No description available.

No description available.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 256-260). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 256-260). Also available on the Internet.

No description available.

<p>The present thesis examined the acute and chronic (training) hemodynamic responses to the unique exercise stimulus of high-intensity "sprint" interval exercise or training (SIT). Previous research has characterized the muscle metabolic and exercise performance adaptations to both short and medium term SIT, however the cardiovascular adjustments and adaptations have not been examined. As part of this thesis two studies were designed to permit evaluations of the chronic cardiovascular responses to a six-week SIT intervention protocol, while two separate studies examined the acute impact of a sprint exercise session on indices of vascular structure and function. Comparisons were made between the SIT and traditional endurance exercise training (ET) in the two exercise training studies, while comparisons were made between a single sprint and that of multiple sprints in the acute exercise studies. The subject population examined in this research was young healthy participants.</p> <p>Our general hypothesis regarding the training adaptations was that similar changes of artery stiffness, vascular endothelial function, blood flow kinetics and oxygen uptake kinetics would occur following SIT compared to ET. Regarding the acute effects of a sprint exercise, we expected arterial stiffness to decrease in the exercising limbs and increase in the central arteries, similar to the responses observed previously immediately following endurance exercise, while we hypothesized that endothelial function would be decreased immediately following the exercise session because of the intense nature of the exercise. The overarching hypothesis guiding these specific hypothesis is that we believe that individual bouts of exercise impact on the arterial wall through the generation of a shear stimulus related to cyclic increases in blood flow and blood pressure. In the short-term the acute response of the artery depends on the composition of the arterial wall and the local stimulus. Over time, functional and structural adjustments occur to normalize the impact of shear forces.</p> <p>Training adaptations in vascular structure and function to SIT were similar to those observed with ET. Both exercise training methods stimulated improved peripheral artery stiffness and endothelial function. The rate of increase in oxygen uptake (kinetic response) was not improved with either training method. However, estimated myocardial demand was reduced with ET but not SIT, which indicates more favourable adaptation in central hemodynamics with ET.</p> <p>Acute sprint exercise markedly reduced peripheral artery stiffness in the exercised limbs well into recovery (~45 minutes), which may benefit central hemodynamics after exercise completion. Sprint exercise also acutely decreased endothelial function, likely because of high oxidative stress generated during the exercise bout and may provide the ideal stimulus for endothelial adaptation.</p> <p>In summary, this thesis highlights the chronic and acute effects of sprint interval exercise and training in young health individuals. The notion that sprint interval exercise provides equivalent benefits to the cardiovascular system as endurance exercise may be true in the peripheral circulation. However, further study focusing is required before the general acceptance of more favorable central hemodynamic effects from endurance exercise training.</p> / Thesis / Doctor of Philosophy (PhD)

