Fluid-structure interaction (FSI) as the name suggests, is the study of dynamic interaction of both fluid and structure motions. Fluid-structure interaction exists in almost all engineering and science fields. Moreover, the random loading caused by fluid motions in uncertain environment conditions present new challenges to the designers. The objective of the present research work is to develop efficient and robust finite element models to solve fluid structure interaction problems effectively. A key advantage of the displacement based FE M is the flexibility and easiness in modifying the existing efficient numerical solvers, and can also be extended easily to a number of problems. The research work carried out in this thesis can be divided into three parts. In the first part, development of displacement based Lagrangian FE models for acoustic fluids is presented. Here, the displacement fields of the 2-D and 3-DFEs are derived based on the consistently assumed constrained strain fields satisfying irrotationality and incompressibility constraints simultaneously. These elements’ behaviour, in terms of number of zero energy modes, non-zero spurious modes, and the integration order is studied. The inf-sup test is carried out on all the elements to examine the performance of each formulated element. Next, a new class of FEs based on Legendre polynomials is presented. The node point locations in this case are obtained by calculating the zero’s of equation(1- ξ2)L’n(ξ) =0,where,Ln is the Legendre polynomial of order n in one dimension. In the second part, the development of a spectral layer element for studying wave propagation in acoustic fluids is presented. Laplace transform based spectral finite element formulation is developed for studying acoustic wave propagation. The partial differential equations(PDE)are converted to ordinary differential equations(ODE) by taking Laplace transform. The Laplace damping parameter is introduced for easy handling of the numerical Laplace transform(NLT).This Laplace damping parameter removes the “wraparound”problem which is present in shortwave guides due to periodicity of the Fourier transform. Later, a technique is developed through which SFEM stiffness matrix can be added to the FEM dynamic stiffness matrix in the frequency domain. Finally, Uncertainty analysis is carried out to understand the effect of randomness in the design parameters on the system response variability. Here, standard uncertainty analysis procedure called Monte Carlo simulation (MCS) is considered first and later Polynomial chaos expansion(PCE). In this analysis, the gravitational forces, bulk modulus of the fluid, and Young’s modulus of the structure are considered as random input variables in the study. The randomness in the system output is measured in terms of coefficient of variation for each random variable considered.

<p><a href="">This work investigates the effect of surface features such as roughness, pits, and cracks on the tribological and fatigue behavior of machine components. It comprises of three main investigations: (i) effect of roughness on non-contacting fatigue, (ii) lubricated contact fluid structure interaction (FSI) behavior in presence of surface cracks, and (iii) the equivalence between non-contacting and contacting fatigue and the effect of roughness.</a></p><p>For the first investigation, a novel microstructure-based approach was developed to model surface roughness. It used a finite element fatigue damage model to predict the effects of roughness on tensile fatigue. AISI 4130 steel specimens with different surface finishes were fabricated and tested in axial fatigue using an MTS machine. The experimental results demonstrated the detrimental effect of roughness on fatigue lives, which was predicted by the model accurately.</p><p>In the second investigation, a partitioned CFD-FEM based FSI solver was developed using Ansys Multiphysics software to model and investigate elastohydrodynamically lubricated contacts typical in gears and cylindrical roller bearings. The FSI model relaxes Reynolds assumptions, and uses Navier-Stokes equations to determine the lubricant flow and utilizes finite element method to model the structural response. The FSI model was evaluated for robustness under various operating conditions. The effect of material plasticity, subsurface features, etc. were also investigated. The model was then extended to investigate the effects of surface cracks in rolling/sliding EHL line contacts. Using CFD based approach enabled the investigation of surface cracks with inclined geometries, overcoming the limitations of standard Reynolds-based solvers. The effects of crack geometry parameters such as crack location, crack length, crack width, crack tip radius and crack orientation on fluid pressure distribution were studied. This investigation identified the crack geometries that affect the contact fatigue behavior by predicting the location and severity of stress concentrations in the material.</p><p>Finally, the relationship between contacting fatigue and non-contacting fatigue was investigated. A test rig was designed and developed to simulate rolling contact fatigue (RCF) surface damage. Experimental investigation revealed that the RCF surface damage stress-life (SN) results can be predicted using torsional fatigue results 10 times faster. A computational contact mechanics model was developed to incorporate the effect of roughness in this prediction, and corroborated against experimental RCF results at different roughness levels.</p>

A Computational Fluid Dynamics (CFD) tool is developed in this thesis to solve complex fluid-structure interaction (FSI) problems. The fluid domain is based on Smoothed Particle Hydro-dynamics (SPH) and the structural domain employs large-deformation Finite Element Method (FEM). Validation tests of SPH and FEM are first performed individually. A loosely-coupled SPH-FEM model is then proposed for solving FSI problems. Validation results of two benchmark FSI problems are illustrated (Antoci et al., 2007; Souto-Iglesias et al., 2008). The first test case is flow in a sloshing tank interacting with an elastic body and the second one is dam-break flow through an elastic gate. The results obtained with the SPH-FEM model show good agreement with published results and suggest that the SPH-FEM model is a viable and effective numerical tool for FSI problems. This research is then applied to simulate a two-dimensional free-stream flow interacting with a deformable, pressurized surface, such as an ACV/SES bow seal. The dynamics of deformable surfaces such as the skirt/seal systems of the ACV/SES utilize the large-deformation FEM model. The fluid part including the air inside the chamber and water are simulated by SPH. A validation case is performed to investigate the application of SPH-FEM model in ACV/SES via comparison with experimental data (Zalek and Doctors, 2010). The thesis provides the theory of the SPH and FEM models incorporated and the derivation of the loosely-coupled SPH-FEM model. The validation results have suggested that this SPH-FEM model can be readily applied to skirt/seal dynamics of ACV/SES interacting with free-surface flow. / Ph. D.

