Michele Ciofalo and Fabrizio Cricchio
The buoyancy‐driven magnetohydrodynamic flow in a cubic enclosure was investigated by three‐dimensional numerical simulation. The enclosure was volumetrically heated by a uniform…
Abstract
The buoyancy‐driven magnetohydrodynamic flow in a cubic enclosure was investigated by three‐dimensional numerical simulation. The enclosure was volumetrically heated by a uniform power density and cooled along two opposite vertical walls, all remaining walls being adiabatic. A uniform magnetic field was applied orthogonally to the gravity vector and to the temperature gradient. The Prandtl number was 0.0321 (characteristic of Pb–17Li at 300°C), the Rayleigh number was 104, and the Hartmann number was made to vary between 0 and 2×103. The steady‐state Navier–Stokes equations, in conjunction with a scalar transport equation for the fluid's enthalpy and with the Poisson equation for the electrical potential, were solved by a finite volume method using a purposely modified CFD code and a computational grid with 643 nodes in the fluid. Emphasis was laid on the effects of increasing the Hartmann number on the complex three‐dimensional flow and current pattern.
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Zehra Ertosun Karabulut, Zafer Kurt, Elifnur Kalemci, Tayfun Dede and Sabriye Banu Ikizler
This study aims to optimize the design of reinforced concrete retaining walls to achieve the lowest possible cost while maintaining structural stability and compliance with…
Abstract
Purpose
This study aims to optimize the design of reinforced concrete retaining walls to achieve the lowest possible cost while maintaining structural stability and compliance with standards.
Design/methodology/approach
The Rao1 algorithm was employed to optimize the design, considering seven independent variables related to geometry and four variables related to the reinforcement ratio. Geotechnical and structural analyses were performed using the Coulomb theory for static loads and the Mononobe–Okabe theory for dynamic loads. Cost calculations included concrete volume and reinforcement quantities across varying horizontal and vertical acceleration coefficients in four scenarios.
Findings
The optimization process revealed that the Rao1 algorithm consistently identified design variables near the lower regulatory limits, achieving the same cost across all scenarios. The results demonstrate that the Rao1 algorithm is an effective tool for optimizing the design of self-supporting reinforced concrete retaining walls, ensuring both cost efficiency and compliance with structural requirements.
Originality/value
In this study, the aim was to achieve an optimal, cost-effective design for retaining walls composed of a two-stage stem structure. Unlike conventional designs that utilize single-tier retaining walls, this study emphasizes the use of a two-stage stem configuration. It was noted that the Rao1 algorithm has not been previously applied to two-stage stem retaining walls in the literature. By applying the Rao1 algorithm, it was observed that a design meeting both minimum cost and required criteria was successfully achieved. Therefore, it was concluded that the Rao1 algorithm could be a valuable tool for retaining wall design. This study differs from other works in the literature both in terms of the two-stage stem-retaining wall design and the algorithm used.
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Tomasz Janusz Teleszewski and Slawomir Adam Sorko
The purpose of this paper is to investigate the effect of the viscous dissipation of laminar flow through a straight regular polygonal duct on forced convection with constant…
Abstract
Purpose
The purpose of this paper is to investigate the effect of the viscous dissipation of laminar flow through a straight regular polygonal duct on forced convection with constant axial wall heat flux with constant peripheral wall temperature using the boundary element method (BEM).
Design/methodology/approach
Both the wall heating case and the wall cooling case are considered. Applying the velocity profile obtained for the duct laminar flow and the energy equation with the viscous dissipation term is solved exactly for the constant wall heat flux using the BEM. The numerical values are obtained by means of a computer program, written by the authors in Fortran. The results of the BEM approach are verified by analytic models. Nusselt numbers are obtained for flows with a different number of sides of a regular polygonal duct and Brinkman numbers.
Findings
When the difference in temperature between the wall temperature and the fluid bulk temperature changes the sign, then the functions of the Nusselt number with the Brinkman number generated some singularities (BrqLs). For the Brinkman number referring to the total wall linear power, with the increasing value of the number of sides of a regular polygonal duct, BrqLs decreases in the range of 3 ≤ n < ∞. If the BrqL < BrqLs, it is possible to note that, in general, the Nusselt number is higher for cross-sections having a lower value of the number of sides of a regular polygonal duct. For BrqL > BrqLs, this rule is reversed.
Originality/value
This paper illustrates the effects of viscous dissipation on laminar forced convective flow in regular polygon ducts with a different number n of sides. A compact relationship for the Nusselt number vs the Brinkman number referring to the temperature difference between the wall temperature and the fluid bulk temperature and the Brinkman number, which is based on the total wall linear power, have been proposed.
