Numerical and experimental investigations for insulation particle transport phenomena in water flow

The investigation of insulation debris generation, transport and sedimentation becomes more important with regard to reactor safety research for pressurized and boiling water reactors, when considering the long-term behaviour of emergency core coolant systems during all types of loss of coolant accidents (LOCA). The insulation debris released near the break during a LOCA incident consists of a mixture of a disparate particle population that varies with size, shape, consistency and other properties. Some fractions of the released insulation debris can be transported into the reactor sump, where it may perturb or impinge on the emergency core cooling systems. Open questions of generic interest are for example the particle load on strainers and corresponding pressure-drop, the sedimentation of the insulation debris in a water pool, its possible re-suspension and transport in the sump water flow. A joint research project on such questions is being performed in cooperation with the University of Applied Science Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation and the development of computational fluid dynamic (CFD) models for the description of particle transport phenomena in coolant flow. While the experiments are performed at the University Zittau/Görlitz, the theoretical work is concentrated at Forschungszentrum Dresden-Rossendorf. In the present paper, the basic concepts for computational fluid dynamic (CFD) modelling are described and experimental results are presented. Further experiments are designed and feasibility studies were performed.

Towards a practical implementation of coherent WDM:analytical, numerical, and experimental studies

Future optical networks will require the implementation of very high capacity (and therefore spectral efficient) technologies. Multi-carrier systems, such as Orthogonal Frequency Division Multiplexing (OFDM) and Coherent WDM (CoWDM), are promising candidates. In this paper, we present analytical, numerical, and experimental investigations of the impact of the relative phases between optical subcarriers of CoWDM systems, as well as the effect that the number of independently modulated subcarriers can have on the performance. We numerically demonstrate a five-subcarrier and three-subcarrier 10-GBd CoWDM system with direct detected amplitude shift keying (ASK) and differentially/coherently detected (D) phase shift keying (PSK). The simulation results are compared with experimental measurements of a 32-Gbit/s DPSK CoWDM system in two configurations. The first configuration was a practical 3-modulator array where all three subcarriers were independently modulated, the second configuration being a traditional 2-modulator odd/even configuration, where only odd and even subcarriers were independently modulated. Simulation and experimental results both indicate that the independent modulation implementation has a greater dependency on the relative phases between subcarriers, with a stronger penalty for the center subcarrier than the odd/even modulation scheme.

Numerical and experimental analysis of sensitivity-enhanced RI sensor based on Ex-TFG in thin cladding fiber

We report a highly sensitive refractive index (RI) sensor in the aqueous solution, which is based on an 81°-tilted fiber grating structure inscribed into a thin cladding fiber with 40 μm cladding radius. The numerical analysis has indicated that the RI sensitivity of cladding resonance mode of the grating can be significantly enhanced with reducing cladding size. This has been proved by the experimental results as the RI sensitivities of TM and TE resonance peaks in the index region of 1.345 have been increased to 1180 nm/RIU and 1150 nm/RIU, respectively, from only 200 and 170 nm/RIU for the same grating structure inscribed in standard telecom fiber with 62.5-μm cladding radius. Although the temperature sensitivity has also increased, the change in temperature sensitivity is still insignificant in comparison with RI sensitivity enhancement.

Thermal analysis during bone drilling using rigid polyurethane foams: numerical and experimental methodologies

Osteotomy or bone cutting is a common procedure in orthopaedic surgery, mainly in the treatment of fractures and reconstructive surgery. However, the excessive heat produced during the bone drilling process is a problem that counters the benefits of this type of surgery, because it can result in thermal osteonecrosis, bone reabsorption and damage the osseointegration of implants. The analysis of different drilling parameters and materials can allow to decrease the temperature during the bone drilling process and contribute to a greater success of this kind of surgical interventions. The main goal of this study was to build a numerical three-dimensional model to simulate the drilling process considering the type of bone, the influence of cooling and the bone density of the different composite materials with similar mechanical properties to the human bone and generally used in experimental biomechanics. The numerical methodology was coupled with an experimental methodology. The use of cooling proved to be essential to decrease the material damage during the drilling process. It was concluded that the materials with less porosity and density present less damage in drilling process. The developed numerical model proved to be a great tool in this kind of analysis. © 2016, The Brazilian Society of Mechanical Sciences and Engineering.

Hamburg model basin : numerical and experimental investigations on the dependence of the fluctuations of thrust and torque on the blade area ratio of four-blade ship-propellers /

Contract no. N 62558-2223.