Η παρούσα διδακτορική διατριβή αναπτύσσεται ο υδροδυναμικός και δομικός (μηχανολογικός) σχεδιασμός μιας υποθαλάσσιας κατασκευής για την απάντληση πετρελαίου σε μεγάλα βάθη. Η κατασκευή αποτελείταια από 6 διαφορετικά τμήματα. Ο μηχανολογικός σχεδιασμός ξεκίνησε με την προσαρμογή κατάλληλων προδιαγραφών για το κάθε εξάρτημα. Το πρώτο εξάρτημα από το οποίο ξεκίνησε η ανάλυση είναι τα καλώδια ενίσχυσης των οποίων το φορτίο προέντασης είναι ήδη γνωστό από τα κριτήρια σχεδιασμού και τον αρχικό σχεδιασμό και περιορίζεται στους 1000 τόνους (10000 kN). Πραγματοποιήθηκε η τελική επιλογή του υλικού και των χαρακτηριστικών που έπρεπε να έχει ώστε να ανταποκρίνεται στις απαιτήσεις του θαλάσσιου περιβάλλοντος. Ο κατακόρυφος αγωγός με βάση την φιλοσοφία ανάπτυξης του συστήματος θα έπρεπε να αποτελείται από επιμέρους τμήματα αγωγών πεπερασμένου μήκους, κατασκευασμένους από πολυαιθυλένιο οι οποίοι καλύπτουν το συνολικό επιχειρησιακό βάθος. Η αλληλεπίδραση του θαλασσίου ρεύματος με τον αγωγό (Fluid Structure Interaction) για την κάθε διαφορετική ταχύτητα του θαλασσίου προφίλ ώστε να αποφευχθεί η πιθανότητα εμφάνισης επαγώμενων στροβίλων που θα μπορούσαν να οδηγήσουν σε ανεπιθύμητες ταλαντώσεις και σε κόπωση (Vortex Induced Vibration, VIV) τέθηκε σε πρώτη πρωτεραιότητα. Ο συνδυασμός αναλυτικών σχέσεων και πειραματικών δεδομένων από την βιβλιογραφία χρησιμοποιήθηκαν για να υπολογιστεί το μήκος των επιμέρους τμημάτων των αγωγών ώστε να περιοριστούν οι υψηλές εγκάρσιες μετατοπίσεις λόγω των ταλαντώσεων. Η μελέτη της διφασικής ροής πετρελαίου/ νερού σε κώδικα πεπερασμένων όγκων (FLUENT) πραγματοποιήθηκε τόσο για κατακόρυφη όσο και για κεκλιμένη θέση του αγωγού για να επιβεβαιωθεί ότι το αργό πετρέλαιο διατηρεί ανωστική πορεία προς την επιφάνεια ξεπερνώντας τις δυνάμεις τριβής που αναπτύσσονται λόγω της επαφής με τα τοιχώματα των αγωγών. Η ταχύτητα του μίγματος της εσωτερικής ροής καταγράφεται ώστε να ελεγχθεί η εσωτερική μεταβολή της πίεσης του αγωγού. Πιθανή υψηλή διαφοροποίηση της υδροστατικής πίεσης στο εσωτερικό του αγωγού σε σχέση με το εξωτερικό θα οδηγούσε σε επιπλέον φορτία στην δομή του αγωγού (ο αγωγός θα λειτουργούσε τοπικά ως πιεστικό δοχείο). Η προσομοίωση της εξωτερικής ροής γύρω από τμήμα του αγωγού με τα καλώδια ενίσχυσης τοποθετημένα στην περιφερειά του σε κώδικα πεπερασμένων όγκων FLUENT πραγματοποιήθηκε για τον προσδιορισμό των υδροδυναμικών συντελεστών στο εύρος ταχυτήτων 0.1-0.7 m/sec. Επίσης η μοντέλοποίηση αυτή έδειξε κατά πόσο η θέση των νημάτων επιρεάζει ή όχι την δημιουργία επαγώμενων στροβίλων γύρω από τον αγωγό. Η δομική ανάλυση με χρήση πακέτου πακέτου πεπερασμένων στοιχείων (NASTRAN/ PATRAN) έδειξε τα επίπεδα των μέγιστων τάσεων και μετατοπίσεων που αναπτύσσονται λόγω της ύπαρξης της δυναμικής πίεσης η οποία και καταπονεί τοπικά τους αγωγούς. Η αποθηκευτική δεξαμενή (πλωτήρας και συλλέκτης) σχεδιάστηκε με χρήση βασικών υπολογισμών ώστε να επιτευχθεί η κατάλληλη χωρητικότητα αλλά και η προδεγεγραμμένη άνωση. Ο προσδιορισμός των υδροδυναμικών συντελεστών πραγματοποιήθηκε σε FLUENT