Abstract The main theme of this thesis is to discuss the specific conditions of motorcycles participation in traffic. Primarily the author of the processing of statistical data relating to road traffic accidents found the most frequent causes leading to the accident of motorcycles, set out a list of typical hazardous situations and provide an opportunity to prevent them, respectively propose the concrete steps for their reduction, while visual processing is done using by the Virtual CRASH software. Secondarily, it is then processed an overview by modern elements of active and passive safety of motorcycles and their effect on the reduction of traffic accidents, or reduce health risks as the consequences of road traffic accidents. Statistical data are then confronted with the subjective perception of participation in traffic, concretely with motorcycle riders. Their opinions are interpreted by the most frequent responses from the questionnaires, the results are included in the last part of this thesis. The objective of this work is in the comparison of both perspectives - statistical data and the opinions of motorcyclists - about the traffic situation in the Czech Republic. The result of this work is the more realistic view on the issue.

This thesis is focused on the design of passive cooling system for a nuclear reactor VVER- 1000.This type of reactor is located in the Czech Republic in the location of Nuclear power plant Temelín. The thesis states an overview of the different cooling systems of nuclear power plants. The thesis is focused on passive safety system especially on passive cooling system, so there was done an overview of currently used passive safety system. In the work is discussed nuclear safety and the maximum projected accident of VVER-1000, which is called LOCA accident. In the design part of the thesis was done thermal calculation of heat exchangers. Exchangers are designed as condensers with a natural flow, where cooling of system is provided by outside airflow in case an accident. The results are evaluated at the end of the thesis.

Thesis in the field of passive safety problems, traffic accidents and health outcomes of participants in road traffic accidents is aimed, inter alia, to create an overview of modern passive safety elements especially cars. The work deals with elements of the passive safety system and the impact on the crew vehicle. It describes the principle of operation, especially airbags, safety belts, belt pretensioner and it includes solution of limiters tensioning force in the safety belt and other elements that have the task of reducing the consequences of a traffic accident. The use of modern elements of passive safety provides increased protection for the crew and eliminates the formation injuries crew. The technical issue is therefore closely related to the healthcare industry and in particular the Court of medicine in the field of personal injury in relation to the types and characters of incidents, or by applying of the safety elements. There are also shown the actual road accidents in which were killed or injured members of crew with an analysis of the mechanism of injury with the use or non-use of safety elements.

Passive safety systems try to lessen the effects of an accident. Airbags are a passive safety feature. They are designed to protect occupants of a vehicle during a crash. These systems have to be configured correctly in order to deploy airbags at the right time in case of a collision. Airbag application tools are used to simulate and interpret crashes. Some factors influence when an airbag should deploy. Based on different parameters, the logic for firing airbags is also different. Under every circumstance, an airbag has to be deployed at the right time in order to prevent injuries and fatalities. During the process of simulation, the data which is simulated is written to a database. During interpretation, this data is extracted from the database. Then, the required information can be analyzed and interpreted for further use. This data contains crash related information. For example, the type of crash, crash code and crash channel assignments. For every crash present in the airbag project, crash channels are assigned to the sensors. Each sensor present has a crash channel assigned to it. This is called the crash channel assignment. An airbag application tool is developed to show the crash channel assignments. This tool should handle the information extraction, and visualization of crash channel assignments. The final output should be in a tabular format, which includes user specific customizations.

