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The effect of vegetation zones on adjacent clear channel flowHirschowitz, Peter Mark 16 May 2008 (has links)
Abstract
Methods are proposed to take account of the effect of emergent vegetation (which covers
only part of the channel bed) on conveyance and depth-averaged velocity in open
channels. For emergent vegetation strips parallel to the flow direction, discharge can be
predicted separately for each vegetated or non-vegetated zone. The equations of Kaiser
(1985) and Nuding (1991, 1994) can predict the influence of the vegetation on
conveyance within the non-vegetated zone via the composite roughness formula of
Pavlovski (1931). In order to predict the lateral distribution of depth-averaged velocity
within the non-vegetated zone, the equations of Nuding (1991, 1994) have been modified
to take account of the relation between non-vegetated zone width, apparent shear stress
on the vegetation interface and the maximum velocity which will occur. For more
complex geometries, two-dimensional numerical hydraulic models using existing
software and existing relations for the prediction of eddy viscosity are recommended.
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Validação experimental de metodologias para quantificação contínua de vazão no Ribeirão da Onça / Experimental validation of methodologies for continuous measurement of flow in the Ribeirão da Onça basinMaldonado, Luiz Henrique 28 August 2009 (has links)
Desde 2004, o grupo de estudos do Laboratório de Hidráulica Computacional (LHC) estuda as taxas de recargas hidráulicas do Aquifero Guarani, na Bacia do Ribeirão da Onça. Entretanto, não havia se estudado a quantificação do escoamento superficial. Para sanar esta deficiência, este trabalho visou analisar as metodologias de estimativa de vazão com qualidade para a Bacia do Ribeirão da Onça. Para a realização do trabalho, foi adquirido o equipamento Flo-Tote3, capaz de medir velocidade e nível d\'água. A princípio, o equipamento foi verificado e comparado em laboratório, medindo velocidades 3% inferiores que o molinete e estimando vazões de 0,5 a 7,2% de diferença que o vertedor triangular. No Ribeirão da Onça, foi escolhida e construída uma seção de controle de vazão e instalado o Flo-Tote. O equipamento mediu velocidades 5% inferiores que o molinete, com variações de 0,3 a 8,7%. Além disso, um vertedor circular foi instalado em 6 ocasiões, resultando em vazões de 3 a 15% inferiores as vazões estimadas pelo molinete, em virtude do vazamento que ocorreu entre o vertedor e a parede de concreto. A partir de dezembro de 2007, foram iniciadas medições de níveis d\'água com a construção do linígrafo e estimadas as vazões de modo contínuo com o auxílio de equações teóricas. Como a jusante da seção de controle de vazão existe um sistema de bombeamento, as equações para determinar a vazão sofrem interferencias. Entretanto, foi aplicado o método das isotáquias, que utiliza valores de velocidades e níveis d\'água para o cálculo da vazão e que não sofre interferências com o represamento e instalações de vertedores. Apesar de ocorrer problemas de falta de energia e de manutenção, o escoamento superficial foi quantificado com qualidade para futuros estudos da área afim. / Since 2004, the group of studies of the Computational Hydraulic Laboratory (LHC) studied the rates of water recharge in the Guarani Aquifer recharges water in the Ribeirão da Onça basin. However, it had not studied the quantification of runoff. To remedy this deficiency, this study aimed to analyze the methodologies for estimation of flow quality for the Ribeirão da Onça basin. To carry out the work, it was acquired a Flo-Tote3, capable of measuring velocities and water levels. First, this equipment was checked and compared in the laboratory, measuring velocities 3% below, those obtained using flowmeters and 0.5 to 7.2% differences when compared with results using triangular weir. In Ribeirão da Onça, was chosen and built a section of control flow and installed the Flo-Tote. The equipment measured velocities 5% below the current meters, with variations from 0.3 to 8.7%. In addition, a circular weir was installed on 6 occasions, resulting in flow rates from 3 to 15% lower than those estimated by current meters because of the flow that occurred between the bridge and weir. Since December 2007, started the measurements of water levels and the estimated flow on a continuous basis with the aid of theoretical equations. As the downstream section of the control flow is a pumping system, the equations to determine the flow are interfered. However, it was applied the method of the lines of the same velocities, which uses values of velocities and water levels to calculate the flow without interference with the impoundment and installation of weirs. Despite the problems of lack of energy and maintenance, the runoff was quantified with quality for future studies of the area.
