Particle-laden turbulent flow through a straight square duct at Reτ = 300 is studied using direct numerical simulation (DNS) and Lagrangian particle tracking. A parallelized 3-D particle tracking direct numerical simulation code has been developed to perform the large-scale turbulent particle transport computations reported in this thesis. The DNS code is validated after demonstrating good agreement with the published DNS results for the same flow and Reynolds number. Lagrangian particle transport computations are carried out using a large ensemble of passive tracers and finite-inertia particles and the assumption of one-way fluid-particle coupling. Using four different types of initial particle distributions, Lagrangian particle dispersion, concentration and deposition are studied in the turbulent straight square duct. Particles are released in a uniform distribution on a cross-sectional plane at the duct inlet, released as particle pairs in the core region of the duct, distributed randomly in the domain or distributed uniformly in planes at certain heights above the walls. One- and two-particle dispersion statistics are computed and discussed for the low Reynolds number inhomogeneous turbulence present in a straight square duct. New detailed statistics on particle number concentration and deposition are also obtained and discussed.

Background The gallstone prevalence in the western world is 10-20%. Most gallstones are silent, but symptoms and complications appear in 20-40%. The incidence of symptom development in patients with silent gallstones is 2-4% per year. The indication for surgical (including endoscopic) treatment of gallstones is symptoms of certain magnitude, and no contraindications. During the past three decades an intense technical development in imaging (ultrasound, computerised tomography and magnetic resonance imaging), endoscopic therapy, and surgery has taken place. The aim of this thesis is to scrutinize changes in management of complicated gallstone disease on a population-based level, using national register data. Have the new methods improved the treatment of acute pancreatitis, common bile duct stones and acute gallbladder disease? Methods Data is collected from National Patient Register (NPR) run by The Swedish National Board of Health and Welfare. NPR collects discharge data from every admission from every Swedish hospital. Mortality is calculated as standardised mortality ratio (SMR) using age-, gender-, and calendar year specific survival estimates. We have studied both general trends in admissions and treatment alternatives and outcomes in defined patient cohorts. Length of hospital stay, readmission, and mortality has been used as proxy indicators of the effectiveness of treatment strategies used. Results During the study period mortality in acute pancreatitis (SMR within 90 days of admission) improved and hospital stay for all patients with acute pancreatitis decreased. Cholecystectomy rate at or shortly after index stay for mild acute biliary pancreatitis increased from 14.5 % to 22.7 %. Of all patients with acute pancreatitis 68.4 % of the patients had no aetiological diagnosis in the register. The incidence of bile duct interventions increased 27.8% from 1988 through 2006. The favoured treatment of bile duct stones changed from open choledocholithectomy to endoscopic sphincterotomy with stone extraction during the same period. However, in 2006, still 19.6% of bile duct interventions for stones were performed as choledochotomy and in the great majority of these cases as open surgery. This indicates a continuing need of education in open bile duct surgery. Mean hospital stay for treatment of common bile duct stones decreased significantly (4.5 days) during the period studied. The mortality (SMR) diminished although without statistical significance during the time period, and there was no significant difference in SMR between choledochotomy and endoscopic sphincterotomy. For acute gallbladder disease a moderate increase of admissions occurred from 1988 through 2006. The relation between acute cholecystectomies versus all cholecystectomies did not change during this period. Of all patients admitted with acute gallbladder disease 32.3 % were cholecystectomised during their first hospital stay, whereas 20.3 % underwent elective cholecystectomy and 6.1 % emergency cholecystectomy within two years of first admission. 41.4 % of patients were not operated on for gallbladder disease within two years of first admission with this diagnosis. Mortality from first admission and 90 days onwards was elevated three-fold during the entire period without time trend, without statistical difference between age groups, and between patients who had cholecystectomy at first admission or later. Conclusion During the audit period treatment of acute pancreatitis improved. However, etiological classification and timing of cholecystectomy in mild acute biliary pancreatitis fell below accepted guidelines. Interventions on the common bile duct for gallstone disease increased significantly. Common bile duct clearance has been separated from cholecystectomy, and cholecystectomy often not done. Only one third of all patients with acute gallbladder disease underwent cholecystectomy at first admission. There is room for improvement in treatment of complicatedgallstone disease, and, gallstone surgeons still need good knowledge in open biliary surgery.

