This thesis covers the design and the construction of vehicle, which is powered by pressured fluid. The vehicle has driving system based on mechanical – hydraulic recuperation of kinetic energy during braking of vehicle. Her secondary part is used only by the start of vehicles. The thesis describes possibilities of kinetic energy recovery and in more detail explaines kinetic energy recovery with use of hydraulic systems and their practice use. The main part of the thesis contains a design of hydromobil with demonstration of individual options in outline. The selection of the whole hydraulic connection and transmission is described in detail as well as the construction of particular components of the vehicle.

This diploma thesis deals with the structural design of a vehicle powered by pressure fluid that is stored in a hydraulic-pneumatic accumulator. The first part described the types of energy recovery, especially hydraulic recovery. Furthermore there are outlined basic parameters of the design of the vehicle driving mechanism. The second part describes the design of hydromobile with emphasis on the chassis, especially the driving and braking system. Additional information on the individual parts of the chassis, that are put through the stress analysis. The final part deals with the actual manufacturing of the hydromobile and is followed by the resume of the thesis.

This thesis report aims to help the client developing their new product. The new product to be developed is a safety bracket for a safety system. The safety bracket connects different parts which create the safety system and it should be able to withstand impacts from moving objects. The client has a set of requirements that needs to be addressed during the product development process. One of the most important requirements that must be fulfilled is the given impact energy that the safety bracket must withstand. The methodology used during this thesis work is the product development processes (PDP). The product development process is used to find concepts that have the potential to answer the research questions and to fulfil the requirements. Some methods used in the product development process are brainstorming, brainwriting and combining working principles. The concepts were evaluated with a combination of Pugh´s matrix and weighting matrix. The three best concepts were selected for further development and tested with FEA simulation with Abaqus CAE. The impact simulation gave indications if the concepts could handle the impact energy and if they could fulfil the requirements. All three concepts could withstand the impact energy based on the simulations and most of the requirements could be fulfilled. The concepts with thinner profile walls had a reduction in stress and an increase in impact duration, where the kinetic energy is distributed throughout the impact. A protective shell helps with the reduction of stress and the energy absorption during the impact simulation.

L’urbanisation croissante fait émerger des enjeux sociétaux et environnementaux relatifs à la pollution atmosphérique et au microclimat urbain. La compréhension des phénomènes physiques de transport de quantité de mouvement, de chaleur et de masse entre la canopée urbaine et la couche limite atmosphérique est primordiale pour évaluer et anticiper les impacts négatifs de l’urbanisation. Les processus turbulents spécifiques à la couche limite urbaine sont étudiés par une approche de simulation des grandes échelles, dans une configuration urbaine représentée par un arrangement de cubes en quinconce. Le modèle de sous-maille de type Smagorinsky dynamique est implémenté pour mieux prendre en compte l’hétérogénéité de l’écoulement et les retours d’énergie des petites vers les grandes structures. Le nombre de Reynolds basé sur la hauteur du domaine et la vitesse de l’écoulement libre est de 50000. L’écoulement est résolu dans les sous-couches visqueuses et le maillage est raffiné dans la canopée. Le domaine est composé de 28 millions de cellules. Les résultats sont comparés à la littérature et aux données récentes obtenues dans la soufflerie du LHEEA. Chaque contribution au bilan d’énergie cinétique turbulente est calculée directement en tout point. Cette information, rare dans la littérature, permet d’étudier les processus dans la sous couche rugueuse. Grâce à ces résultats 3D, l’organisation complexe de l’écoulement moyen (recirculations, vorticité, points singuliers) est analysée en relation avec la production de turbulence. Enfin, une simulation où les obstacles sont remplacés par une force de traînée équivalente est réalisée à des fins d’évaluation de cette approche. / The rapid development of urbanization raises social and environmental challenges related to air pollution and urban climate. Understanding the physical processes of momentum, heat, and mass exchanges between the urban canopy and the atmospheric boundary-layer is a key to assess,predict and prevent negative impacts of urbanization. The turbulent processes occurring in the urban boundary-layer are investigated using computational fluid dynamics (CFD). The unsteady flow over an urban-like canopy modelled by a staggered arrangement of cubes is simulated using large eddy simulation (LES). Considering the highspatial and temporal in homogeneity of the flow, a dynamic Smagorinsky subgrid-scale model is implemented in the code to allow energyback scatter from small to large scales. The Reynolds number based on the domain height and free-stream velocity is 50000. The near-wall viscous sub-layers are resolved and the grid is refined in the canopy resulting in about 28 million grid cells. LES results are assessed by comparison with literature and data recently acquired in the wind tunnel of the LHEEA. The turbulent kinetic energy budget in which all contributions are independently computed is investigated. These rarely available data are used to analyse the turbulent processes in the urban canopy. By taking advantage of the three-dimensionality of the simulated flow, the complex 3D time-averaged organization of the flow (recirculation, vorticesor singular points) is analyzed in relation with production of turbulence. Finally a drag approach where obstacles are replaced by an equivalent drag force is implemented in the same domain and results are compared to obstacle-resolved data.

