The experimental research presented in this dissertation aims to develop a new rubber&ndash / based seismic isolator type on the basis of the idea that the damping of a conventional annular elastomeric bearing (EB) can be increased by filling its central core with small diameter steel balls, which dissipate energy via friction inside the confined hole of the bearing during their movements under horizontal loads. The proposed bearing type is called &ldquo / Ball Rubber Bearing (BRB)&rdquo / . A large set of BRBs with different geometrical and material properties are manufactured and tested under reversed cyclic horizontal loading at different vertical compressive load levels. Effect of supplementary confinement in the central hole of the bearing to performance of BRB is studied by performing some additional tests. Test results are used to develop design equations for BRB. A detailed non-linear finite element model is developed to verify the test results. The proposed analytical model is determined to simulate the structural hysteretic behaviour of the bearings. In design of BRBs, the proposed design guideline can be used in conjunction with the proposed non-linear finite element analysis. Extensive test results indicate that steel balls do not only increase the energy dissipation capacity of the elastomeric bearing (EB) but also increase its horizontal and vertical stiffness. It is also observed that the energy dissipation capacity of a BRB does not degrade as the number of loading cycles increases, which indicates remarkably reliable seismic performance.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第18977号 / 工博第4019号 / 新制||工||1619 / 31928 / 京都大学大学院工学研究科建築学専攻 / (主査)教授 中島 正愛, 教授 金子 佳生, 教授 吹田 啓一郎 / 学位規則第4条第1項該当

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The main goal of the present study is to investigate the energy dissipation through inclined screens. Recent studies have shown that screens arranged vertically may dissipate more energy than a hydraulic jump does below small hydraulic structures. In the present study a series of laboratory experiments were performed in order to determine the effect of inclination of the screen on the energy dissipated by the screen. The porosity of the screen used in the experiments is 40%. Inclination angle, thickness of the screen, location of the screen, upstream flow depth, and the Froude number of the upstream flow are the major parameters for the laboratory experiments. Froude number of the upstream flow covered a range of 5 to 24. A screen was located up to a distance 100 times the undisturbed upstream flow depth from the gate and the thickness of the screen was changed in correlation with the depth of upstream flow. The results of the experiments show that the inclination parameter has an insignificant effect on the energy dissipated by the screen. Namely, inclination of the screen does not contribute much in reducing the energy of the flowing water further, compared to vertically placed screens.

The objective of this study is to determine the effect of different roughness types and arrangements on hydraulic jump characteristics in a rectangular channel. Three different types of roughness were used along experiments. All of them had rectangular prism shapes and that were placed normal to the flow direction. To avoid cavitation, height of roughness elements were arranged according to level of the channel inlet, so that the crests of roughness elements would not be protruding into the flow. The effects of roughness type and arrangement on hydraulic jump properties, i.e. energy dissipation, length of the jump and tail water depth were investigated. These properties were compared with the available data in literature and with the properties of hydraulic jump occurred on smooth bed.

ABSTRACT EXPERIMENTAL INVESTIGATION OF ENERGY DISSIPATION THROUGH TRIANGULAR SCREENS G&uuml / ng&ouml / r, Endam M.Sc., Department of Civil Engineering Supervisor: Assoc. Prof. Dr. Zafer BozkuS Co-Supervisor: Prof. Dr. Metin Ger May 2005, 82 pages For the present study, a series of experimental works are executed to dissipate energy through triangular screens. Recent studies have shown that the implementation of the screen for energy dissipation is an effective way to extract out the excessive energy of water downstream of small hydraulic structures located in rivers of relatively negligible sediment content. In the present study, double screen arrangement with a porosity of 40% is used. The inclination angle of the screens is opted as 60 degree. The major parameters for the present study are upstream flow depth, location of the screen together with the supercritical upstream flow Froude number for a range covering from 7.5 to 25.5. The gate opening simulating a hydraulic structure is adjusted with various heights of 1 cm, 1.25 cm, 1.6 cm, 1.7 cm, 2 cm, 2.5 cm, 2.7 cm, 3.2 cm and 3.3 cm during the study. The results of the experiments show that the triangular screen configuration with the same pore geometry has no significant additional contribution on the energy dissipation as compared to vertically placed screens. Keywords: Screen, energy dissipation, triangular configuration, porosity, hydraulic jump, supercritical flow.