New methodologies and concepts for developing compact and energy efficient automotive exhaust systems have been studied. This originates in the growing concern for global warming, to which road transportation is a major contributor. The focus has been on commercial vehicles—most often powered by diesel engines—for which the emission legislation has been dramatically increased over the last decade. The emissions of particulates and nitrogen oxides have been successfully reduced by the introduction of filters and catalytic converters, but the fuel consumption, which basically determines the emissions of carbon dioxides, has not been improved accordingly. The potential reduction of fuel consumption by optimising the exhaust after-treatment system (assuming fixed after-treatment components) of a typical heavy-duty commercial vehicle is ~4%, which would have a significant impact on both the environment and the overall economy of the vehicle. First, methodologies to efficiently model complex flow duct networks such as exhaust systems are investigated. The well-established linear multiport approach is extended to include flow-acoustic interaction effects. This introduces an effective way of quantifying amplification and attenuation of incident sound, and, perhaps more importantly, the possibility of predicting nonlinear phenomena such as self-sustained oscillations—whistling—using linear models. The methodology is demonstrated on T-junctions, which is a configuration well known to be prone to self-sustained oscillations for grazing flow past the side branch orifice. It is shown, and validated experimentally, that the existence and frequency of self-sustained oscillations can be predicted using linear theory. Further, the aeroacoustics of T-junctions are studied. A test rig for the full determination of the scattering matrix defining the linear three-port representing the T-junction is developed, allowing for any combination of grazing-bias flow. It is shown that the constructive flow-acoustic coupling not only varies with the flow configuration but also with the incidence of the acoustic disturbance. Configurations where flow from the side branch joins the grazing flow are still prone to whistling, while flow bleeding off from the main branch effectively cancels any constructive flow-acoustic coupling. Two silencer concepts are evaluated: first the classic Herschel-Quincke tube and second a novel modified flow reversal silencer. The Herschel-Quincke tube is capable of providing effective attenuation with very low pressure loss penalty. The attenuation conditions are derived and their sensitivity to mean flow explained. Two implementations have been modelled using the multiport methodology and then validated experimentally. The first configuration, where the nodal points are composed of T-junctions, proves to be an example where internal reflections in the system can provide sufficient feedback for self-sustained oscillation. Again, this is predicted accurately by the linear theory. The second implementation, with nodal points made from Y-junctions, was designed to allow for equal flow distribution between the two parallel ducts, thus allowing for the demonstration of the passive properties of the system. Experimental results presented for these two configurations correlate well with the derived theory. The second silencer concept studied consists of a flow reversal chamber that is converted to a resonator by acoustically short-circuiting the inlet and outlet ducts. The eigenfrequency of the resonator is easily shifted by varying the geometry of the short circuit, thus making the proposed concept ideal for implementation as a semi-active device. Again the concept is modelled using the multiport approach and validated experimentally. It is shown to provide significant attenuation over a wide frequency range with a very compact design, while adding little or no pressure loss to the system. / QC 20110208

Single Duct Variable Air Volume (SDVAV) systems use series and parallel Fan Powered Terminal Units to control the air flow in conditioned spaces. This research developed a laboratory verified model of SDVAV systems that used series and parallel fan terminal units where the fan speeds were controlled by either Silicon Controlled Rectifiers (SCR) or Electronically Commutated Motors (ECM) motors. As part of the research, the model was used to compare the performance of the systems and to predict the harmonics generated by ECM systems. All research objectives were achieved. The CFD model, which was verified with laboratory measurements, showed the potential to identify opportunities for improvement in the design of the FPTU and accurately predicted the static pressure drop as air passed through the unit over the full operating range of the FPTU. Computational fluid dynamics (CFD) models of typical a FPTU were developed and used to investigate opportunities for optimizing the design of FPTUs. The CFD model identified key parameters required to conduct numerical simulations of FPTU and some of the internal components used to manufacture the units. One key internal component was a porous baffle used to enhance mixing when primary air and induced air entered the mixing chamber. The CFD analysis showed that a pressure-drop based on face velocity model could be used to accurately predict the performance of the FPTU. The SDVAV simulation results showed that parallel FPTUs used less energy overall than series systems that used SCR motors as long as primary air leakage was not considered. Simulation results also showed that series ECM FPTUs used about the same amount of energy, within 3 percent, of parallel FPTU even when leakage was not considered. A leakage rate of 10 percent was enough to reduce the performance of the parallel FPTU to the level of the series SCR system and the series ECM FPTUs outperformed the parallel FPTUs at all weather locations used in the study.