The analytical modelling of complex turbulent airflow remains one of the great unsolved mysteries of physics, but in this paper two widely used Reynolds Averaged Navier-Stokes models (k-$\epsilon$ and k-$\omega$ SST) are compared while designing a heat exchanger for the KTH Formula Student electric race car. CAD software was used to design lattices for the heat exchanger core and theorise about how to increase heat transfer while also taking into account the utilisation of metal additive manufacturing. The models were then analysed using Computational Fluid Dynamics to determine their characteristics as well as the effects of the two turbulence models.  It was found that the first iteration of the second design performed best in terms of pressure drop and generating turbulent kinetic energy closely followed by the second iteration of the second design and the second iteration of the first design. When comparing the turbulence models the results indicated agreement with their theoretical foundations. The first model overestimating turbulent kinetic energy relative to the second, which picked up more detail of near-wall turbulence thanks to better boundary layer formulation. Future work includes improving the simulation setup, correlating the results with wind tunnel testing and further evaluating more complex designs.

Modeling the effects of surface roughness is an area of concern in many practical engineering applications. Many current roughness models to this point have involved the use of empirical 'constants' and equivalent sand grain roughness. These underdeveloped concepts have little direct relationship to realistic roughness and cannot predict accurately and consistently the flow characteristics for different roughness shapes. In order to aid in the development of turbulence models, the present research is centered around the experimental investigation of seven various shaped single roughness elements and their effects on turbulence quantities in a two-dimensional turbulent boundary layer. The elements under scrutiny are as follows: cone, cone with spatial variations equal to the smallest sublayer structure length scale, cone with spatial variations equal to 2.5 times the smallest sublayer structure length scale, Gaussian-shaped element, hemisphere, cube aligned perpendicular to the flow (cube at 90°), and a cube rotated 45° relative to the flow. The roughness element heights, k+, non-dimensionalized by the friction velocity (U_tau) of the approaching turbulent boundary layer, are 145, 145, 145, 145, 80, 98, and 98 respectively. Analysis of a three-dimensional fetch of the same Gaussian-shaped elements described previously was also undertaken. In order to analyze the complex flow fields, detailed measurements were obtained using a fine-measurement-volume (50 micron diameter) three-velocity component laser-Doppler velocimetry (LDV) system. The data reveals the formation of a horseshoe vortex in front of the element, which induces the downwash of higher momentum fluid toward the wall. This 'sweep' motion not only creates high Reynolds stresses (v^2, w^2, -uv) downstream of the element, but also leads to higher skin-friction drag. Triple products were also found to be very significant near the height of the element. These parameters are important in regards to the contribution of the production and diffusion of the turbulent kinetic energy in the flow. The 'peakiness' of the roughness element was found to have a direct correlation to the production of circulation, whereas the spatial smoothing does not have an immense effect on this parameter. The peaked elements were found to have a similar trend in the decay of circulation in the streamwise direction. These elements tend to show a decay proportional to (x/d)^-1.12, whereas the cube elements and the hemisphere do not have a common trend. A model equation is proposed for a drag correlation common to all roughness elements. This equation takes into account the viscous drag and pressure drag terms in the calculation of the actual drag due to the roughness elements presence in the boundary layer. The size, shape, frontal and wetted surface areas of the roughness elements are related to one another via this model equation. Flow drawings related to each element are presented which gives rise to a deeper understanding of the physics of the flow associated with each roughness element. / Master of Science

No description available.

