicable to the middle and lower reaches of Yangtze River in China, which flow through Nanchang and have a climate similar to that of the said area. Future research should be directed toward applying artificial neural networks to quantitatively evaluate the effects of a design strategy and produce the best design strategy combination.

Details

Open House International, vol. 41 no. 3
Type: Research Article
ISSN: 0168-2601

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Article
Publication date: 13 May 2019

Andrzej Frąckowiak, David Spura, Uwe Gampe and Michał Ciałkowski

T-shaped cavities occur by design in many technical applications. An example of such a stator cavity is the side space between the guide vane carriers and the outer casing…

Abstract

Purpose

T-shaped cavities occur by design in many technical applications. An example of such a stator cavity is the side space between the guide vane carriers and the outer casing of a steam turbine. Thermal conditions inside it have a significant impact on the deformation of the turbine casing. In order to improve its prediction, the purpose of this paper is to provide a methodology to gain better knowledge of the local heat transfer at the cavity boundaries based on experimental results.

Design/methodology/approach

To determine the heat transfer coefficient distribution inside a model cavity with the help of a scaled generic test rig, an inverse heat conduction problem is posed and a method for solving such type of problems in the form of linear combinations of Trefftz functions is presented.

Findings

The results of the calculations are compared with another inverse method using first-order gradient optimization technique as well as with estimated values obtained with an analytic two-dimensional thermal network model, and they show an excellent agreement. The calculation procedure is proved to be numerically stable for different degrees of complexity of the sought boundary conditions.

Originality/value

This paper provides a universal and robust methodology for the fast direct determination of an arbitrary distribution of heat transfer coefficients based on material temperature measurements spread over the confining wall.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 12 June 2017

Hussain Altammar, Sudhir Kaul and Anoop K. Dhingra

Wavelets are being increasingly used for damage diagnostics. The purpose of this paper is to present an algorithm that uses the wavelet transform for detecting mixed-mode…

Abstract

Purpose

Wavelets are being increasingly used for damage diagnostics. The purpose of this paper is to present an algorithm that uses the wavelet transform for detecting mixed-mode, also known as combined mode, cracks in large truss structures.

Design/methodology/approach

The mixed-mode crack is modeled by superposing two damage modes, and this model is combined with a finite element model of the truss. The natural modes of the truss are processed through the wavelet transform and then used to determine the damage location. The influence of multiple parameters such as truss geometry, crack geometry, number of truss members, orientation of truss members, etc. is investigated as part of the study.

Findings

The proposed damage detection algorithm is found to be successful in detecting single mode as well as mixed-mode cracks even in the presence of significant end effects, and even when a relatively coarse sampling of natural modes is used. Results from multiple simulations that involve three commonly used truss structures are presented. A correlation between damage severity and the magnitude of wavelet coefficients is observed.

Originality/value

The proposed algorithm is found to be successful in accurately detecting damage, but direct determination of damage severity is found to be challenging.

Details

International Journal of Structural Integrity, vol. 8 no. 3
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 1 June 2000

C.G. Guo and G.H. Xu

Some of the fundamental problems associated with the aerodynamic configuration of a single‐rotor remotely piloted helicopter are discussed in this paper. A method for…

Abstract

Some of the fundamental problems associated with the aerodynamic configuration of a single‐rotor remotely piloted helicopter are discussed in this paper. A method for selecting the aerodynamic shape of a fuselage and determining the locations and parameters of a horizontal stabilizer and a tail rotor in the preliminary design analysis is given. The application of this method to a remotely piloted single main rotor and tail rotor helicopter developed at the Nanjing University of Aeronautics and Astronautics is described. A raindrop shaped fuselage is chosen for the remotely piloted helicopter and the low drag characteristics of the fuselage are demonstrated from the wind‐tunnel experimental data. The experimental results on the pitching moment characteristics of the horizontal stabilizer are also presented and analyzed. The design considerations of the horizontal stabilizer and tail rotor of the helicopter are discussed in detail.

Details

Aircraft Engineering and Aerospace Technology, vol. 72 no. 3
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 17 August 2012

G.S. Aglietti, S.J.I. Walker and A. Kiley

The purpose of this paper is to assess the suitability of various methods for the reduction of a large finite element model (FEM) of satellites to produce models to be…

Abstract

Purpose

The purpose of this paper is to assess the suitability of various methods for the reduction of a large finite element model (FEM) of satellites to produce models to be used for correlation of the FEM with test results. The robustness of the cross‐orthogonality checks (COC) for the correlation process carried out utilizing the reduced model is investigated, showing its dependence on the number of mode shapes used in the reduction process. Finally the paper investigates the improvement in the robustness of the COC that can be achieved utilizing optimality criteria for the selection of the degrees of freedom (DOF) used for the correlation process.

Design/methodology/approach

A Monte Carlo approach has been used to simulate inaccuracies in the mode shapes (analysis and experimental) of a satellite FEM that are compared during the COC. The sensitivity of the COC to the parameters utilized during the reduction process, i.e. mode shapes and DOFs, is then assessed for different levels of inaccuracy in the mode shapes.

Findings

The System Equivalent Expansion Reduction Process (SEREP) has been identified as a particularly suitable method, with the advantage that a SEREP reduced model has the same eigenvalues and eigenvector of the whole system therefore automatically meeting the criteria on the quality of the reduced model. The inclusion of a high number of mode shapes in the reduction process makes the check very sensitive to minor experimental or modelling inaccuracies. Finally it was shown that utilizing optimality criteria in the selection of the DOFs to carry out the correlation can significantly improve the probability of meeting the COC criteria.

Research limitations/implications

This work is based on the FEM of the satellite Aeolus, and therefore the numerical values obtained in this study are specific for this application. However, this model represents a typical satellite FEM and therefore the trends identified in this work are expected to be generally valid for this type of structure.

Practical implications

The correlation of satellite FEM with test results involves a substantial effort, and it is crucial to avoid failures of the COC due to numerical issues rather than real model inaccuracies. This work shows also how an inappropriate choice of reduction parameters can lead to failure of the COC in cases when there are only very minor differences (e.g. due to minor amount of noise in the results) between analytical and test results. Vice versa, the work also shows how the robustness of the reduced model can be improved.

Originality/value

The paper shows how the robustness of the correlation process for a satellite FEM carried out utilising a SEREP reduced model needed to be investigated, to demonstrate the suitability of this method to reduce large FEM of satellites.

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