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Article
Publication date: 1 February 2000

A.N. Pavlov, S.S. Sazhin, R.P. Fedorenko and M.R. Heikal

Detailed results of numerical calculations of transient, 2D incompressible flow around and in the wake of a square prism at Re = 100, 200 and 500 are presented. An…

Abstract

Detailed results of numerical calculations of transient, 2D incompressible flow around and in the wake of a square prism at Re = 100, 200 and 500 are presented. An implicit finite‐difference operator‐splitting method, a version of the known SIMPLEC‐like method on a staggered grid, is described. Appropriate theoretical results are presented. The method has second‐order accuracy in space, conserving mass, momentum and kinetic energy. A new modification of the multigrid method is employed to solve the elliptic pressure problem. Calculations are performed on a sequence of spatial grids with up to 401 × 321 grid points, at sequentially halved time steps to ensure grid‐independent results. Three types of flow are shown to exist at Re = 500: a steady‐state unstable flow and two which are transient, fully periodic and asymmetric about the centre line but mirror symmetric to each other. Discrete frequency spectra of drag and lift coefficients are presented.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 10 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 11 July 2018

Xin Liu, Yuming Xing and Liang Zhao

The purpose of this study is to investigate structure parameters that influence the mixing process of droplets-gas in underwater depth-adjustable launcher cooling chamber…

Abstract

Purpose

The purpose of this study is to investigate structure parameters that influence the mixing process of droplets-gas in underwater depth-adjustable launcher cooling chamber and help engineers who design the launcher to distinguish the most important factor that impacts mixing performance in the cooling chamber.

Design/methodology/approach

Euler–Lagrangian droplet tracking method was used to simulate droplets-gas mixing process in the cooling chamber. The SST k-w model was adopted to simulate turbulence. Droplet breakup was described by KHRT hybrid model using modified contains which are more fit to the supersonic main flow condition.

Findings

The results show the counter-rotating vortex pairs which caused by injected liquid accelerate the mixing process. High-pressure supersonic freestream makes the liquid jet break into more small droplets due to the high momentum of the main stream. Axial injection angle has the greatest influence on Sauter mean diameter (SMD). Penetration height, SMD and total pressure loss slightly change in different tangential injection conditions. However, mixedness decreases with reduction of tangential injection angle due to a more limited space for spray developing. Enlarging orifice diameter raises penetration and mixedness greatly, while SMD and total pressure loss increase slightly.

Originality/value

The findings of this study confirm the key structure parameter to improve mixing performance in the cooling chamber. Engineers who design the underwater depth-adjustable launcher can refer the findings in this study to make control of launching power more accurate.

Details

Engineering Computations, vol. 35 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 March 2003

Massimo Fabbri, Francesco Galante, Francesco Negrini, Eiichi Takeuchi and Takehiko Toh

Electro‐magnetic stirrers, applied to the mold of a continuous caster, induces electromagnetic forces that influence the steel flow pattern modifying the casting…

Abstract

Electro‐magnetic stirrers, applied to the mold of a continuous caster, induces electromagnetic forces that influence the steel flow pattern modifying the casting parameters. The steel quality has been highly improved by the application of this magneto‐hydro‐dynamic (MHD) technique. Anyway, the complexity of the MHD interaction made difficult the complete comprehension of the factors that contribute to eliminate the defects due to the inclusions in the cast products. The optimization of the MHD techniques is still the object of a large research effort, which utilizes both experimental activity and numerical simulation. In this paper, the numerical simulation of the 2D flow pattern of the molten steel in a mold for billets has been done. The attention is focused on the gradient of the velocity of the molten steel near the wall and on the effects that the gradient change determines on the inclusions, which are present in the metallic pool. Actually the increase of the velocity gradient corresponds to the increase of the forces that can clean the solidifying shell from the inclusions.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 22 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 5 May 2015

Sajjad Miran and Chang Hyun Sohn

– The purpose of this paper is to numerically investigate the influence of corner radius on flow past a square cylinder at a Reynolds number 500.

