Academic literature on the topic 'Hydrodynamic nonlinearities'
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Journal articles on the topic "Hydrodynamic nonlinearities"
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Giorgi, Giuseppe, and John V. Ringwood. "Articulating Parametric Nonlinearities in Computationally Efficient Hydrodynamic Models." IFAC-PapersOnLine 51, no. 29 (2018): 56–61. http://dx.doi.org/10.1016/j.ifacol.2018.09.469.
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Mockutė, Agota, Enzo Marino, Claudio Lugni, and Claudio Borri. "Comparison of Nonlinear Wave-Loading Models on Rigid Cylinders in Regular Waves." Energies 12, no. 21 (October 23, 2019): 4022. http://dx.doi.org/10.3390/en12214022.
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Monopiles able to support very large offshore wind turbines are slender structures susceptible to nonlinear resonant phenomena. With the aim to better understand and model the wave-loading on these structures in very steep waves where ringing occurs and the numerical wave-loading models tend to lose validity, this study investigates the distinct influences of nonlinearities in the wave kinematics and in the hydrodynamic loading models. Six wave kinematics from linear to fully nonlinear are modelled in combination with four hydrodynamic loading models from three theories, assessing the effects of both types of nonlinearities and the wave conditions where each type has stronger influence. The main findings include that the nonlinearities in the wave kinematics have stronger influence in the intermediate water depth, while the choice of the hydrodynamic loading model has larger influence in deep water. Moreover, finite-depth FNV theory captures the loading in the widest range of wave and cylinder conditions. The areas of worst prediction by the numerical models were found to be the largest steepness and wave numbers for second harmonic, as well as the vicinity of the wave-breaking limit, especially for the third harmonic. The main cause is the non-monotonic growth of the experimental loading with increasing steepness due to flow separation, which leads to increasing numerical overpredictions since the numerical wave-loading models increase monotonically.
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Viana, Carlos Alberto Alves, Diogo Stuani Alves, and Tiago Henrique Machado. "Linear and Nonlinear Performance Analysis of Hydrodynamic Journal Bearings with Different Geometries." Applied Sciences 12, no. 7 (March 22, 2022): 3215. http://dx.doi.org/10.3390/app12073215.
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In rotor dynamics, a traditional way of representing the dynamics of hydrodynamic bearings is using stiffness/damping coefficients. It is thus necessary to carry out a linearization of hydrodynamic forces around the shaft’s equilibrium position. However, hydrodynamic bearings have highly nonlinear nature, depending on operating conditions. Therefore, this paper discusses the applicability of these linear/nonlinear approaches using a computational model of the rotating system, where the finite element method is used for rotor modelling and the finite volume method for bearing calculation. The main goal is to investigate the boundaries for linear approximation of the hydrodynamic forces present in lobed hydrodynamic bearings, with the system operating under high loading conditions. Several numerical simulations were performed varying preload parameter and rotating speed. A comparison of the system’s responses, in time domain (shaft orbits) and frequency domain (full spectrum), is made for linear and nonlinear models. Results showed that trilobed bearings are more susceptible to nonlinearities, even in situations of smaller vibration amplitudes, while elliptical bearings are sensitive only under larger vibration amplitudes. These analyses are of great importance for mapping the influence of nonlinearities in different types of lobed hydrodynamic bearings with fixed geometry, varying the preload parameter to verify the influence on the system’s dynamic response. This study is important and serves as the basis for cases of monitoring and fault diagnosis (in the field of structural health monitoring) since it is crucial to distinguish what would be a fault signature or a standard nonlinear effect created by the use of hydrodynamic bearings.
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Huang, Yifeng, and Paul D. Sclavounos. "Nonlinear Ship Motions." Journal of Ship Research 42, no. 02 (June 1, 1998): 120–30. http://dx.doi.org/10.5957/jsr.1998.42.2.120.
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A nonlinear numerical method has been developed to compute motion responses for a ship traveling in steep ambient waves. The method is based on an approximate theory and is an extension to a well-established linear time-domain numerical method. The nonlinear solution is found to be greatly improved over the classical linear and quasi-nonlinear solutions, in comparison to experimental measurements for conventional commercial ships. Through this study, it is also demonstrated that the free surface hydrodynamic nonlinearities are at least as important as, if not more than, the hydrostatic and Froude-Krylov nonlinearities. Stability, consistency and convergence for the nonlinear method are also addressed.