έτσι ώστε να διερευνηθεί το ροικό πεδίο γύρω από την δεξαμενή καθώς και το μέγεθος των δυνάμεων που μεταφέρονται στο σύστημα από την αλληλεπιδρασή της με το θαλάσσιο ρεύμα. Η δομή του πλωτήρα σχεδιάστηκε με χρήση βασικών δομικών υπολογισμών και η συνολική του συμπεριφορά κάτω από τα φορτία υδροστατικής πίεσης ελέγχθηκε με πεπερασμένα στοιχεία (NASTRAN/ PATRAN). Η δομή του συλλέκτη διαστασιολογήθηκε με βάση την επίδραση της δυναμικής πίεσης ένεκα της ροής γύρω του. Επίσης παρατίθονται οι βασικές δομικές αναλύσεις των συνδέσμων που χρησιμοποιήθηκαν για την ένωση των διαφόρων τμημάτων πλωτήρα και συλλέκτη. Το μοντέλο πλήρους κλίμακας αναπτύχθηκε με βάση τα πειράματα της υδροσήραγγας που πραγματοποιήθηκαν στην MARIN και με βάση του μοντέλου δυναμικής απόκρισης που δημιουργήθηκε στο ORCAFLEX από την SIREHNA. Σκοπός του μοντέλου πλήρους κλίμακας (με την χρήση NASTRAN/PATRAN) ήταν να εξομοιώσει την απόκριση του μοντέλου του ORCAFLEX το οποίο είχε ρυθμιστεί με βάση την υδροσήραγγα ώστε να υπολογιστούν οι δυνάμεις που μεταφέρονται στους δακτυλίους ενίσχυσης και τα φορτία (δυνάμεις και ροπές) που μεταφέρονται στο ενδιάμεσο στοιχείο. Τα δύο μοντέλα θα έπρεπε να εμφανίζουν την ίδια μέγιστη μετατόπιση ώστε να θεωρηθούν όμοια. Στην φάση αυτή τα καλώδια ενίσχυσης που μοντελοποιούνται με μονοδιάστατα στοιχεία στο NASTRAN/PATRAN . Το ενδιάμεσο στοιχείο αποτέλεσε το εξάρτημα στο οποίο μεταφέρονται τα φορτία του αγωγού στο σημείο σύνδεσης (δυνάμεις και οι ροπές) καθώς και οι δυνάμεις από τα καλώδια ενίσχυσης. Η δομική του ανάλυση περιλαμβάνει την διαστασιολόγηση του με βασικούς υπολογισμούς και την χρήση πεπερασμένων στοιχείων για τον έλεγχο τοπικών υπεφορτίσεων που δεν ήταν εφικτό να προσδιοριστούν με αναλυτικές σχέσεις. Ο θόλος επιρεάζεται από την ταχύτητα των θαλασσίων ρευμάτων που κινούνται γύρω του και αποτελούν τις κύριες δυνάμεις που τον επιρεάζουν. Η μοντελοποίηση της δυναμικής πίεσης πάνω στον αγωγό γίνεται με την χρήση υδροδυναμικού μοντέλου σε FLUENT ενώ η δομική του αντοχή προσδιορίστηκε με χρήση μοντέλου πεπερασμένων στοιχείων σε NASTRAN/ PATRAN. Οι δυνάμεις μεταφέρονταν στα καλώδια ενίσχυσης του θόλου που με την σειρά τους τις μμετέφεραν στο σύστημα αγκύρωσης στον βυθό. Το σύστημα αγκύρωσης διαστασιολογείται με αναλυτικούς υπολογισμούς από την βιβλιογραφία με βάση την μέγιστη δύναμη που μεταφέρεται από τα καλώδια αγκύρωσης του θόλου. Οι διαστάσεις του είναι συνάρτηση τόσο της σύστασης του βυθού όσο και της μέγιστης επιτρεπόμενης διάστασης που επιλέγεται από τα πλοία που συμμετέχουν στην ανάπτυξη του συστήματος. Τα βασικά συμπεράσματα που προέκυψαν από την ανάλυση ήταν η δυνατότητα της περαιτέρω ανάπτυξης του συστήματος σε ρηχά και πολύ βαθιά ύδατα καθώς και η ανάγκη για την μείωση του χρόνου κατασκευής ώστε να αυξηθεί η αποδοτικότητα του συστήματος. / In this PhD work, the mechanical design of a Sub sea Oil Recovery Structure is carried out. The structure is consisted of 6 different parts. The mechanical design methodology starts with the calculation of the diameter of the mooring lines