Controlling unsteady combustion induced gas flow fluctuations and the resultant motor vibrations is a very significant step in rocket motor design. It occurs when the unsteady heat release due to combustion happens to feed the acoustic oscillations of the closed duct forming a feed-back system. The resultant vibrations concerned may even lead to total failure of the rocket system unless analysed and tested thoroughly. This thesis aims developing a linear numerical analysis method for the growth rate of instabilities and possible mode shape of a liquid-propelled chamber geometry. In particular, A 3-D Helmholtz code, utilizing Culicks spatial averaging linear iterative method, is developed to find the form of deformed mode shapes iteratively to obtain possible effects of heat source and impedance boundary conditions. The natural mode shape phase is solved through finite volume discretization and the open-source eigenvalue extractor, ARPACK, and its parallel implementation PARPACK. The iterative method is particularly used for analyzing the geometries with complex shapes and essentially for disturbances of small magnitudes to natural mode shapes. The developed tools are tested via two simple cases, a duct with inactive flame and a Rijke tube, used as validation cases for the code particularly with only boundary contribution and heat contribution respectively. A sample 2-D and 3-D liquid-propelled combustion chamber is also analysed with heat sources. After comparing with the expected values, it is eventually proved that the method should be only used for determining the modes instability analysis, as to whether it keeps vibrating or decays. The methodology described can be used as a preliminary design tool for the design of liquid-propellant rocket engine combustors, rapidly revealing only the onset of instabilities.

Η ηπατική εγκεφαλοπάθεια είναι ένα πολύπλοκο νευροψυχιατρικό σύνδρομο που έχει συσχετισθεί με οξείες και χρόνιες ηπατοπάθειες. Τα τελευταία χρόνια συσσωρεύονται πληροφορίες που εμπλέκουν το οξειδωτικό στρες (φορτίο) ως παράγοντα-κλειδί στην παθογένεση της ηπατικής εγκεφαλοπάθειας σε μελέτες που χρησιμοποιούν ως μετρούμενους δείκτες την υπεροξείδωση λιπιδίων και το οξειδοαναγωγικό ζεύγος της γλουταθειόνης (GSH/GSSG). Στην παρούσα μελέτη χρησιμοποιήθηκε ένα μοντέλο πειραματικού αποφρακτικού ίκτερου με απολίνωση του χοληδόχου πόρου. Αρσενικοί αρουραίοι χωρίστηκαν σε ομάδες ελέγχου, ψευδώς χειρουργημένων, και σε ομάδες απολίνωσης χοληδόχου πόρου που είτε θυσιάστηκαν την 5η ημέρα, είτε τη 10η ημέρα, ή τους χορηγήθηκαν αντιοξειδωτικοί παράγοντες (NAC, ALP, Vit-E). Στη συνέχεια, μελετήθηκε η θειολική οξειδοαναγωγική κατάσταση στον εγκέφαλο των αρουραίων, και μάλιστα ανά περιοχές (εγκεφαλικός φλοιός, στέλεχος, παρεγκεφαλίδα), καθώς και η επίδραση των επιλεγμένων αντιοξειδωτικών παραγόντων σε αυτήν. Χρησιμοποιήθηκε για πρώτη φορά μια πιο αντιπροσωπευτική εκτίμηση του οξειδωτικού στρες, καθώς ποσοτικοποιήθηκαν συγκεκριμένοι δείκτες υψηλού (GSSG, NPSSR, NPSSC, PSSR, PSSC, PSSP, υπεροξείδια λιπιδίων) και χαμηλού (GSH, CSH, PSH) οξειδωτικού στρες. Τα αποτελέσματά μας δείχνουν αύξηση των πρώτων και μείωση των τελευταίων σε όλες τις εγκεφαλικές περιοχές καταδεικνύοντας έτσι την παρουσία αυξημένου οξειδωτικού φορτίου στον αποφρακτικό ίκτερο. Το σημαντικότερο αποτέλεσμα αυτής της μελέτης είναι ότι κατέδειξε πρώιμα σημεία οξειδωτικού στρες στον εγκέφαλο ήδη από την 5η ημέρα μετά την απολίνωση του χοληδόχου