The scientific literature on airflow in the respiratory system is usually associated with rigid ducts. Many studies have been conducted in the frequency domain to assess respiratory system mechanics. Time-domain analyses appear more independent from the hypotheses of periodicity, required by frequency analysis, providing data that are simpler to interpret since features can be easily associated to time. However, the complexity of the bronchial tree makes 3-D simulations too expensive computationally, limiting the analysis to few generations. 1-D modelling in space-time variables has been extensively applied to simulate blood pressure and flow waveforms in arteries, providing a good compromise between accuracy and computational cost. This work represents the first attempt to apply this formulation to study pulse waveforms in the human bronchial tree. Experiments have been carried out, in this work, to validate the model capabilities in modelling pressure and velocity waveforms when air pulses propagate in flexible tubes with different mechanical and geometrical properties. The experiments have shown that the arrival of reflected air waves occurs in correspondence of the theoretical timing once the wave speed is known. Reflected backward compression waves have generated an increase of pressure (P) and decrease of velocity (U) while expansion backward waves have produced a decrease of P and increase of U according to the linear analysis of wave reflections. The experiments have demonstrated also the capabilities of Wave intensity analysis (WIA), an analytical technique used to study wave propagation in cardiovascular system, in separating forward and backward components of pressure and velocity also for the air case. After validating the 1-D modelling in space and time variables, several models for human airways have been considered starting from simplified versions (bifurcation trachea- main bronchi, series of tubes) to more complex systems up to seven generations of bifurcations according to both symmetrical and asymmetrical models. Calculated pressures waveforms in trachea are shown to change accordingly to both peripheral resistance and compliance variations, suggesting a possible non-invasive assessment of peripheral conditions. A favourable comparison with typical pressure and flow waveforms from impulse oscillometry system, which has recently been introduced as a clinical diagnostic technique, is also shown. The results suggested that a deeper investigation of the mechanisms underlying air wave propagation in lungs could be a useful tool to better understand the differences between normal and pathologic conditions and how pathologies may affect the pattern of pressure and velocity waveforms.

A auto-suficiência adquirida pelo Brasil em termos de produção de petróleo representou uma conquista inédita e de extrema importância para o país. As pesquisas e desenvolvimento técnico-científico associados a esse fato impulsionaram a produção oceânica de petróleo e gás para lâminas dágua cada vez maiores, fazendo com que os sistemas oceânicos fossem obrigados a evoluir concomitantemente. Intrinsecamente, os problemas associados aos sistemas de prospecção se tornaram mais desafiadores. Os cabos e tubos submersos normalmente lançados sob configuração de catenária direta e utilizados para essa tarefa possuem importância fundamental para a Engenharia Oceânica e seu estudo é parte da motivação para esta dissertação. Adicionalmente, os avanços computacionais das últimas décadas permitiram que outras áreas do conhecimento experimentassem um desenvolvimento sem precedentes na história da ciência. Dentre elas, destaca-se o Processamento Digital de Imagens. O presente trabalho busca estudar a estática e a dinâmica de linhas sob configuração de catenária, através da identificação geométrica, processamento e análise de imagens digitais, promovendo um ponto de convergência entre a Engenharia Oceânica e o Processamento Digital de Imagens. A fim de caminha nesse sentido, diversos experimentos e simulações foram concebidos e realizados e estão descritos ao longo do presente texto. A metodologia utilizada consiste em extrair informações de um sistema físico, a partir da análise de imagens e vídeos. O principal intuito é a investigação da estática e dinâmica locais de uma linha flexível, na região próxima ao solo, conhecida como TDZ. Em particular, foi possível observar, em um dos experimentos, a ocorrência do fenômeno de compressão dinâmica que foi, então, brevemente discutido. Os resultados obtidos experimentalmente foram confrontados com um sistema comercial de captura de movimentos e com resultados advindos da revisão bibliográfica ou de simulações numéricas, mostrando adequação frente às confrontações realizadas e apresentando o mesmo nível de precisão que o sistema comercial utilizado. Como conseqüência, a metodologia proposta e empregada para as investigações físicas ao longo desta dissertação parece sugerir a extrapolação de seus resultados na concepção de formas pouco invasivas de ensaios físicos e para a análise e desenvolvimento de sistemas oceânicos. / The self-sufficiency acquired by Brazil in terms of oil production represents an unprecedented achievement and it was extremely important for the country. The scientific researches and technical development associated with that fact push the oceanic production of oil and gas to increasing depths, obligating ocean systems to evolve concurrently. As a result, the problems associated with exploration systems have become more challenging. The submerged cables and pipes commonly launched in catenary configuration are crucial for the Offshore Engineering and its study is part of the motivation for this dissertation. In addition, computational advances in the last decades have allowed other areas of knowledge experienced an unprecedented development in the history of science. Among them, one can highlight the Digital Image Processing. This work was concerned with studies about static and dynamic lines in catenary configuration, in a convergence between Offshore Engineering and Digital Image Processing. In order to move towards this direction, several experiments and simulations have been designed and performed and are described throughout this text. The proposed methodology consisted in extract information from a physical system, through processing and analysis of images and/or videos. The main focus was the investigation of local static and dynamic behavior of a flexible line, in the touchdown zone. In particular, it was observed, in one of the experiments, the occurrence of dynamic compression in the line, and this subject was then briefly discussed. The experimental results were compared with a commercial motion capture system and results stemming from the literature or numerical simulations, indicating a fairly good agreement and providing the same level of accuracy with the employed commercial system. As a result, the proposed and used methodology for physical investigations along this work seems to suggest the extrapolation of their results to develop less invasive forms of physical tests and promoting the development of marine systems.