Study and experimental characterization of the laser welding process for the manufacturing of electric powertrain components in the automotive industry

The PhD project that will be presented in this thesis is focused on the study and optimization of the production process for the manufacturing of electrical powertrain components in the automotive field using the laser beam welding process (LBW). The objective is to define, through experimental activities, an optimized process condition for applications in the electrical field that can be generalized, that is, which guarantees its reproducibility as the types of connections vary and which represents the basis for extending the method to future applications in e-mobility sector. The work developed along two lines of research, the convergence of which made it possible to create prototypes of battery modules based on different types of lithium-ion cells and stator windings for electric motors. On the one hand, the different welding configurations involving the production of batteries based on pouch cells and therefore the welding of aluminum and copper in dissimilar configuration were studied, while for the prismatic cells only one configuration was analyzed. On the other hand, the welding of pure copper hairpins with rectangular shape in edge joint configuration was studied for the production of stator windings. The experimental tests carried out have demonstrated the feasibility of using the LBW process for the production of electric powertrain components entirely designed and developed internally as the types of materials and welding configurations vary; the methodologies required for the characterization methods, necessary for the end-of-line tests, for the evaluation of the properties of the different joint configurations and components (battery and electric motor) were also defined with the aim of obtaining the best performance. The entire doctorate program was conducted in collaboration with Ferrari Auto S.p.A. and the direct industrial application of the issues addressed has been faced.

Numerical and experimental analysis of 3D printed smart structures and systems

Three dimensional (3D) printers of continuous fiber reinforced composites, such as MarkTwo (MT) by Markforged, can be used to manufacture such structures. To date, research works devoted to the study and application of flexible elements and CMs realized with MT printer are only a few and very recent. A good numerical and/or analytical tool for the mechanical behavior analysis of the new composites is still missing. In addition, there is still a gap in obtaining the material properties used (e.g. elastic modulus) as it is usually unknown and sensitive to printing parameters used (e.g. infill density), making the numerical simulation inaccurate. Consequently, the aim of this thesis is to present several work developed. The first is a preliminary investigation on the tensile and flexural response of Straight Beam Flexures (SBF) realized with MT printer and featuring different interlayer fiber volume-fraction and orientation, as well as different laminate position within the sample. The second is to develop a numerical analysis within the Carrera' s Unified Formulation (CUF) framework, based on component-wise (CW) approach, including a novel preprocessing tool that has been developed to account all regions printed in an easy and time efficient way. Among its benefits, the CUF-CW approach enables building an accurate database for collecting first natural frequencies modes results, then predicting Young' s modulus based on an inverse problem formulation. To validate the tool, the numerical results are compared to the experimental natural frequencies evaluated using a digital image correlation method. Further, we take the CUF-CW model and use static condensation to analyze smart structures which can be decomposed into a large number of similar components. Third, the potentiality of MT in combination with topology optimization and compliant joints design (CJD) is investigated for the realization of automated machinery mechanisms subjected to inertial loads.

Experimental characterization of hydrogen containing flames

The current environmental and socio-economic situation promotes the development of carbon-neutral and sustainable solutions for energy supply. In this framework, the use of hydrogen has been largely indicated as a promising alternative. However, safety aspects are of concern for storage and transportation technologies. Indeed, the current know-how promotes its transportation via pipeline as compressed gas. However, the peculiar properties of hydrogen make the selection of suitable materials challenging. For these reasons, dilution with less reactive species has been considered a short and medium solution. As a way of example, methane-hydrogen mixtures are currently transported via pipelines. In this case, the hydrogen content is limited to 20% in volume, thus keeping the dependence on natural gas sources. On the contrary, hydrogen can be conveniently transported by mixing it with carbon dioxide deriving from carbon capture and storage technologies. In this sense, the interactions between hydrogen and carbon dioxide have been poorly studied. In particular, the effects of composition and operative conditions in the case of accidental release or for direct use in the energy supply chain are unknown. For these reasons, the present work was devoted to the characterization of the chemical phenomena ruling the system. To this aim, laminar flames containing hydrogen and carbon dioxide in the air were investigated experimentally and numerically. Different detailed kinetic mechanisms largely validated were considered at this stage. Significant discrepancies were observed among numerical and experimental data, especially once a fuel consisting of 40%v of hydrogen was studied. This deviation was attributed to the formation of a cellular flame increasing the overall reactivity. Hence, this observation suggests the need for combined models accounting for peculiar physical phenomena and detailed kinetic mechanisms characterizing the hydrogen-containing flames.

