EARTH RESOURCE PROBLEMS AND RELATED ENVIRONMENTAL CONSIDERATIONS

The paper discusses some of the problems of geology and earth resources management in relation to environmental problems of the technosphere. It deals also with some aspects of environmental monitoring of areas where surveying or mining operations are planned or in progress

The Web2 environment as a platform for making natural and cultural values accessible to potential and actual clients

Services like tourism have to use the possibilities of modern advertising. In particular, these include the World Wide Web (WWW). This platform brings its products and services directly to the customers. To place the information about a region and its tourist offer in optimal manner requires exact definition of elements in the Web based tourist information system (WETIS) and their presentation. We discuss the elements and their integration in other services, the data structures and types, maps and their interactivity. Furthermore, we present tourism related data of selected Slovakian villages and cities. Finally, we give a report regarding our demonstration web page and future development. The usual tourist information on the web usually relates to the most interesting historical or cultural sights in the region and is marketing oriented. In this way the full image of history and beauty of the characteristic towns and villages is usually missed. Our intention was - in cooperation with the Geotourism students of the Institute if Geotourism - to map also these features of Eastern Slovakia and of the NE Carpathians. As the web is to serve mainly the tourist community, the map connects to useful information on various facilities available at the given locality. The detailed photo-documentation makes it possible e.g. also to see each traditional house. This is interesting as the number of these houses is decreasing. They are replaced by modern buildings, which lack the regional and local flavour.

Proudění ve zpětné klapce

The essay concerns issues connected with modelling of flow in a non-return flap and determination of force effects on the flap disc. The task was researched in collaboration with ARMATURY Group, a.s. The flow is on-compressible and the flow medium is water. Boundary conditions determined by a measurement were applied in the modelling.The target of the project is finding a suitable mathematical model and comparison of the measured and calculated values dissipation factor of the non-return flap for various opening angles of the flap disc.Článek se věnuje problematice modelování proudění ve zpětné klapce a určení silových účinků na klapku. Úloha je řešena ve spolupráci s firmou ARMATURY Group, a.s. Proudění je nestlačitelné a proudící medium je voda. Pro modelování jsou použity okrajové podmínky určené měřením. Cílem je určit vhodný matematický model a srovnat naměřené a vypočtené hodnoty ztrátového součinitele zpětné klapky pro různé úhly otevření talíře klapky

Flow of oil and water through the nozzle and cavitation

Today, the correct understanding of the issue of oil and water cavitation is important due to the growing demands on working conditions in hydraulic systems (pressure and flow rate). This article deals with the measurement and subsequent mathematical modeling of cavitation in a convergent-divergent nozzle of circular cross-section. Cavitation depends on the physical properties of the flowing medium as a function of temperature. Usually, cavitation in water is defined by a two-phase flow of water and vapor, but the air contained in the water significantly affects cavitation. There is usually no vapor cavitation in the oil. Far more often, cavitation in oil is caused by the air it contains. For comparison, cavitation in water and oil was generated in experiments with an identical nozzle. The measurement was used to define boundary conditions in mathematical models and to verify simulations. The problem of cavitation was solved by three variants of multiphase flow, single-phase flow (water, oil), two-phase flow (water-vapor, oil-air) and three-phase flow (water-vapor-air, oil-vapor-air). A turbulent model with cavitation was used for all variants. The verification of simulations shows that for water cavitation it is necessary to use a three-phase model (water, vapor, air) and for oil cavitation a two-phase model (oil, air) is sufficient. The measurement results confirm the importance of the air phase in modeling cavitation in both water and oil.Web of Science911art. no. 193

CFD model of SNCR with shifting effect of CO

The paper deals with CFD simulation of SNCR technology with implemented CO temperature shift. The influence of CO on the SNCR process is described by empirical adjustment of kinetics parameters of chemical reactions. Results of CFD simulation were compared with results of experimental measurements. Although the proposed kinetics model of SNCR technology is simplified, it is able to describe reduction of NOx and other phenomena of SNCR with good precision. The model can be used to verify of injection levels and injection lances arrangement at design phase.Web of Science2012210

