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Vladimír Liška, Zuzana Šútova and Dušan Pavliak

Abstract

In this paper we analyze the sensitivity of solutions to a nonlinear singularly perturbed dynamical system based on different rewriting into a System of the First Order Differential Equations to a numerical scheme. Numerical simulations of the solutions use numerical methods implemented in MATLAB.

Open access

Grzegorz Porembski and Janusz Kozak

Simulation of damage process of containership's side structure due to collision with a rock

This paper presents methods and results of a simplified numerical simulation of collision process of containership's side structure and a rock. Analysis of results of the modeling makes it possible to draw conclusions as to a character of the event as well as to estimate area and depth of damage caused by the penetrating rock, in order to select geometry of a filler and impermeable layer of 2nd protection barrier.

Open access

P. Chabera, A. Boczkowska, A. Morka, T. Niezgoda, A. Oziębło and A. Witek

Abstract

The paper presents numerical and experimental results in the study of composite armour systems for ballistic protection. The modelling of protective structures and simulation methods of experiment as well as the finite elements method were implemented in LS DYNA software. Three armour systems with different thickness of layers were analyzed. Discretization for each option was built with three dimensional elements guaranteeing satisfactory accuracy of the calculations. Two selected armour configurations have been ballistically tested using the armour piercing (AP) 7.62 mm calibre. The composite armour systems were made of Al2O3 ceramics placed on the strike face and high strength steel as a backing material. In case of one ballistic structure system an intermediate ceramic- elastomer layer was applied. Ceramic- elastomer composites were obtained from porous ceramics with porosity gradient using pressure infiltration of porous ceramics by elastomer. The urea-urethane elastomer, as a reactive liquid was introduced into pores. As a result composites, in which two phases were interconnecting three-dimensionally and topologically throughout the microstructure, were obtained. Upon ballistic impact, kinetic energy was dissipated by ceramic body The residual energy was absorbed by intermediate composite layer. Effect of the composite shell application on crack propagation of ceramic body was observed.

Open access

Catalina Raluca Mocanu and Liviu Valentin Balanescu

Abstract

To reduce the negative effects of eutrophication processes in water bodies it is necessary to improve water quality by ensuring the necessary oxygen concentration. The paper proposes a new innovative solution for the improvement of lake water quality. The premises for the implementation of the experimental floating platform which will aerate the lake waters will be presented. To give a specific view over the oxygen dispersion into the lake, numerical simulations in CFD software will be presented in different cases.

The protection of drinking water resources against pollution is a common task of outstanding importance for the water management and environment protection sectors. To prevent water supply problems arising from the short and medium-term quality deterioration of resources caused by pollution incidents, it is vital to develop methods for monitoring the quality of resources as well as methods for monitoring and predicting serious pollution events to protect water users. In the case of vulnerable drinking water resources, the establishment and maintenance of an early warning monitoring system is important. Emergency treatment technologies are also needed by the waterworks to treat the water for periods when the quality of the water has temporarily deteriorated.

Innovative solutions for the improvement of water quality consist in using a floating platform equipped with aeration systems. The equipment used to aerate the lake waters is powered by the area renewable energy (solar, wind). So, this platform can be used in isolated area, where there is no energy supply from the national network.

Open access

Krzysztof Wacławiak and Sylwester Kalisz

Abstract

Widely used CFD codes enable modelling of PC boilers operation. One of the areas where these numerical simulations are especially promising is predicting deposition on heat transfer surfaces, mostly superheaters. The basic goal of all simulations is to determine trajectories of ash particles in the vicinity of superheater tubes. It results in finding where on the surface the tube will be hit by particles, and what diameter and mass flow of the particles are. This paper presents results of CFD simulations for a single tube and a bundle of in-line tubes as well. It has been shown that available parameters like ash particle density, shape factor, reflection coefficients affect the trajectories in a different way. All the simulations were carried out with Fluent code of Ansys software.

