Wyniki wyszukiwania - Biblioteka Nauki

1

The modified XFEM for solving problems of a phase change with natural convection

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Stąpór P.

Archive of Mechanical Engineering

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2019

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tom Vol. LXVI, nr 3

273--294

EN

This paper presents an extended finite element method applied to solve phase change problems taking into account natural convection in the liquid phase. It is assumed that the transition from one state to another, e.g., during the solidification of pure metals, is discontinuous and that the physical properties of the phases vary across the interface. According to the classical Stefan condition, the location, topology and rate of the interface changes are determined by the jump in the heat flux. The incompressible Navier–Stokes equations with the Boussinesq approximation of the natural convection flow are solved for the liquid phase. The no-slip condition for velocity and the melting/freezing condition for temperature are imposed on the interface using penalty method. The fractional four-step method is employed for analysing conjugate heat transfer and unsteady viscous flow. The phase interface is tracked by the level set method defined on the same finite element mesh. A new combination of extended basis functions is proposed to approximate the discontinuity in the derivative of the temperature, velocity and the pressure fields. The single-mesh approach is demonstrated using three two-dimensional benchmark problems. The results are compared with the numerical and experimental data obtained by other authors.

2

An enhanced XFEM for the discontinuous Poisson problem

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Stąpór P.

Archive of Mechanical Engineering

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2019

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tom Vol. LXVI, nr 1

25--37

EN

In the paper, the extended finite element method (XFEM) is combined with a recovery procedure in the analysis of the discontinuous Poisson problem. The model considers the weak as well as the strong discontinuity. Computationally efficient low-order finite elements provided good convergence are used. The combination of the XFEM with a recovery procedure allows for optimal convergence rates in the gradient i.e. as the same order as the primary solution. The discontinuity is modelled independently of the finite element mesh using a step-enrichment and level set approach. The results show improved gradient prediction locally for the interface element and globally for the entire domain.

3

Dedicated data management system for university didactic processes

51%

Koczubiej S. , Nowakowska M. , Stąpór P. , Świetlik P.

Zeszyty Naukowe. Organizacja i Zarządzanie / Politechnika Śląska

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2022

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tom z. 162

315--337

EN

Purpose: The objective of the work is to develop and implement the original concept of Repository of Didactic Processes Data (RDPD) for universities. The task of the Repository is to handle formally organised content in a digital form, covering resources created in connection with didactic processes, and the origin of which is a university community. These data should be: as complete as possible, available on the Internet at any time and easy to find and retrieve, stored in commonly used formats, contain a clear indication of the stored resources, without any costs for the user downloading them. Design/methodology/approach: The concept of the Repository was developed on the basis of the results of consultations with the academic community - its primary target audience. Comments from the representatives of the Repository future main users were taken into account. An analysis of the existing available repository systems in terms of their functionality, adaptability to the specificity of data, and popularity was carried out in order to select the solution that could be the foundation for RDPD. Then, the following tasks were undertaken in the environment of the selected system: adapting the data schema developed for RDPD, the implementation of the operations of loading, browsing, and searching of data, and user management. Findings: As a result of research and analyses, DSpace was proposed as the basis for the RDPD system. The logical metadata layers as well as the technical implementation of the proposed Repository in the DSpace system were elaborated. Practical implications: The implementation of the RDPD system may significantly facilitate and support the university management process. Originality/value: There are many initiatives regarding institutional repositories within the higher education sector. However, there is no institutional repository dedicated strictly to the storage and management of data generated by university educational processes. The developed repository is the solution to the problem.