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Article
Publication date: 13 September 2011

Kirill Blinov, Alexander Nikanorov, Bernard Nacke and Markus Klöpzig

Because of their widespread use in industry, induction through‐heaters of various metal products must be of high effectiveness not only in “quasi” steady‐state operation but in…

Abstract

Purpose

Because of their widespread use in industry, induction through‐heaters of various metal products must be of high effectiveness not only in “quasi” steady‐state operation but in different transient modes as well. Nowadays, they are usually designed to provide the required characteristics in “quasi” steady‐state operation mode mainly. The purpose of this paper is to examine numerical simulation of transient processes in induction through‐heating lines generally and investigate dynamic temperature fields during the first start of the heaters particularly.

Design/methodology/approach

The research methodology is based on coupled numerical electromagnetic and thermal analyses using FEM approach. ANSYS simulations are supported with the developed tools for imitation of mass transfer effects in continuous induction heating lines.

Findings

The results show that transient temperature fields in the heated strip or slab significantly differ from their “quasi” steady‐state descriptions. Local temperature variations acquired in longitudinal as well as transverse flux induction heaters during the first start have been predicted.

Practical implications

The received results can be used for design of induction through‐heaters and improvement of their characteristics in dynamic operation modes.

Originality/value

Investigation of dynamic characteristics of the heaters in dynamic modes can be only done by numerical modelling based on special algorithms providing a time loop additional to coupling between electromagnetic and thermal analyses. Such algorithms have been developed and used for investigation of two types of induction installations: through‐heaters of cylindrical billets for forging and heating lines of strip or thin slab for rolling mills.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 27 May 2021

Runqiang Zhang, Guoyong Sun, Yuchuan Wang and Sebastián Leguizamón

The study aims to display the bubbles' evolution in the shear layer and their relationship with the pressure fluctuations. Furthermore, the coherent structures of the first six…

Abstract

Purpose

The study aims to display the bubbles' evolution in the shear layer and their relationship with the pressure fluctuations. Furthermore, the coherent structures of the first six modes are extracted, in order to provide insight into their temporal and spatial evolution and determine the relationship between cavitating bubbles and coherent structures.

Design/methodology/approach

In the present study, numerical simulations of submerged jet cavitating flow were carried out at a cavitation inception condition inside an axisymmetric cavity using the large eddy simulation (LES) turbulence model and the Schnerr–Sauer (S–S) cavitation model. Based on snapshots produced by the numerical simulation, dynamic mode decomposition (DMD) was performed to extract the three-dimensional coherent structures of the first six modes in the shear layer.

Findings

The cavitating bubbles in the shear layer are deformed to elongated ellipsoid shapes by shear forces. The significant pressure fluctuations are induced by the collapse of the biggest bubble in the group. The first mode illustrates the mean characteristics of the flow field. The flow in the peripheral region of the shear layer is mainly dominated by large-scale coherent structures revealed by the second and third modes, while different small-scale coherent structures are contained in the central region. The cavitating bubbles are associated with small size coherent structures as the sixth or higher modes.

Practical implications

This work demonstrates the feasibility of LES for high Reynolds number shear layer flow. The dynamic mode decomposition method is a novel method to extract coherent structures and obtain their dynamic information that will help us to optimize and control the flow.

Originality/value

(1) This paper first displays the three-dimensional coherent structures and their characteristics in the shear layer of confined jet flow. (2) The relationship of bubbles shape and pressure fluctuations is illustrated. (3) The visualization of coherent structures benefits the understanding of the mixing process and cavitation inception in jet shear layers.

Article
Publication date: 8 May 2018

Stephie Edwige, Yoann Eulalie, Philippe Gilotte and Iraj Mortazavi

The purpose of this paper is to present numerical investigations of the flow dynamic characteristics of a 47° Ahmed Body to identify wake flow control strategy leading to drag…

Abstract

Purpose

The purpose of this paper is to present numerical investigations of the flow dynamic characteristics of a 47° Ahmed Body to identify wake flow control strategy leading to drag coefficient reduction, which could be tested later on sport utility vehicles.

