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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Analysis of the Optimal Gripping Location on the Hammer Handle

Kuo, Rong-Ho 10 August 2006 (has links)
This research investigates the influence of the reacting force which suffered from the handle of a hammer to strike an object. To achieve the study purpose, an impulse on the hammer face in a very short time was investigated. The researcher used computer-aided design software Solidworks to set up the hammer model and he used finite element software LS-DYNA to analysis the dynamic problem of the hammer by impulse loading. This study aims to find out the reaction force at the gripping position of different shape of cross-section, length, gripping position and angle of the handle and compares the results along x, y, and z axis respectively. After summing up an optimum handle shape and gripping position, users can operate the tool easily. The optimum also reduces the probability of musculoskeletal disorders. It is expected the study findings can not only provide some reliable data for the reference in hammer manufactures but also make a breakthrough in computing aided engineering.
22

Rotordynamics/discharge water-hammer coupling via seals in pump rotordynamics

Zhang, Kaikai 30 September 2004 (has links)
A new closed-loop frequency-domain model is developed to incorporate the water hammer effect with pump rotordynamics, in order to investigate the sub-synchronous instability problem observed in a field pump. Seal flow-rate perturbations due to eccentricity are calculated from Soulas and San Andres's seal code. A complete transfer function matrix between rotor motion and reaction force due to pressure perturbation is developed in detail. Stability analysis with transfer-function'add-in' modules is conducted in XLTRC2. Seal clearances and the reaction force angle are found to be important in shifting natural frequencies and damping. The sub-synchronous instability observed in field is duplicated successfully with double-clearance seals.
23

Water hammer fracture diagnostics

Carey, Michael Andrew 03 February 2015 (has links)
A sudden change in flow in a confined system results in the formation of a series of pressure pulses known as a water hammer. Pump shutdown at the conclusion of a hydraulic fracture treatment frequently generates a water hammer, which sends a pressure pulse down the wellbore that interacts with the created fracture before returning towards the surface. This study confirms that created hydraulic fractures alter the period, amplitude, and duration of the water hammer signal. Water hammer pressure signals were simulated with a previously presented numerical model that combined the continuity and momentum equations of the wellbore with a created hydraulic fracture represented by a RCI series circuit. Field data from several multi-stage stimulation treatments were history matched with the numerical model by iteratively altering R, C, and I until an appropriate match was obtained. Equivalent fracture dimensions were calculated from R, C, and I, and were in agreement with acquired micro-seismic SRV. Finally, the obtained R, C, and I values were compared to SRV and production log data. Capacitance was directly correlated with SRV, while resistance was inversely correlated with SRV, and no correlations with production data were observed. / text
24

PREDICTING THE LOCATION AND DURATION OF TRANSIENT INDUCED LOW OR NEGATIVE PRESSURES WITHIN A LARGE WATER DISTRIBUTION SYSTEM

Svindland, Richard C. 01 January 2005 (has links)
Surge modeling is a tool used by engineers and utility owners in determining the surge pressures or transients that may result from routine pump and valve operations. Recent surge modeling work has focused on low and/or negative pressures within water distribution systems and how those occurrences could lead to intrusions. Effective surge modeling is needed in order to determine if the intrusion potential exists and what mitigation is needed to prevent intrusions. This work focuses on the generally unexplored area of using surge models to predict the location and duration of transient induced low and/or negative pressures within large complex water distribution systems. The studied system serves 350,000 people in the southeast United States, has 65 MGD of pumping capacity at two treatment plants, over 1500 miles of main and 12 storage tanks. This work focuses on the correlation between field data and the surge model using the author's extensive operational knowledge of the system, access to real-time SCADA data, and different celerity or wave speed values. This work also traces the steps taken by the author to locate areas within the system that experienced transient induced low and / or negative pressure.
25