Creation of vacuum is very slow, energetically and technologicaly demanding process. Closing of valve is very simple and fast process which produces pressure surges when moving cylinder of fluid is stopped. The goal of this thesis is to find out, if it is possible to combine these processes. To reach this goal, 1D model of compressible gas flow and pressure surges in direct pipeline was made. Then follows experimental measurement evaluation and assessment of potential that the technology offers.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Dr. Seyed M. Ghiaasiaan; Committee Member: Dr. Marc K. Smith; Committee Member: Dr. Sheldon M. Jeter

Pumping is the most efficient transportation and placing method for concrete. Despite the immense progress in the field of concrete technology in the last years, so far there are still neither official regulations nor verified theoretical foundations to be used for the assessment and accurate prediction pumping behaviour of ordinary and high performance concretes. This thesis aims at purposefully investigating pumping of modern concretes and bridging the existing knowledge gap. The main achievement of the present research is the development and verification of a sitecompliant and scientifically based methodology for characterisation and prediction of fresh concrete pumping behaviour. The research focus is set on the importance of the forming lubricating layer (LL) during pumping. Within an extended experimental program, the properties of the LL are captured and quantified. They determine the reduction of friction at the pipe wallconcrete interface and thereby govern the concrete flow. It is proven that the composition and the rheological properties of the forming LL exert an enormous impact on pumping since most of the induced shear stress by pumping pressure is concentrated in this layer. In a further step, the flow pattern of concrete is analytically and numerically determined. The concrete exhibits various principal flow types which are already defined at low flow rates: plug flow in case of strainhardening cementbased composite (SHCC), partial concrete bulk shear in ordinary concretes and pronounced bulk shear for selfcompacting concrete (SCC). The results from the fullscale pumping campaign are confronted with the existing pressure performance nomogram on the determination of pumping parameters. The nomogram’s prediction capacity is extended and verified for highly flowable concretes by replacing the slump and flow table results with the viscosity parameter of the LL. Furthermore, the challenges during pumping of concrete, inter alia, priming of the pipeline, blockage formation and final cleaning, are exemplified, and recommendations for the practitioners are provided. Finally, the transfer of the developed scientifically based and ready to use methodology on site is strongly advocated as a part of the future in situ rheology monitoring concept towards envisaged full automation of concrete production and casting processes.:ZUSAMMENFASSUNG V ABSTRACT VII VORWORT DES HERAUSGEBERS IX DANKSAGUNG XI SYMBOLS XVII INTRODUCTION 1 1.1 FLASHLIGHTS ON HISTORY 1 1.2 MOTIVATION 1 1.3 RESEARCH FIELD 3 1.4 RESEARCH CONCEPT 6 1.5 ECONOMIC RELEVANCE 8 1.6 STRUCTURE AND BOUNDARIES OF THE THESIS 10 STATE OF THE ART 13 