Design/methodology/approach

This study begins with a mean flow topology description owing to dynamic and spectral analysis of the aerodynamic tensor. Then, the sparse promoting dynamic modal decomposition method is discussed and compared to other modal approaches. This method is then applied on the wall and wake pressure to determine frequencies of the highest energy pressure modes and their transfers to other frequency modes. This analysis is then used to design appropriated feedback flow control strategies.

Findings

This dynamic modal decomposition highlights a reduced number of modes at low frequency which drive the flow dynamics. The authors especially notice that the pressure mode at a Strouhal number of 0.22, based on the width between feet, induces aerodynamic losses close to the rear end. Strategy of the proposed control loop enables to dampen the energy of this mode, but it has been transferred to lower frequency mode outside of the selected region of interest.

Originality/value

This analysis and methodology of feedback control shows potential drag reduction with appropriated modal energy transfer management.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Open Access
Article
Publication date: 12 October 2022

Chenhao Wei, Gang Lin, Jun Huang, Lei Song and Howard Smith

Unlike conventional aircraft, birds can glide without a vertical tail. The purpose of this paper is to analyse the influence of dihedral angle spanwise distribution on…

Abstract

Purpose

Unlike conventional aircraft, birds can glide without a vertical tail. The purpose of this paper is to analyse the influence of dihedral angle spanwise distribution on lateral-directional dynamic stability by the simulation, calculation in the development of the bird-inspired aircraft and the flight testing.

Design/methodology/approach

The gliding magnificent frigatebird (Fregata magnificens) was selected as the study object. The geometric and mass model of the study object were developed. Stability derivatives and moments of inertia were obtained. The lateral-directional stability was assessed under different spanwise distributions of dihedral angle. A bird-inspired aircraft was developed, and a flight test was carried out to verify the analysed results.

Findings

The results show that spanwise distribution changing of dihedral angle has influence on the lateral-directional mode stability. All of the analysed configurations have convergent Dutch roll mode and rolling mode. The key role of dihedral angle changing is to achieve a convergent spiral mode. Flight test results show that the bird-inspired aircraft has a well-convergent Dutch roll mode.

Practical implications

The theory that birds can achieve its lateral-directional stability by changing its dihedral angle spanwise distribution may explain the stability mechanism of gliding birds.

Originality/value

This paper helps to improve the understanding of bird gliding stability mechanism and provides bio-inspired solutions in aircraft designing.

Details

Aircraft Engineering and Aerospace Technology, vol. 94 no. 11
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 8 May 2007

Yi Zhang, Zigang Zhang and Zhixue Liu

This paper seeks to challenge the traditional wisdom that sheds light upon sequential entry modes in developed countries by exploring the dynamic entry mode choice in sequential…

11453

Abstract

Purpose

This paper seeks to challenge the traditional wisdom that sheds light upon sequential entry modes in developed countries by exploring the dynamic entry mode choice in sequential foreign direct investment (FDI) in emerging economies.

Design/methodology/approach

A review of the literature on the entry mode choice is undertaken. Based on analysing two related theories consisting of the knowledge‐based theory of the firm and organizational learning theory, entry mode choices in sequential FDI in emerging economies are investigated using both an internationalisation process model and the capability‐developing perspective, and exclusive propositions are put forward accordingly. Then, these propositions are tested on the context of China with the methodology of paired‐samples t‐tests.

Findings

Based on macro‐level longitudinal data in China from 1979 to 2005, the choice of entry mode in sequential FDI in emerging economies is inconsistent with the capability‐developing theory of the firm, but is consistent with the international process model.

Practical implications

This study provides four practical implications. First, managers intending to invest abroad need to consider the cost and return of a specific entry mode. Second, knowledge about host markets has a more important effect on entry mode choice in emerging markets than MNCs' internal organizational capabilities. Third, MNCs adopt sequential investment in emerging economies, in which they adopt joint ventures in earlier entries and then shift to green‐field investment in later entries. Fourth, experiential learning, which consists of learning about host markets and local partners' skills, is emphasized in sequentially entering emerging markets.