Abstract

Purpose

The purpose of this paper is to numerically investigate the influence of corner radius on flow past a square cylinder at a Reynolds number 500.

Design/methodology/approach

Six models were studied, for R/D=0 (square cylinder), 0.1, 0.2, 0.3, 0.4, and 0.5 (circular cylinder), where R is the corner radius and D is the characteristic dimension of the body. The transient two-dimensional (2D) laminar and large eddy simulations (LES) models were employed using finite volume code. The Strouhal number, mean drag coefficient (CD), and root mean square (RMS) value of lift coefficient (CL,RMS), for different R/D values, were computed and compared with experimental and other numerical results.

Findings

The computational results showed good agreement with previously published results for a Reynolds number, Re=500. It was found that the corner effect on a square cylinder greatly influences the flow characteristics around the cylinder. Results indicate that, as the corner radius ratio, R/D, increases, the Strouhal number increases rapidly for R/D=0-0.2, and then gradually rises between R/D=0.2 and 0.5. The minimum values of the mean drag coefficient and the RMS value of lift coefficient were found around R/D=0.2, which is verified by the time averaged streamwise velocity deficit profile.

Originality/value

On the basis of the numerical results, it is concluded that rounded corners on a square cylinder are useful in reducing the drag and lift forces generated behind a cylinder. Finally, it is suggested that with a rounded corner ratio of around R/D=0.2, the drag and oscillation of the cylinder can be greatly reduced, as compared to circular and square cylinders.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 25 no. 4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 4 January 2016

Sajjad Miran and Chang Hyun Sohn

– The purpose of this paper is to focus on the variation of wake structures and aerodynamic forces with changes in the cylinder corner radius and orientation.

Abstract

Purpose

The purpose of this paper is to focus on the variation of wake structures and aerodynamic forces with changes in the cylinder corner radius and orientation.

Design/methodology/approach

Numerical simulations were performed for flow past a square cylinder with different corner radii placed at an angle to the incoming flow. In the present study, the rounded corner ratio R/D=0 (square cylinder), 0.1, 0.2, 0.3, and 0.4 (where R is the corner radius and D is the characteristic dimension of the body) and the angle of incidence α in the range of 0°-45° were considered.

Findings

The numerical model was validated by comparing the present results with results in the available literature, and they were found to be in good agreement. The critical incidence angle for the rounded corner cylinder – corresponding to the minimum mean drag coefficient (C D ), the minimum root mean square value of the lift coefficient C L,RMS), and the maximum Strouhal number – shifted to a lower incidence angle compared with the sharp corner square cylinder. The minimum drag and lift coefficient at R/D=0 were observed for the critical incidence angle αcri=12°, whereas for R/D=0.1-0.4, the minimum drag and lift coefficient were found to be within the range of 5°-10° for α.

Originality/value

The presented results shows the importance of the incidence angle and rounded corners of the square cylinder for reduction of aerodynamic forces. The two parameters support the shear layer flow reattachment on the lateral surface of the cylinder, have a strong correlation with the reduction of the wake width, and hence reduced the values of C D and C L .

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 30 July 2019

Ivan Poliakov and Maria Smirnova

This paper aims to characterize community archives in the common array of the manuscript collection of the National Library of Russia (NLR). The purpose of the paper is to…

Abstract

Purpose

This paper aims to characterize community archives in the common array of the manuscript collection of the National Library of Russia (NLR). The purpose of the paper is to identify the features of organization of the archival system of Russia and the place of community archives in it. The authors intend to characterize the features of origin, history of existence and preservation of archives of public organizations in Russia on the example of the archives of Russian societies of the nineteenth and twentieth centuries; to spread knowledge about historical communities of Russia and their archival heritage and to discuss the value of community archives and their information potential.

Design/methodology/approach

The research is based on the traditional methodology of the academic archival studies. At the same time interdisciplinary approach plays a great role in the field of study of community archives. The findings of the study were obtained as a result of the application of methods of historical research and special historical disciplines: archival heuristics, archive studies, source studies and archeography. The data were complemented by documentary analysis, including materials of nine archives, documents concerning acquisition and storage of these archives.