2.1 GENERAL 13 2.2 CONCRETE FLOW IN PIPELINE 13 2.3 INFLUENCE OF CONCRETE RHEOLOGY ON PUMPING BEHAVIOUR 16 2.3.1 CEMENT HYDRATION 16 2.3.2 MIXTURE COMPOSITION 17 2.3.2.1 WATER-TO-BINDER RATIO AND PASTE VOLUME 18 2.3.2.2 AGGREGATES 20 2.3.2.3 ADMIXTURES AS PUMPING AIDS 22 2.3.3 HYDRODYNAMIC INTERACTIONS 25 2.3.4 SHEAR HISTORY 27 2.3.5 TEMPERATURE 28 2.4 FORMATION OF LUBRICATING LAYER 30 2.4.1 FLOW-INDUCED PARTICLE MIGRATION 30 2.4.2 PROPERTIES 31 2.4.3 EXPERIMENTAL CHARACTERISATION 32 2.5 BOUNDARY CONDITIONS 32 2.6 PUMPING EQUIPMENT 34 2.7 PRIMING 35 3 APPLIED METHODS 37 3.1 GENERAL 37 3.2 RHEOMETRY 37 3.3 DIRECT DETERMINATION OF PUMPING PRESSURE 40 3.4 SAMPLING AND PRODUCTION OF LUBRICATING MATERIAL 42 3.5 MEASUREMENT OF FILTRATE AMOUNT 45 3.6 ANALYTICAL DETERMINATION OF LUBRICATING LAYER THICKNESS 47 3.7 SMALL-SCALE PUMPING 49 3.8 FULL-SCALE PUMPING 50 3.9 NUMERICAL METHOD 56 3.9.1 MATERIAL MODEL 56 3.9.2 NUMERICAL IMPLEMENTATION 58 4 CHARACTERISATION OF CONCRETE PUMPABILITY 63 4.1 GENERAL 63 4.2 MIXTURE DESIGN PARAMETERS 63 4.3 COMPARISON BETWEEN REFERENCE AND DESIGN MORTARS 65 4.4 RESULTS AND DISCUSSION 65 4.4.1 RHEOLOGICAL BEHAVIOUR OF CONCRETES AND DESIGN MORTARS 65 4.4.2 INFLUENCE OF WALL ROUGHNESS ON RHEOLOGICAL PARAMETERS 67 4.4.3 PREDICTION OF PUMPING PRESSURE 72 4.5 SUMMARY 74 5 LUBRICATING LAYER THICKNESS AND CONCRETE FLOW 75 5.1 GENERAL 75 5.2 MIXTURE DESIGN PARAMETERS 75 5.3 RESULTS AND DISCUSSION 76 5.3.1 CONCRETE FLOW TYPE 76 5.3.2 PREDICTION AND VERIFICATION OF PUMPING PRESSURE 77 5.3.3 QUANTIFICATION OF LUBRICATING LAYER THICKNESS 79 5.4 SUMMARY 82 6 FULL-SCALE PUMPING EXPERIMENTS 83 6.1 GENERAL 83 6.2 MIXTURES AND DESIGN PARAMETERS 83 6.3 RESULTS AND DISCUSSION 85 6.3.1 PRESSURE LOSS AND PRESSURE-FLOW RATE CURVES 85 6.3.2 NUMERICAL SIMULATION RESULTS 86 6.3.3 PRESSURE PREDICTION USING MODIFIED NOMOGRAM 88 6.3.4 COMPARISON BETWEEN PREDICTED AND ACTUAL PRESSURE-FLOW RATE CURVES 90 6.4 SUMMARY 92 7 EFFECT OF PUMPING ON FRESH PROPERTIES OF CONCRETE AND FILTRATE FORMATION 95 7.1 GENERAL 95 7.2 MIXTURES DESIGN PARAMETERS 95 7.3 INFLUENCE OF PUMPING ON PROPERTIES OF FRESH CONCRETE 97 7.4 INFLUENCE OF CONCRETE PROPERTIES ON KINETICS OF FILTRATE FORMATION 98 7.5 IMPACT OF FILTRATE AMOUNT ON PUMPABILITY 101 7.6 SUMMARY 104 8 CHALLENGES RELATED TO PUMPING OF CONCRETE 105 8.1 GENERAL 105 8.2 PRIMING GROUT 105 8.3 PIPELINE GEOMETRY 108 8.4 BLOCKAGES 113 8.5 FILLING DEGREE OF PUMP PISTONS 116 8.6 TEMPERATURE CONTROL 117 8.7 VERTICAL PUMPING 118 8.8 CLEANING THE PIPELINE 119 8.9 SUMMARY 120 9 FINAL CONCLUSIONS AND OUTLOOK 121 9.1 GENERAL 121 9.2 CONCRETE FLOW TYPE 121 9.3 LUBRICATING LAYER PROPERTIES 121 9.4 RHEOLOGICAL DEVICES 122 9.5 FILTRATE FORMATION 122 9.6 NUMERICAL SIMULATIONS 122 9.7 MODIFIED NOMOGRAM 123 9.8 RELEVANCE OF PUMPING EXPERIMENTS 123 9.9 INFLUENCE OF PUMPING ON FRESH CONCRETE PROPERTIES 124 9.10 GENERATED DATABASE 124 9.11 IMPROVING NUMERICAL MODEL 124 9.12 TODAY AND TOMORROW 124 BIBLIOGRAPHY 127 APPENDIX A 135 A.1 MATERIALS DESCRIPTION, CHAPTERS 4 AND 5 135 A.2 MATERIALS DESCRIPTION, CHAPTERS 6, 7 AND 8 136 APPENDIX B 137 APPENDIX C 141 LIST OF SELECTED PUBLICATIONS 143 JOURNALS 143 CONFERENCE PAPERS 143 CURRICULUM VITAE 145 / Das Pumpen stellt die effektivste Methode für das Fördern und Einbringen von Frischbeton auf der Baustelle dar. Trotz der in den letzten Jahren erreichten deutlichen Fortschritte auf betontechnologischem Gebiet existieren für die Beurteilung der Pumpbarkeit von Beton bisher weder offiziell