πόρου. Οι μεταβολές των βιοχημικών δεικτών, και αυτό αφορά σε όλους τους δείκτες και σε όλες τις εγκεφαλικές περιοχές, αρχίζουν να φαίνονται από την 5η ημέρα και γίνονται στατιστικά σημαντικές τη 10η ημέρα από την απολίνωση του χοληδόχου πόρου. Διαπιστώσαμε επιπλέον ότι η GSH είχε περίπου διπλάσιες τιμές στον εγκεφαλικό φλοιό από ό, τι στο στέλεχος και την παρεγκεφαλίδα, και ότι στο στέλεχος παρατηρήθηκε μια δραματική αύξηση των επιπέδων των NPSSR τη 10η ημέρα μετά την απολίνωση του χοληδόχου πόρου, τα οποία όμως παρέμειναν χαμηλά στις άλλες δύο περιοχές. Καθώς είναι γνωστό πως το οξειδωτικό στρες έχει ενοχοποιηθεί στην παθογένεση διαφόρων νευροεκφυλιστικών παθήσεων στον άνθρωπο, τα ευρήματα αυτά θα μπορούσαν να συσχετισθούν με διαφορές στη φυσιολογία και τη βιοχημεία των περιοχών αυτών και ενδεχομένως να σχετίζονται με τον τρόπο που το οξειδωτικό στρες εκφράζεται στην παθοφυσιολογία και άλλων νοσολογικών καταστάσεων όπως η πλάγια αμυοτροφική σκλήρυνση, η νόσος Parkinson, και η νόσος Alzheimer. Έχει ενδιαφέρον το γεγονός ότι τα βασικά γάγγλια και οι πυρήνες του στελέχους είναι θέσεις εκλεκτικής βλάβης στην εγκεφαλοπάθεια από χολερυθρίνη στο νεογνικό ίκτερο. Στη δεύτερη πειραματική φάση, στους ικτερικούς αρουραίους χορηγήσαμε αντιοξειδωτικούς παράγοντες, που έχουν επανειλημμένα μελετηθεί τόσο in vitro όσο και σε ζωικά μοντέλα, σε μια προσπάθεια να αναστρέψουμε τις διαταραχές που είχαν παρατηρηθεί. Ένα πρώτο εύρημα ήταν η ευεργετική δράση στην υπεροξείδωση των λιπιδίων, που ποσοτικοποιήθηκε με τον υπολογισμό της MDA, στις ομάδες και των τριών αντιοξειδωτών αλλά κυρίως στις ALP και Vit-E. Και στις τρεις ομάδες που έλαβαν αντιοξειδωτικά, αντίθετα με την ομάδα απολίνωσης χοληδόχου πόρου, δεν παρατηρήθηκε εξάντληση του συνολικού κυτταρικού περιεχόμενου γλουταθειόνης. Επιπλέον, και στις τρεις ομάδες αντιοξειδωτικών δεν παρατηρήθηκε αύξηση των NPSSR στο εγκεφαλικό στέλεχος, γεγονός που υποδηλώνει ότι η συσσώρευση των μη-πρωτεϊνικών δισουλφιδίων στο στέλεχος εμποδίστηκε από τους αντιοξειδωτικούς παράγοντες. Η ανισορροπία των πρωτεϊνικών θειολών, όπως αυτή φάνηκε από τη μείωση της PSH και την αύξηση του PSSP, αναστράφηκε σημαντικά μόνο στην ομάδα NAC στην οποία η PSH αυξήθηκε στα φυσιολογικά επίπεδα. Εν συντομία, η παρούσα μελέτη είναι η πρώτη που καταδεικνύει με σαφήνεια το οξειδωτικό στρες στον εγκέφαλο στο μοντέλο του αποφρακτικού ίκτερου και μάλιστα αρκετά πρώιμα. Χρησιμοποιεί μια συστοιχία βιοχημικών δεικτών που περιγράφουν την θειολική αναγωγική κατάσταση και την υπεροξείδωση των λιπιδίων και μελετά τις ευεργετικές επιδράσεις γνωστών αντιοξειδωτικών παραγόντων στον πειραματικό αποφρακτικό ίκτερο. Τα αποτελέσματά της θα μπορούσαν να προσφέρουν κάποια βοήθεια στην κατανόηση ορισμένων μηχανισμών της ηπατικής εγκεφαλοπάθειας στους ανθρώπους. Μελλοντικές έρευνες θα απαντήσουν ερωτήματα σχετικά με τα γενεσιουργά αίτια του οξειδωτικού στρες, την ίδια την παρουσία των ελευθέρων ριζών και την παθοφυσιολογία του φαινομένου. / Hepatic encephalopathy is a complex neuropsychiatric syndrome that has been associated with acute and chronic liver diseases. Accumulated evidence over the last several years has implicated oxidative stress a key factor in the pathogenesis of hepatic encephalopathy. These studies utilize measurements of lipid peroxidation products and glutathione (GSH) and its oxidized disulfide GSSG. A model of experimental obstructive jaundice after ligation of the biliary duct has been used in the present