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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.
1

Uniform Flow Development Length in a Rough Laboratory Flume

Sharma, Sanjib 01 May 2015 (has links)
Test sections in laboratory studies should be fully developed and uniform if they are to be generalized. The objective of this study is to develop a model for predicting the uniform flow development length (Lunif) in a rough laboratory flume as a function of hydraulic parameters and bed particle roughness height (ks). Using an ADV time-averaged point velocity was measured in developing and fully developed turbulent subcritical rough open-channel flows. A series of laboratory tests were carried out in a 6.1-m-long and 0.46-m-wide rectangular channel. Tests were conducted with fine gravel (d50 = 5.8 mm, ks = 3.1d90 = 0.026 m), medium gravel (d50 = 14 mm, ks = 0.068 m), and with fine /medium gravel (d50 = 11 mm, ks = 0.04 m). For each test, longitudinal point velocity measurements were made along the center of the channel at five elevations, and at thirteen longitudinal stations. The study concluded that for flow to be uniform, the flow depth and mean cross-sectional velocity must be constant. In addition, root mean square of the fluctuating component of the velocity, RMS(u'), which is the measure of the turbulence intensity, should be uniform in order for a flow to consider uniform. Thus, RMS(u') is one of the indicative measures for determining the location where the developing flow is fully developed and uniform. The results showed that increasing the bed roughness height decreases the uniform flow development length. Using the dimensional and statistical analyses Lunif was estimated as a linear function of Reynold's particle number and Froude number.
2

Investigation of the Effect of Non-Darcy Flow and Multi-Phase Flow on the Productivity of Hydraulically Fractured Gas Wells

Alarbi, Nasraldin Abdulslam A. 2011 August 1900 (has links)
Hydraulic fracturing has recently been the completion of choice for most tight gas bearing formations. It has proven successful to produce these formations in a commercial manner. However, some considerations have to be taken into account to design an optimum stimulation treatment that leads to the maximum possible productivity. These considerations include, but not limited to, non-Darcy flow and multiphase flow effects inside the fracture. These effects reduce the fracture conductivity significantly. Failing to account for that results in overestimating the deliverability of the well and, consequently, to designing a fracture treatment that is not optimum. In this work a thorough investigation of non-Darcy flow and multi-phase flow effects on the productivity of hydraulically fractured wells is conducted and an optimum fracture design is proposed for a tight gas formation in south Texas using the Unified Fracture Design (UFD) Technique to compensate for the mentioned effects by calculating the effective fracture permeability in an iterative way. Incorporating non-Darcy effects results in an optimum fracture that is shorter and wider than the fracture when only Darcy calculations are considered. That leads to a loss of production of 5, 18 percent due to dry and multiphase non-Darcy flow effects respectively. A comparison between the UFD and 3D simulators is also done to point out the differences in terms of methodology and results. Since UFD incorporated the maximum dimensionless productivity index in the fracture dimensions design, unlike 3D simulators, it can be concluded that using UFD to design the fracture treatment and then use the most important fracture parameters outputs (half length and CfDopt) as inputs in the simulators is a recommended approach.
3

Gas condensate damage in hydraulically fractured wells

Reza, Rostami Ravari 15 November 2004 (has links)
This project is a research into the effect of gas condensate damage in hydraulically fractured wells. It is the result of a problem encountered in producing a low permeability formation from a well in South Texas owned by the El Paso Production Company. The well was producing from a gas condensate reservoir. Questions were raised about whether flowing bottomhole pressure below dewpoint would be appropriate. Condensate damage in the hydraulic fracture was expected to be of significant effect. In the most recent work done by Adedeji Ayoola Adeyeye, this subject was studied when the effects of reservoir depletion were minimized by introduction of an injector well with fluid composition the same as the original reservoir fluid. He also used an infinite conductivity hydraulic fracture along with a linear model as an adequate analogy. He concluded that the skin due to liquid build-up is not enough to prevent lower flowing bottomhole pressures from producing more gas. This current study investigated the condensate damage at the face of the hydraulic fracture in transient and boundary dominated periods when the effects of reservoir depletion are taken into account. As a first step, simulation of liquid flow into the fracture was performed using a 2D 1-phase simulator in order to help us to better understand the results of gas condensate simulation. Then during the research, gas condensate models with various gas compositions were simulated using a commercial simulator (CMG). The results of this research are a step forward in helping to improve the management of gas condensate reservoirs by understanding the mechanics of liquid build-up. It also provides methodology for quantifying the condensate damage that impairs linear flow of gas into the hydraulic fracture.
4