La sécurité routière est un enjeu majeur de santé publique et de protection des personnes. D'après l'organisation mondiale de la santé (OMS), près de 1,2 millions de personnes meurent chaque année dans le monde suite à des accidents de la route (2015). D’après des données accidentologiques, 36,7% des blessures graves ont pour origine des lésions au thorax (Page et collab., 2012). La biomécanique en sécurité passive a pour rôle d'améliorer notre compréhension du corps humain dans le but de construire de meilleurs outils pour évaluer le risque de blessure.Les modèles numériques d'être humain sont employés pour simuler virtuellement les conditions d'un accident. Aujourd'hui, ils sont de plus en plus utilisés par les constructeurs automobiles et équipementiers pour mieux comprendre les mécanismes lésionnels. Cependant, ils n’existent que dans certaines tailles et ne prennent alors pas en compte les variations morphologiques observées dans la population.L'imagerie médicale 3D donne accès aux géométries des différentes structures anatomiques composant le corps humain. Les hôpitaux regorgent aujourd'hui de quantités d'images 3D couvrant une très large partie de la population en termes d'âge, de corpulence et de sexe.L’objectif global de cette thèse est de modéliser statistiquement la géométrie 3D de la cage thoracique à partir d'images médicales afin de personnaliser un modèle numérique de corps humain pour simuler par éléments finis des conditions de choc automobile. Le premier objectif est d’élaborer un protocole de segmentation une base de CT-scans de manière à obtenir des données géométriques adaptées à la construction d’un modèle statistique de forme de la cage thoracique.Le deuxième objectif est de construire un modèle statistique de forme de la cage thoracique, en prenant en compte sa structure articulée.Le troisième objectif est d’utiliser le modèle statistique de la cage thoracique pour déformer un modèle numérique d’être humain, de manière à étudier l’influence de certains paramètres sur le risque de blessure. / Road safety is a major issue of public health and personal safety. According to the World Health Organization (WHO), nearly 1.2 million people die each year worldwide due to road accidents (2015). According to accident data, 36.7% of serious injuries are caused by thoracic injuries (Page et al., 2012). The aim of biomechanics in passive safety is to improve our understanding of the human body in order to build better tools for assessing the risk of injury.Numerical human body models are used to virtually simulate the conditions of an accident. Today, they are increasingly used by car manufacturers and equipment manufacturers to better understand injury mechanisms. However, they exist only in few sizes and do not take into account the morphological variations observed in the population.3D medical imaging gives access to the geometries of the different anatomical structures that make up the human body. Today, hospitals are full of 3D images covering a very large part of the population in terms of age, body size and sex.The overall objective of this thesis is to statistically model the 3D geometry of the rib cage from medical images in order to personalize a numerical human body model to simulate car crash conditions.The first objective is to develop a segmentation process based on CT-scans in order to obtain geometric data adapted to the construction of a statistical model of shape of the rib cage.The second objective is to build a statistical model of the shape of the rib cage, taking into account its articulated structure.The third objective is to use the statistical model of the rib cage to deform a numerical human body model, in order to study the influence of certain parameters on the risk of injury.

The safety performance of nuclear power reactors is a very important factor in evaluating nuclear energy sustainability. Improving the safety performance of nuclear reactors can enhance nuclear energy sustainability as it will improve the environmental indicator used to evaluate the overall sustainability of nuclear energy. Great interest is given now to advanced nuclear reactors especially those using passive safety components. Investigation of the improvement in nuclear safety using advanced reactors was done by comparing the safety performance of a conventional reactor which uses active safety systems, such as Pressurized Water Reactor (PWR), with an advanced reactor which uses passive safety systems, such as AP1000, during a design basis accident, such as Loss of Coolant Accident (LOCA), using the PCTran as a simulation code. To assess the safety performance of PWR and AP1000, the “Global Safety Index” GSI model was developed by introducing three indicators: probability of accident occurrence, performance of safety system in case of an accident occurrence, and the consequences of the accident. Only the second indicator was considered in this work. A more detailed model for studying the performance of passive safety systems in AP1000 was developed. That was done using SCDAPSIM/RELAP5 code as it is capable of modelling design basis accidents (DBAs) in advanced nuclear reactors.

This dissertation describes the issue of a complex system for analyzing the collision of a motorcycle with another vehicle and suggests a suitable methodology for solving this type of traffic accident. It summarizes the current knowledge in the field of motorcycle accidents withother vehicles, including their statistics and categorization. The author statistically evaluates accidents by their causes and proposes a methodology for solving individual types of motorcycle collisions with vehicles. To supplement and refine the input data for the analysis of road accidents involving motorcycles, a set of author’s own measurements made on different types of motorcycles is included. The thesis contains measurements of their acceleration, deceleration and avoidance maneuvers. Other actual contributions of the thesis are represented also by flowcharts, offering a comprehensive approach to solving individual types of colissions of motorcycles with other vehicles.

This diploma thesis deal with safety components of trailer and semitrailer technology, especially the elements for underrun protection. The first part deals with the legislative requirements on which safety elements are based. In another part are mentioned the construction solutions of underrun protection devices from the portfolio of company SVAN Chrudim s.r.o. Finally, the computational part is processed to verify sufficient strength of underpass protections.

