Search results

1 – 5 of 5
Article
Publication date: 15 May 2009

Junye Wang and Geoffrey H. Priestman

The purpose of this paper is to simulate the behaviour of the symmetrical turn‐up vortex amplifier (STuVA) to obtain insight into its maximum through‐flow operation within…

Abstract

Purpose

The purpose of this paper is to simulate the behaviour of the symmetrical turn‐up vortex amplifier (STuVA) to obtain insight into its maximum through‐flow operation within the eight‐port STuVA, and understand the relation between its design parameters and flow characteristics. Furthermore, it is to test the performance of different turbulent models and near‐wall models using the same grid, the same numerical methods and the same computational fluid dynamics code under multiple impingement conditions.

Design/methodology/approach

Three turbulence models, the standard k‐ε, the renormalization group (RNG) k‐ε model and the Reynolds stress model (RSM), and three near‐wall models have been used to simulate the confined incompressible turbulent flow in an eight‐port STuVA using unstructured meshes. The STuVA is a special symmetrical design of turn‐up vortex amplifier, and the simulation focused on its extreme operation in the maximum flow state with no swirling. The predictions were compared with basic pressure‐drop flow rate measurements made using air at ambient conditions. The effect of different combinations of turbulence and near‐wall models was evaluated.

Findings

The RSM gave predictions slightly closer to the experimental data than the other models, although the RNG k‐ε model predicted nearly as accurately as the RSM. They both improved errors by about 3 per cent compared to the standard k‐ε model but took a long time for convergence. The modelling of complex flows depends not only on the turbulence model but also on the near‐wall treatments and computational economy. In this study a good combination was the RSM, the two layer wall model and the higher order discretization scheme, which improved accuracy by more than 10 per cent compared to the standard k‐ε model, the standard wall function and first order upwind.

Research limitation/implications

The results of this paper are valid for the global pressure drop flow rate. It should be desirable to compare some local information with the experiment.

Originality/value

This paper provides insight into the maximum through‐flow operation within the eight‐port STuVA to understand the relation between its design parameters and flow characteristics and study the performance of turbulence and near wall models.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 19 no. 3/4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 27 June 2008

Junye Wang, Xiaoxian Zhang, Anthony G. Bengough and John W. Crawford

The cell‐based method of domain decomposition was first introduced for complex 3D geometries. To further assess the method, the aim is to carry out flow simulation in…

Abstract

Purpose

The cell‐based method of domain decomposition was first introduced for complex 3D geometries. To further assess the method, the aim is to carry out flow simulation in rectangular ducts to compare the known analytical solutions.

Design/methodology/approach

The method is not based on equal subvolumes but on equal numbers of active cells. The variables of the simulation are stored in ordered 1D arrays to replace the conventional 3D arrays, and the domain decomposition of the complex 3D problems therefore becomes 1D. Finally, the 3D results can be recovered using a coordinate matrix. Through the flow simulation in the rectangular ducts how the algorithm of the domain decompositions works was illustrated clearly, and the numerical solution was compared with the exact solutions.

Findings

The cell‐based method can find the subdomain interfaces successfully. The parallelization based on the algorithm does not cause additional errors. The numerical results agree well with the exact solutions. Furthermore, the results of the parallelization show again that domains of 3D geometries can be decomposed automatically without inducing load imbalances.

Practical implications

Although, the approach is illustrated with lattice Boltzmann method, it is also applicable to other numerical methods in fluid dynamics and molecular dynamics.

Originality/value

Unlike the existing methods, the cell‐based method performs the load balance first based on the total number of fluid cells and then decomposes the domain into a number of groups (or subdomains). Thus, the task of the cell‐based method is to recover the interface rather than to balance the load as in the traditional methods. This work has examined the celled‐based method for the flow in rectangular ducts. The benchmark test confirms that the cell‐based domain decomposition is reliable and convenient in comparison with the well‐known exact solutions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 18 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 December 2006

Junye Wang, Geoffrey H. Priestman and John R. Tippetts

Seeks to examine the performance of conventional turbulence models modelling strongly swirling flows within a Symmetrical Turn up Vortex Amplifier, with adjustment of the…

Abstract

Purpose

Seeks to examine the performance of conventional turbulence models modelling strongly swirling flows within a Symmetrical Turn up Vortex Amplifier, with adjustment of the turbulence model constants to improve agreement with experimental data.

Design/methodology/approach

First, the standard kε model and the Reynolds Stress Model (RSM) were used with standard values of model constants, using both the first order upwind and the quadratic upstream interpolation for convective kinetics (QUICK) schemes. Then, the swirling effect was corrected by adjusting the model coefficients.