Numeric Modelling of Water Hammer Effects in Penstocks

Bernard, Dominic 08 May 2013 (has links)
Water hammer represents a complex hydraulic phenomenon with significant consequences on the proper functioning and safety of operation for pipe and conduit systems. The complexity and intricate physics of water hammer translated into significant difficulties associated firstly, with finding a proper solution for understanding the mechanism of its occurrence and, secondly, relating to proposing technically and economically viable design methods and devices that would help reduce and mitigate water hammer effects. In this context, the present thesis deals with the numerical modeling of the transient behaviour of water pipe segments. Following an extensive literature review of the state-of-the-art on the water hammer mechanisms and past work on experimental, analytical and numerical analysis of this phenomenon, a three dimensional numerical model of the water hammer in a pipe which considers the fluid-structure interaction (FSI) is developed using a Finite Element Method – Finite Volume Method (FEM-FVM) technique. Structural and fluid computational results based on rapid and slow gate closure scenarios are compared with existing closed-form solutions of the water hammer. A parametric study is also performed on a simply supported pipe segment to determine the influence of various design parameter. A systematic sensitivity analysis was conducted and a ranking mechanism was established for the importance of each parameter on the fluid fields and structural response. A first comparative analysis is conducted on horizontally and vertically bent elevated pipe segments to quantify the influence of the bend angle on the results. A second comparative analysis is performed on a horizontally bent segment buried in soil to determine the influence of the pipe interaction with the soil on the response. It is observed that the thickness, span, initial velocity and bend angle had a significant impact on the pressure and structural response. The presence of soil was observed to have a significant benefit in decreasing the von-Mises stresses.
26

Numeric Modelling of Water Hammer Effects in Penstocks

Bernard, Dominic January 2013 (has links)
Water hammer represents a complex hydraulic phenomenon with significant consequences on the proper functioning and safety of operation for pipe and conduit systems. The complexity and intricate physics of water hammer translated into significant difficulties associated firstly, with finding a proper solution for understanding the mechanism of its occurrence and, secondly, relating to proposing technically and economically viable design methods and devices that would help reduce and mitigate water hammer effects. In this context, the present thesis deals with the numerical modeling of the transient behaviour of water pipe segments. Following an extensive literature review of the state-of-the-art on the water hammer mechanisms and past work on experimental, analytical and numerical analysis of this phenomenon, a three dimensional numerical model of the water hammer in a pipe which considers the fluid-structure interaction (FSI) is developed using a Finite Element Method – Finite Volume Method (FEM-FVM) technique. Structural and fluid computational results based on rapid and slow gate closure scenarios are compared with existing closed-form solutions of the water hammer. A parametric study is also performed on a simply supported pipe segment to determine the influence of various design parameter. A systematic sensitivity analysis was conducted and a ranking mechanism was established for the importance of each parameter on the fluid fields and structural response. A first comparative analysis is conducted on horizontally and vertically bent elevated pipe segments to quantify the influence of the bend angle on the results. A second comparative analysis is performed on a horizontally bent segment buried in soil to determine the influence of the pipe interaction with the soil on the response. It is observed that the thickness, span, initial velocity and bend angle had a significant impact on the pressure and structural response. The presence of soil was observed to have a significant benefit in decreasing the von-Mises stresses.
27

Influencia do fator de atrito variavel na avaliação do escoamento transitorio em sistemas hidraulicos / It influences of the factor of variable attrition in the evaluation of the Transitory flowing in waterworks

Viaro, Vivien Luciane 04 April 2001 (has links)
Orientador: Edevar Luvizotto Jr / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil / Made available in DSpace on 2018-07-31T23:13:39Z (GMT). No. of bitstreams: 1 Viaro_VivienLuciane_M.pdf: 4505576 bytes, checksum: 18be75ce76921d4bee282a5330042a53 (MD5) Previous issue date: 2001 / Resumo: O transiente hidráulico é definido como a transição entre duas condições de escoamento permanente. Nessa transição a variação das grandezas associadas ao escoamento, principalmente a pressão, é importante no dimensionamento e exploração da instalação hidráulica. Os estudos das situações transitórias e das manobras que as provocaram, são fundamentais para se garantir a segurança operacional das instalações hidráulicas em geral. A análise do escoamento transitório em condutos forcados é feita com base nas equações da continuidade e da quantidade de movimento. Uma das imprecisões associadas à mo delação convencional está no uso de uma formulação quase-estática para o termo de atrito, a qual é válida somente para escoamento permanente. Este trabalho faz uma comparação entre os resultados obtidos em modelo fisico e os da modelação matemática, considerando ou não uma modelação especial para o termo de atrito transitório. Foram utilizados os modelos propostos por Brunone et. al. (1991) e Vardy et. al. (1993), na descrição do termo de atrito variável / Abstract: Hydraulic transient is defined as the transition between two permanent flowing conditions. In this transition, the greatness variation related to the flowing, mainly the pressure, is important to the measuring and exploration of hydraulic installation. Studies about transitory situations and the shuntings that caused them are fundamental to guarantee operational safety of the hydraulic plants in general. The transitory flowing analysis in forced conduits is based on equations of continuity and on the amount of movement. One of the imprecisions related to the conventional modeling is in using a almost-static formulation for the friction term, which is only valid for permanent flowing. This paper compares the results obtained from physical model with the one from the mathematical modeling, considering or not a special modeling for transitory friction term. The models used proposed by Brunone et. al. (1991) and Vardy et. al. (1993), to describe the variable friction term / Mestrado / Recursos Hidricos / Mestre em Engenharia Civil
28