for a tension force of 10000 kN. The fluid/ structure interaction is a design aspect for the Riser tube. Analytical equations were used to identify the dimensions of each riser tube’s part in order to avoid Vortex Induced Vibrations (VIV). As a second step, the oil upward movement into the riser tube was investigated. The buoyancy flow was examined using CFD analysis for both, vertical and inclined tube position to confirm that the crude oil could overcome the frictional forces due to contact with the internal tube’s wall. The external flow field around the riser tube, with the mooring lines along its periphery, was investigated in order to calculate the hydrodynamic coefficients for a range from 0.1 to 0.7 m/sec. This analysis was necessary since it helps to quantify the hydrodynamic load for the structural analysis. The structural analysis for the riser tube parts was performed using FEM and it was used for the study of the behavior under “local” loads such as the sea current’s dynamic pressure. The Buffer Bell’s analysis is based on the prediction of hydrodynamic coefficients (obtained from CFD analysis) and the use of a FE model for the structural analysis of the Buffer Bell hull subject to the hydrostatic pressure. The maximum displacement of the system due to the sea currents was also examined. A scale model test was performed in a water tunnel and a dynamic response model was created in order to predict the system’s behavior under operational loads and during the deployment phase. Additional, a FE model was developed to predict the loads (forces and moments) acting on the stiffening rings and the dome interface unit during the operational scenario. This FE model was compared with the Dynamic Response Model for the maximum displacement criterion. The maximum loads (forces and moments) from the Maximum Displacement FE model was used for the calculation of the dimensions of the stiffening ring and the dome interface unit. Finite element models were developed for these two components. A CFD analysis was performed to investigate the pressure distribution over the surface of the Dome. This pressure load and the reaction forces resulted from the analysis of the Dome Interface Unit were used to calculate the stresses faced by the Dome and the total force applied on the mooring system. For the dimensioning of the anchoring system, the highest force calculated for the mooring lines was chosen. The volume of cement for the anchoring system was calculated in order to withstand this force. Analytical equations were used to secure the anchor’s stability on different types of seabed (cohesion or cohesion less). At the end, the maximum calculated force on the mooring line was compared against the force resulted during the first step in order to confirm that fracture does not occur. The conclusions from this analysis is that the system can be applied to all depths (shallow waters, ultra deep waters) but also the final erection time should be minimized in order to increase the system’s efficiency.