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Relationship Between Concentric Velocities at Varying Intensity in the Back Squat Using a Wireless Inertial SensorCarroll, Kevin M., Sato, Kimitake, Beckham, George K., Triplett, N. Travis, Griggs, Cameron V., Stone, Michael H. 01 January 2017 (has links)
Objectives: The purpose of this study was to examine the relationship of velocities in the back squat between one repetition maximum (1RM) and submaximally loaded repetition maximum (RM) conditions, specifically in regard to what has been described as the minimal velocity threshold (MVT). The MVT describes a minimum concentric velocity that an individual must reach or surpass in order to successfully complete a repetition. Design: To test the presence of a MVT, participants were tested for 1RM and RM back squat ability. The mean concentric veloci ties (MCV) of the last successful repetition of each condition were then compared. Methods: Fourteen male participants familiar with the back squat volunteered to participate in the current study (age = 25.0 y ± 2.6, height = 178.9 cm ± 8.1, body mass = 88.2 kg ± 15.8). The mean concentric velocity (MCV) during the last successful repetition from each testing condition was considered for the comparison. Results: Results indicated a non-significant negative relationship of MCV between the 1RM and RM conditions (r = -0.135), no statistical difference between testing conditions (p = 0.266), with a small-to-moderate effect size (d = 0.468). Conclusions: The results of this study suggest that MVT should be further investigated to enhance its use in the practical setting. Additionally, coaches considering using a velocity-based approach for testing athletes should use data from either 1RM or RM conditions, but not both interchangeably. Coaches should be cautious when considering group averages or comparing velocity data between athletes, which may not be appropriate based on our results.
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Precise GPS-based position, velocity and acceleration determination: algorithms and toolsSalazar Hernández, Dagoberto José 29 April 2010 (has links)
Esta tesis doctoral llevó a cabo el estudio, desarrollo e implementación de algoritmos para la navegación con
sistemas globales de navegación por satélite (GNSS), enfocándose en la determinación precisa de la posición,
velocidad y aceleración usando GPS, en modo post-procesado y lejos de estaciones de referencia.
Uno de los objetivos era desarrollar herramientas en esta área y hacerlas disponibles a la comunidad GNSS. Por ello
el desarrollo se hizo dentro del marco del proyecto preexistente de software libre llamado GPS Toolkit (GPSTk). Una
de las primeras tareas realizadas fue la validación de las capacidades de la GPSTk para el procesado del
pseudorango, realizando comparaciones con una herramienta de procesamiento de datos probada (BRUS).
La gestión de datos GNSS demostró ser un asunto importante cuando se intentó extender las capacidades de la
GPSTk al procesamiento de datos obtenidos de las fases de la señal GPS. Por ello se desarrollaron las Estructuras
de Datos GNSS (GDS), que combinadas con su paradigma de procesamiento aceleran el proceso de desarrollo de
software y reducen errores.
La extensión de la GPSTk a los algoritmos de procesado en fase se hizo mediante la ayuda de las GDS,
proporcionándose importantes clases accesorias que facilitan el trabajo. Se implementó el procesado de datos
Precise Point Positioning (PPP) con ejemplos relativamente simples basados en las GDS, y al comparar sus
resultados con otras aplicaciones de reputación ya establecida, se encontró que destacan entre los mejores.
También se estudió cómo obtener la posición precisa, en post-proceso, de un receptor GPS a cientos de kilómetros
de la estación de referencia más cercana y usando tasas de datos arbitrarias (una limitación del método PPP). Las
ventajas aportadas por las GDS permitieron la implementación de un procesado semejante a un PPP cinemático
basado en una red de estaciones de referencia, estrategia bautizada como Precise Orbits Positioning (POP) porque
sólo necesita órbitas precisas para trabajar y es independiente de la información de los relojes de los satélites GPS.
Los resultados de este enfoque fueron muy similares a los del método PPP cinemático estándar, pero
proporcionando soluciones de posición con una tasa mayor y de manera más robusta.
