Ladislav Halada

On elliptical model for forest fire spread modeling and simulation

A new approach for the derivation of elliptical model of steady-state forest fire spread in time based on classical envelope theory is described. The derivation of this model known in the literature is based on the introduction of a special transform of co-ordinate system which allows to utilize geometrical properties of points lying on common tangent line of two circles. However, the use of this transform means the necessity to apply some specific assumptions onto the model. The proposed new procedure allows us to derive the model without the use of this transform. The new approach enables to better explain the internal coherence of studied problem, assumptions and limitations of the model, as well as to suggest its further generalizations.

Computer Modelling of Automobile Fires

The use of the CFD (Computer Fluid Dynamics) theory and its practical knowledge has become widespread in such academic disciplines as aerodynamics, fluid dynamics, combustion engineering and other fields. However, in the disciplines, which examine the ongoing processes in larger sizes, CFD was applied during the last decades only. One of such discipline is a spread of fire. Fire processes are a very complicated and complex phenomenon consisting of combustion, radiation, turbulence, fluid dynamics and other physical and chemical processes. A good knowledge about complex phenomena and processes occurring during fire in different environments is a significant component of fire safety. As fire itself is very complicated phenomenon, interdisciplinary approach to the problem is required.

Cinema Fire Modelling by FDS

Recent advances in computer fluid dynamics (CFD) and rapid increase of computational power of current computers have led to the development of CFD models capable to describe fire in complex geometries incorporating a wide variety of physical phenomena related to fire. In this paper, we demonstrate the use of Fire Dynamics Simulator (FDS) for cinema fire modelling. FDS is an advanced CFD system intended for simulation of the fire and smoke spread and prediction of thermal flows, toxic substances concentrations and other relevant parameters of fire. The course of fire in a cinema hall is described focusing on related safety risks. Fire properties of flammable materials used in the simulation were determined by laboratory measurements and validated by fire tests and computer simulations

Application of multistage stochastic programs solved in parallel in portfolio management

We present a multistage model for allocation of financial resources to bond indices in different currencies. The model was tested on historical data of interest and exchange rates. We compare a two-stage and a three-stage stochastic programming model from a financial performance point of view. For solving two-stage and three-stage stochastic programs the interior point method (IPM) in the frame of the primal-dual path following formulation is used. An application of the Birge and Qi factorization to the IPM allows decomposition of large linear system to smaller blocks allowing thus to solve it in parallel. The parallel code is written in the Fortran programming language, using the message passing interface (MPI) for communication. Parallel and financial performance is illustrated on experiments executed on the IBM 1350 Linux cluster.

Cluster Computation for Flood Simulations

Simulation of the water flood problems often leads to solving of large sparse systems of partial differential equations. For such systems, the numerical method is veiN CPU-time consumiilg. Therefore, the parallel simulation is essential for water flood study with satisfsctoiN accuracy. In this paper, we present some experimental results of parallel numerical solutions done on Linux clusters. Our measurements indicate that Linux cluster can provide satisfactory power for parallel numerical solutions, especially for large problems. We also provide experimental results done on a SGI Origin2000 machine for comparison with Linux clusters.

A Parallel Strongly Implicit Algorithm for Solving of Diffusion Equations

We present a parallel algorithm for the solution of partial differential equations representing a 3-D diffusion process of the underground water by a finite difference method. The algorithm belongs to a class of the incomplete LU factorization methods, where corresponding system of linear algebraic equations is solved by a quasi LU decomposition in every time step. A code realizing the algorithm was written in Fortran 90 programming language using the MPI message passing interface system and was tested on a SGI Origin 2000 parallel computer.

Automobile interior fire and its spread to an adjacent vehicle: parallel simulation

Knowledge of the course of an automobile fire is an important issue in automobile fire safety and can have a significant impact on fire safety measures in car parks and other structures with a high concentration of automobiles. In this article, computer simulations of fire in an automobile interior and its influence on an adjacent vehicle are investigated. The results of simulations are compared with the results of the measurements obtained during a full-scale fire experiment conducted in Povazsky Chlmec (Slovakia) in 2009. The comparison confirms the accuracy of the simulation. A parameter study related to some selected material properties, which shows that seat material properties are the most important for the fire development, is described. Due to high computational requirements, a parallel version of the calculation is studied, and the influence of parallelization on performance and accuracy is tested as well. As the glass breakage is one of the most important factors affecting the course of an automobile fire, a simple practical criterion to determine when window breakage will occur is proposed.

A parallel algorithm for solving band systems and matrix inversion

In this paper new parallel algorithms for solving a band system of linear equations with bandwidth 2m+1 and for matrix inversion of such matrix are proposed. The algorithms are based on the simultaneous computation of m band triangular systems differing from each other only at the right-hand side. Thus, a computational complexity of our algorithm for the band system is the same as of a band triangular system solver. A difference is only at the number of processors used. The application of the algorithm for solving the inversion is advantageous if this computation is a part of the solving of system and it is necessary to know only selected rows or columns of the matrix inverse.

Impact of Turned Cars in Tunnel on Modelling People Evacuation in Fire Conditions

People evacuation in tunnel in fire conditions belongs to important tunnel safety problems. In this paper, simulation of fire in a short unidirectional 2-lane road tunnel and its evacuation using the FDS+Evac system are analysed. FDS+Evac enables to simulate fire spread in the tunnel utilizing the obtained fire characteristics for modelling evacuation of people. Three evacuation scenarios which differ from each other by cars location in the tunnel are illustrated. The impact of turned cars on fire spread and people egress is demonstrated. Some specific particularities of the current version of FDS+Evac, which must be taken into account in modelling the egress in tunnel fire conditions to avoid misrepresentation of input representation, are discussed.

Multiperiod Portfolio Management Using Parallel Interior Point Method

Publisher Summary This chapter describes an algorithm for solving a three-stage stochastic linear program based on the Birge and Qi factorization of a constraint matrix product in the frame of the primaldual path-following interior point method. The algorithm is scalable and enables to solve large linear programs raising from the portfolio management problems. The parallelization of the method for distributed-memory machines using fortran/mpi and the linear algebra package Lapack, is outlined. Parallel implementation of the three stage algorithm in the frame of the parallel interior point algorithm (IPM) method is based on the message passing interface (MPI). The algorithm based on the parallel BQ decomposition used in the frame of the MPC algorithm for three-stage stochastic problems, was implemented in the Fortran 90 programming language and executed on cluster of SMPs. The performance results of the experiments are discussed in the chapter.