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Esmail M.A. Mokheimer and Maged El‐Shaarawi
Obtaining the maximum possible flow rates that can be induced by free convection in open‐ended vertical eccentric annuli under fundamental thermal boundary conditions of the…
Abstract
Purpose
Obtaining the maximum possible flow rates that can be induced by free convection in open‐ended vertical eccentric annuli under fundamental thermal boundary conditions of the fourth kind (heating or cooling one of the annulus walls with a uniform heat flux while keeping the other wall at ambient temperature). Obtaining the maximum possible flow rates that can be induced by free convection in open‐ended vertical eccentric annuli under fundamental thermal boundary conditions of the fourth kind (heating or cooling one of the annulus walls with a uniform heat flux while keeping the other wall at ambient temperature).
Design/methodology/approach
The fully‐developed laminar free convection momentum equation has been solved numerically using an analytical solution of the governing energy equation.
Findings
Results are presented to show the effect of the annulus radius ratio and the dimensionless eccentricity on the induced flow rate, the total heat absorbed by the fluid, and the fully developed Nusselt numbers on the two boundaries of the annulus for a fluid of Prandtl number 0.7.
Practical implications
Applications of the obtained results can be of value in the heat‐exchanger industry, in cooling of underground electric cables, and in cooling small vertical electric motors and generators.
Originality/value
The paper presents a solution that is not available in the literature for the problem of fully developed free convection in open‐ended vertical eccentric annular channels under thermal boundary conditions of the fourth kind. Also presents the maximum possible induced flow rates, the total heat absorbed by the fluid, and the Nusselt numbers on the two boundaries of the annulus. The effects of N and E (the radius ratio and eccentricity, respectively) on these results are presented. Such results are very much needed for design purposes of heat transfer equipment.
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Maged A.I. El‐Shaarawi, Esmail M.A. Mokheimer and Ahmad Jamal
To explore the effect of the annulus geometrical parameters on the induced flow rate and the heat transfer under the conjugate (combined conduction and free convection) thermal…
Abstract
Purpose
To explore the effect of the annulus geometrical parameters on the induced flow rate and the heat transfer under the conjugate (combined conduction and free convection) thermal boundary conditions with one cylinder heated isothermally while the other cylinder is kept at the inlet fluid temperature.
Design/methodology/approach
A finite‐difference algorithm has been developed to solve the bipolar boundary‐layer equations for the conjugate laminar free convection heat transfer in vertical eccentric annuli.
Findings
Numerical results are presented for a fluid of Prandtl number, Pr=0.7 in eccentric annuli. The geometry parameters of NR2 and E (the fluid‐annulus radius ratio and the eccentricity, respectively) have considerable effects on the results.
Practical implications
Applications of the obtained results can be of value in the heat‐exchanger industry, in cooling of underground electric cables, and in cooling small vertical electric motors and generators.
Originality/value
The paper presents results that are not available in the literature for the problem of conjugate laminar free convection in open‐ended vertical eccentric annular channels. Geometry effects having been investigated by considering fluid annuli having radii ratios NR2=0.1 and 0.3, 0.5 and 0.7 and four values of the eccentricity E=0.1, 0.3, 0.5 and 0.7. Moreover, practical ranges of the solid‐fluid conductivity ratio (KR) and the wall thicknesses that are commonly available in pipe standards have been investigated. Such results are very much needed for design purposes of heat transfer equipment.
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Jun-Hui Chai, Jun-Ping Zhong, Bo Xu, Zi-Jian Zhang, Zhengxiang Shen, Xiao-Long Zhang and Jian-Min Shen
The high-pressure accumulator has been widely used in the hydraulic system. Failure pressure prediction is crucial for the safe design and integrity assessment of the…
Abstract
Purpose
The high-pressure accumulator has been widely used in the hydraulic system. Failure pressure prediction is crucial for the safe design and integrity assessment of the accumulators. The purpose of this study is to accurately predict the burst pressure and location for the accumulator shells due to internal pressure.
Design/methodology/approach
This study concentrates the non-linear finite element simulation procedure, which allows determination of the burst pressure and crack location using extensive plastic straining criterion. Meanwhile, the full-scale hydraulic burst test and the analytical solution are conducted for comparative analysis.
Findings
A good agreement between predicted and measured the burst pressure that was obtained, and the predicted failure point coincided very well with the fracture location of the actual shell very well. Meanwhile, the burst pressure of the shells increases with wall thickness, independent of the length. It can be said that the non-linear finite element method can be employed to predict the failure behavior of a cylindrical shell with sufficient accuracy.
Originality/value
This paper can provide a designer with additional insight into how the pressurized hollow cylinder might fail, and the failure pressure has been predicted accurately with a minimum error below 1%, comparing the numerical results with experimental data.