A auto-suficiência adquirida pelo Brasil em termos de produção de petróleo representou uma conquista inédita e de extrema importância para o país. As pesquisas e desenvolvimento técnico-científico associados a esse fato impulsionaram a produção oceânica de petróleo e gás para lâminas dágua cada vez maiores, fazendo com que os sistemas oceânicos fossem obrigados a evoluir concomitantemente. Intrinsecamente, os problemas associados aos sistemas de prospecção se tornaram mais desafiadores. Os cabos e tubos submersos normalmente lançados sob configuração de catenária direta e utilizados para essa tarefa possuem importância fundamental para a Engenharia Oceânica e seu estudo é parte da motivação para esta dissertação. Adicionalmente, os avanços computacionais das últimas décadas permitiram que outras áreas do conhecimento experimentassem um desenvolvimento sem precedentes na história da ciência. Dentre elas, destaca-se o Processamento Digital de Imagens. O presente trabalho busca estudar a estática e a dinâmica de linhas sob configuração de catenária, através da identificação geométrica, processamento e análise de imagens digitais, promovendo um ponto de convergência entre a Engenharia Oceânica e o Processamento Digital de Imagens. A fim de caminha nesse sentido, diversos experimentos e simulações foram concebidos e realizados e estão descritos ao longo do presente texto. A metodologia utilizada consiste em extrair informações de um sistema físico, a partir da análise de imagens e vídeos. O principal intuito é a investigação da estática e dinâmica locais de uma linha flexível, na região próxima ao solo, conhecida como TDZ. Em particular, foi possível observar, em um dos experimentos, a ocorrência do fenômeno de compressão dinâmica que foi, então, brevemente discutido. Os resultados obtidos experimentalmente foram confrontados com um sistema comercial de captura de movimentos e com resultados advindos da revisão bibliográfica ou de simulações numéricas, mostrando adequação frente às confrontações realizadas e apresentando o mesmo nível de precisão que o sistema comercial utilizado. Como conseqüência, a metodologia proposta e empregada para as investigações físicas ao longo desta dissertação parece sugerir a extrapolação de seus resultados na concepção de formas pouco invasivas de ensaios físicos e para a análise e desenvolvimento de sistemas oceânicos. / The self-sufficiency acquired by Brazil in terms of oil production represents an unprecedented achievement and it was extremely important for the country. The scientific researches and technical development associated with that fact push the oceanic production of oil and gas to increasing depths, obligating ocean systems to evolve concurrently. As a result, the problems associated with exploration systems have become more challenging. The submerged cables and pipes commonly launched in catenary configuration are crucial for the Offshore Engineering and its study is part of the motivation for this dissertation. In addition, computational advances in the last decades have allowed other areas of knowledge experienced an unprecedented development in the history of science. Among them, one can highlight the Digital Image Processing. This work was concerned with studies about static and dynamic lines in catenary configuration, in a convergence between Offshore Engineering and Digital Image Processing. In order to move towards this direction, several experiments and simulations have been designed and performed and are described throughout this text. The proposed methodology consisted in extract information from a physical system, through processing and analysis of images and/or videos. The main focus was the investigation of local static and dynamic behavior of a flexible line, in the touchdown zone. In particular, it was observed, in one of the experiments, the occurrence of dynamic compression in the line, and this subject was then briefly discussed. The experimental results were compared with a commercial motion capture system and results stemming from the literature or numerical simulations, indicating a fairly good agreement and providing the same level of accuracy with the employed commercial system. As a result, the proposed and used methodology for physical investigations along this work seems to suggest the extrapolation of their results to develop less invasive forms of physical tests and promoting the development of marine systems.