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Ande, Raghu, Stefanie Gutschmidt, and Mathieu Sellier. "Non-linear finite-amplitude oscillations of the large beam arrays oscillating in viscous fluids." Journal of Applied Physics 132, no. 17 (November 7, 2022): 174904. http://dx.doi.org/10.1063/5.0106293.
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Over the past decade, several studies have been conducted on a single and multiple oscillating thin cantilever beams in an unbounded viscous fluid. With an increase in the applications of large array oscillators in a fluid environment for fields like medicine, biology, and energy harvesting devices, it is crucial to understand the nature of the surrounding fluid dynamics. In this present study, we perform a two-dimensional computational fluid dynamics (CFD) analysis of an array of beams oscillating in an unbounded viscous fluid. The two-dimensional Navier Stokes and continuity equations are solved to investigate the hydrodynamic forces exerted on the array members from interaction with the fluid environment. A complex hydrodynamic function is proposed here to represent the distributed hydrodynamic loading experienced by the oscillating beams. Results suggest that there is an increase in viscous damping with an increase in the size of the array. In addition, the nonlinearities become dominant when an array of beams is subjected to large amplitude oscillations. The number of beams in an array determines the overall hydrodynamics and the array effect. CFD analysis can predict the non-linearities unlike boundary integral method (BIM) approach, which is limited for low amplitudes. The results from the full Navier–Stokes simulations compared favorably with results using the BIM for the time-harmonic linearized Stokes equations.
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Abroug, Iskander, Nizar Abcha, Fahd Mejri, Emma Imen Turki, and Elena Ojeda. "The Hydrodynamic Behavior of Vortex Shedding behind Circular Cylinder in the Presence of Group Focused Waves." Fluids 7, no. 1 (December 22, 2021): 4. http://dx.doi.org/10.3390/fluids7010004.
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Vortex shedding behind an elastically mounted circular cylinder in the presence of group focused waves propagating upstream was investigated using a classical approach (time series and FFT) and nonclassical approach (complex 2D Morlet wavelets). Wavelet analysis emerged as a novel solution in this regard. Our results include wave trains with different nonlinearities propagating in different water depths and derived from three types of spectra (Pierson–Moskowitz, JONSWAP (γ = 3.3 or γ = 7)). It was found that the generated wave trains could modify regimes of shedding behind the cylinder, and subharmonic frequency lock-in could arise in particular situations. The occurrence of a lock-in regime in the case of wave trains propagating in intermediate water locations was shown experimentally even for small nonlinearities. Moreover, the application of time-localized wavelet analysis was found to be a powerful approach. In fact, the frequency lock-in regime and its duration could be readily identified from the wavelet-based energy and its corresponding ridges.
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Krasavin, Alexey V., Pavel Ginzburg, and Anatoly V. Zayats. "Free-electron Optical Nonlinearities in Plasmonic Nanostructures: A Review of the Hydrodynamic Description." Laser & Photonics Reviews 12, no. 1 (December 13, 2017): 1700082. http://dx.doi.org/10.1002/lpor.201700082.
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DIAZ-GUILERA, ALBERT. "NONLINEAR STOCHASTIC DIFFERENTIAL EQUATIONS AND SELF-ORGANIZED CRITICALITY." Fractals 01, no. 04 (December 1993): 963–67. http://dx.doi.org/10.1142/s0218348x93001039.
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Several nonlinear stochastic differential equations have been proposed in connection with self-organized critical phenomena. Due to the threshold condition involved in its dynamic evolution, an infinite number of nonlinearities arise in a hydrodynamic description. We study two models with different noise correlations which make all nonlinear contributions to be equally relevant below the upper critical dimension. The asymptotic values of the critical exponents are estimated from a systematic expansion in the number of coupling constants by means of the dynamic renormalization group.
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Gong, Yihui, Lin Li, Shengbo Qi, Changbin Wang, and Dalei Song. "Enhanced disturbance observer-based robust yaw servo control for ROVs with multi-vector propulsion." Industrial Robot: the international journal of robotics research and application 48, no. 3 (April 6, 2021): 366–77. http://dx.doi.org/10.1108/ir-09-2020-0184.