Multiphase fluid models to deal with fluid flow dynamics

When dealing with dynamic issues, we often encounter problems of hydraulic shock (water hammer) and cavitation causing distortion of the surrounding material, destruction of material, accompanied by sounds and vibrations. These dynamic behavior of the liquids is due to the presence of gases in the liquid, especially air, vapor and possibly other gases in smaller quantities. The density of such a liquid is assumed to be a function of a liquid elastic modulus depending on pressure or it is defined as the density of a multiphase mixture of incompressible liquid and compressible gases (vapour, air) depending on pressure too. The article is focused on specification of mathematical models of multiphase flow for piping (one dimensional) hydraulic systems and spatial (three dimensional) hydraulic elements and systems. The electrohydraulic analogue (Matlab-SimHydraulics) method and finite volume method (Ansys-Fluent) are used for illustrative fluid dynamics tasks.Web of Science20192896289

Compressibility of the fluid

The presence of air in the liquid causes the dynamic system behaviour. When solve to issue of the dynamics we often meet problems of cavitation. Cavitation is an undesirable phenomenon, since it causes a disruption of the surrounding material and material destruction. Cavitation is accompanied by loud sound effects and reduces the efficiency of such pumps, etc. Therefore, it is desirable to model systems in which the cavitation might occur. A typical example is a solution of water hammer

Flow of Oil and Water through the Nozzle and Cavitation

Today, the correct understanding of the issue of oil and water cavitation is important due to the growing demands on working conditions in hydraulic systems (pressure and flow rate). This article deals with the measurement and subsequent mathematical modeling of cavitation in a convergent-divergent nozzle of circular cross-section. Cavitation depends on the physical properties of the flowing medium as a function of temperature. Usually, cavitation in water is defined by a two-phase flow of water and vapor, but the air contained in the water significantly affects cavitation. There is usually no vapor cavitation in the oil. Far more often, cavitation in oil is caused by the air it contains. For comparison, cavitation in water and oil was generated in experiments with an identical nozzle. The measurement was used to define boundary conditions in mathematical models and to verify simulations. The problem of cavitation was solved by three variants of multiphase flow, single-phase flow (water, oil), two-phase flow (water–vapor, oil–air) and three-phase flow (water–vapor–air, oil–vapor–air). A turbulent model with cavitation was used for all variants. The verification of simulations shows that for water cavitation it is necessary to use a three-phase model (water, vapor, air) and for oil cavitation a two-phase model (oil, air) is sufficient. The measurement results confirm the importance of the air phase in modeling cavitation in both water and oil

Mathematical and experimental modelling of flow of air-saturated water through a convergent-divergent nozzle

In hydraulic elements an under-pressure is generated during fluid flow around sharp edges or changing the flow cross-section (e.g. for valves, switchgear, nozzles). In these locations air suction by leakages or release of air from the liquid during cavitation may occur. When flow modelling using classical mathematical model of cavitation at higher flow rates there is disagreement in the measured and calculated hydraulic variables before and behind hydraulic element. Therefore, it is necessary to use a mathematical model of cavitation applied to the three-phase flow (water, vapour, air). Nowadays it is necessary to look for mathematical approaches, which are suitable for quick engineering use in sufficiently precision numerical calculations. The article is devoted to theoretical investigation of multiphase mathematical model of cavitation and its verification using a laboratory experiment. At first case the k-ε RNG turbulent mathematical model with cavitation was chosen in accordance [9] and was applied on water flow with cavitation (water and vapour) in a convergent-divergent nozzle. In other cases a solution of water flow with cavitation and air saturation was investigated. Subsequently, the results of mathematical modelling and experimental investigation focused on monitoring of air content and its impact on the value of hydraulic parameters and the size of the cavitation area were verified