Orientador: João Batista Campos Silva / Resumo: Nas últimas décadas, há uma crescente preocupação em mensurar os parâmetros dinâmicos do sangue, dadas as imensas perdas de vidas por doenças cardiovasculares sendo, muitas delas, por aneurismas. A formação e desenvolvimento de um aneurisma é, predominantemente, degenerativo e provém de uma complexa interação entre os efeitos biológicos da parede arterial, os estímulos de escoamento e tensões provenientes da hemodinâmica. A tensão cisalhante na parede e o cíclico campo de pressão são um dos principais fatores responsáveis pela formação e crescimento de um aneurisma. Logo, há a necessidade de se conhecer os campos de velocidades e pressão além das tensões cisalhantes e efetivas na parede. Uma análise numérica é mais promissora que uma experimental. Uma análise experimental in-vivo possui impasses éticos e morais, sem contar a necessidade de um grande investimento. Outra vantagem de um estudo numérico é a disponibilidade de softwares livres de extração de tomografias que permite a extração da geometria sem a necessidade de um método invasivo que ocorreria em estudo experimental in vivo. Portanto com o auxílio de simulações numéricas (Ansys®), considerando o efeito multi-física de interação fluido estrutura (FSI) pela metodologia de elementos e volumes finitos foi possível verificar o efeito dos fatores que levam a formação e crescimento de aneurisma na aorta abdominal. Os aneurismas estudados foram modelos geométricos e reais sendo um dos reais obtidos através de imagens DICOM... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In recent decades, there is growing concern in measuring the dynamic parameters of the blood, given the immense loss of life from cardiovascular disease in human history, including, aneurysms. The formation and development of an aneurysm is predominantly degenerative and results from a complex interaction between the biological effects of the arterial wall and the flow and stress effects from hemodynamics. The stress in the wall and in the cyclic field of pressure is one of the main factors for the formation and growth of an aneurysm that degenerates until its rupture. Therefore, it is necessary to know the velocity and pressure fields as well as the shear stress and effective stress on the wall. A numerical analysis is more promising than an experimental one since an in-vivo experimental analysis has ethical and moral impasses, not counting the need for a large investment. Another advantage of a numerical study is the availability of free softwares for tomography analysis that allows the extraction of the geometry without the need for an invasive method that would occur in an in vivo experimental study. Therefore, with the aid of numerical simulations (Ansys®), considering the multi-physical effect of fluid structure interaction (FSI) by the methodology of finite elements and finite volumes it was possible to verify the effect of factors that lead to the formation and growth of abdominal aortic aneurysm. The studied aneurysms came from geometric models and from real examples... (Complete abstract click electronic access below) / Mestre

Submitted by Jeane Batista de Carvalho null (carvalhojeanetiagina@yahoo.com.br) on 2017-05-23T15:08:27Z No. of bitstreams: 1 Dissertação_CarvalhoJeane.pdf: 8189158 bytes, checksum: ebb9bc23a7d48fbc4154db51680f263e (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-05-23T18:27:50Z (GMT) No. of bitstreams: 1 carvalho_jb_me_ilha.pdf: 8189158 bytes, checksum: ebb9bc23a7d48fbc4154db51680f263e (MD5) / Made available in DSpace on 2017-05-23T18:27:50Z (GMT). No. of bitstreams: 1 carvalho_jb_me_ilha.pdf: 8189158 bytes, checksum: ebb9bc23a7d48fbc4154db51680f263e (MD5) Previous issue date: 2017-03-24 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Nas últimas décadas, há uma crescente preocupação em mensurar os parâmetros dinâmicos do sangue, dadas as imensas perdas de vidas por doenças cardiovasculares sendo, muitas delas, por aneurismas. A formação e desenvolvimento de um aneurisma é, predominantemente, degenerativo e provém de uma complexa interação entre os efeitos biológicos da parede arterial, os estímulos de escoamento e tensões provenientes da hemodinâmica. A tensão cisalhante na parede e o cíclico campo de pressão são um dos principais fatores responsáveis pela formação e crescimento de um aneurisma. Logo, há a necessidade de se conhecer os campos de velocidades e pressão além das tensões cisalhantes e efetivas na parede. Uma análise numérica é mais promissora que uma experimental. Uma análise experimental in-vivo possui impasses éticos e morais, sem contar a necessidade de um grande investimento. Outra vantagem de um estudo numérico é a disponibilidade de softwares livres de extração de tomografias que permite a extração da geometria sem a necessidade de um método invasivo que ocorreria em estudo experimental in vivo. Portanto com o auxílio de simulações numéricas (Ansys®), considerando o efeito multi-física de interação fluido estrutura (FSI) pela metodologia de elementos e volumes finitos foi possível verificar o efeito dos fatores que levam a formação e crescimento de aneurisma na aorta abdominal. Os aneurismas estudados foram modelos geométricos e reais sendo um dos reais obtidos através de imagens DICOM. / In recent decades, there is growing concern in measuring the dynamic parameters of the blood, given the immense loss of life from cardiovascular disease in human history, including, aneurysms. The formation and development of an aneurysm is predominantly degenerative and results from a complex interaction between the biological effects of the arterial wall and