study. Male Wistar rats were divided into control, sham operated and bile duct ligated groups that were sacrificed either on the 5th or the 10th day, or they have been treated with antioxidant agents (NAC, ALP, Vit-E). Subsequently, the thiol redox state of various areas (cortex, midbrain and cerebellum) of the rat brain and the effect of selected antioxidants were studied. For the first time specific markers of high oxidative stress (GSSG, NPSSR, NPSSC, PSSR, PSSC, PSSP, lipid peroxides) and low oxidative stress (GSH, CSH, PSH) were quantified providing a more detailed assessment of the phenomenon. Our results show increase in the first and decrease in the latter group of markers in all studied brain areas, therefore demonstrating high oxidative stress in the obstructive jaundice. The major impact of the present study is the demonstration of early signs of oxidative stress in the brain. Using this battery of biochemical markers, deviations from control and sham animals occurred as early as 5 days following bile duct ligation; by the 10th day the majority of these changes became statistically significant. It was also observed that GSH values in cerebral cortex were twice as high as those in midbrain and cerebellum and a dramatic increase in the levels of NPSSR on the 10th day after bile duct ligation in midbrain that was not observed in the other brain areas. These findings could be attributed to specificities of metabolic or biochemical status of neurons and astrocytes and alterations of blood-brain barrier permeability in different brain areas and probably should be taken into account in further studies, since, as we know, oxidative stress has been implicated in the pathogenesis of many human diseases like Parkinson’s , Alzheimer’s and Amyotrophic Lateral Sclerosis (ALS). It is of interest that basal ganglia and brainstem nuclei are, as well, the sites of selective damage in bilirubin encephalopathy in jaundiced neonates. Jaundiced rats were treated with agents that have frequently been used in vitro and in vivo for their antioxidant effects, in an effort to reverse the observed alterations in redox state. In the treated groups, there was no decrease in the total cell glutathione content unlike the bile duct ligated rats. There was also no significant difference in the levels of lipid peroxidation as compared with control and sham groups. The imbalance of protein thiols demonstrated by the decrease of PSH and the increase of PSSP was considerably reversed only in the NAC group. In all treated groups, no NPSSR increase was found suggesting that the antioxidant agents suppressed the accumulation of non-protein disulfides in the midbrain. In brief, this experimental study demonstrates the oxidative profile of the brain associated with obstructive jaundice at an early and later stage. A battery of biochemical markers that define the thiol redox state is utilized and the beneficial effects of known antioxidants are examined. The evidence presented supports the concept that oxidative stress is neither a uniform matter affecting brain in a general way nor that any antioxidant agent could prevent damage by enhancing equally well different defence system. It is also likely that oxidative stress is one of the important mechanisms of jaundice-induced encephalopathy. Further studies could provide with more evidence on the pathogenetic mechanisms and generative causes of the oxidative stress in obstructive jaundice.