Φαινόμενα άντλησης με ή χωρίς βαλβίδες εξετάζονται πειραματικά και θεωρητικά μέσω κυλινδρικών εύκαμπτων αγωγών. Το φαινόμενο της άντλησης ρευστού χωρίς βαλβίδες μελετάται πειραματικά σε κλειστό βρόχο αποτελούμενο από δύο αγωγούς, έναν εύκαμπτο και έναν άκαμπτο. Αναπτύσσεται μη μηδενική μέση χρονικά παροχή ρευστού όταν διεγείρεται τμήμα του εύκαμπτου αγωγού σε συγκεκριμένες συχνότητες και πλάτη διέγερσης. Η διέγερση επιτυγχάνεται μέσω συμπίεσης και αποσυμπίεσης του εύκαμπτου αγωγού από έναν κατάλληλο παλινδρομικό μηχανισμό. Εξετάζονται τέσσερις παράμετροι επιρροής του φαινομένου, η συχνότητα, το μήκος, το πλάτος και η θέση της διέγερσης. Καταγράφονται τα σήματα μέτρησης της παροχής στο μέσον του άκαμπτου αγωγού, οι τιμές της στατικής πίεσης στα άκρα του άκαμπτου αγωγού και η κατακόρυφη μετατόπιση της πλάκας συμπίεσης. Επιπλέον, προσδιορίζεται η παραμόρφωση της εγκάρσιας διατομής του ελαστικού αγωγού στην περιοχή της διέγερσης, κατά τη συμπίεση και αποσυμπίεσή του για διάφορα πλάτη διέγερσης. Τα αποτελέσματα φανερώνουν την ανάπτυξη ροής προς μία κατεύθυνση με την αύξηση της συχνότητας διέγερσης. Η ροή αυτή μεγιστοποιείται όταν η συχνότητα διέγερσης ταυτίζεται με την ιδιοσυχνότητα του υδραυλικού κυκλώματος. Η μέση χρονικά παροχή αυξάνει καθώς το σημείο διέγερσης απομακρύνεται από το μέσον του εύκαμπτου αγωγού και επίσης με την αύξηση του πλάτους ή του μήκους διέγερσης. Θεωρητικά το φαινόμενο της άντλησης χωρίς βαλβίδες μελετάται μέσω της ανάπτυξης ενός κατάλληλου ψευδο-μονοδιάστατου μοντέλου που επιλύεται αριθμητικά, θεωρώντας ξανά κλειστό βρόχο ενός εύκαμπτου και ενός άκαμπτου αγωγού. Οι εξισώσεις του μοντέλου διαμορφώνονται με την ολοκλήρωση των εξισώσεων ροής (συνέχειας και ορμής) επί της εγκάρσιας διατομής του κλειστού βρόχου, θεωρώντας αξονοσυμμετρική ροή ασυμπίεστου ρευστού με σταθερό ιξώδες. Χρησιμοποιείται επίσης μία καταστατική εξίσωση που σχετίζει την αναπτυσσόμενη πίεση με την μεταβαλλόμενη εγκάρσια διατομή του βρόχου, έχοντας υποθέσει λεπτά ελαστικά τοιχώματα αγωγών με γραμμικές παραμορφώσεις. Επιλύεται αριθμητικά μη γραμμικό σύστημα μερικών διαφορικών εξισώσεων υπερβολικού τύπου, μέσω τριών αριθμητικών σχημάτων: Lax-Wendroff, MacCormack, και Dispersion Relation Preserving (DRP), το οποίο παρουσιάζει και την υψηλότερη ακρίβεια. Οι τρεις άγνωστες συναρτήσεις που υπολογίζονται στο χώρο και το χρόνο είναι η εγκάρσια διατομή του κλειστού κυκλώματος, η αναπτυσσόμενη εσωτερική πίεση του ρευστού και η ταχύτητά του. Σε κάποιο σημείο του εύκαμπτου αγωγού η περιοδική διέγερση προκαλεί κατευθυνόμενη ροή του ρευστού υπό συγκεκριμένες συνθήκες. Όταν η διέγερση απομακρύνεται από το μέσον του εύκαμπτου αγωγού, αναπτύσσεται διαφορά φάσης μεταξύ των κυματομορφών της πίεσης στα σημεία σύνδεσης των δύο αγωγών. Η κυματομορφή της πίεσης που προηγείται είναι αυτή που διαμορφώνεται στο σημείο σύνδεσης των δύο αγωγών που είναι πιο κοντά στη διέγερση. Με αύξηση του πλάτους ή του μήκους του διεγειρόμενου τμήματος του κλειστού κυκλώματος, η μέση χρονικά παροχή αυξάνει και μεγιστοποιείται στην ιδιοσυχνότητα του συστήματος. Μεταβάλλοντας τη συχνότητα διέγερσης στο πεδίο μακριά της συχνότητας συντονισμού, εμφανίζονται τοπικά ακρότατα της συνάρτησης της μέσης χρονικά παροχής με τη συχνότητα, τα οποία αναδεικνύουν τον περίπλοκο χαρακτήρα του φαινομένου της άντλησης χωρίς βαλβίδες. Τα αποτελέσματα του μοντέλου παρουσιάζουν την ίδια συστηματικότητα με τα αντίστοιχα του πειράματος, διατηρώντας τα περισσότερα χαρακτηριστικά και τάσεις στις μεταβολές. Κατά το πρώιμο στάδιο κύησης του εμβρύου το αίμα κυκλοφορεί προς μία κατεύθυνση στο πρωταρχικό