Kalibrace rázového kladívka / Impact hammer calibration

Bilík, Šimon January 2019 (has links)
The theoretical part of this thesis focus on the description of the piezoelectric accelerometers and their use for the impact measurements. It also characterizes the construction and the calibration process of the impact hammers with the use of the piezoelectric accelerometers. The practical part describes the place of calibration with the calibration tools, identifies the source of the oscillations on the output signal of the accelerometer and suggests its compensation. Part of the thesis is a service program for the impact measurement, analysis and the impact hammer calibration. Thesis also describes the methodology of the calibration and quantifies the measurement uncertainty.
29

Optimalizace použití chladítek u výroby masivních odlitků / Utilization and the metal chill optimization in production of heavy casting

Rybička, Petr January 2010 (has links)
Grauation Theses is dealing with optimalization of using chills during the manfufacturing procedures of the casts. The first part is giving an overview about the chills itself in foundry industry. The second part is describing the heating procedures in Cast - chill – mould scheme. In the following part the options of calculations to design the chills are described. The practical part is solving the experimental optimalizations of the chills shape in accordance with the hammer ram.
30

Co-Simulation Development for Improved Cavitation Predictions in Oil-Hydraulics Systems : An investigation into the cavitating flow behavior of repetitive water hammers.

Sugathapala, Thisal Mandula, Bakker, Twan, Gudur Suresh, Rahul, Delir, Aryan January 2022 (has links)
Numerical modeling of cavitation using computational software is a highly pursued topic of research due to its impact in different industrial sectors. While some industrial applications such as wastewater treatment and mineral processing are known to advantageously use this phenomena, it remains an unwanted process in others where it is known to induce vibration, reduce performance and cause structural damage. The main objective of the current research study is to investigate the accuracy to which cavitating flow behavior inside oil-hydraulic systems can be computationally modeled, what limitations exist and how to improve numerical predictions. An experimental test-rig has been built in the preceding years with plexiglass tube to observed the vapor formations during cavitation and the pressure readings at three points have been recorded. The current study uses a computational model with the same geometry as the experimental test-rig, and uses the experimentally recorded pressure values for validating numerical results. Two main software are used to setup the simulation framework. The first is Hopsan, one open source simulation software for hydraulic systems developed by Link\"oping University and the second is ANSYS Fluent, a commercial software for modeling complex fluid flow applications. Four different orifices are used to create different outlet pressures. For orifices of diameter 2 mm, 3 mm, and 5 mm, good correlation between numerical and experimental results were observed. Further investigations into complex cavitating flow behavior of repetitive water hammers were also carried out. Different valve profile movements were used to investigate what the impact of having and not having vapor bubbles in the plexiglass tube would have on the pressure distribution when oil starts to re-circulate in the system. Furthermore, repetitive water hammer flow behavior for oscillations of 2, 3, and 4 water hammers were investigated. This investigation revealed several important findings.  The first is that if valve opens to the point that the flow starts to re-circulate in the system while vapor bubbles already exist in the plexiglass tube, massive pressure peaks, as high as 350 bar, will be created in the plexiglass pipe. The strength of this pressure surge will be dependent on the amount of vapor in the pipe when flow is re-introduced. The second is that if the valve starts to re-open (move backwards) while no vapor exists in the plexiglass tube, this movement will result in the formation of vapor. However, this vapor only lasts for a small duration and disappears before the valve reaches a point that allows flow move again. The third and final finding for repetitive water hammers was that the strength of the pressure surges will reduce with each sequential water hammer.

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