Particle-laden turbulent flow through a straight square duct at Reτ = 300 is studied using direct numerical simulation (DNS) and Lagrangian particle tracking. A parallelized 3-D particle tracking direct numerical simulation code has been developed to perform the large-scale turbulent particle transport computations reported in this thesis. The DNS code is validated after demonstrating good agreement with the published DNS results for the same flow and Reynolds number. Lagrangian particle transport computations are carried out using a large ensemble of passive tracers and finite-inertia particles and the assumption of one-way fluid-particle coupling. Using four different types of initial particle distributions, Lagrangian particle dispersion, concentration and deposition are studied in the turbulent straight square duct. Particles are released in a uniform distribution on a cross-sectional plane at the duct inlet, released as particle pairs in the core region of the duct, distributed randomly in the domain or distributed uniformly in planes at certain heights above the walls. One- and two-particle dispersion statistics are computed and discussed for the low Reynolds number inhomogeneous turbulence present in a straight square duct. New detailed statistics on particle number concentration and deposition are also obtained and discussed.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-11-05T12:39:57Z No. of bitstreams: 1 GENILDO RIBEIRO DO NASCIMENTO - TESE (PPGEP) 2011.pdf: 15030089 bytes, checksum: e81e7db2dc5710f5ef448ea2e4b1e612 (MD5) / Made available in DSpace on 2018-11-05T12:39:57Z (GMT). No. of bitstreams: 1 GENILDO RIBEIRO DO NASCIMENTO - TESE (PPGEP) 2011.pdf: 15030089 bytes, checksum: e81e7db2dc5710f5ef448ea2e4b1e612 (MD5) Previous issue date: 2011-08-24 / Este trabalho apresenta um estudo teórico sobre escoamento multifásico (gás-óleo pesado-água) em dutos flexíveis que tem uso em diversas aplicações da indústria petrolífera e não petrolífera. As equações governantes são baseadas no modelo multifluido Euleriano-Euleriano não-homogêneo, considerando o escoamento tridimensional em regime permanente laminar e não-isotérmico. As simulações foram efetuadas usando-se o código computacional CFX-3D. Os resultados das distribuições de velocidade, pressão, fração volumétrica e temperatura ao longo do duto são apresentadas e analisadas. Verificou-se que a curvatura do duto e a fração volumétrica das fases presentes têm forte influência na hidrodinâmica do escoamento. Fez-se uma avaliação da região onde pode ocorrer precipitação de parafina e os resultados obtidos são consistentes fisicamente e permitem um melhor conhecimento acerca do escoamento multifásico (água, óleo pesado e gás). / This work presents a theoretical study on multiphase flow (gas-heavy oil-water) in flexible pipe which is used in many applications of petroleum industry and others industries. The governing equations are based on Eulerian-Eulerian multifluid model and non-omogeneous, by considering the steady non-isothermal laminar flow. The simulations were performed using the computer code CFX-3D. Results of the velocity, pressure, volume fraction and temperature distributions along the pipeline are presented and analyzed. It was verified that the curvature of the pipe and the volumetric fraction of the phases has large influence in the hydrodynamic of flow. An evaluation of paraffin precipitation and the results are consistent physically and allow a better knowledge of multiphase flow (water, heavy oil, gas).