Findings

As a result of the study of different community archives in the Manuscript Department of the NLR the authors came to the conclusion about poor preservation and diffusion of these archives. It suggests the necessity of developing methods of virtual archive reconstruction.

Originality/value

This is the first study to date on the community archives in Russia. The first attempt to attribute and classify community archives of the NLR.

Details

Global Knowledge, Memory and Communication, vol. 68 no. 8/9
Type: Research Article
ISSN: 2514-9342

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Article
Publication date: 19 March 2021

Chengxi Zhang, Jin Wu, Yulong Huang, Yu Jiang, Ming-zhe Dai and Mingjiang Wang

Recent spacecraft attitude control systems tend to use wireless communication for cost-saving and distributed mission purposes while encountering limited communication…

Abstract

Purpose

Recent spacecraft attitude control systems tend to use wireless communication for cost-saving and distributed mission purposes while encountering limited communication resources and data exposure issues. This paper aims to study the attitude control problem with low communication frequency under the sampled-data.

Design/methodology/approach

The authors propose constructive control system structures based on quantization and event-triggered methods for intra-spacecraft and multi-spacecraft systems, and they also provide potential solutions to shield the control system's data security. The proposed control architectures can effectively save communication resources for both intra-spacecraft and multi-spacecraft systems.

Findings

The proposed control architectures no longer require sensors with trigger-ing mechanism and can achieve distributed control schemes. This paper also provides proposals of employing the public key encryption to secure the data in control-loop, which is transmitted by the event-triggered control mechanism.

Practical implications

Spacecraft attempts to use wireless communication, yet the attitude control system does not follow up promptly to accommodate these variations. Compared with existing approaches, the proposed control structures can save communication resources of control-loop in multi-sections effectively, and systematically, by rationally configuring the location of quantization and event-triggered mechanisms.

Originality/value

This paper presents several new control schemes and a necessary condition for the employment of encryption algorithms for control systems based on event-based communication.

Details

Aircraft Engineering and Aerospace Technology, vol. 93 no. 2
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 10 September 2018

Lisa Kawatsu, Kazuhiro Uchimura, Makoto Kobayashi and Nobukatsu Ishikawa

Although globally, prisoners are considered one of the vulnerable groups to tuberculosis (TB), little is known about the situation of TB in prison setting in Japan. The…

Abstract

Purpose

Although globally, prisoners are considered one of the vulnerable groups to tuberculosis (TB), little is known about the situation of TB in prison setting in Japan. The purpose of this paper is to examine the characteristics of TB among prisoners in Japan.

Design/methodology/approach

Records of TB patients from one medical prison were analyzed in terms of general demographic characteristics, clinical manifestations, risk factors and delay in diagnosis and in initiating treatment, and compared with data from the national TB surveillance and other published data on health of inmates, where appropriate. Continuous variables were compared using student independent samples t-test. Proportions were compared using χ2 or Fisher exact test as appropriate. Kaplan–Meier survival analysis was conducted to determine the time from entry to prison institution to diagnosis of TB.

Findings

A total of 49 patients were analyzed. The mean age was 49.5 (±14.3) and 69.4 percent were males. Being unemployed and homeless prior to incarceration, and several co-morbidities were potential risk factors for TB (p<0.01). Analysis of diagnosis and treatment delay showed that 16.1 percent of smear positive patients took more than a week to be placed on treatment after being diagnosed of TB. Approximately 50 percent of the patients were diagnosed within four months of entering the prison institution.

Practical implications

Several potential risk factors identified suggest the need to strengthen screening for specific sub-groups within the prison population, such as those with poor socio-economic status and co-morbidities, as well as to consider the possible role of systematic screening for latent TB infection.

Originality/value

This study presents some important data to help understand the profile of TB patients in prisons in Japan, as well as showing that a detailed epidemiological analysis of existing records can provide useful insight.

Details

International Journal of Prisoner Health, vol. 14 no. 3
Type: Research Article
ISSN: 1744-9200

Keywords

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