Open access

Mária Čarnogurská, Miroslav Příhoda, René Pyszko, Ľubomíra Širillová and Ján Palkóci

Abstract

This paper presents the results of research focused on the lowering of ash flow temperature at semianthracite coal from Donbas district by means of additive (calcite) dosing. Ash fusion temperatures were set for two coal samples (A, B) and for five various states (samples of ash without any additives, with 1%, with 3%, with 5% and with 7% of the additive) in total. The macroscopicphotographic method was used for identifying all specific temperatures. Obtained outputs prove that A type coal has a lower value of sphere temperature than B type coal in the whole scope of percentage representation of the additive. The flow temperature dropped in total from 1489 °C to 1280 °C, i.e. by 14% during the test of coal of type A with 7% of the additive; while it was near 10% for coal of type B (from 1450 °C to 1308 °C). Numerical simulations of the process showed that it is not effective to add an additive with a grain size lower than 280 μm by means of wastevapour burners.

Open access

Janusz Ćwiklak

Abstract

The aim of this article is to present findings of simulation research of a stork impact with a helicopter windshield. Besides we developed a numerical model of the stork, based on biometrical data, taking into account various properties of its head, neck, torso and wings. It appears that the research findings which take into consideration the bird’s shape differ from those using a simplified bird model in the shape of a cylinder or a sphere. In order to conduct an analysis of a bird impact onto an aircraft windshield, we used the LS_DYNA software package. In the classic variant with the 3.6 kg bird model, cylinder-shaped with spherical endings, the windshield became damaged at the velocity of 200 km/h for a standard windshield (3.81 mm). For the same velocity, we conducted simulation which used the multimaterial model. It appeared that the windshield did not become damaged. Therefore, the shape of the dummy bird also affects the velocity at which the damage occurs. Too wide simplification of the dummy bird shape may lead to lowered values of the velocity.

Open access

Hou-lin Liu, Jian Wang, Yong Wang, Hua Zhang and Haoqin Huang

Abstract

The phenomenon of cavitation is an unsteady flow, which is nearly inevitable in pump. It would degrade the pump performance, produce vibration and noise and even damage the pump. Hence, to improve accuracy of the nu¬merical prediction of the pump cavitation performance is much desirable. In the present work, a homogenous model, the Zwart-Gerber-Belamri cavitation model, is considered to investigate the influence of the empirical coefficients on predicting the pump cavitation performance, concerning a centrifugal pump. Three coefficients are analyzed, namely the nucleation site radius, evaporation and condensation coefficients. Also, the experiments are carried out to validate the numerical simulations. The results indicate that, to get a precise prediction, the approaches of declining the initial bubble radius, the condensation coefficient or increasing the evaporation coefficient are all feasible, especially for de¬clining the condensation coefficient, which is the most effective way.

Open access

Dongqiao Zhang, Yajun Yin, Jianxin Zhou and Zhixin Tu

Abstract

Eutectoid growth, as the important reaction mechanism of the carbon steel heat treatment, is the basis to control the microstructure and performance. At present, most studies have focused on lamellar growth, and did not consider the nucleation process. Mainly due to the nucleation theory is inconclusive, a lot of research can support their own theory in a certain range. Based on the existing nucleation theory, this paper proposes a cooperative nucleation model to simulate the nucleation process of eutectoid growth. In order to ensure that the nucleation process is more suitable to the theoretical results, different correction methods were used to amend the model respectively. The results of numerical simulation show that when the model is unmodified, the lateral growth of single phase is faster than that of longitudinal growth, so the morphology is oval. Then, the effects of diffusion correction, mobility correction and ledges nucleation mechanism correction on the morphology of nucleation and the nucleation rate were studied respectively. It was found that the introduction of boundary diffusion and the nucleation mechanism of the ledges could lead to a more realistic pearlite.

Open access

J. Adamus and P. Lacki

In the paper the results of investigation of sheet-titanium forming with flexible tool are presented. Titanium alloy sheets belong to a group of materials which are very hard to deform at ambient temperature. To improve sheet formability forming technology using a semi-flexible tool was implemented. Experiments were carried out on a specially designed for this purpose device. Due to the application of a rubber pad the stress state similar to triaxial compression was produced in the deformed material. Such a stress state made it possible to obtain higher material deformation without risk of fracture. The numerical simulations were used for analysing the flexible forming process. The ADINA System basing on the Finite Element Method (FEM) was applied.