La última parte se enfocó en la implementación y mejora de algoritmos para determinar con precisión la velocidad y
aceleración de un receptor GPS. Se hizo énfasis en el método de las fases de Kennedy debido a su buen
rendimiento, desarrollando una implementación de referencia y demostrando la existencia de una falla en el
procedimiento propuesto originalmente para el cálculo de las velocidades de los satélites. Se propuso entonces una
modificación relativamente sencilla que redujo en un factor mayor que 35 el RMS de los errores 3D en velocidad.
Tomando ideas de los métodos Kennedy y POP se desarrolló e implementó un nuevo procedimiento de
determinación de velocidad y aceleración que extiende el alcance. Este método fue llamado Extended Velocity and
Acceleration determination (EVA). Un experimento usando una aeronave ligera volando sobre los Pirineos mostró
que tanto el método de Kennedy (modificado) como el método EVA son capaces de responder ante la dinámica de
este tipo de vuelos.
Finalmente, tanto el método de Kennedy modificado como el método EVA fueron aplicados a una red en la zona
ecuatorial de Sur América con líneas de base mayores a 1770 km. En este escenario el método EVA mostró una
clara ventaja tanto en los promedios como en las desviaciones estándar para todas las componentes de la velocidad
y la aceleración. / This Ph.D. Thesis focuses on the development of algorithms and tools for precise GPS-based position, velocity and
acceleration determination very far from reference stations in post-process mode.
One of the goals of this thesis was to develop a set of state-of-the-art GNSS data processing tools, and make them
available for the research community. Therefore, the software development effort was done within the frame of a
preexistent open source project called the GPSTk. Therefore, validation of the GPSTk pseudorange-based processing
capabilities with a trusted GPS data processing tool was one of the initial task carried out in this work.
GNSS data management proved to be an important issue when trying to extend GPSTk capabilities to carrier phasebased
data processing algorithms. In order to tackle this problem the GNSS Data Structures (GDS) and their
associated processing paradigm were developed. With this approach the GNSS data processing becomes like an
assembly line, providing an easy and straightforward way to write clean, simple to read and use software that speeds
up development and reduces errors.
The extension of GPSTk capabilities to carrier phase-based data processing algorithms was carried out with the help
of the GDS, adding important accessory classes necessary for this kind of data processing and providing reference
implementations. The performance comparison of these relatively simple GDS-based source code examples with
other state-of-the art Precise Point Positioning (PPP) suites demonstrated that their results are among the best.
Furthermore, given that the GDS design is based on data abstraction, it allows a very flexible handling of concepts
beyond mere data encapsulation, including programmable general solvers, among others.
The problem of post-process precise positioning of GPS receivers hundreds of kilometers away from nearest
reference station at arbitrary data rates was dealt with, overcoming an important limitation of classical post-processing
strategies like PPP. The advantages of GDS data abstraction regarding solvers were used to implement a kinematic
PPP-like processing based on a network of stations. This procedure was named Precise Orbits Positioning (POP)
because it is independent of precise clock information and it only needs precise orbits to work. The results from this
approach were very similar (as expected) to the standard kinematic PPP processing strategy, but yielding a higher
positioning rate. Also, the network-based processing of POP seems to provide additional robustness to the results,
even for receivers outside the network area.
The last part of this thesis focused on implementing, improving and testing algorithms for the precise determination of
velocity and acceleration hundreds of kilometers away from nearest reference station. Special emphasis was done on
the Kennedy method because of its good performance. A reference implementation of Kennedy method was
developed, and several experiments were carried out. Experiments done with very short baselines showed a flaw in
the way satellite velocities were computed, introducing biases in the velocity solution. A relatively simple modification
was proposed, and it reduced the RMS of 5-min average velocity 3D errors by a factor of over 35.
Then, borrowing ideas from Kennedy method and the POP method, a new velocity and acceleration determination
procedure named EVA was developed and implemented that greatly extends the effective range. An experiment using
a light aircraft flying over the Pyrenees showed that both the modified-Kennedy and EVA methods were able to cope
with the dynamics of this type of flight. Finally, both modified-Kennedy and EVA method were applied to a challenging
scenario in equatorial South America, with baselines over 1770 km, where EVA method showed a clear advantage in
both averages and standard deviations for all components of velocity and acceleration.
