Passive autocatalytic recombiners (PAR) is the only used method for hydrogen removal from the containment buildings in modern nuclear reactors. Numerical models of such devices, based on the CFD approach, are the subject of this paper. The models may be coupled with two types of computer codes: the lumped parameter codes, and the computational fluid dynamics codes. This work deals with 2D numerical model of PAR and its validation. Gaseous hydrogen may be generated in water nuclear reactor systems in a course of a severe accident with core overheating. Therefore, a risk of its uncontrolled combustion appears which may be destructive to the containment structure.

Exploitation of hard coal seams by roadway system is applied by two coal mines in southern Poland in Upper Silesian Basin. It is a secondary mining exploitation carries out in safety pillars of urban areas and shafts within mining areas of closed coal mines. Roadway system is the excavation process of gateways which are made in parallel order leaving coal pillars between them. An optimal width of coal pillar makes roadway stable and reduces subsidence of terrain surface. The article presents results of subsidence simulation caused by partial extraction using empirical and numerical methods on the example of one exploitation field of “Siltech” coal mine. The asymptotic state of subsidence was considered after mining ceased in the study area. In order to simulate of subsidence, numerical model of rock mass and model of Knothe-Budryk theory were calibrated. Simulation of vertical displacements in numerical method was carried out using RS3 program by Rocscience based on finite element method. The assumption was made that model of rock mass is transversely isotropic medium, in which panels were designed according to order of extraction of coal seams. The results of empirical and numerical methods were compared with measured values of subsidence at benchmarks along drawn lines (subsidence profiles).

This work presents the results of numerical modeling of Karman vortex street generation performed with ANSYS/FLUENT package application. The influence of the mechanical elements located downstream of the bluff body on the vortex frequency has been found during earlier laboratory investigations. Five various geometrical configurations have been tested. Considerable differences in pictures of distributions of pressure, horizontal and vertical velocities have appeared for various configurations. Qualitative as well as quantitative results are presented in the paper. They confirm the significant dependence of the Karman vortex street parameters on the meter configuration.

The Dez dam was commissioned in 1963 and since sediments accumulated in the reservoir up to an elevation of approximately 15m below the intake of the power tunnel. One of the possible measures to improve operation of the reservoir is by heightening of the existing dam. This paper describes the conducted procedure for static and thermal calibration of this 203m dam in Iran based on micro geodesies measurements. Also the nonlinear response of existing dam is investigated under maximum credible earthquake ground motions considering joint behavior and mass concrete cracking and safety of dam is evaluated for possible heightening. For thermal calibration of provided numerical model, transient thermal analysis was conducted and results were compared with thermometers records installed in central block. In addition, for static calibration; thermal distribution within dam body, dam self weight, hydrostatic pressure and silt load applied on the 3D fi nite element model of dam-reservoir-foundation were considered. Results show that the distribution of stresses will be critical within dam for heightening case under seismic loads in MCL.

The paper presents a dynamic analysis of the damaged masonry building repaired with the Flexible Joint Method. Numerical analysis helped to determine the effect of the applied repairing method on natural frequencies as well as values of stresses and accelerations in the analyzed variants of numerical model. They confirmed efficiency of the proposed repair method.

This paper constitutes the sensitivity study of application the Polar WRF

model to the Svalbard area with testing selected parameterizations, including planetary

boundary layer, radiation and microphysics schemes. The model was configured, using

three one-way nested domains with 27 km, 9 km and 3 km grid cell resolutions. Results

from the innermost domain were presented and compared against measured wind speed

and air temperature at 10 meteorological stations. The study period covers two months:

June 2008 and January 2009. Significant differences between simulations results occurred

for planetary boundary layer (PBL) schemes in January 2009. The Mellor-Yamada-Janjic

(MYJ) planetary boundary layer (PBL) scheme resulted in the lowest errors for air

temperature, according to mean error (ME), mean absolute error (MAE) and correlation

coefficient values, where for wind speed this scheme was the worst from all the PBL

schemes tested. In the case of June 2008, shortwave and longwave radiation schemes

influenced the results the most. Generally, higher correlations were obtained for January,

both for air temperature and wind speed. However, the model performs better for June

in terms of ME and MAE error statistics. The results were also analyzed spatially, to

summarize the uncertainty of the model results related to the analyzed parameterization

schemes groups. Significant variability among simulations was calculated for January

2009 over the northern part of Spitsbergen and fjords for the PBL schemes. Standard

deviations for monthly average simulated values were up to 3.5°C for air temperature

and around 1 m s-1 for wind speed.

The stability of gateroads is one of the key factors for the mining process of hard coal by a longwall system. Wrong designed and applied the gateroad support at the stage of drilling, may adversely affect the functionality of the gateroad and the safety of the crew throughout its existence.

The article presents the results of the underground tests and observations such as: convergence of the gateroad, stratification and the fractured zone range in the roof rocks, carried out in four longwall gateroads at the stage of their drilling.

The obtained test results were the basis for the assessment of the possibility of using a convergence control method in the design of the gateroad support. The method is based on three interdependent relationships, such as: Ground Reaction Curve (GRC), Longitudinal Displacement Profile (LDP), and a Support Characteristic Curve (SCC). All calculations were performed using numerical modeling in the Phase2 program, based on the finite element method (FEM).

