Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. Includes bibliographical references.

A study of the pressure drop characteristics of the flow of highly viscous fluids through small diameter orifices was conducted to obtain a better understanding of hydraulic fluid flow loops in vehicles. Pressure drops were measured for each of nine orifices, including orifices of nominal diameter 0.5, 1 and 3 mm, and three thicknesses (nominally 1, 2 and 3 mm), and over a wide range of flow rates (2.86x10sup-7/sup Q 3.33x10sup-4/sup msup3/sup/s). The fluid under consideration exhibits steep dependence of the properties (changes of several orders of magnitude) as a function of temperature and pressure, and is also non-Newtonian at the lower temperatures. The data were non-dimensionalized to obtain Euler numbers and Reynolds numbers using non-Newtonian treatment. It was found that at small values of Reynolds numbers, an increase in aspect ratio (length/diameter ratio of the orifice) causes an increase in Euler number. It was also found that at extremely low Reynolds numbers, the Euler number was very strongly influenced by the Reynolds number, while the dependence becomes weaker as the Reynolds number increases toward the turbulent regime, and the Euler number tends to assume a constant value determined by the aspect ratio and the diameter ratio. A two-region (based on Reynolds number) model was developed to predict Euler number as a function of diameter ratio, aspect ratio, viscosity ratio and generalized Reynolds number. This model also includes data at higher temperatures (20 and le; T and le; 50supo/supC) obtained by Mincks (2002). It was shown that for such highly viscous fluids with non-Newtonian behavior at some conditions, accounting for the shear rate through the generalized Reynolds number resulted in a considerable improvement in the predictive capabilities of the model. Over the laminar, transition and turbulent regions, the model predicts 86% of the data within and plusmn25% for 0.32 l/d (orifice thickness/diameter ratio) 5.72, 0.023 and beta; (orifice/pipe diameter ratio) 0.137, 0.09 Resubge/sub 9677, and 0.0194 and mu;subge/sub 9.589 (kg/m-s)

Orifices are essential devices for measurement and control of flow. It is important to define the flow field and understand the flow characteristics behind an orifice for the sake of reliability measures in many hydraulic engineering applications. Since analytical and experimental solutions are restricted, a numerical solution is obtained using volume of fluid (VOF) method with the CFD solver, FLUENT, for sharp crested orifices, orifice tubes and slots. The results are compared to the available data in the literature / also a large spectrum of data collection has been achieved.

Heavy load equipment, such as tractors, shovels, cranes, airplanes, etc, often employ fluid power (i.e. hydraulic) systems to control their loads by way of valve adjustment in a pump-valve control configuration. Most of these systems have low energy efficiency as a consequence of pressure losses across throttle valves. Much of the energy is converted into heat energy which can have determinantal effects on component life and the surrounding environment. From an energy efficiency point of view, an ideal hydraulic system is one that does not include any throttling valve. One such circuit is made of a variable pump and motor load (pump/motor configuration). The velocity of the load is controlled by manipulating the pump displacement or by changing the rotary speed of the pump shaft. In such a system, the transient response of the load is often unsatisfactory because it is difficult to quickly and accurately manipulate the pump displacement or change shaft speed. Thus circuit design must be a compromise between the energy efficiency of the pump/motor system and the controllability of a pump/valve/motor combination. One possible compromise is to use a pump-valve configuration which reduces energy losses across the valve. One way to achieve this is by controlling the pressure drop across the valve and limiting it to a small value, independent of load pressure. Based on this idea, a type of hydraulic control system, usually called load-sensing (LS), has recently been used in the flow power area. This type of system, however, is complex and under certain operating conditions exhibits instability problems. Methods for compensating these instabilities are usually based on a trial-and-error approach. Although some research has resulted in the definition of some instability criterion, a comprehensive and verifiable approach is still lacking. This research concentrates on identifying the relationship between system parameters and instability in one particular type of LS system. Due to the high degree of non-linearity in LS systems, the instabilities are dependent on the steady state operating point. The study therefore concentrates first on identifying all of the steady state operating points and then classifying them into three steady state operating regions. A dynamic model for each operating region is developed to predict the presence of instabilities. Each model is then validated experimentally. This procedure, used in the study of the LS system, is also applied to a pressure compensated (PC) valve. A PC valve is one in which the flow rate is independent in variations to load pressure. A system which combines a LS pump and a PC valve (for the controlling orifice) is called a load sensing pressure compensated (LSPC) system. This research, then, examines the dynamic performance of the LSPC system using the operating points and steady state operating regions identified in the first part of the research. The original contributions of this research include: (a) establishment of three steady state operating conditions defined as Condition I, II & III, which are based on the solution of steady state non-linear equations; (b) the provision of an empirical model of the orifice discharge coefficient suitable for laminar and turbulent flow, and the transition region between them; (c) and the development of an analytical expression for orifice flow which makes it possible to accurately model and simulate a hydraulic system with pilot stage valve or pump/motor compensator. These contributions result in a practical and reliable method to determine the stability of a LS or LSPC system at any operating point and to optimize the design of the LS or LSPC system.