gültige Vorschriften noch abgesicherte theoretische Grundlagen, die eine zielsichere Vorhersage des Pumpverhaltens von Normal- als auch Hochleistungsbetonen ermöglichen. Die vorliegende Arbeit schließt entsprechende Wissenslücken und befasst sich gezielt mit dem Pumpen moderner Betone. Grundlegenden Erkenntnisgewinn stellt die Entwicklung einer wissenschaftlich fundierten, baustellengerechten Prüfmethodik zur Charakterisierung und Vorhersage des Pumpverhaltens von Frischbeton dar. Der Untersuchungsfokus richtet sich auf die Wirkung der sich beim Pumpvorgang ausbildenden Gleitschicht. Ein umfangreiches Untersuchungsprogramm gestattet die Erfassung und Quantifizierung der Eigenschaften dieser Schicht. Sie bestimmen infolge deutlicher Reduzierung der Reibung an der Grenzfläche zwischen Rohrwandung und Beton die Betonströmung entscheidend. Bewiesen wird, dass Betonzusammensetzung und rheologische Eigenschaften der Gleitschicht maßgebende Auswirkungen auf den Pumpvorgang haben, da sich die pumpdruckinduzierte Scherspannung in dieser Schicht konzentriert. Weiterhin erfolgt sowohl eine analytische als auch numerische Charakterisierung der Betonströmung im Rohr. Nachgewiesen wird, dass sich beim Pumpvorgang betonspezifisch unterschiedliche Strömungsarten einstellen, die bereits bei niedrigen Durchflussmengen definiert sind: Pfropfenströmung in hochduktilen Betonen, partielle Scherung des Kernbetons in Normalbetonen und signifikante Scherung in selbstverdichtenden Betonen. Aus großtechnisch durchgeführten Pumpversuchen gewonnene Ergebnisse werden dem derzeit vorhandenen, verbesserungsbedürftigen Betondruck-Leistungs-Nomogramm zur Einstellung von Parametern an der Betonpumpe gegenübergestellt. Die Vorhersagekapazität des Nomogramms kann durch den Ersatz der Ausbreit- bzw. Setzfließmaßangaben mit Viskositätsangaben der Gleitschicht erweitert und verifiziert werden. Des Weiteren werden baustellenbezogene Herausforderungen im Gesamtprozess des Betonpumpvorgangs, u. a. Vorbereitung der Rohrleitung vor dem Pumpen, Auftreten von Stopfern und Endreinigung exemplarisch dargestellt sowie Empfehlungen für die Praktiker erarbeitet. Schließlich wird der Transfer der in dieser Arbeit entwickelten wissenschaftlich basierten und anwendungsbereiten Methodik als Teil des zukünftigen Konzeptes für die in-situ Rheologie-Überwachung hinsichtlich einer angestrebten vollständigen Automatisierung von Fertigungs- und Einbringprozessen von Beton mit Nachdruck empfohlen.:ZUSAMMENFASSUNG V ABSTRACT VII VORWORT DES HERAUSGEBERS IX DANKSAGUNG XI SYMBOLS XVII INTRODUCTION 1 1.1 FLASHLIGHTS ON HISTORY 1 1.2 MOTIVATION 1 1.3 RESEARCH FIELD 3 1.4 RESEARCH CONCEPT 6 1.5 ECONOMIC RELEVANCE 8 1.6 STRUCTURE AND BOUNDARIES OF THE THESIS 10 STATE OF THE ART 13 2.1 GENERAL 13 2.2 CONCRETE FLOW IN PIPELINE 13 2.3 INFLUENCE OF CONCRETE RHEOLOGY ON PUMPING BEHAVIOUR 16 2.3.1 CEMENT HYDRATION 16 2.3.2 MIXTURE COMPOSITION 17 2.3.2.1 WATER-TO-BINDER RATIO AND PASTE VOLUME 18 2.3.2.2 AGGREGATES 20 2.3.2.3 ADMIXTURES AS PUMPING AIDS 22 2.3.3 HYDRODYNAMIC INTERACTIONS 25 2.3.4 SHEAR HISTORY 27 2.3.5 TEMPERATURE 28 2.4 FORMATION OF LUBRICATING LAYER 30 2.4.1 FLOW-INDUCED PARTICLE MIGRATION 30 2.4.2 PROPERTIES 31 2.4.3 EXPERIMENTAL CHARACTERISATION 32 2.5 BOUNDARY CONDITIONS 32 2.6 PUMPING EQUIPMENT 34 2.7 PRIMING 35 3 APPLIED METHODS 37 3.1 GENERAL 37 3.2 RHEOMETRY 37 3.3 DIRECT DETERMINATION OF PUMPING PRESSURE 40 3.4 SAMPLING AND PRODUCTION OF LUBRICATING MATERIAL 42 3.5 MEASUREMENT OF