Theoretical and experimental study of the thermal degradation of Eucalyptus timber

Thermal action on timber causes it to degrade through combustion of its chemical components, which leads to the release of vapors, combustible gases and surface char. This diminishes its load capacity, due to the reduction of its cross section by charring and to changes in its mechanical properties of strength and stiffness as a function of its exposure to high temperatures. This paper reports the charring rates observed on Eucalyptus structural beams and presents a numerical and experimental study of the behavior of these beams when exposed to fire, in which the properties of strength and stiffness were evaluated as a function of rising temperatures, allowing an analysis of the effect of the section factor on the internal rise in temperature of structural Eucalyptus beams.

Numerical and ExperimentalModelling of Gas Flow and Heat Transfer in the Air Gap of An Electric Machine

This work deals with the cooling of high-speed electric machines, such as motors and generators, through an air gap. It consists of numerical and experimental modelling of gas flow and heat transfer in an annular channel. Velocity and temperature profiles are modelled in the air gap of a high-speed testmachine. Local and mean heat transfer coefficients and total friction coefficients are attained for a smooth rotor-stator combination at a large velocity range. The aim is to solve the heat transfer numerically and experimentally. The FINFLO software, developed at Helsinki University of Technology, has been used in the flow solution, and the commercial IGG and Field view programs for the grid generation and post processing. The annular channel is discretized as a sector mesh. Calculation is performed with constant mass flow rate on six rotational speeds. The effect of turbulence is calculated using three turbulence models. The friction coefficient and velocity factor are attained via total friction power. The first part of experimental section consists of finding the proper sensors and calibrating them in a straight pipe. After preliminary tests, a RdF-sensor is glued on the walls of stator and rotor surfaces. Telemetry is needed to be able to measure the heat transfer coefficients at the rotor. The mean heat transfer coefficients are measured in a test machine on four cooling air mass flow rates at a wide Couette Reynolds number range. The calculated values concerning the friction and heat transfer coefficients are compared with measured and semi-empirical data. Heat is transferred from the hotter stator and rotor surfaces to the coolerair flow in the air gap, not from the rotor to the stator via the air gap, althought the stator temperature is lower than the rotor temperature. The calculatedfriction coefficients fits well with the semi-empirical equations and precedingmeasurements. On constant mass flow rate the rotor heat transfer coefficient attains a saturation point at a higher rotational speed, while the heat transfer coefficient of the stator grows uniformly. The magnitudes of the heat transfer coefficients are almost constant with different turbulence models. The calibrationof sensors in a straight pipe is only an advisory step in the selection process. Telemetry is tested in the pipe conditions and compared to the same measurements with a plain sensor. The magnitudes of the measured data and the data from the semi-empirical equation are higher for the heat transfer coefficients than thenumerical data considered on the velocity range. Friction and heat transfer coefficients are presented in a large velocity range in the report. The goals are reached acceptably using numerical and experimental research. The next challenge is to achieve results for grooved stator-rotor combinations. The work contains also results for an air gap with a grooved stator with 36 slots. The velocity field by the numerical method does not match in every respect the estimated flow mode. The absence of secondary Taylor vortices is evident when using time averagednumerical simulation.

Uma proposta de FSS fractal com geometria simplificada

Frequency Selective Surfaces (FSS) are periodic structures in one or two dimensions that act as spatial filters, can be formed by elements of type conductors patches or apertures, functioning as filters band-stop or band-pass respectively. The interest in the study of FSS has grown through the years, because such structures meet specific requirements as low-cost, reduced dimensions and weighs, beyond the possibility to integrate with other microwave circuits. The most varied applications for such structures have been investigated, as for example, radomes, antennas systems for airplanes, electromagnetic filters for reflective antennas, absorbers structures, etc. Several methods have been used for the analysis of FSS, among them, the Wave Method (WCIP). Are various shapes of elements that can be used in FSS, as for example, fractal type, which presents a relative geometric complexity. This work has as main objective to propose a simplification geometric procedure a fractal FSS, from the analysis of influence of details (gaps) of geometry of the same in behavior of the resonance frequency. Complementarily is shown a simple method to adjust the frequency resonance through analysis of a FSS, which uses a square basic cell, in which are inserted two reentrance and dimensions these reentrance are varied, making it possible to adjust the frequency. For this, the structures are analyzed numerically, using WCIP, and later are characterized experimentally comparing the results obtained. For the two cases is evaluated, the influence of electric and magnetic fields, the latter through the electric current density vector. Is realized a bibliographic study about the theme and are presented suggestions for the continuation of this work