As part of the work, the error level of simulations of uniform optical-fibre Bragg gratings was determined using the transitionmatrixmethod. The errorswere established by comparing the transmission characteristics of the structures obtained by simulation with the corresponding characteristics arrived at experimentally. To compile these objects, elementary properties of the characteristics were specified, also affecting the applications of Bragg gratings, and compared with each other. The level of error in determining each of these features was estimated. Relationships were also found between the size of the physical properties of Bragg gratings and the level of errors obtained. Based on the findings, the correctness of the simulation of structures with the said method was verified, giving satisfying results.

Biskupin is one of the most recognizable archaeological site in Poland and Central Europe. The origins of the excavations dates back to year 1934 and had lasted almost continuously until 1974. In the framework of the grant from the Ministry of Culture and National Heritage interdisciplinary team of scientists from Archaeological Museum in Biskupin and Warsaw University of Technology performed multi-dimensional analysis of the settlement. Based on the integrated vector documentation, resulting from the photographic documentation, numerical models of structural systems of main types of buildings and defensive rampart were prepared. The aim of the analysis was a verification of the earlier findings of archaeological and architectural researches. The analysis allowed to verify both the arrangement of individual parts of structure of buildings, their work and the interconnection, as well as the possible dimensions of the individual components.

Balanced distribution of air in coal-fired boiler is one of the most important factors in the combustion process and is strongly connected to the overall system efficiency. Reliable and continuous information about combustion airflow and fuel rate is essential for achieving optimal stoichiometric ratio as well as efficient and safe operation of a boiler. Imbalances in air distribution result in reduced boiler efficiency, increased gas pollutant emission and operating problems, such as corrosion, slagging or fouling. Monitoring of air flow trends in boiler is an effective method for further analysis and can help to appoint important dependences and start optimization actions. Accurate real-time monitoring of the air distribution in boiler can bring economical, environmental and operational benefits. The paper presents a novel concept for online monitoring system of air distribution in coal-fired boiler based on real-time numerical calculations. The proposed mathematical model allows for identification of mass flow rates of secondary air to individual burners and to overfire air (OFA) nozzles. Numerical models of air and flue gas system were developed using software for power plant simulation. The correctness of the developed model was verified and validated with the reference measurement values. The presented numerical model for real-time monitoring of air distribution is capable of giving continuous determination of the complete air flows based on available digital communication system (DCS) data.

In many therapeutic applications of a pulsed focused ultrasound with various intensities the finite- amplitude acoustic waves propagate in water before penetrating into tissues and their local heating. Water is used as the matching, cooling and harmonics generating medium. In order to design ultrasonic probes for various therapeutic applications based on the local tissue heating induced in selected organs as well as to plan ultrasonic regimes of treatment a knowledge of pressure variations in pulsed focused nonlinear acoustic beams produced in layered media is necessary. The main objective of this work was to verify experimentally the applicability of the recently developed numerical model based on the Time- Averaged Wave Envelope (TAWE) approach (Wójcik et al., 2006) as an effective research tool for predicting the pulsed focused nonlinear fields produced in two-layer media comprising of water and tested materials (with attenuation arbitrarily dependent on frequency) by clinically relevant axially-symmetric therapeutic sources. First, the model was verified in water as a reference medium with known linear and nonlinear acoustic properties. The measurements in water were carried out at a 25◦C temperature using a 2.25 MHz circular focused (f/3.0) transducer with an effective diameter of 29 mm. The measurement results obtained for 8-cycle tone bursts with three different initial pressure amplitudes varied between 37 kPa and 113 kPa were compared with the numerical predictions obtained for the source boundary condition parameters determined experimentally. The comparison of the experimental results with those simulated numerically has shown that the model based on the TAWE approach predicts well both the spatial-peak and spatial-spectral pressure variations in the pulsed focused nonlinear beams produced by the transducer used in water for all excitation levels complying with the condition corresponding to weak or moderate source-pressure levels. Quantitative analysis of the simulated nonlinear beams from circular transducers with ka ≫ 1 allowed to show that the axial distance at which sudden accretion of the 2nd or higher harmonics amplitude appears is specific for this transducer regardless of the excitation level providing weak to moderate nonlinear fields. For the transducer used, the axial distance at which the 2nd harmonics amplitude suddenly begins to grow was found to be equal to 60 mm. Then, the model was verified experimentally for two-layer parallel media comprising of a 60-mm water layer and a 60-mm layer of 1.3-butanediol (99%, Sigma-Aldrich Chemie GmbH, Steinheim, Germany). This medium was selected because of its tissue-mimicking acoustic properties and known nonlinearity parameter B/A. The measurements of both, the peak- and harmonic-pressure variations in the pulsed nonlinear acoustic beams produced in two-layer media (water/1.3-butanediol) were performed for the same source boundary conditions as in water. The measurement results were compared with those simulated numerically. The good agreement between the measured data and numerical calculations has shown that the model based on the TAWE approach is well suited to predict both the peak and harmonic pressure variations in the pulsed focused nonlinear sound beams produced in layered media by clinically relevant therapeutic sources. Finally, the pulsed focused nonlinear fields from the transducer used in two-layer media: water/castor oil, water/silicone oil (Dow Corning Ltd., Coventry, UK), water/human brain and water/pig liver were predicted for various values of the nonlinearity parameter of tested media.