This master thesis deals with the strain, stress and reliability analysis of the safety frame of racing car. The safety frame is a part of passive safety, which it becomes active in a case of impact. The safety frame makes a reinforcement of the car body and provides its sufficient stiffness. The first part of the master thesis is focused on determination of stress and strain states during the static loading tests and their analysis. The loading conditions are prescribed by homologation regulations of Fédération Internationale de l´Automobile (FIA). The problem is solved, making use of computational modeling utilizing the Finite Element Method (FEM). The first part of thesis is used for the stiffness and safety analysis under the static loading test. The second part deals with the effect of loading velocity on the stress and strain states using the computational modeling and solver LS-DYNA.

Safe and reliable operation of nuclear power plants is the basic requirement for the utilization of nuclear energy since accidents can release radioactivity and with that cause irreversible damage to human beings. Reliability and safety of nuclear reactors are highly dependent on the stability of thermal hydraulic processes occurring in them. Nucleate boiling occurs in Pressurized Water Reactors (PWRs) and Boiling Water Reactors (BWRs) as well as in their passive safety systems during an accident. Passive safety systems are solely driven by thermal gradients and gravitational force removing residual heat from the reactor core independent of any external power supply in the case of accidents. Instability of flow boiling in these passive circuits can cause flow oscillations. These oscillations may induce insufficient local cooling and mechanical loads, which threatens the reactors’ safety. Analysis of boiling two-phase flow and associated heat and mass transfer requires an accurate modeling of flow regime transitions and prediction of boiling parameters such as void fraction, steam bubble sizes, heat transfer coefficient, etc. Flow boiling has been intensively investigated through experiments, one-dimensional codes, and Computational Fluid Dynamics (CFD) methods. Costly hardware and no accessibility to all locations in complex geometries restrict the experimental investigation of flow boiling. Since one-dimensional codes such as ATHLET, RELAP and TRACE are ”lumped parameter” codes, they are unable to simulate complex flow boiling transition patterns. In the last decades, with the development of supercomputers, CFD has been considered as a useful tool to model heat and mass transfer occurring in flow boiling regimes. In many industrial applications and system designs, CFD codes and particularly the Eulerian-Eulerian (E-E) two-fluid model are quickly replacing the experimental and analytical methods. However, the application of this approach for flow boiling modelling poses a challenge for the development of bubble dynamics and wall boiling models to predict heat and mass transfer at the heating wall as well as phase-change mechanism. Many empirical and mechanistic models have been proposed for bubble dynamics modelling. Nevertheless, the validity of these models for only a narrow range of operating conditions and their uncertainties limit their applicability and consequently presently necessitate us to calibrate them for a given boundary condition via calibration factors. For that reason, the first aim of this thesis is the development of a bubble dynamics model for subcooled boiling flow, which needs no calibration factor to predict the bubble growth and detachment. This mechanistic model is formulated based on the force balance approach, physics of a single nucleated bubble and several well-developed models to cover the whole bubble life cycle including formation, growth and departure. This model considers dynamic inclination angle and contact angles between the bubble and the heating wall as well as the contribution of microlayer evaporation, thermal diffusion and condensation around the bubble cap. Validation against four experimental flow boiling data sets was conducted with no case-dependent recalibration and yielded good agreement. The second goal is the implementation of the developed bubble dynamics model in the E-E two-fluid model as a sub-model to improve the accuracy of boiling flow simulation and reduce the case dependency. This implementation requires an extension of the nucleation site activation and wall heat-partitioning models. The bubble dynamics and heat-partitioning models were coupled with the Population Balance Model (PBM) to handle bubble interactions and predict the Bubble Size Distribution (BSD). In addition, the contribution of bubble sliding to wall heat transfer, which has been rarely considered in other modelling approaches, is considered. Validation for model implementation in the E-E two-fluid model was made with ten experimental cases including R12 and R134a flow boiling in a pipe and an annulus. These test cases cover a wide range of operating parameters such as wall heat flux, fluid velocity, subcooling temperature and pressure. The validated