the flow and stress effects from hemodynamics. The stress in the wall and in the cyclic field of pressure is one of the main factors for the formation and growth of an aneurysm that degenerates until its rupture. Therefore, it is necessary to know the velocity and pressure fields as well as the shear stress and effective stress on the wall. A numerical analysis is more promising than an experimental one since an in-vivo experimental analysis has ethical and moral impasses, not counting the need for a large investment. Another advantage of a numerical study is the availability of free softwares for tomography analysis that allows the extraction of the geometry without the need for an invasive method that would occur in an in vivo experimental study. Therefore, with the aid of numerical simulations (Ansys®), considering the multi-physical effect of fluid structure interaction (FSI) by the methodology of finite elements and finite volumes it was possible to verify the effect of factors that lead to the formation and growth of abdominal aortic aneurysm. The studied aneurysms came from geometric models and from real examples, being one of the real ones obtained through DICOM images. / CNPq: 131153/2015-3

Made available in DSpace on 2014-12-17T14:58:00Z (GMT). No. of bitstreams: 1 RairamFCA_DISSERT2.pdf: 4758176 bytes, checksum: bfb1653549a50848b4721bda9a78bd6e (MD5) Previous issue date: 2010-03-26 / The pumping through progressing cavities system has been more and more employed in the petroleum industry. This occurs because of its capacity of elevation of highly viscous oils or fluids with great concentration of sand or other solid particles. A Progressing Cavity Pump (PCP) consists, basically, of a rotor - a metallic device similar to an eccentric screw, and a stator - a steel tube internally covered by a double helix, which may be rigid or deformable/elastomeric. In general, it is submitted to a combination of well pressure with the pressure generated by the pumping process itself. In elastomeric PCPs, this combined effort compresses the stator and generates, or enlarges, the clearance existing between the rotor and the stator, thus reducing the closing effect between their cavities. Such opening of the sealing region produces what is known as fluid slip or slippage, reducing the efficiency of the PCP pumping system. Therefore, this research aims to develop a transient three-dimensional computational model that, based on single-lobe PCP kinematics, is able to simulate the fluid-structure interaction that occurs in the interior of metallic and elastomeric PCPs. The main goal is to evaluate the dynamic characteristics of PCP s efficiency based on detailed and instantaneous information of velocity, pressure and deformation fields in their interior. To reach these goals (development and use of the model), it was also necessary the development of a methodology for generation of dynamic, mobile and deformable, computational meshes representing fluid and structural regions of a PCP. This additional intermediary step has been characterized as the biggest challenge for the elaboration and running of the computational model due to the complex kinematic and critical geometry of this type of pump (different helix angles between rotor and stator as well as large length scale aspect ratios). The processes of dynamic generation of meshes and of simultaneous evaluation of the deformations suffered by the elastomer are fulfilled through subroutines written in Fortan 90 language that dynamically interact with the CFX/ANSYS fluid dynamic software. Since a structural elastic linear model is employed to evaluate elastomer deformations, it is not necessary to use any CAE package for structural analysis. However, an initial proposal for dynamic simulation using hyperelastic models through ANSYS software is also presented in this research. Validation of the results produced with the present methodology (mesh generation, flow simulation in metallic PCPs and simulation of fluid-structure interaction in elastomeric PCPs) is obtained through comparison with experimental results reported by the literature. It is expected that the development and application of such a computational model may provide better details of the dynamics of the flow within metallic and elastomeric PCPs, so that better control systems may be implemented in the artificial elevation area by PCP / O sistema de bombeamento por cavidades progressivas est? sendo cada vez mais empregado na ind?stria do petr?leo, devido ? sua capacidade de eleva??o de ?leos altamente viscosos ou de fluidos com grandes concentra??es de areia ou outras part?culas s?lidas. Uma Bomba de Cavidades Progressivas (BCP) ? composta, basicamente, por um rotor - uma pe?a met?lica de forma semelhante a um parafuso exc?ntrico, e um estator - um tubo de a?o revestido internamente por uma h?lice dupla, a qual pode ser r?gida ou deform?vel/elastom?rica. Em geral, uma BCP ? submetida a uma combina??o de press?o do po?o com press?o gerada pelo pr?prio processo de bombeio. Em BCPs elastom?ricas, essa combina??o de esfor?os comprime o estator, gerando ou aumentando a folga existente entre o rotor e o estator, reduzindo, portanto, o efeito de veda??o entre suas cavidades. Tal abertura da regi?o de selagem produz o que ? conhecido como escorregamento do fluido, diminuindo, com isso, a efici?ncia de sistema de bombeio por BCP. Dessa maneira, este trabalho se prop?e a desenvolver um modelo computacional tridimensional transiente do processo din?mico da intera??o fluido-estrutural (FSI) que ocorre no interior de BCPs met?licas e elastom?ricas. O objetivo principal ? avaliar, a partir