The confined impinging jet reactor gives efficient mixing performance as required for fast reactions. In this work the mixing performance of CIJR is characterized through three measures: estimates of the energy dissipation, micromixing efficiency based on the yield of a homogeneous (iodide-iodate) reaction and particle size resulting from a heterogeneous (iron oxide) precipitation reaction. Whereas product yield and energy dissipation are used to test operational robustness of CIJR, iron oxide model system is used to study the effect of feed flow rate (mixing) and reactant concentration on precipitate agglomerate size. Mixing and concentration effects on nucleation, particle growth and particle agglomeration are tracked to understand the agglomeration process. Various types of stabilizers and additive concentrations to limit particle agglomeration are also tested. Effects of in situ and post-reaction sonication on agglomerate size are also investigated. Efforts are made to determine variations in mixing efficiency the operational robustness of the scale-up (2X and 4X) geometries. Also efforts are made to identify scaling parameters and the limit on geometric scale-up for good mixing performance. Energy dissipation is found to vary between 20 W/kg and 6800 W/kg in CIJR and decreases on scale-up at constant Reynolds number. The operation of the CIJR and the scale-up geometries is robust to changes in flow rate, exhibiting stable performance up to 30% difference in inlet flow rates. Reliable mixing performance is obtained until 2X scale-up, while at low flow rates, the jets fail to impinge in 4X scale-up, and sometimes failing to fill the reactor volume. Iron oxide primary and agglomerate particles are seen to vary with flow rate and reactant concentrations. Largest primary particles (and smallest agglomerates) are obtained at high flow rates and high reactant concentrations, which indicate to size dependent agglomerative tendency of the primary particles. Stabilizers added in situ see limited success. Post-reaction sonication is helpful in dispersing soft agglomerates, but in situ sonication shows no significant reduction in agglomerate size with or without stabilizer. Primary particles are understood to agglomerate due to collisions induced by Brownian motion, simple shear and velocity fluctuations in turbulent flows. These collision mechanisms operate at different length scales in the fluid mass. / Chemical Engineering

Zugl.: Dresden, Techn. Universiẗat, Diss., 2007.

Thesis (Ph. D.)--Michigan State University. Dept. of Electrical and Computer Engineering, 2006. / Title from PDF t.p. (viewed on Nov. 17, 2008) Includes bibliographical references (p. 183-195). Also issued in print.

