M. Mulas, S. Chibbaro, G. Delussu, I. Di Piazza and M. Talice
This paper presents a unified numerical method able to address a wide class of fluid flow problems of engineering interest. Arbitrary fluids are treated specifying totally…
Abstract
This paper presents a unified numerical method able to address a wide class of fluid flow problems of engineering interest. Arbitrary fluids are treated specifying totally arbitrary equations of state, either in analytical form or through look‐up tables. The most general system of the unsteady Navier–Stokes equations is integrated with a coupled implicit preconditioned method. The method can stand infinite CFL number and shows the efficiency of a quasi‐Newton method independent of the multi‐block partitioning on parallel machines. Computed test cases ranging from inviscid hydrodynamics, to natural convection loops of liquid metals, and to supersonic gasdynamics, show a solution efficiency independent of the class of fluid flow problem.
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Baris Sezer, Ramazan Yilmaz and Fatma Gizem Karaoglan Yilmaz
The purpose of this paper is to determine the awareness levels of teachers with regard to cyber bullying. In line with this purpose, the extent of awareness levels of teachers in…
Abstract
Purpose
The purpose of this paper is to determine the awareness levels of teachers with regard to cyber bullying. In line with this purpose, the extent of awareness levels of teachers in general, regarding the issue of personal cyber security in their daily lives and the precautions that can be taken in this context have been measured.
Design/methodology/approach
Survey method is used in this study. The participants of this research were 184 teachers working at various provinces in Turkey during 2012-2013 academic year. A scale was used in this study.
Findings
The findings of the study reveal that the teachers in the sample group of the study have an average level of awareness on cyber bullying, in general. According to the findings of the study, based on branch, gender and frequency of internet use, there are statistically significant differences among teachers’ awareness levels on cyber bullying.
Research limitations/implications
The data collection tool used for the study is a self-report scale and it is restricted to determining the awareness levels of teachers with respect to personal cyber security within the context of cyber bullying awareness and the precautions that need to be taken in this respect.
Practical implications
The data obtained from the study, the authors have conducted, can contribute to updating in-service and pre-service educational contents developed for teachers and prospective teachers, by providing insight for the policy makers.
Originality/value
It is believed that this research will contribute to the literature. On the other hand, this study will guide the policy makers/implementers in Turkey, as well.
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Chiara Biscarini, Silvia Di Francesco and Matteo Mencattini
The purpose of this paper is to prove the validity of the front‐tracking variant of the lattice Boltzmann method (LBM) to simulate free surface hydraulic flows (i.e. dam break…
Abstract
Purpose
The purpose of this paper is to prove the validity of the front‐tracking variant of the lattice Boltzmann method (LBM) to simulate free surface hydraulic flows (i.e. dam break flows).
Design/methodology/approach
In this paper, an algorithm for free surface simulations with the LBM method is presented. The method is chosen for its computational efficiency and ability to deal with complex geometries. The LBM is combined to a surface‐tracking technique applied to a fixed Eulerian mesh in order to simulate free surface flows.
Findings
The numerical method is then validated against two typical cases of environmental‐hydraulic interest (i.e. dam break) by comparing LBM results with experimental data available in literature. The results show that the model is able to reproduce the observed water levels and the wave fronts with reasonable accuracy in the whole period of the transient simulations, thus highlighting that the present method may be a promising tool for practical dam break analyses.
Originality/value
Even if the main philosophy of the proposed method is equal to the volume of fluid technique usually coupled to Navier‐Stokes models, no additional differential equation is needed to determine the relative volume fraction of the two phases, or phase fraction, in each computational cell, as the free‐surface tracking is automatically performed. This results in a method very simple to be coded with high computational efficiency. The results presented in this paper are the first, to the best of the authors' knowledge, in the field of hydraulic engineering.
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H. Parhizkar and S.M.H. Karimian
The purpose of this paper is to present an engineering inviscid‐boundary layer method for the calculation of convective heating rates on three‐dimensional non‐axisymmetric…
Abstract
Purpose
The purpose of this paper is to present an engineering inviscid‐boundary layer method for the calculation of convective heating rates on three‐dimensional non‐axisymmetric geometries at angle of attack.
Design/methodology/approach
Based on the axisymmetric analog, convective heating rates are calculated along the surface streamlines which are determined using the inviscid properties calculated on an unstructured grid.
Findings
Since the method is capable of using inviscid properties calculated on an unstructured grid, it is applicable to a variety of configurations and it requires much less computational effort than a Navier‐Stokes code. The results of the present method are evaluated on different wing body configurations in laminar and turbulent hypersonic equilibrium flows. In comparison to experimental data, the present results are found to be fairly accurate in the windward and leeward regions.
Practical implications
With this approach, heating rates can be predicted on general three‐dimensional configurations at hypersonic speeds in an accurate and fast scheme.
Originality/value
In order to calculate the heating rates at any specific point on the surface, a technique is developed to calculate the inviscid surface streamlines in a backward manner using the inviscid velocity components. The metric coefficients are also calculated using a new simple technique.
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Nikhil Kalkote, Ashwani Assam and Vinayak Eswaran
The purpose of this paper is to solve unsteady compressible Navier–Stokes equations without the commonly used dual-time loop. The authors would like to use an adaptive…
Abstract
Purpose
The purpose of this paper is to solve unsteady compressible Navier–Stokes equations without the commonly used dual-time loop. The authors would like to use an adaptive time-stepping (ATS)-based local error control instead of CFL-based time-stepping technique. Also, an all-speed flow algorithm is implemented with simple low dissipation AUSM convective scheme, which can be computed without preconditioning which in general destroys the time accuracy.
Design/methodology/approach
In transient flow computations, the time-step is generally determined from the CFL condition. In this paper, the authors demonstrate the usefulness of ATS based on local time-stepping previously used extensively in ordinary differential equations (ODE) integration. This method is implemented in an implicit framework to ensure the numerical domain of dependence always contains the physical domain of dependence.
Findings
In this paper, the authors limit their focus to capture the unsteady physics for three cases: Sod’s shock-tube problem, Stokes’ second problem and a circular cylinder. The use of ATS with local truncation error control enables the solver to use the maximum allowable time-step, for the prescribed tolerance of error. The algorithm is also capable of converging very rapidly to the steady state (if there is any) after the initial transient phase. The authors present here only the first-order time-stepping scheme. An algorithmic comparison is made between the proposed adaptive time-stepping method and the commonly used dual time-stepping approach that indicates the former will be more efficient.
Originality/value
The original method of ATS based on local error control is used extensively in ODE integration, whereas, this method is not so popular in the computational fluid dynamics (CFD) community. In this paper, the authors investigate its use in the unsteady CFD computations. The authors hope that it would provide CFD researchers with an algorithm based on an adaptive time-stepping approach for unsteady calculations.
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This chapter presents a case study of the lesbian and gay rights movement following the Supreme Court's decision in Bowers v. Hardwick, which was a critical defeat in the campaign…
Abstract
This chapter presents a case study of the lesbian and gay rights movement following the Supreme Court's decision in Bowers v. Hardwick, which was a critical defeat in the campaign for sodomy repeal. Activists responded with a dramatic wave of mobilization by staging protests, successful appeals for organizational donations, building coalitions, and shifting institutional venues. This case provides a paradox for the dominant perspectives within social movement theory and legal mobilization literature, which often traces mobilization back to the expansion of political opportunities. The defeat in Bowers signaled a closing of political opportunities for activists. Drawing from a growing body of literature on political threats and heeding the call to specify the mechanisms of movement dynamics, I show how the defeat in Bowers was translated into proactive mobilization.