The bifunctional formalism presents an alternative how to obtain the functional value from its functional derivative by exploiting homogeneous density scaling. In the bifunctional formalism the density dependence of the functional derivative is suppressed. Consequently, those derivatives have to be treated as formal functional derivatives. For a pointwise correspondence between the true and the formal functional derivative, the bifunctional expression yields the same value as the density functional. Within the bifunctional formalismthe functional value can directly be obtained fromits derivative (while the functional itself remains unknown). Since functional derivatives are up to a constant uniquely defined, this approach allows for a pointwise comparison between approximate potentials and reference potentials. This aspect is especially important in the field of orbital-free density functional theory, where the burden is to approximate the kinetic energy. Since in the bifunctional approach the potential is approximated directly, full control is given over the latter, and consequently over the final electron densities obtained from variational procedure. Besides the bifunctional formalismitself another concept is introduced, dividing the total non-interacting kinetic energy into a known functional part and a remainder, called Pauli kinetic energy. Only the remainder requires further approximations. For practical purposes sufficiently accurate Pauli potentials for application on atoms, molecular and solid-state systems are presented.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this study, using the Method of Characteristics and numeric resources, presents a solution to the equation Spectral Density Evolution of Turbulent Kinetic Energy for a Convective Boundary Layer (CBL) in the morning. It presents three models for the evolution of spectral energy density. The first model, based on the assumption of a system of isotropic turbulence, considering only terms of energy transfer inertial and viscous dissipation. The second model adds the term energy production due to the onset of action of the parameter of heat flux on the surface, but consider it a term of energy transfer inertial anisotropy. The third model employs a mixed configuration of the two previous models, assuming thus distinct regions of operation to inertial transfer terms. The results shaped the evolution of the CLC. In this case, the growth of the energy spectrum is modeled by inserting energy in the region of low wave numbers, a region in which the term of anisotropic energy transfer can not transfer the energy introduced by the energy production term. It is observed that in a region of wave number higher there is a stabilization of the parameter variation temporal on the plane characteristics curves (PCC), indicating that the variation of wave number govern the evolution of the energy spectrum. This fact establishes a kind of criterion for stationarity of turbulent flow regimes. / No presente trabalho, utilizando o Método das Característica e recursos numéricos, apresenta-se uma solução para a Equação de Evolução Espectral de Densidade de Energia Cinética Turbulenta para uma Camada Limite Convectiva (CLC) no período da manhã. Apresenta-se três modelos para a evolução espectral da densidade de energia. O primeiro modelo, baseado na suposição de um regime de turbulência isotrópica, considera apenas termos de transferência de energia inercial e de dissipação viscosa. O segundo modelo adiciona o termo de produção de energia devido o início da ação do parâmetro de fluxo de calor na superfície, porém considerá-se um termo de transferência de energia inercial anisotrópico. O terceiro modelo emprega uma configuração mista dos dois modelos anteriores, admitindo, desta forma, regiões distintas de atuação para os termos de transferência inercial. Os resultados obtidos modelaram a evolução da CLC. Neste caso, o crescimento do espectro de energia modelado se deu pela inserção de energia na região de baixos números de onda, região em que o termo de transferência de energia anisotrópico não consegue transferir a energia inserida pelo termo de produção de energia. Observa-se que em uma região de número de onda mais alto existe uma estabilização da variação do parâmetro temporal sobre as curvas características planas (CCP), indicando que a variação do número de onda governará a evolução do espectro de energia. Fato que estabelece um tipo de critério de estacionariedade para de regimes de escoamento turbulento.

Les rendements de fission sont des données importantes pour les applications nucléaires ainsi que pour les modèles théoriques qui cherchent à reproduire ces distributions. Les rendements des produits de fission légers pour de nombreux noyaux ont été mesurés par le passé sur le spectromètre Lohengrin. Mais la méthode expérimentale utilisée, détection par chambre à ionisation, ne permet pas la séparation des isotopes pour les produits de fission lourds. Pour valider la méthode dans cette région et compléter les bibliothèques, les rendements isobariques de l’235U(nth,f), du 239Pu(nth,f) et du 241Pu(nth,f) ont été mesurés. La mise en place d’un nouveau dispositif de détection gamma sur le spectromètre a permis de déterminer les rendements isotopiques du 239Pu(nth,f). De plus les distributions en charge ionique et en énergie cinétique des produits de fission ont été étudiées, et ont mis en évidence la présence d'isomères nanosecondes pour certains de ces noyaux. / In spite of the huge amount of fission yield data available in different libraries, more accurate values are still needed for nuclear energy applications and to improve our understanding of the fission process. Thus measurements of fission yields were performed at the mass spectrometer Lohengrin at the Institut Laue-Langevin in Grenoble, France. The mass separator Lohengrin is situated at the research reactor of the institute and permits the placement of an actinide layer in a high thermal neutron flux. It separates fragments according to their atomic mass, kinetic energy and ionic charge state by the action of magnetic and electric fields. Coupling with a high resolution ionization chamber the experiment was used to investigate the mass and isotopic yields in the light mass region. Almost all fission yields of isotopes from Th to Cf have been measured at Lohengrin with this method. It has been extended in this work to the heavy mass region for the reactions 235U(nth,f), 239Pu(nth,f) and 241Pu(nth,f). For these higher masses an isotopic separation is no longer possible. That is why a new method was undertaken with the reaction 239Pu(nth,f) to determine the isotopic yields by gamma spectrometry. During these experiments the ionic charge state and kinetic energy distributions have been measured. Nanosecond isomers have been discovered for some nuclei thanks to a non gaussian charge state distribution. The kinetic energy distributions present very interesting structures which have been also discussed.