FILTRATE AMOUNT 45 3.6 ANALYTICAL DETERMINATION OF LUBRICATING LAYER THICKNESS 47 3.7 SMALL-SCALE PUMPING 49 3.8 FULL-SCALE PUMPING 50 3.9 NUMERICAL METHOD 56 3.9.1 MATERIAL MODEL 56 3.9.2 NUMERICAL IMPLEMENTATION 58 4 CHARACTERISATION OF CONCRETE PUMPABILITY 63 4.1 GENERAL 63 4.2 MIXTURE DESIGN PARAMETERS 63 4.3 COMPARISON BETWEEN REFERENCE AND DESIGN MORTARS 65 4.4 RESULTS AND DISCUSSION 65 4.4.1 RHEOLOGICAL BEHAVIOUR OF CONCRETES AND DESIGN MORTARS 65 4.4.2 INFLUENCE OF WALL ROUGHNESS ON RHEOLOGICAL PARAMETERS 67 4.4.3 PREDICTION OF PUMPING PRESSURE 72 4.5 SUMMARY 74 5 LUBRICATING LAYER THICKNESS AND CONCRETE FLOW 75 5.1 GENERAL 75 5.2 MIXTURE DESIGN PARAMETERS 75 5.3 RESULTS AND DISCUSSION 76 5.3.1 CONCRETE FLOW TYPE 76 5.3.2 PREDICTION AND VERIFICATION OF PUMPING PRESSURE 77 5.3.3 QUANTIFICATION OF LUBRICATING LAYER THICKNESS 79 5.4 SUMMARY 82 6 FULL-SCALE PUMPING EXPERIMENTS 83 6.1 GENERAL 83 6.2 MIXTURES AND DESIGN PARAMETERS 83 6.3 RESULTS AND DISCUSSION 85 6.3.1 PRESSURE LOSS AND PRESSURE-FLOW RATE CURVES 85 6.3.2 NUMERICAL SIMULATION RESULTS 86 6.3.3 PRESSURE PREDICTION USING MODIFIED NOMOGRAM 88 6.3.4 COMPARISON BETWEEN PREDICTED AND ACTUAL PRESSURE-FLOW RATE CURVES 90 6.4 SUMMARY 92 7 EFFECT OF PUMPING ON FRESH PROPERTIES OF CONCRETE AND FILTRATE FORMATION 95 7.1 GENERAL 95 7.2 MIXTURES DESIGN PARAMETERS 95 7.3 INFLUENCE OF PUMPING ON PROPERTIES OF FRESH CONCRETE 97 7.4 INFLUENCE OF CONCRETE PROPERTIES ON KINETICS OF FILTRATE FORMATION 98 7.5 IMPACT OF FILTRATE AMOUNT ON PUMPABILITY 101 7.6 SUMMARY 104 8 CHALLENGES RELATED TO PUMPING OF CONCRETE 105 8.1 GENERAL 105 8.2 PRIMING GROUT 105 8.3 PIPELINE GEOMETRY 108 8.4 BLOCKAGES 113 8.5 FILLING DEGREE OF PUMP PISTONS 116 8.6 TEMPERATURE CONTROL 117 8.7 VERTICAL PUMPING 118 8.8 CLEANING THE PIPELINE 119 8.9 SUMMARY 120 9 FINAL CONCLUSIONS AND OUTLOOK 121 9.1 GENERAL 121 9.2 CONCRETE FLOW TYPE 121 9.3 LUBRICATING LAYER PROPERTIES 121 9.4 RHEOLOGICAL DEVICES 122 9.5 FILTRATE FORMATION 122 9.6 NUMERICAL SIMULATIONS 122 9.7 MODIFIED NOMOGRAM 123 9.8 RELEVANCE OF PUMPING EXPERIMENTS 123 9.9 INFLUENCE OF PUMPING ON FRESH CONCRETE PROPERTIES 124 9.10 GENERATED DATABASE 124 9.11 IMPROVING NUMERICAL MODEL 124 9.12 TODAY AND TOMORROW 124 BIBLIOGRAPHY 127 APPENDIX A 135 A.1 MATERIALS DESCRIPTION, CHAPTERS 4 AND 5 135 A.2 MATERIALS DESCRIPTION, CHAPTERS 6, 7 AND 8 136 APPENDIX B 137 APPENDIX C 141 LIST OF SELECTED PUBLICATIONS 143 JOURNALS 143 CONFERENCE PAPERS 143 CURRICULUM VITAE 145

Gas-liquid annular two phase flow in pipes is important in the oil and gas, nuclear and the process industries. It has been identified as one of the most frequently encountered flow regimes and many models (empirical and theoretical) for the film flow and droplet behaviour for example have been developed since the 1950s. However, the behaviour in large pipes (those with diameter greater than 100 mm) has not been fully explored. As a result, the two- phase flow characteristics, data, and models specifically for such pipes are scarce or non-existent such that those from smaller pipes are extrapolated for use in design and operation. Many authors have cautioned against this approach since multiphase pipe flow behaviour is different between small and large pipes. For instance the typical slug flows seem not to occur in vertical upwards flows when the pipe diameter exceeds 100 mm. It is therefore imperative that theoretical models and empirical correlations for such large diameter pipes are specifically developed.