Originality/value

This paper expands the research scope of previous studies that either explore a static choice of entry mode in foreign markets or only examine the entry mode choice in sequential FDI in developed countries. Taking into consideration the dynamic choice of entry modes, the paper studies sequential FDI in emerging economies, which throws light upon theoretical analysis of sequential FDI in China, and which has practical implications for foreign firms that are interested in China and planning to enter China's markets.

Details

Management Decision, vol. 45 no. 4
Type: Research Article
ISSN: 0025-1747

Keywords

Article
Publication date: 3 October 2016

Yanhong Yao and Huiping Zhou

The purpose of this paper is to build a symbiotic evolution model to analyze the symbiotic modes and dynamic equilibrium of mobile internet platform innovation ecosystem (MIPIE…

Abstract

Purpose

The purpose of this paper is to build a symbiotic evolution model to analyze the symbiotic modes and dynamic equilibrium of mobile internet platform innovation ecosystem (MIPIE) in order to explore its evolutionary path.

Design/methodology/approach

From a symbiosis theory perspective, the authors studied the dynamic evolution stages and symbiotic mode of MIPIE. By adopting logistic model, the symbiotic evolution model of MIPIE is established. After calculating the steady conditions and equilibrium point of this model, numerical simulation was done with MATLAB software to illustrate the impact of symbiotic parameters on evolution path in this ecosystem.

Findings

The symbiotic evolution mode of MIPIE experienced parasitism, commensalism to asymmetric mutualism, and symmetry mutualism or independence. In given conditions, the dynamic evolution of MIPIE eventually tends to a steady equilibrium point. The evolutionary consequence of innovative subjects is not only determined by the natural growth rate, but symbiotic modes can also affect the evolutionary path. Different symbiotic modes result in different evolutionary paths.

Practical implications

Improved understanding of symbiosis in MIPIE could help policy makers to promote value co-creation and dynamic interests balance while facilitating the cooperation of others for successful platform ecosystem management.

Originality/value

The logistic model introduced here bridge theory and practice while establishing a stronger link between symbiosis theory and platform ecosystem management.

Details

Kybernetes, vol. 45 no. 9
Type: Research Article
ISSN: 0368-492X

Keywords

Article
Publication date: 1 December 2001

Nasr Eddine Debbache

Increases in air traffic and air traffic controller workload lead to a need to provide assistance to the air traffic controller. Proposes and validates a new organization of air…

Abstract

Increases in air traffic and air traffic controller workload lead to a need to provide assistance to the air traffic controller. Proposes and validates a new organization of air traffic control, which allows air traffic controllers to remain active in the control and supervisory loop of the process, in order to maintain the present traffic safety level and to improve the global system performances. Consists of decomposing the problem according to the two levels of the air traffic control organization. Directs the first step towards a horizontal cooperation that consists of a dynamic allocation of the tactical level control tasks between human air traffic controllers and an assistance tool. Presents the dynamic task allocation principles, and describes the experimental platform for task allocation in air traffic control. Describes the experimental protocol used for the experiments with qualified controllers and presents the first results. They show the real help a dynamic task allocation provides to the air traffic controllers.

Details

Aircraft Engineering and Aerospace Technology, vol. 73 no. 6
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 13 February 2020

Liping Ying, Yijiang Peng and Mahmoud M.A. Kamel

Based on the random aggregate model of recycled aggregate concrete (RAC), this paper aims to focus on the effect of loading rate on the failure pattern and the macroscopic…

Abstract

Purpose

Based on the random aggregate model of recycled aggregate concrete (RAC), this paper aims to focus on the effect of loading rate on the failure pattern and the macroscopic mechanical properties.