Este trabalho tem por finalidade o estudo da resistência à pressão hidrostática do reparo realizado com chapa de aço de baixo carbono, colada com adesivo estrutural à base de epóxi em tubulações de aço com furo. Tubulações de parede fina, sob pressão interna, a tensão na direção longitudinal é a metade da tensão circunferencial do tubo, deste modo, o fator de forma da área do reparo, ou seja, a variação das dimensões da chapa nas direções longitudinal e circunferencial do tubo foi investigado. A influência da força de falha do reparo, quando varia-se a dimensão da chapa nas direções citadas, foram analisadas estatisticamente utilizando-se um planejamento fatorial de experimentos. Altos valores de resistência hidrostática do reparo foram encontrados (em torno de 240 bar) quando comparados com as pressões normais de trabalho (em torno de 70 bar) de uma tubulação similar as utilizadas nos testes. Os resultados da pressão de falha do reparo dos 10 grupos analisados apresentaram desvios padrão pequenos, menor que 12 %, demonstrando a eficiência dos procedimentos adotados na confecção do reparo. Os estudos demonstram a não existência de um fator de forma na resistência do reparo devido a variação nas dimensões da chapa nas direções longitudinal e circunferencial do tubo bem como a alta influência na resistência do reparo quando aumenta a área da chapa. Os resultados apontam para o desenvolvimento de um novo procedimento de reparo de contingência. / In this work, the resistance to hydrostatic pressure of repair with steel plate low carbon, glued with structural adhesive epoxy in the steel pipes with hole was investigated. Thin-wall pipes under internal pressure, the tension in the longitudinal direction is half the circumferential stress the pipe, thus the shape factor of repair area, that is, the change of the plate size in the longitudinal and circumferential directions tube was evaluated. The influence of repair failure strength when vary the size of the plate in the mentioned directions, were statistically analyzed using a factorial experiments desing. High values of the hydrostatic resistance in the repair were found (around 240 bar) compared with the normal working pressure (around 70 bar) in a similar pipe used in the tests. The results of repair failure pressure of the 10 groups analyzed small standard deviations, less than 12%, demonstrating the efficiency of the procedures adopted in the bonding mechanism. The study demonstrated of any existence of the form factor in the repair resistance due to variation in the dimensions of the plate in the longitudinal and circumferential direction, even as the high influence in the repair resistance with the increase from the area plate. The results point to the development of a new contingency repair procedure.

Este trabalho tem por finalidade o estudo da resistência à pressão hidrostática do reparo realizado com chapa de aço de baixo carbono, colada com adesivo estrutural à base de epóxi em tubulações de aço com furo. Tubulações de parede fina, sob pressão interna, a tensão na direção longitudinal é a metade da tensão circunferencial do tubo, deste modo, o fator de forma da área do reparo, ou seja, a variação das dimensões da chapa nas direções longitudinal e circunferencial do tubo foi investigado. A influência da força de falha do reparo, quando varia-se a dimensão da chapa nas direções citadas, foram analisadas estatisticamente utilizando-se um planejamento fatorial de experimentos. Altos valores de resistência hidrostática do reparo foram encontrados (em torno de 240 bar) quando comparados com as pressões normais de trabalho (em torno de 70 bar) de uma tubulação similar as utilizadas nos testes. Os resultados da pressão de falha do reparo dos 10 grupos analisados apresentaram desvios padrão pequenos, menor que 12 %, demonstrando a eficiência dos procedimentos adotados na confecção do reparo. Os estudos demonstram a não existência de um fator de forma na resistência do reparo devido a variação nas dimensões da chapa nas direções longitudinal e circunferencial do tubo bem como a alta influência na resistência do reparo quando aumenta a área da chapa. Os resultados apontam para o desenvolvimento de um novo procedimento de reparo de contingência. / In this work, the resistance to hydrostatic pressure of repair with steel plate low carbon, glued with structural adhesive epoxy in the steel pipes with hole was investigated. Thin-wall pipes under internal pressure, the tension in the longitudinal direction is half the circumferential stress the pipe, thus the shape factor of repair area, that is, the change of the plate size in the longitudinal and circumferential directions tube was evaluated. The influence of repair failure strength when vary the size of the plate in the mentioned directions, were statistically analyzed using a factorial experiments desing. High values of the hydrostatic resistance in the repair were found (around 240 bar) compared with the normal working pressure (around 70 bar) in a similar pipe used in the tests. The results of repair failure pressure of the 10 groups analyzed small standard deviations, less than 12%, demonstrating the efficiency of the procedures adopted in the bonding mechanism. The study demonstrated of any existence of the form factor in the repair resistance due to variation in the dimensions of the plate in the longitudinal and circumferential direction, even as the high influence in the repair resistance with the increase from the area plate. The results point to the development of a new contingency repair procedure.