do uso do modelo desenvolvido, as caracter?sticas din?micas de efici?ncia de bombeio por BCPs, em fun??o de informa??es locais e instant?neas detalhadas dos campos de velocidade, press?o e deforma??o no seu interior. Para o alcance de tais metas (desenvolvimento e uso do modelo), fez-se necess?rio o desenvolvimento de uma metodologia pr?pria para gera??o de malhas computacionais din?micas, m?veis e deform?veis, representando as regi?es fluida e estrutural de uma BCP. Tal procedimento caracterizou-se como o maior desafio para a elabora??o do modelo computacional, devido ? cinem?tica complexa e ? geometria cr?tica desse tipo de bomba (?ngulos de h?lice diferentes entre rotor e estator e grandes diferen?as de escala de comprimento). Os processos de gera??o din?mica das malhas e de avalia??o simult?nea das deforma??es sofridas pelo elast?mero s?o realizados atrav?s de sub-rotinas em linguagem Fortran 90, as quais interagem dinamicamente com o software de din?mica dos fluidos computacional CFX/ANSYS. Desde que o modelo linear el?stico ? empregado para avaliar as deforma??es elastom?ricas, n?o ? necess?rio usar nenhum software para an?lise estrutural. Entretanto, uma proposta inicial para simula??o din?mica no ANSYS empregando-se modelos constitutivos hiper-el?sticos para o elast?mero ? tamb?m apresentada no presente trabalho. A valida??o dos resultados produzidos com a presente metodologia (gera??o de malha, simula??o do escoamento em BCPs met?licas e simula??o da intera??o fluido-estrutural em BCPs elastom?ricas) ? obtida atrav?s da compara??o com resultados experimentais reportados pela literatura. Vislumbra-se que o desenvolvimento e aplica??o de tal ferramenta computacional poder?o fornecer maiores detalhes da din?mica do escoamento no interior de BCPs met?licas e elastom?ricas, de maneira que melhores sistemas de controle possam ser implementados na ?rea de eleva??o artificial por BCPs

The purpose of this study is to perform an investigation of the numerical methods that may contribute to the design and analysis of liquid containers. The study examines several of these methods individually, namely Computational Fluid Dynamics (CFD) analysis of sloshing and Finite Element Methods (FEM) analysis of impact, to evaluate their contribution to the design cycle. Techniques that enhance the use of the various methods are presented and examined to demonstrate effectiveness. In the case of sloshing analysis, experimental tests performed add to the understanding of the phenomena at hand and qualifies the validity of the numerical method used (CFD). As a final contribution, the study presents a method of utilising impact analysis tools, FEM, and CFD in a Multidisciplinary Design Optimisation (MDO) environment. This is an introductory attempt at demonstrating a single coupled multidisciplinary method of designing liquid containers. The results of the study demonstrate a number of valuable numerical techniques that may be used in the design of liquid containers. The presented Total Deviation Value (TDV) proves to be an effective single quantification of sloshing performance and the CFD tools used to determine the value demonstrate sufficient ability to reproduce the sloshing event itself. More advanced experimental facilities would provide a more in-depth understanding of the limitations of the CFD analysis. The use of numerical optimisation adds a valuable dimension to the use of numerical simulations. Significant design improvements are possible for several design variables without performing exhaustive studies and provide interesting information about design trends. Finally, the use of multiple disciplines, FEM and CFD, in conjunction with the available numerical optimisation routines offers a powerful multidisciplinary design tool that can be adapted to any base geometry and is capable of finding optimal trade offs between the two disciplines according to the designer’s needs. This study provides a platform for further investigations in the use and coupling of sloshing and impact analysis in the design of industrial liquid container applications. / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted

L’émergence de bruits auparavant inaudibles dans les réservoirs à carburants automobiles requiert des constructeurs une meilleure compréhension des phénomènes physiques intervenants au sein de leurs produits. Dans cette thèse, différents travaux ont été conduits autour de l’étude du ballottement de fluide dans une cuve rigide rectangulaire partiellement remplie de fluide et soumise à une excitation extérieure. La première partie présente un état de l’art sur le sloshing suivant trois approches complémentaires - approche analytique, approche numérique et approche expérimentale - permettant d’orienter les travaux. Dans une deuxième partie, une étude préliminaire sur le sloshing dans une cuve rectangulaire soumise à une excitation harmonique forcée est réalisée. La confrontation des résultats numériques entre une approche linéaire - basée sur la théorie d’écoulement potentiel tenant compte de la viscosité du fluide [Schotté et Ohayon, 2013] - et une approche non linéaire commerciale – basée sur la résolution des équations de Navier-Stokes - permet de définir un paramètre de linéarité. Ce dernier permet de déterminer les cas de sloshing qui nécessitent une résolution non linéaire et ceux pour lesquels la théorie linéaire suffit pour prédire le phénomène. La troisième partie de ce document présente une étude expérimentale du ballottement de fluide dans une cuve rectangulaire rigide soumise à un freinage automobile. Deux niveaux de remplissage créant deux types d’impacts contre les parois (avec