Modeling, Identification and Control Design for an Electro-Hydraulic Rotator

Zanhar, Andrej January 2010 (has links)
<p>Robotic manipulators have been introduced in industry as a form of increasing productivity. Today, there exist an interest to enlarge the application of these manipulators to outdoor environments. Forestry cranes used in the forestry industry are a clear example. A long term goal in this industry is the development of autonomous systems to increase the logging efficiency. In this thesis, we consider how to control the rotator of these cranes, which is an electro-hydraulically actuated motor, and is used to control the end ffector tool. Control system design for the rotator is a challenging task since the sensing is not available to full extent. The main reason is the harsh environment that these machines are exposed to and sensors such as encoders are very fragile and cannot be used. In this thesis we use alternative sensing devices, such as a magnetic sensor and a stereo camera. In the case of the camera we face a problem with big delay. A prediction method has been used to compute desired values. Due to various reasons certain measuring devices can not be used in the industry. We consider four cases for control system design where dfferent combinations of available sensors have been used. Initially angular position of the rotator is controlled using only the magnetic sensor. A cascade control setup is used where pressure and position are measurable, first using the magnetic sensor and later using the camera. When only pressure measurements are available identified models have replaced sensors for position feedback. All tests and experiments have been done using a scaled version of a real forestry crane. The available crane has similar configuration and dynamics as the real one and is therefor useful for experimental purposes.</p>
5

Modeling, Identification and Control Design for an Electro-Hydraulic Rotator

Zanhar, Andrej January 2010 (has links)
Robotic manipulators have been introduced in industry as a form of increasing productivity. Today, there exist an interest to enlarge the application of these manipulators to outdoor environments. Forestry cranes used in the forestry industry are a clear example. A long term goal in this industry is the development of autonomous systems to increase the logging efficiency. In this thesis, we consider how to control the rotator of these cranes, which is an electro-hydraulically actuated motor, and is used to control the end ffector tool. Control system design for the rotator is a challenging task since the sensing is not available to full extent. The main reason is the harsh environment that these machines are exposed to and sensors such as encoders are very fragile and cannot be used. In this thesis we use alternative sensing devices, such as a magnetic sensor and a stereo camera. In the case of the camera we face a problem with big delay. A prediction method has been used to compute desired values. Due to various reasons certain measuring devices can not be used in the industry. We consider four cases for control system design where dfferent combinations of available sensors have been used. Initially angular position of the rotator is controlled using only the magnetic sensor. A cascade control setup is used where pressure and position are measurable, first using the magnetic sensor and later using the camera. When only pressure measurements are available identified models have replaced sensors for position feedback. All tests and experiments have been done using a scaled version of a real forestry crane. The available crane has similar configuration and dynamics as the real one and is therefor useful for experimental purposes.
6

Využití vedlejších produktů z výroby cementotřískových desek pro podkladní vrstvy / Utilization of by-products from cement-bonded particleboards production in base layers

Dobrovolná, Martina January 2019 (has links)
This thesis deals with the use of by–products from the production of cement–bonded particle boards as an alternative raw material for the stabilization of the subsoil or into a ground solid. The theoretical part briefly describes the current status of waste management. A set of alterantive raw materials used to hydraulically cemented mixtures is listed here as well as the recherche of the foreign research is elaborated from this area. The experimental part of the thesis firstly deals with the choice of raw materials and basic recipes. In the advanced stage the laboratory analyses are carried out on the modified formulas. Based on the results of these analyses the posibility of using by–products from the production of cement–bonded boards for the stabilization of the subsoil is evaluated here.
7