κυκλοφορικό σύστημα του εμβρύου, παρότι οι βαλβίδες απουσιάζουν. Το παραπάνω θεωρητικό μοντέλο επιλύεται με αριθμητικά δεδομένα από τη φυσιολογία του εμβρύου, γι’ αυτό το πρώιμο στάδιο κύησης, χρησιμοποιώντας τη μέθοδο DRP 4ης τάξης ακρίβειας στο χώρο και το χρόνο. Το μέγεθος της μέσης παροχής του αίματος εξαρτάται από τους εμβρυϊκούς καρδιακούς παλμούς και το βαθμό συστολής του αρχέγονου καρδιακού σωλήνα. Η αντλητική ικανότητα του κυκλοφορικού συστήματος του εμβρύου εκφράζεται με τη μέση παροχή αίματος ως συνάρτηση των καρδιακών παλμών και του βαθμού συστολής του αρχέγονου καρδιακού σωλήνα. Το φαινόμενο της άντλησης με βαλβίδες μελετάται πειραματικά μέσω ενός ανατάξιμου εύκαμπτου αγωγού, ο οποίος συμπιέζεται από ένα μηχανισμό δίχρονης περισταλτικής αντλίας. Μία πρότυπη συσκευή έχει σχεδιαστεί και κατασκευαστεί, ώστε να αναλυθεί η συμπεριφορά και να εξαχθούν οι χαρακτηριστικές καμπύλες της δίχρονης περισταλτικής αντλίας. Περισταλτικές αντλίες αυτού του τύπου χρησιμοποιούνται στην ιατρική σε εφαρμογές παρεντερικής διατροφής, άντλησης του αίματος και ειδικότερα σε έγχυση φαρμάκων. Για την κατασκευή της πρότυπης αντλίας, σχεδιάστηκε και κατασκευάστηκε ένας καινοτομικός μηχανισμός εκκεντροφόρου άξονα, ο οποίος επιτυγχάνει σταθερό ρυθμό έγχυσης. Η πειραματική διάταξη αποτελείται από δύο δεξαμενές υπερχείλισης που συνδέονται μέσω ενός σωλήνα ελαστικού σιλικόνης. Το όλο σύστημα πληρώνεται με αποσταγμένο νερό και η άντληση επιτυγχάνεται από τη μία δεξαμενή στην άλλη με κατάλληλη προοδευτική συμπίεση ενός τμήματος του ελαστικού αγωγού μέσω του μηχανισμού της αντλίας. Η παροχή μετράται ζυγίζοντας τη δεξαμενή κατάθλιψης, η οποία είναι τοποθετημένη σε δυναμοκυψέλη γι’ αυτό το σκοπό. Για χαμηλές συχνότητες λειτουργίας η έγχυση είναι σχεδόν ομαλή χωρίς πάλμωση. Επίσης, η παροχή εξαρτάται κυρίως από τη συχνότητα περιστροφής του άξονα της αντλίας και μεγιστοποιείται γύρω από την ιδιοσυχνότητα της συσκευής. / Valveless and valvate pumping phenomena are investigated experimentally and theoretically through cylindrical distensible tubes. The phenomenon of valveless pumping is studied experimentally in a loop consisting of two tubes, a soft and a hard one filled with salted water. A non zero mean flow-rate is established via a reciprocating flat plate mechanism compressing and decompressing a portion of the flexible tube with a controllable frequency and depth of compression. Four parameters of the problem were examined, namely the frequency of the oscillating plate, its length, the depth of compression and the location where the tube is compressed. Four signals were simultaneously recorded, namely the flow-rate at the mid length of the hard tube, the static pressure at the tube’s ends and the displacement of the oscillating plate. Also, the tube cross-sectional area was measured versus the displacement of the oscillating plate for various values of the maximum depth of compression. Analysis of the obtained data showed that a unidirectional flow is established increasing the frequency of compression and it maximizes when the compression frequency coincides with the natural frequency of the hydraulic loop. The mean value of the flow-rate increases when the point of compression moves far from the mid length of the flexible tube, when the length of the reciprocating plate increases and when the depth of compression increases. Additionally, the development of a theoretical model of valveless pumping and its numerical solution is presented, applied for the case of the closed hydraulic loop, consisting of a flexible and a rigid tube. The