et sans enfermement de poche d’air) ont été analysés. Les essais menés ont permis de mesurer les forces engendrées par le mouvement du fluide, les pressions d’impact en paroi ainsi que le champ de vitesse par méthode Particle Image Velocimetry (PIV). Ce chapitre constitue une importante base de données expérimentales ayant permis d’étudier précisément le phénomène physique. L’étude est complétée par une confrontation des résultats expérimentaux avec des résultats Computational Fluid Dynamics (CFD). Enfin, pour conclure ce mémoire, une étude du sloshing dans un réservoir en tenant compte de la Fluid-Structure Interaction (FSI) est présentée. Le choix du couplage a été porté sur un schéma partitionné itératif faible avec, dans un premier temps, une approche potentielle instationnaire, puis avec une approche Volume Of Fluid (VOF) pour la physique fluide. Les limites d’un tel couplage dans le cas d’étude d’un réservoir partiellement rempli de fluide et attaché de manière flexible en fonction du rapport de masse fluide-réservoir ont été mises en évidence. La correction du schéma de couplage par l’effet de masse ajoutée présentée dans [Song et al., 2013] permet la résolution d’un système couplé quel que soit le rapport de masse en jeu et améliore de manière significative la convergence en réduisant également fortement le temps de calcul. / The present thesis focuses on an investigation of the sloshing phenomenon in a partially filled fuel tank submitted to a harmonic excitation motion. In the first part, the confrontation of numerical results between a linear approach - taking into account viscosity - and a nonlinear approach based on a commercial code leads to define a parameter of linearity. This parameter allows determining cases of sloshing who require non-linear resolution and those who need a linear theory to predict the phenomenon. An experimental study of fluid sloshing in a rectangular tank submitted to an automotive braking is conducted. Tests leaded allow measuring global forces engendered by the motion of the fluid, pressure of fluid impact and velocity field by PIV. This chapter provides an important data base and helps to investigate on the physical phenomenon. This study is completed by CFD results. To conclude, a numerical model for fluid-structure interactions is presented. Limits of this segregated partitioned coupling in case of sloshing in tank flexibly attached are highlighted, depending mostly on the mass ratio between fluid and tank structure. An added-mass term is integrated to the corrected staggered scheme ensuring systematically the convergence of the coupled solution and reducing significantly the iterations required.

Cette thèse porte sur le développement d’une nouvelle technique de modélisation des problèmes IFS utilisant les méthodes particulaires. Ce travail s’inscrit dans la continuité des travaux de recherche de l’équipe biomécanique du LAMIH, concernant la compréhension du comportement de l’os humain dans son environnement de moelle osseuse. La méthode SPH a été utilisée pour la modélisation des travées osseuses, supposées dans une première approche comme des solides élastiques. La méthode LB a été développée pour la modélisation des écoulements de moelle considérée comme un fluide visqueux incompressible. L’efficacité et la performance de ces deux méthodes ont été démontrées grâce aux benchmarks académiques évalués et les résultats comparés à ceux de la littérature ou ceux obtenus par des logiciels commerciaux. A l’issue d’une revue de l’état de l’art des techniques de couplage fluide-structure, une approche partitionnée en temps a été choisie, permettant d’utiliser deux codes distincts basés sur des algorithmes de résolution de type dynamique explicite. La discrétisation spatiale est faite par une technique spécifique basée sur les domaines fictifs, cette technique est très efficace car elle ne nécessite pas de rediscrétisation des domaines. L’approche de couplage développée a été appliquée à des benchmarks académiques ainsi qu’à une application en biomécanique, ayant permis d’aboutir à des résultats numériques satisfaisants. Plusieurs pistes d’amélioration sont maintenant nécessaires afin d’aller vers des modélisations plus biofidèles telles que la prise en compte du contact et de l’endommagement. / The objective of this thesis is the development of a new technique for the FSI problems modelling using particulars methods. This work is in the continuity of the LAMIH biomechanics team research works, regarding the comprehension of behavior of bone in its environment of marrow. The SPH method was used for the trabeculae modelling, supposed in a first attempt as an elastic solid. The LB method was developed for the marrow flow modelling considered as a viscous incompressible liquid. The efficacy and performance of these two methods were demonstrated using academics benchmarks which were evaluated and the results were compared of those of literature and of those obtained from commercials softwares. Following a bibliographic review of FSI coupling techniques, a partitioned approach in time was chosen, allowing the use of two separates codes, both based on a dynamic explicit algorithm resolution scheme. The special discretization was done based on a specific technique of fictional domain, this technique is very efficient because it doesn’t require an additional domain discretization. The coupling approach developed was applied on academic benchmarks and on a biomechanical application, leading to satisfactory numerical results. Many Improvement track are now necessary to go towards more biofidelic modeling as taking into account the contact and the damage.