Evaluation of Hydraulically InterconnectedSuspension Systems on TARA Machine

Yu, Jingyao January 2023 (has links)
The TARA machine from Volvo is equipped with hydraulic suspension which can be connected with each other in different ways. The present study focuses on enhancing the dynamic performance of the TARA machine during its operations through the investigation of various hydraulically interconnected suspension (HIS) systems. Employing a comprehensive cosimulation approach using Adams Car (ACar) and MATLAB Simulink, a full-vehicle analysis was conducted. The TARA machine was modeled in ACar, while the Simulink environment was utilized to design the control system and implement the HIS configuration. The HIS system was connected within two wheels, explored with three different connection types: pendulum, cross or individual connections. The model was simulated in pitch, roll, bounce and warp modes, achieved by running on different road conditions generated in ACar. The change of different HIS systems were achieved by manipulation of the hydraulic circuit in Simulink. By analyzing the dynamic performance of the HIS systems in terms of acceleration, the study aims to identify the most favorable HIS configuration on TARA machine. This investigation provides valuable insights for optimizing the overall operational dynamics of TARA machines, thereby contributing to the development of advanced HIS systems in the field. / Den TARA-maskinen från Volvo är utrustad med hydraulisk fjädring som kan kopplas samman på olika sätt. Den aktuella studien fokuserar på att förbättra den dynamiska prestandan hos TARA-maskinen under dess drift genom undersökning av olika hydrauliskt sammanlänkade fjädringssystem (HIS). Genom att använda en omfattande sam-simulering med Adams Car (ACar) och MATLAB Simulink utfördes en helhetsanalys av fordonet. TARA-maskinen modellerades i ACar medan Simulink-miljön användes för att utforma kontrollsystemet och implementera HIS-konfigurationen. HIS-systemet var kopplat mellan två hjul och utforskades med tre olika typer av kopplingar: pendel, korsning eller individuella kopplingar. Modellen simulerades i lutning, roll, studs och förvrängning, vilket åstadkoms genom att köra på olika vägförhållanden genererade i ACar. Förändringen av olika HIS-system åstadkoms genom manipulering av hydraulikkretsen i Simulink. Genom att analysera HIS-systemens dynamiska prestanda i form av acceleration syftar studien till att identifiera den mest fördelaktiga HIS-konfigurationen för TARA-maskinen. Denna undersökning ger värdefulla insikter för att optimera den övergripande operationella dynamiken hos TARA-maskiner och bidrar därmed till utvecklingen av avancerade HIS-system inom området.
8

Stavební recykláty pro stmelené směsi vozovek / The building waste for bound mixtures of the pavements

Pokluda, Radim January 2013 (has links)
In the theoretical part of the thesis are generally characterized hydraulically bound mixtures, their types, classification systems, manufacturing technology and the laying. There are also described experiences from abroad with the use secondary and recycled materials in hydraulically bound mixtures. The practical part deals with the experimental verification of the possibility of the use of secondary materials in hydraulically bound mixtures in construction of road infrastructure. In road laboratory Institute of road structures Brno university of technology was the five proposed mixtures, an assessment of their parameters with regard to the possibility of using these mixtures in the road sub-base layers. The work is also aimed at comparison of results elasticity modules reached laboratory testing and experimental measurements on road polygon.
9

Využití recyklátů z vozovek do pozemních komunikací / The utilization of the pavement waste materials to roads

Furdaničová, Alice Unknown Date (has links)
The diploma thesis deals with the use of recycled asphalt with aggregate in a hydraulically bound mixtures. The mixture is determined in the base or sub-base course of the pavement. The theoretical part of the diploma thesis describes the base course of the pavement, the production of recyclates from construction demolition waste, the acquisition and processing of recycled asphalt, the road reuse and recycling. The thesis is enriched by a contribution from the implementation of recycled asphalt laying into the base course of the communication company SKANSKA a.s. and ČNES a.s. The next chapter describes detailed experiences with recycling abroad. The thesis also contains a description of laboratory tests, which are important for evaluating the properties of mixtures with recycled asphalt. The practical part verifies the suitability of the mixture of recycled asphalt and aggregate for the road surface by testing the transverse tensile strength, compressive strength and frost and water resistance. The mixtures used are found to be suitable for pavement base course.

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