Design/methodology/approach

RAC is regarded as a five-phase inhomogeneous composite material at the mesoscopic level. The number and position of the aggregates are modeled by the Walraven formula and Monte–Carlo stochastic method, respectively. The RAC specimen is divided by the finite-element mesh to establish the dynamic base force element model. In this model, the element mechanical parameters of each material phase satisfy Weibull distribution. To simulate and analyze the dynamic mechanical behavior of RAC under axial tension, flexural tension and shear tension, the dynamic tensile modes of the double-notched specimens, the simply supported beam and the L specimens are modeled, respectively. In addition, the different concrete samples are numerically investigated under different loading rates.

Findings

The failure strength and failure pattern of RAC have strong rate-dependent characteristics because of the inhomogeneity and the inertial effect of the material.

Originality/value

The dynamic base force element method has been successfully applied to the study of recycled concrete.

Details

Engineering Computations, vol. 37 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 12 February 2019

S. Abolfazl Mokhtari and Mehdi Sabzehparvar

The paper aims to present an innovative method for identification of flight modes in the spin maneuver, which is highly nonlinear and coupled dynamic.

Abstract

Purpose

The paper aims to present an innovative method for identification of flight modes in the spin maneuver, which is highly nonlinear and coupled dynamic.

Design/methodology/approach

To fix the mode mixing problem which is mostly happen in the EMD algorithm, the authors focused on the proposal of an optimized ensemble empirical mode decomposition (OEEMD) algorithm for processing of the flight complex signals that originate from FDR. There are two improvements with the OEEMD respect to the EEMD. First, this algorithm is able to make a precise reconstruction of the original signal. The second improvement is that the OEEMD performs the task of signal decomposition with fewer iterations and so with less complexity order rather than the competitor approaches.

Findings

By applying the OEEMD algorithm to the spin flight parameter signals, flight modes extracted, then with using systematic technique, flight modes characteristics are obtained. The results indicate that there are some non-standard modes in the nonlinear region due to couplings between the longitudinal and lateral motions.

Practical implications

Application of the proposed method to the spin flight test data may result accurate identification of nonlinear dynamics with high coupling in this regime.

Originality/value

First, to fix the mode mixing problem in EMD, an optimized ensemble empirical mode decomposition algorithm is introduced, which disturbed the original signal with a sort of white Gaussian noise, and by using white noise statistical characteristics the OEEMD fix the mode mixing problem with high precision and fewer calculations. Second, by applying the OEEMD to the flight output signals and with using the systematic method, flight mode characteristics which is very important in the simulation and controller designing are obtained.

Details

Aircraft Engineering and Aerospace Technology, vol. 91 no. 4
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 12 July 2022

Guoqiang Zhu, He Li, Huan Zhang, Sen Wang and Xiuyu Zhang

The purpose of this study is to propose an adaptive fault-tolerant control approach based on output feedback for a class of quadrotor unmanned aerial vehicles system. In the event…

Abstract

Purpose

The purpose of this study is to propose an adaptive fault-tolerant control approach based on output feedback for a class of quadrotor unmanned aerial vehicles system. In the event of a controlled actuator failure, a stable flying of the aircraft can be achieved by selecting an appropriate sliding mode surface.

Design/methodology/approach

Aiming at the actuator failure of quadrotor aircraft during flight in the controllable range, a dynamic surface sliding mode passive fault-tolerant controller based on output feedback is designed based on the strong robustness of sliding mode method. Due to the unknown nonlinearity dynamics and parameter uncertainties in the system, a nonlinear observer is used to estimate them online.

Findings

The stability of the suggested algorithm is established using appropriate Lyapunov functions, and the performance of the proposed control approach is demonstrated using hardware-in-the-loop simulation.

Originality/value

An error performance function is introduced into the controller to ensure the convergence speed and accuracy of errors are within the predetermined range. By using the norm estimation method, there is only one parameter that needs to be updated in each step of the control process, which considerably minimizes the calculation burden. Finally, the validity of the proposed control scheme is verified on the hardware-in-the-loop simulation, and the results show that the proposed control method has achieved the desired results.

Details

Assembly Automation, vol. 42 no. 4
Type: Research Article
ISSN: 0144-5154

Keywords

1 – 10 of over 38000