parameters were the bubble diameter, void fraction, bubble velocity, Interfacial Area Density (IAD), bubble passing frequency, liquid and wall temperatures. Two-phase flow morphologies for an upward flow in a vertical heating pipe may change from bubbly to slug, plug, and annular flow. Since these flow patterns have a great impact on the heat and mass transfer rates, an accurate prediction of them is critical. The aim of this thesis is the implementation of the developed bubble dynamics and heat-partitioning models in the recently developed GENeralized TwO-Phase flow (GENTOP) framework for the modelling of these flow patterns transition as well. An adopted wall heat-partitioning model for high void fractions is presented and for a generic test case, flow boiling regimes of water in a vertical heating pipe were modelled using ANSYS CFX 18.2. Moreover, the impacts of wall superheat, subcooling temperature and fluid velocity on the flow boiling transition patterns and the effects of these patterns on the wall heat transfer coefficient were evaluated.:Nomenclature xi 1 Introduction 1 1.1 Background and motivation . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.3 Outline of the thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2 State-of-the-art in modelling of subcooled flow boiling 11 2.1 Physics of boiling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2 Bubble growth modelling . . . . . . . . . . . . . . . . . . . . . . . . 15 2.3 CFD simulation of boiling flows . . . . . . . . . . . . . . . . . . . . . 21 2.3.1 The Eulerian-Eulerian two-fluid model . . . . . . . . . . . . . 21 2.3.2 The Population Balance Model (PBM) . . . . . . . . . . . . . 22 2.3.3 Governing equations of the two-fluid model . . . . . . . . . . 25 2.3.4 Closure models for adiabatic bubbly flow . . . . . . . . . . . . 28 2.3.5 Phase transfer models . . . . . . . . . . . . . . . . . . . . . . 37 2.3.6 The Rensselaer Polytechnic Institute (RPI) wall boiling model 37 2.4 Flow boiling transition patterns in vertical pipes . . . . . . . . . . . . 42 2.5 The GENeralized TwO-Phase flow (GENTOP) concept . . . . . . . . . 45 2.5.1 Treatment of the continuous gas . . . . . . . . . . . . . . . . 46 2.5.2 The Algebraic Interfacial Area Density (AIAD) model . . . . . 46 2.6 Interfacial transfers of continuous gas . . . . . . . . . . . . . . . . . 47 2.6.1 Drag and lift forces . . . . . . . . . . . . . . . . . . . . . . . . 48 2.6.2 Cluster and surface tension forces . . . . . . . . . . . . . . . . 49 2.6.3 Complete coalescence . . . . . . . . . . . . . . . . . . . . . . 50 2.6.4 Entrainment modelling . . . . . . . . . . . . . . . . . . . . . . 51 2.6.5 Turbulence modelling . . . . . . . . . . . . . . . . . . . . . . 51 2.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 3 An improved bubble dynamics model for flow boiling 55 3.1 Modelling of the bubble formation . . . . . . . . . . . . . . . . . . . 55 3.1.1 Bubble growth rate . . . . . . . . . . . . . . . . . . . . . . . . 57 3.1.2 Force balance . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 ix 3.1.3 Detachment criteria . . . . . . . . . . . . . . . . . . . . . . . 63 3.1.4 Wall heat flux model . . . . . . . . . . . . . . . . . . . . . . . 69 3.1.5 Heat transfer in the heating wall . . . . . . . . . . . . . . . . 70 3.2 Results and discussions . . . . . . . . . . . . . . . . . . . . . . . . . . 72 3.2.1 Discretization dependency study . . . . . . . . . . . . . . . . 72 3.2.2 Model validation . . . . . . . . . . . . . . . . . . . . . . . . . 72 3.2.3 Sensitivity analysis . . . . . . . . . . . . . . . . . . . . . . . . 79 3.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4 An improved wall heat-partitioning model 85 4.1 The cavity group activation model . . . . . . . . . . . . . . . . . . . . 85 4.1.1 Bubble sliding length and influence area . . . . . . . . . . . . 88 4.1.2 Model implementation in the Eulerian-Eulerian framework . . 89 4.2 Results and discussions . . . . . . . . . . . . . . . . . . . . . . . . . . 90 4.2.1 DEBORA experiments . . . . . . . . . . . . . . . . . . . . . . 90 4.2.2 Subcooled flow boiling of R134a in an annulus . . . . . . . . 102 4.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 5 Modelling of flow boiling patterns in vertical pipes 115 5.1 Adopted wall heat-partitioning model for high void fractions . . . . . 115 5.2 Results and discussions . . . . . . . . . . . . . . . . . . . . . . . . . . 118 5.2.1 Effect of wall superheat on the flow boiling transition patterns 118 5.2.2 Effect of flow morphologies on the wall heat transfer coefficient124 5.2.3 Comparison of GENTOP and Eulerian-Eulerian two-fluid models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 5.2.4 Effect of subcooling on the flow boiling transition patterns . . 129 5.2.5 Effect of inlet fluid velocity on the flow boiling transition patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 5.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 6 Conclusions and outlook 133 6.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 6.2 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 References 137 Declaration 155