Lloc i
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A Comparison of Least-Squares Finite Element Models with the Conventional Finite Element Models of Problems in Heat Transfer and Fluid MechanicsNellie Rajarova, 2009 May 1900 (has links)
In this thesis, least-squares based finite element models (LSFEM) for the Poisson equation and Navier-Stokes equation are presented. The least-squares method is simple, general and reliable. Least-squares formulations offer several computational and theoretical advantages. The resulting coefficient matrix is symmetric and positive-definite. Using these formulations, the choice of approximating space is not subject to any compatibility condition.
The Poisson equation is cast as a set of first order equations involving gradient of the primary variable as auxiliary variables for the mixed least-square finite element model. Equal order C0 continuous approximation functions is used for primary and auxiliary variables. Least-squares principle was directly applied to develop another model which requires C1continous approximation functions for the primary variable. Each developed model is compared with the conventional model to verify its performance.
Penalty based least-squares formulation was implemented to develop a finite element for the Navier Stokes equations. The continuity equation is treated as a constraint on the velocity field and the constraint is enforced using the penalty method. Velocity gradients are introduced as auxiliary variables to get the first order equivalent system. Both the primary and auxiliary variables are interpolated using equal order C0 continuous, p-version approximation functions. Numerical examples are presented to demonstrate the convergence characteristics and accuracy of the method.
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Observations of Tidal-Current ProfilesShi, Mon-Shen 31 January 2002 (has links)
This study aims to better understand the characteristics of the tidal- current profiles and the near-bed boundary layer structures off the southwestern coast of Taiwan. The velocity profile is measured by a bottom-mounted ADCP. Six experiments were conducted, each lasted 10~20 days and the water depth ranging 12~18 m. Twenty-minute averaged velocity profiles have been fitted to a logarithmic form with 4% accuracy. The friction velocity (u*) and roughness length (z0) are then derived from the slope and intercept of the best-fitted straight lines. Our results show that the profile shape and friction velocity vary tidally, the latter reaches O(0.06)ms-1 during peak current flow. The magnitude of z0 is large and scattered, but it shows a general trend of decrease with increasing flow speed. The observed log-layer height increases, and the bottom drag coefficient (CD) decrease, respectively with increasing flow speed. Measurements also show that water turbidity increases with rainfall, as a result the z0 and CD also increase. Finally, harmonic analysis of the tidal currents indicate significant changes between winter (homogeneous) and summer (stratified) conditions. In winter the vertical variation of orientation and phase is small, whereas in summer there was a 150 orientation and 250 phase difference (the bottom currents lead the surface currents) between the near surface and near bed regions.
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Design of regulated velocity flow assurance device for petroleum industryYardi, Chaitanya Narendra 17 February 2005 (has links)
The petroleum industry faces problems in transportation of crude petroleum be-
cause of the deposition of paraffins, hydrates and asphaltenes on the insides of the
pipeline. These are conventionally removed using either chemical inhibitors or mechani-
cal devices, called pigs, which travel through the pipeline and mechanically scrape away
the deposits. These pigs are propelled by the pipeline product itself and hence travel at
the same velocity as the product. Research has indicated that cleaning would be better
if the pigs are traveling at a relatively constant velocity of around 70% of the product
velocity.
This research utilizes the concept of regulating the bypass flow velocity in order to
maintain the pig velocity. The bypass flow is regulated by the control unit based on
the feedback from the turbine flowmeter, which monitors the bypass flow. A motorized
butterfly valve is used for actually controlling the bypass flow.
In addition to cleaning, the proposed pig utilizes on-board electronics like accelerom-
eter and pressure transducers to store the data gathered during the pig run. This data
can then be analyzed and the condition of the pipeline predicted.
Thus, this research addresses the problem of designing a pig to maintain a constant
velocity in order to achieve better cleaning. It also helps gather elementary data that
can be used to predict the internal conditions in the pipe.