Caracterização de superfícies seletivas de freqüência e de antenas fractais para aplicações em redes sem fio

This work aims to investigate the behavior of fractal elements in planar microstrip structures. In particular, microstrip antennas and frequency selective surfaces (FSSs) had changed its conventional elements to fractal shapes. For microstrip antennas, was used as the radiating element of Minkowski fractal. The feeding method used was microstrip line. Some prototypes were built and the analysis revealed the possibility of miniaturization of structures, besides the multiband behavior, provided by the fractal element. In particular, the Minkowski fractal antenna level 3 was used to exploit the multiband feature, enabling simultaneous operation of two commercial tracks (Wi-Fi and WiMAX) regulated by ANATEL. After, we investigated the effect of switches that have been placed on the at the pre-fractal edges of radiating element. For the FSSs, the fractal used to elements of FSSs was Dürer s pentagon. Some prototypes were built and measured. The results showed a multiband behavior of the structure provided by fractal geometry. Then, a parametric analysis allowed the analysis of the variation of periodicity on the electromagnetic behavior of FSS, and its bandwidth and quality factor. For numerical and experimental characterization of the structures discussed was used, respectively, the commercial software Ansoft DesignerTM and a vector network analyzer, Agilent N5230A model

Estudo da variação da periodicidade e do acoplamento entre superfícies seletivas de frequência com elementos fractais e helicoidais em estruturas de multicamadas

This work aims to investigate the behavior of fractal and helical elements structures in planar microstrip. In particular, the frequency selective surfaces (FSSs) had changed its conventional elements to fractal and helical formats. The dielectric substrate used was fiberglass (FR-4) and has a thickness of 1.5 mm, a relative permittivity 4.4 and tangent loss equal to 0.02. For FSSs, was adopting the Dürer’s fractal geometry and helical geometry. To make the measurements, we used two antennas horns in direct line of sight, connected by coaxial cable to the vector network analyzer. Some prototypes were select for built and measured. From preliminary results, it was aimed to find practical applications for structures from the cascading between them. For FSSs with Dürer’s fractal elements was observed behavior provided by the multiband fractal geometry, while the bandwidth has become narrow as the level of iteration fractal increased, making it a more selective frequency with a higher quality factor. A parametric analysis allowed the analysis of the variation of the air layer between them. The cascading between fractal elements structure were considered, presented a tri-band behavior for certain values of the layer of air between them, and find applications in the licensed 2.5GHz band (2.3-2.7) and 3.5GHz band (3.3-3.8). For FSSs with helical elements, six structures were considered, namely H0, H1, H2, H3, H4 and H5. The electromagnetic behavior of them was analyzed separately and cascaded. From preliminary results obtained from the separate analysis of structures, including the cascade, the higher the bandwidth, in that the thickness of the air layer increases. In order to find practical applications for helical structures cascaded, the helical elements structure has been cascaded find applications in the X-band (8.0-12.0) and unlicensed band (5.25-5.85). For numerical and experimental characterization of the structures discussed was used, respectively, the commercial software Ansoft Designer and a vector network analyzer, Agilent N5230A model.

Comparative analysis between experimental characterization results and numerical fdtd modeling of self-assembled photonic crystals

This paper presents a comparative analysis between the experimental characterization and the numerical simulation results for a three-dimensional FCC photonic crystal (PhC) based on a self-assembly synthesis of monodispersive latex spheres. Specifically, experimental optical characterization, by means of reflectance measurements under variable angles over the lattice plane family [1,1, 1], are compared to theoretical calculations based on the Finite Di®erence Time Domain (FDTD) method, in order to investigate the correlation between theoretical predictions and experimental data. The goal is to highlight the influence of crystal defects on the achieved performance.

The Transverse Crack Tension test revisited: An experimental and numerical study

Several problems arise when measuring the mode II interlaminar fracture toughness using a Transverse Crack Tension specimen; in particular, the fracture toughness depends on the geometry of the specimen and cannot be considered a material parameter. A preliminary experimental campaign was conducted on TCTs of different sizes but no fracture toughness was measured because the TCTs failed in an unacceptable way, invalidating the tests. A comprehensive numerical and experimental investigation is conducted to identify the main causes of this behaviour and a modification of the geometry of the specimen is proposed. It is believed that the obtained results represent a significant contribution in the understanding of the TCT test as a mode II characterization procedure and, at the same time, provide new guidelines to characterize the mode II crack propagation under tensile loads.