Heavy load equipment, such as tractors, shovels, cranes, airplanes, etc, often employ fluid power (i.e. hydraulic) systems to control their loads by way of valve adjustment in a pump-valve control configuration. Most of these systems have low energy efficiency as a consequence of pressure losses across throttle valves. Much of the energy is converted into heat energy which can have determinantal effects on component life and the surrounding environment. From an energy efficiency point of view, an ideal hydraulic system is one that does not include any throttling valve. One such circuit is made of a variable pump and motor load (pump/motor configuration). The velocity of the load is controlled by manipulating the pump displacement or by changing the rotary speed of the pump shaft. In such a system, the transient response of the load is often unsatisfactory because it is difficult to quickly and accurately manipulate the pump displacement or change shaft speed. Thus circuit design must be a compromise between the energy efficiency of the pump/motor system and the controllability of a pump/valve/motor combination. One possible compromise is to use a pump-valve configuration which reduces energy losses across the valve. One way to achieve this is by controlling the pressure drop across the valve and limiting it to a small value, independent of load pressure. Based on this idea, a type of hydraulic control system, usually called load-sensing (LS), has recently been used in the flow power area. This type of system, however, is complex and under certain operating conditions exhibits instability problems. Methods for compensating these instabilities are usually based on a trial-and-error approach. Although some research has resulted in the definition of some instability criterion, a comprehensive and verifiable approach is still lacking. This research concentrates on identifying the relationship between system parameters and instability in one particular type of LS system. Due to the high degree of non-linearity in LS systems, the instabilities are dependent on the steady state operating point. The study therefore concentrates first on identifying all of the steady state operating points and then classifying them into three steady state operating regions. A dynamic model for each operating region is developed to predict the presence of instabilities. Each model is then validated experimentally. This procedure, used in the study of the LS system, is also applied to a pressure compensated (PC) valve. A PC valve is one in which the flow rate is independent in variations to load pressure. A system which combines a LS pump and a PC valve (for the controlling orifice) is called a load sensing pressure compensated (LSPC) system. This research, then, examines the dynamic performance of the LSPC system using the operating points and steady state operating regions identified in the first part of the research. The original contributions of this research include: (a) establishment of three steady state operating conditions defined as Condition I, II & III, which are based on the solution of steady state non-linear equations; (b) the provision of an empirical model of the orifice discharge coefficient suitable for laminar and turbulent flow, and the transition region between them; (c) and the development of an analytical expression for orifice flow which makes it possible to accurately model and simulate a hydraulic system with pilot stage valve or pump/motor compensator. These contributions result in a practical and reliable method to determine the stability of a LS or LSPC system at any operating point and to optimize the design of the LS or LSPC system.

Extreme rainfall events associated with global warming are likely to produce an increasing number of flooding scenarios. A large magnitude of hydrologic events can often result in submerged orifice flow (also called pressure flow) or embankment and bridge overtopping flow, in which the foundation of a bridge is subjected to severe scour at the sediment bed. This phenomenon can cause bridge failure during large floods. However, current laboratory studies have focused on only cases of free-surface flow conditions, and they do not take bridge submergence into account. In this study, abutment scour experiments were carried out in a compound channel to investigate the characteristics of abutment scour in free-surface flow, submerged orifice flow, and overtopping flow cases. Detailed bed contours and three components of velocities and turbulent intensities were measured by acoustic Doppler velocimeters. The results show that the contracted flow around an abutment because of lateral and/or vertical contraction and local turbulent structures at the downstream region of the bridge are the main features of the flow responsible for the maximum scour depth around an abutment. The effects of local turbulent structures on abutment scour are discussed in terms of turbulent kinetic energy (TKE) profiles measured in a wide range of flow contraction ratios. The experimental results showed that maximum abutment scour can be predicted by a suggested single relationship even in different flow types (i.e., free, submerged orifice, and overtopping flow) if the turbulent kinetic energy and discharge under the bridge can be accurately measured.