Esta tese objetiva caracterizar o escoamento provocado pela incidência de um jato vertical em um fundo plano, descrevendo assim as características médias e flutuantes das pressões a partir da investigação experimental. O modelo utilizado é composto por um jato retangular posicionado, perpendicularmente, a uma distância de 0,92 m do fundo plano de um canal. Utilizando transdutores de pressão instalados na posição de incidência do jato, adquiriu-se os valores de pressão “instantânea” a uma frequência de 128 Hz durante 10 minutos. Foram ensaiadas cinco (5) vazões: 25 l/s (Fr1 = 7,12), 30 l/s (Fr1 = 8,51), 36,6 l/s (Fr1 = 10,35), 42,7 l/s (Fr1 = 12,12) e 50l/s (Fr1 = 14,23), além de vinte (20) diferentes espessuras de colchão d'água. Com os dados de pressão, efetuou-se análises no domínio do tempo, da frequência e da posição. No domínio do tempo, analisou-se a variação dos parâmetros estatísticos essenciais (média, desvio padrão, assimetria e curtose) bem como a identificação de valores máximo e mínimos das pressões. No domínio da frequência, procurou-se avaliar por meio da análise espectral a identificação de frequências significativas associadas à energia macroturbulenta. No que tange à análise no domínio da posição buscou-se analisar a faixa de influência do jato junto ao fundo, a região de subpressões e o alcance das pressões dinâmicas. Outro aspecto importante abordado é a apresentação dos resultados em gráficos adimensionalizados, o que confere ao estudo um caráter geral dentro da faixa de valores ensaiados. Os resultados definem um colchão mínimo de água da ordem de 3 vezes a altura crítica do escoamento, para o amortecimento das pressões dinâmicas. A análise dos momentos estatísticos demonstra que a distribuição das pressões não segue a distribuição normal. Dentro disso, estão disponibilizados coeficientes estatísticos de probabilidade para a determinação das pressões extremas. Ainda, estão definidas quatro zonas a jusante do impacto do jato: Zona I - região do impacto, Zona II - reflexão do jato, Zona III - Acomodação do escoamento e por fim, a Zona IV - caracterizada pelo fim da influência do jato. Além disso, uma análise deste escoamento sob a perspectiva da formação de um ressalto hidráulico é realizada, indicando que apenas os parâmetros utilizados, não descrevem o escoamento como tal. Esta tese é produto da parceria entre Laboratório de Obras Hidráulicas do Instituto de Pesquisas Hidráulicas da Universidade Federal do Rio Grande do Sul (LOH/IPH/UFRGS) e o Laboratório de Hidráulica Experimental e Recursos Hídricos de Furnas Centrais Elétricas S. A. (LAHE/FURNAS). / This thesis aims to characterize the flow prompted by the incidence of a vertical jet on a flat bottom, thus describing the mean and floating characteristics of the pressures from the experimental investigation. The model used is comprised of a rectangular jet positioned perpendicularly at a distance of 0.92 m from the flat bottom of a channel. Using pressure transducers installed in the jet incidence position, the "instantaneous" pressure values were acquired at a frequency of 128 Hz for 10 minutes. Five (5) discharges were tested: 25 l/s (Fr1 = 7.12), 30 l/s (Fr1 = 8.51), 36.6 l/s (Fr1 = 10.35), 42.7 l/s (Fr1 = 12.12) and 50 1/s (Fr1 = 14.23), as well as twenty (20) different waterbed thicknesses. The pressure data were analyzed in terms of time, frequency and position domains. In the time domain, the variation of the essential statistical parameters (mean, standard deviation, asymmetry and kurtosis) was analyzed, as well as the identification of maximum and minimum pressure values. In the frequency domain, it was sought to assess, by means of the spectral analysis, the identification of significant frequencies associated with macroturbulent energy. Regarding the analysis in the position domain, this study aimed to analyze the range of influence of the jet near the bottom, the region of subpressions and the reach of the dynamic pressures. Another important aspect is the presentation of the results in dimensionless graphs, which grants the study a general character within the range of values tested. The results define a minimum waterbed of the order of 3 times the critical height of the flow for the damping of the dynamic pressures. Statistical moments analysis shows that the distribution of pressures does not follow the normal distribution. Therein, probability statistical coefficients are available for the determination of extreme pressures. Also, four zones are defined downstream of the impact of the jet: Zone I - region of impact, Zone II - reflection of the jet, Zone III - accommodation of the flow and, finally, Zone IV - characterized by the end of the influence of the jet. Furthermore, an analysis of this flow from the perspective of the formation of a hydraulic jump is conducted, indicating that the parameters used alone do not describe the flow as such. This thesis is a product of the partnership between the Hydraulic Works Laboratory of the Hydraulic Research Institute of the Federal University of Rio Grande do Sul (LOH/IPH/UFRGS) and the Laboratory of Experimental Hydraulics and Hydraulic Resources of Furnas Centrais Elétricas SA (LAHE/FURNAS).