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This chapter offers a case study (Yin, 2018) of Super Bowl LIII as a special opportunity for diversity, equity, and inclusion (DEI) initiatives for arts organizations. It uses…
Abstract
This chapter offers a case study (Yin, 2018) of Super Bowl LIII as a special opportunity for diversity, equity, and inclusion (DEI) initiatives for arts organizations. It uses mega-event legacy theory (Preuss, 2015) to frame the outcomes as legacies. The Atlanta Super Bowl Host Committee created a specific initiative entitled Legacy 53. The Legacy 53 initiative consists of five pillars: Business Connection, Capital Improvement Project, Civil Rights and Social Justice, Sustainability, and Youth Engagement (Reed, 2018). This study offers a particular perspective on DEI structures because it examines the Civil Rights and Social Justice pillar's public art project that involved community-driven installations across Atlanta with partners including WonderRoot, an arts organization. The project highlights how administrators can prepare for and take advantage of this unique funding opportunity during future Super Bowls. By reviewing literature on mega-events, urban development, the Olympics, and Super Bowls, I examine the funding structure of the Atlanta Super Bowl Host Committee and investigate how arts organizations relate to DEI initiatives. This work addresses a gap in the literature by highlighting funding with a focus related to systemic justice because it is a unique approach that does not reflect historical Super Bowl funding trends.
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James A. Wall, Dong‐Won Sohn, Natalie Cleeton and Deng Jian Jin
This study investigated the mediations of 125 community mediators in the People's Republic of China. The mediators' reports on two mediations each—one in a community…
Abstract
This study investigated the mediations of 125 community mediators in the People's Republic of China. The mediators' reports on two mediations each—one in a community (inter‐family) and one in a family (intra‐family) dispute—indicated the frequency with which they used 33 mediation techniques. In family (versus community) mediations, Chinese mediators were found to rely more heavily upon the techniques of separating the parties, getting assistance from third parties, calling for empathy, stating the other side's point of view, and utilizing logic. As for the strategies (combinations of techniques) employed, we found three distinct ones—separate, analyze together, criticize—in the family mediations. Two sets—reason together and criticize—were detected in the community mediations.
Taher Armaghani, A. Kasaeipoor, Mohsen Izadi and Ioan Pop
The purpose of this paper is to numerically study MHD natural convection and entropy generation of Al2O3-water alumina nanofluid inside of T-shaped baffled cavity which is…
Abstract
Purpose
The purpose of this paper is to numerically study MHD natural convection and entropy generation of Al2O3-water alumina nanofluid inside of T-shaped baffled cavity which is subjected to a magnetic field.
Design/methodology/approach
Effect of various geometrical, fluid and flow factors such as aspect ratio of enclosure and baffle length, Rayleigh and Hartmann number of nanofluid have been considered in detail. The hydrodynamics and thermal indexes of nanofluid have been described using streamlines, isotherms and isentropic lines.
Findings
It is found that by enhancing Hartmann number, symmetrical streamlines gradually lose symmetry and their values decline. It is found that by enhancing Hartmann number, symmetrical streamlines gradually lose symmetry and their values decline. The interesting finding is an increase in the impact of Hartmann number on heat transfer indexes with augmenting Rayleigh number. However, with augmenting Rayleigh number and, thus, strengthening the buoyant forces, the efficacy of Hartmann number one, an index indicating the simultaneous impact of natural heat transfer to entropy generation increases. It is clearly seen that the efficacy of nanofluid on increased Nusselt number enhances with increasing aspect ratio of the enclosure. Based on the results, the Nusselt number generally enhances with the larger baffle length in the enclosure. Finally, with larger Hartmann number and lesser Nusselt one, entropy production is reduced.
Originality/value
The authors believe that all the results, both numerical and asymptotic, are original and have not been published elsewhere.
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Vinicius Malatesta, Josuel Kruppa Rogenski and Leandro Franco de Souza
The centrifugal instability mechanism of boundary layers over concave surfaces is responsible for the development of quasi-periodic, counter-rotating vortices aligned in a…
Abstract
Purpose
The centrifugal instability mechanism of boundary layers over concave surfaces is responsible for the development of quasi-periodic, counter-rotating vortices aligned in a streamwise direction known as Görtler vortices. By distorting the boundary layer structure in both the spanwise and the wall-normal directions, Görtler vortices may modify heat transfer rates. The purpose of this study is to conduct spatial numerical simulation experiments based on a vorticity–velocity formulation of the incompressible Navier–Stokes system of equations to quantify the role of the transition in the heat transfer process.
Design/methodology/approach
Experiments are conducted using an in-house, parallel, message-passing code. Compact finite difference approximations and a spectral method are used to approximate spatial derivatives. A fourth-order Runge–Kutta method is adopted for time integration. The Poisson equation is solved using a geometric multigrid method.
Findings
Results show that the numerical method can capture the physics of transitional flows over concave geometries. They also show that the heat transfer rates in the late stages of the transition may be greater than those for either laminar or turbulent ones.
Originality/value
The numerical method can be considered as a robust alternative to investigate heat transfer properties in transitional boundary layer flows over concave surfaces.