Findings

The standard RSM with the QUICK did produce better predictions but still significantly overestimated the experimental data. Much improved simulation was obtained with the systematic adjustment of the model constants in the standard kε model using the QUICK. The physical significance of the model constants accounted for changes of the eddy viscosity, and the production and destruction of k and ε.

Research limitations/implications

More industrial cases could benefit from this simple and useful approach.

Originality/value

The constant adjustment is regular and directed, based on the eddy viscosity and the production and destruction of k and ε. The regularity of the effect of the model constants on the solutions makes it easier to quickly adjust them for other industrial applications.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 16 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 11 April 2022

Bakhtiyar Khudayarov and Fozilzhon Turaev

The purpose of this study is to create a mathematical model, a numerical algorithm and a computer program for studying the vibration of composite pipelines based on the…

Abstract

Purpose

The purpose of this study is to create a mathematical model, a numerical algorithm and a computer program for studying the vibration of composite pipelines based on the theory of beams used in the oil and gas industry, agriculture and water management, housing and communal services and other areas.

Design/methodology/approach

A mathematical model of vibration of a viscoelastic pipeline based on the theory of beams with a pulsating fluid flowing through it was developed. Using the Bubnov-Galerkin method, based on the polynomial approximation of deflections, the problem is reduced to the study of systems of ordinary integro-differential equations, the solution of which is found by a numerical method. A computational algorithm was developed for solving problems of vibrations of composite pipelines conveying pulsating liquid.

Findings

The stability and amplitude-time characteristics of vibration of composite pipelines with a pulsating fluid flowing in it are studied for wide range of changes in the parameters of deformable systems and fluid flow. The critical velocities of fluid flow at which the viscoelastic pipe loses its rectilinear equilibrium shape are found. The effect of singularity in the kernels of heredity on the vibrations of structures with viscoelastic properties was numerically studied. It is shown that with an increase in the viscosity parameter of the pipeline material, the critical flow velocity decreases. It was determined that an increase in the value of the fluid pulsation frequency and the excitation coefficient leads to a decrease in the critical velocity of the fluid flow. It was established that an increase in the parameters of the Winkler foundation and the rigidity parameter of the continuous layer leads to an increase in the critical flow velocity.

Originality/value

The study of the vibration of pipelines made of composite materials is of great theoretical and applied interest. The solution to this problem is an effective application of the theory of viscoelasticity to real processes. Therefore, the methods and problems of pipeline vibrations attract much attention from researchers. This study is devoted to solving the above problems and therefore its subject is relevant. The paper considers the results of numerical simulation of the processes of vibration of a composite pipeline based on the theory of shells during the flow of a pulsating liquid through it. A mathematical model of vibration of a composite pipeline was developed. A computational algorithm was developed for solving problems of vibrations of composite pipelines conveying pulsating liquid.

Details

Multidiscipline Modeling in Materials and Structures, vol. 18 no. 2
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 2 February 2018

Jiangwei Liu

The rail transport sector in China represents one of the largest consumers of energy today, and the primary purpose of this paper is to examine the causes of changes in…

Abstract

Purpose

The rail transport sector in China represents one of the largest consumers of energy today, and the primary purpose of this paper is to examine the causes of changes in energy consumption of Chinese national rail transport (ECCNRT).

Design/methodology/approach

For this study, reasonable indicators as factors that affected conversion volume (CV) and unit energy consumption (UEC) based on statistical data from 1990 to 2010 were selected. CV and UEC models were established by regression analysis and tested using real data of 2011-2014. The CV model indicates it has an exponential relationship with GDP. Besides, there is a quantitative relationship between UEC and the quantity of locomotives. The ECCNRT calculation model was proposed and ECCNRT model data were compared with the real data. Impacts of different factors on ECCNRT were analyzed with economic principles.

Findings

The analysis conducted shows that the calculation model can reflect variation of ECCNRT precisely, and ECCNRT has a quantitative relation with GDP and quantities of locomotives. GDP accounts for changes of ECCNRT 20.02 per cent, while those for quantity of diesel locomotives and electric locomotives are 26.87 and 53.11 per cent, respectively. The number of electric locomotives is the main factor that influences variation of ECCNRT.

Originality/value

Through regression analysis, this study discovered the inner quantitative relationship between the conversion volume (important index of Chinese national rail transport production) and GDP. In addition, this study establishes the ECCNRT model according to the Chinese national rail transport data, which can be used to calculate the amount of ECCNRT and conduct quantitative analysis for different impacts of various factors on ECCNRT’s changes.

Details

International Journal of Energy Sector Management, vol. 12 no. 1
Type: Research Article
ISSN: 1750-6220

Keywords

1 – 5 of 5