integration of the governing flow equations (continuity and momentum), over the tube cross-sectional area results in a quasi-one-dimensional unsteady model, considering axisymmetric flow of incompressible fluid with constant viscosity. There was also used a constitutive state equation, relating pressure and cross-sectional area, and assuming that the deformations of the thin-walled tubes are purely elastic. A system of nonlinear partial differential equations of the hyperbolic type is solved numerically, employing three finite difference schemes: Lax-Wendroff, MacCormack, and Dispersion Relation Preserving (DRP), the last being the most accurate one. Three functions in time and space are calculated, the cross-sectional area of the closed loop, the building up internal pressure and the velocity of the fluid inside the loop. A periodic compression and decompression of the flexible tube causes a unidirectional flow, under certain conditions. When the excitation takes place far from the midlength of the flexible tube, a phase difference between the pressures at the two edges of each tube is developed, being in advance the one that is closer to the excitation area. Increasing the tube occlusion or the length of the excited part of the loop the mean flow rate increases and maximizes at the natural frequency of the loop. Varying the excitation frequency both above and below the resonance frequency, local flow rate extremes appear, manifesting the complex character of the valveless pumping phenomenon. The simulated results maintain most of the characteristics found in the experiment. During early embryonic life, blood circulates in one direction through the primitive circulatory system, in spite of the complete lack of valves. The above mathematical model described the coordinated fashion of the blood circulation in the circulatory system of the embryo. The one-dimensional model is analysed numerically and solved with the DRP scheme, which is of fourth order accurate in time and space. The mean blood flow-rate depends on the embryonic heart rate and the contraction grade of the primordial heart tube. The pumping activity of the embryo circulatory system is shown by presenting the mean blood flow-rate as a function of embryonic heart rate for several contraction grades of the primordial heart tube. Furthermore, the phenomenon of valvate pumping is studied experimentally through a resilient tube, compressed by a two-cycle peristaltic pump mechanism. A prototype device was designed and manufactured in order to analyze the behaviour and reveal the characteristic curves of such a pump. This kind of pump can be used in medicine for nutrition, pumping blood and especially for drug infusion therapies. Concerning the manufacturing of this prototype device, an innovative mechanism was applied, regarding the camshaft of the pump, in order to achieve constant infusion flow-rate in time. The experimental set-up consists of two rigid overflow vessels filled with distilled water, communicating via a silicone rubber tube. Pumping is achieved from one vessel to the other by inducing a progressive deformation (shrinkage) on a segment of the silicone rubber tube through the pump. The flow-rate is measured by weighing the fluid-receiver vessel, which is placed on a single point load-cell platform. At low pumping frequencies the flow-rate is almost steady. Also it is shown that the flow-rate is mainly dependent on the rotating frequency of the pump and maximizes when the excitation frequency coincides with the natural frequency of the device.