The generic mathematical model and computational algorithm considering hydrodynamics, heat and mass transfer processes during casting

and forming steel ingots and castings are offered. Usage domains for turbulent, convective and non-convective models are determined

depending on ingot geometry and thermal overheating of the poured melt. The expert system is developed, enabling to choose a

mathematical model depending on the physical statement of a problem.

The main purpose of the present work was to validate the numerical model for the pulse-step liquid steel alloying method using a physical simulator that enables the observation and recording of phenomena occurring during the continuous steel casting process. The facility under investigation was a single-nozzle tundish equipped with a dam. To physical trials the glass water model was made on a scale of 2:5. For the mathematical description of turbulence during liquid steel alloying process, the k-ε and k-ω models were employed in the simulations. Based on the computer simulations and physical trials carried out, alloy addition behaviour and mixing curves for different tundish alloy addition feeding positions were obtained. The change in the location of alloy addition feeding to the liquid steel had an effect on the process of alloy addition spread in the liquid steel bulk and on the mixing time.

This paper presents a complex study of anhydrite interbeds influence on the cavern stability in the Mechelinki salt deposit. The impact of interbeds on the cavern shape and the stress concentrations were also considered. The stability analysis was based on the 3D numerical modelling. Numerical simulations were performed with use of the Finite Difference Method (FDM) and the FLAC3D v. 6.00 software. The numerical model in a cuboidal shape and the following dimensions: length 1400, width 1400, height 1400 m, comprised the part of the Mechelinki salt deposit. Three (K-6, K-8, K-9) caverns were projected inside this model. The mesh of the numerical model contained about 15 million tetrahedral elements. The occurrence of anhydrite interbeds within the rock salt beds had contributed to the reduction in a diameter and irregular shape of the analysed caverns. The results of the 3D numerical modelling had indicated that the contact area between the rock salt beds and the anhydrite interbeds is likely to the occurrence of displacements. Irregularities in a shape of the analysed caverns are prone to the stress concentration. However, the stability of the analysed caverns are not expected to be affected in the assumed operation conditions and time period (9.5 years).

Tremors occur randomly in terms of time, energy as well as the location of their focus. The present state of knowledge and technology does not allow for the precise prediction of these values. Therefore, it is extremely important to correctly select a powered roof support for specific geological and mining conditions, especially in the case of areas where dynamic phenomena are often registered. This article presents information on rock burst hazard associated with the occurrence of rock mass tremors and their influence on a powered roof support. Furthermore, protection methods of a powered roof support against the negative effects of dynamic phenomena are discussed. As a result of an analysis the methodology, to determine the impact of dynamic phenomena on the powered roof support in given geological and mining conditions is presented.

2-phase composites are often used for high demanding parts that can undergo impact loads. However, most of the papers on dynamic loading concerns layered composites. In our opinion, the impact loads are not considered thoroughly enough. Good examples of 2-phase composites are: (1) a WC/Co cermet or (2) a monolithic ceramic Al2O3/ZrO2. The WC/Co cermet is often modelled as having ductile elasto-plastic Co matrix and ideally elastic WC grains. It is because of very high crushing resistivity of the WC.

In this paper, we present an extension to earlier elaborated models ([44]) with the assumption of ideal elasticity of the grains. The new and general numerical model for high-velocity impact of the 2-phase composites is proposed. The idea of this novelty relies on the introduction of crushability of grains in the composite and thermo-mechanical coupling. The model allows for description of the dynamic response both composite polycrystals made of: (1) 2 different purely elastic phases (e.g. Al2O3/ZrO2) or (2) one elastic phase and the second one plastic (e.g. cermet WC/Co), or (3) 2 elasto-plastic phases with different material properties and damage processes. In particular, the analysis was limited to the cases (2) and (3), i.e. we investigated the WC/Co polycrystal that impacted a rigid wall with the initial velocity equal to 50 m/s.

Products of complex geometry, aerodynamic shape and high quality surface finishes are among the most difficult to produce by using stamping methods. When additionally materials with special properties are intended, the task of determining their technological character becomes difficult to solve without the use of physical and numerical methods of process modeling. The paper presents the results of modeling the process of producing a single tube of the jet engine tubular diffuser subassembly. This is a product representative of such a complex geometry one. The charge material for this element requires resistance to operating conditions at elevated temperature and high durability. Therefore, an Inconel type nickel superalloy was proposed for the charge material. In the solution of designing the method of producing a single diffuser tube task, the capabilities of the AutoGrid automatic strain analyzer and the FEM simulation software Eta / Dynaform 5.9 were combined. Numerical simulations of different variants of the manufacturing process of the diffuser tube were made using the Eta / Dynaform 5.9 software. The results of forming simulations became the basis for the alternative technological cycle design of this drawpiece.