Numerical simulation of the fire diffusion in mining passage

Numerical simulations of the stable stratified flow in a 3D passage affected by a thermal source have been calculated with a standard k-e model. Furthermore, the radiation heat transfer model is implemented and species transport equations are defined too. The model allows a correct stratification and produces fairly accurate heat wall transfer

Modelling HM Processes in Porous Media

The report contains an overview of modelling hydro-mechanical (HM) processes in porous media. It starts with an introduction to continuum approach to porous media. Next, a succession of various continuum models is derived, namely, for saturated and unsaturated flow, both with and without coupling to deformation of the porous medium. Each model is developed from balance equations, which are supplied by constitutive relationships

Optimization variant of the shear strength reduction method and its usage for stability of embankments with unconfined seepage

In this paper, an optimization variant of the shear strength reduction method is introduced and used for the solution of embankment stability problems with unconfined seepage. The optimization framework is based on approximations of non-associated Mohr–Coulomb plastic models with associated ones, especially by using various Davis’ approaches. Next, the finite element method is considered and mesh adaptive solution concepts are developed for both the unconfined seepage and stability problems. In-house codes in Matlab are used for their implementation. Finally, two numerical examples inspired by geotechnical practice are investigated in order to demonstrate the accuracy of the optimization framework and to evaluate three different Davis’ approaches. The results are compared with commercial codes in Plaxis and Comsol Multiphysics.Web of Science281art. no. 10703

Optimization and variational principles for the shear strength reduction method

In this paper, a modified shear strength reduction method (MSSR) and its optimization variant (OPT-MSSR) are suggested. The idea of MSSR is to approximate the standard shear strength reduction to be more stable and rigorous from the numerical point of view. The MSSR method consists of a simplified associated elasto-plastic model completed by the strength reduction depending on the dilatancy angle. Three Davis' modifications suggested by Tschuchnigg et al. (2015) are interpreted as special cases of MSSR and their factors of safety are compared. The OPT-MSSR method is derived from MSSR on the basis of rigid plastic assumption, similarly as in limit analysis. Using the variational approach, the duality between the static and kinematic principles of OPT-MSSR is shown. The numerical solution of OPT-MSRR is obtained by performing a regularization method in combination with the finite element method, mesh adaptivity and a damped Newton method. In-house codes (Matlab) are used for the implementation of this solution concept. Finally, two slope stability problems are considered, one of which follows from analysis of a real slope. The softwares packages Plaxis and Comsol Multiphysics are used for comparison of the results.Web of Science45162407238

CFD simulations of the effect of wind on the spontaneous heating of coal stockpiles

A commercial CFD software program, fluent, was used to study the effect of wind on the spontaneous heating process of a coal stockpile. A two-domain model was developed to simultaneously solve the governing equations of an open porous medium (coal stockpile domain) situated in a homogeneous atmosphere (wind flow domain). Simulations with air blowing from a fixed direction as well as real fluctuations of the airflow both in velocity and direction were performed. Numerical calculations confirmed the promoting role of wind on the dynamics of the development of spontaneous heating. Under the conditions of the simulations, three possible shifts of the hot spot in the stockpile were distinguished when coal undergoes the self-heating process: (1) Shift of the hot spot to the pile surface when spontaneous heating of coal is in progress. (2) Movement of the hot spot inwards the stockpile as the wind speed increases. (3) Transfer of the hot spot from the upper part of the stockpile to the lower part when the self-heating process progresses. Such movement was found for wind speeds ⩽3 m s−1 and clearly is mainly connected with the effect of buoyancy.Web of Science11811210