<p>Уз растуће цене енергената, данас је од пресудног значаја тачно мерење<br />протока флуида у индустријским процесима. Због своје једноставности,<br />поузданости и једноставног одржавања, мерне бленде су често<br />распрострањени мерни инструменти у многим индустријама.<br />Конвенционална мерна бленда са једним отвором (БЈО) је широко<br />заступљен мерни инструмент на бази диференцијалног притиска, али овај<br />инструмент има и одређене недостатке, који се могу превазићи мерном<br />блендом са више отвора (БВО). Предмет истраживања докторске<br />дисертације је била БВО. За истраживање су се користиле<br />експериментална и нумеричка метода, а истражили су се однос површине<br />отвора бленде и површине попречног пресека цеви &beta;, пад притисака,<br />губитак притисака, утицај угла излазне ивице мерне бленде, утицај<br />влажности гаса и утицај равних деоница испред и иза мерне бленде на<br />тачност мерења. Такође поред овога одредио се и губитак снаге који<br />настаје код различитих мерних бленди, поврат притиска, коефицијент<br />протока тј. коефицијент пада притиска. Представљени резултати у оквиру<br />докторске дисертације су показали бројне предности БВО у односу на БЈО.</p> / <p>Uz rastuće cene energenata, danas je od presudnog značaja tačno merenje<br />protoka fluida u industrijskim procesima. Zbog svoje jednostavnosti,<br />pouzdanosti i jednostavnog održavanja, merne blende su često<br />rasprostranjeni merni instrumenti u mnogim industrijama.<br />Konvencionalna merna blenda sa jednim otvorom (BJO) je široko<br />zastupljen merni instrument na bazi diferencijalnog pritiska, ali ovaj<br />instrument ima i određene nedostatke, koji se mogu prevazići mernom<br />blendom sa više otvora (BVO). Predmet istraživanja doktorske<br />disertacije je bila BVO. Za istraživanje su se koristile<br />eksperimentalna i numerička metoda, a istražili su se odnos površine<br />otvora blende i površine poprečnog preseka cevi &beta;, pad pritisaka,<br />gubitak pritisaka, uticaj ugla izlazne ivice merne blende, uticaj<br />vlažnosti gasa i uticaj ravnih deonica ispred i iza merne blende na<br />tačnost merenja. Takođe pored ovoga odredio se i gubitak snage koji<br />nastaje kod različitih mernih blendi, povrat pritiska, koeficijent<br />protoka tj. koeficijent pada pritiska. Predstavljeni rezultati u okviru<br />doktorske disertacije su pokazali brojne prednosti BVO u odnosu na BJO.</p> / <p>Nowadays, with rising energy prices, accurate flow measurement is playing an<br />important role in industrial processes. Due to its simplicity, reliability and ease of<br />maintenance, orifice flow meters are very common measuring instruments in<br />many industries. Conventional single-hole orifice (SHO) flow meter is widely<br />used differential pressure-based instrument, but this instrument has some<br />disadvantages that can be overcome by multi-hole orifice (MHO) flow meter. The<br />subject of the doctoral dissertation research was MHO flow meter. Experimental<br />and numerical methods were used for the research, whereas the ratio of the<br />orifice area and the cross-sectional pipe area &beta;, pressure drop, pressure loss,<br />angle of bevel influence, gas humidity influence and straight sections upstream<br />and downstream of the orifice influence on measurement accuracy were<br />investigated. Also, power loss for different orifice flow meters, pressure recovery,<br />discharge coefficient i.e. pressure drop coefficient were determined. Results<br />presented within the doctoral dissertation showed numerous advantages of<br />MHO compared to SHO.</p>

This thesis deals with the influence of the wall roughness on discharge coefficient of sharp-edged circular bottom orifice. It supposed to verify, summarize and extend knowledge of orifice discharge. Author of this thesis determine a discharge coefficient by measurement. Values of discharge coefficient were measured for roughness of the wall represented by different diameters of grains and these values were compared with available values published in specialized bibliography by different scientists. At the thesis end was made a summary evaluation.