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HNO3-Induced Atmospheric Corrosion of Copper, Zinc and Carbon SteelSamie, Farid January 2006 (has links)
<p>The role of nitric acid (HNO<sub>3</sub>) on the atmospheric corrosion of metals has so far received little or no attention. However, the last decades of decreasing sulphur dioxide (SO<sub>2</sub>) levels and unchanged HNO<sub>3</sub> levels in many industrialized countries have resulted in an increased interest in possible HNO<sub>3</sub>-induced atmospheric corrosion effects. In this study a new method was developed for studying the corrosion effects of HNO<sub>3</sub> on metals at well-defined laboratory exposure conditions. The method has enabled studies to be performed on the influence of individual exposure parameters, namely HNO<sub>3</sub>-concentration, air velocity, temperature and relative humidity, as well as comparisons with newly generated field exposure data.</p><p>The corrosion rate and deposition rate of HNO<sub>3</sub> on copper was shown to follow a linear increase with HNO3 concentration. The deposition velocity (Vd) of HNO<sub>3</sub> increased up to an air velocity of 11.8 cm s<sup>-1</sup>. Only at a higher air velocity (35.4 cm s<sup>-1</sup>) the Vd on copper was lower than the Vd on an ideal absorbent, implying the Vd of HNO3 at lower air velocities to be mass-transport limited.</p><p>Within the investigated temperature range of 15 to 35 ºC only a minor decrease in the HNO<sub>3</sub>-induced copper corrosion rate could be observed. The effect of relative humidity (RH) was more evident. Already at 20 % RH a significant corrosion rate could be measured and at 65 % RH the Vd of HNO<sub>3</sub> on copper, zinc and carbon steel reached maximum and nearly ideal absorption conditions.</p><p>During identical exposure conditions in HNO<sub>3-</sub>containing atmosphere, the corrosion rate of carbon steel was nearly three times higher than that of copper and zinc. The HNO<sub>3</sub>-induced corrosion effect of copper, zinc and steel turned out to be significantly higher than that induced by SO2 alone or in combination with either NO<sub>2</sub> or O<sub>3</sub>. This is mainly attributed to the much higher water solubility and reactivity of HNO3 compared to SO<sub>2</sub>, NO<sub>2</sub> and O<sub>3.</sub> Relative to SO<sub>2</sub>, zinc exhibits the highest sensitivity to HNO<sub>3</sub>, followed by copper, and carbon steel with the lowest sensitivity.</p><p>Extrapolation of laboratory data to an assumed average outdoor wind velocity of 3.6 m s-1 enabled a good comparison with field data. Despite the fact that ambient SO<sub>2</sub> levels are still much higher than HNO<sub>3</sub> levels, the results show that HNO<sub>3</sub> plays a significant role for the atmospheric corrosion of copper and zinc, but not for carbon steel. The results generated within this doctoral study emphasize the importance of further research on the influence of HNO<sub>3</sub> on degradation of other materials, e.g. stone and glass, as well as of other metals. </p>
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非定常対向流予混合火炎の火炎構造に与える流入速度変動の影響に関する数値解析YAMAMOTO, Kazuhiro, HAYASHI, Naoki, YAMASHITA, Hiroshi, NONOMURA, Kazuki, 山本, 和弘, 林, 直樹, 山下, 博史, 野々村, 一樹 January 2008 (has links)
No description available.
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Hydrate-bearing sediments: formation and geophysical propertiesLee, Joo-yong 09 July 2007 (has links)
Hydrate-bearing sediments may contribute to the availability of energy resources, affect climate change, or cause seafloor instability. The comprehensive study of hydrate-bearing sediments documented in this manuscript includes physicochemical aspects of hydrate nucleation near mineral surfaces, the validity of THF as a substitute guest molecule for the study of hydrate-bearing sediments, and the effects of hydrate formation on the electromagnetic and the mechanical properties of various soils with a wide range of specific surface. Natural marine sediments are included as part of this investigation to explore the effects of inherent fabric, salts, organic matter, and stress history on the geophysical properties of hydrate-bearing sediments. Experiments are designed to reproduce the state of effective stress in the field at the time of hydrate formation. A comprehensive set of instruments is deployed in this study, and the unprecedented development of electrical resistivity tomography for the study of hydrate formation and dissociation is also documented in detail. Results from this research have important implications for geophysical field characterization and monitoring processes such as production.
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