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Purpose A novel proportional integral derivative-extended state disturbance observer-based control (PID-ESDOBC) algorithm is proposed to solve the nonlinear hydrodynamics, parameters perturbation and external disturbance in yaw control of remote operated vehicles (ROVs). The effectiveness of PID-ESDOBC is verified through the experiments and the results indicate that the proposed method can effectively track the desired attitude and attenuate the external disturbance. Design/methodology/approach This study fully investigates the hydrodynamic model of ROVs and proposes a control-oriented hydrodynamic state space model of ROVs in yaw direction. Based on this, this study designs the PID-ESDOBC controller, whose stability is also analyzed through Kharitonov theorem and Mikhailov criterion. The conventional proportional-integral-derivative (PID) and active disturbance rejection control (ADRC) are compared with our method in our experiment. Findings In this paper, the authors address the nonlinear hydrodynamics, parameters perturbation and external disturbance problems of ROVs with multi-vector propulsion by using PID-ESDOBC control scheme. The advantage is that the nonlinearities and external disturbance can be estimated accurately and attenuate promptly without requiring the precise model of ROVs. Compared to PID and ADRC, both in overshoot and settling time, the improvement is 2X on average compared to conventional PID and ADRC in the pool experiment. Research limitations/implications The delays occurred in the control process can be solved in the future work. Practical implications The attitude control is a kernel problem for ROVs. A precise kinematic and dynamic model for ROVs and an advanced control system are the key factors to obtain the better maneuverability in attitude control. The PID-ESDOBC method proposed in this paper can effectively attenuate nonlinearities and external disturbance, which leads to a quick response and good tracking performance to baseline controller. Social implications The PID-ESDOBC algorithm proposed in this paper can be ensure the precise and fast maneuverability in attitude control of ROVs or other underwater equipment operating in the complex underwater environment. In this way, the robot can better perform undersea work and tasks. Originality/value The dynamics of the ROV and the nominal control model are investigated. A novel control scheme PID-ESDOBC is proposed to achieve rapidly yaw attitude tracking and effectively reject the external disturbance. The robustness of the controller is also analyzed which provides parameters tuning guidelines. The effectiveness of the proposed controller is experimental verified with a comparison by conventional PID, ADRC.
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Matthaeus, William H., Gary P. Zank, and Sean Oughton. "Phenomenology of hydromagnetic turbulence in a uniformly expanding medium." Journal of Plasma Physics 56, no. 3 (December 1996): 659–75. http://dx.doi.org/10.1017/s0022377800019516.
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A simple phenomenology is developed for the decay and transport of turbulence in a constant-speed, uniformly expanding medium. The fluctuations are assumed to be locally incompressible, and either of the hydrodynamic or non-Alfvénic magnetohydrodynamic (MHD) type. In order to represent local effects of nonlinearities, a simple model of the Kaármá-Dryden type for locally homogeneous turbulent decay is adopted. A detailed discussion of the parameters of this familiar one-point hydrodynamic closure is given, which has been shown recently to be applicable to non-Alfvénic MHD as well. The effects of the large-scale flow and expansion are incorporated using a two-scale approach, in which assumptions of particular turbulence symmetries provide simplifications. The derived model is tractable and provides a basis for understanding turbulence in the outer heliosphere, as well as in other astrophysical applications.
Dissertations / Theses on the topic "Hydrodynamic nonlinearities"
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Rocha, Mariana Vieira Lima Matias da. "Observation and modelling of wave nonlinearities and infragravity waves in the nearshore." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17142.
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Doutoramento em Física e GeofísicaWave nonlinearities have long been recognised as being among the main drivers of sediment transport in the coastal zone. However, there are still signi cant errors in the prediction of this transport associated, partially due to inaccurate predictions of the velocity nonlinearities. The infragravity waves, which coexist with the short waves in the coastal zone, are long-period waves (with 20-200 s) associated to the shortwave groups. Their generation, propagation and dissipation mechanisms are already reasonably well understood, but their in uence on sediment transport is still very poorly characterised. In order to (i) improve current predictions of velocity nonlinearities and (ii) investigate the role of infragravity waves in sediment transport, new experiments were carried out both in a xed-bed wave ume and in a light-weight-sediment wave ume. The physical-modelling data set is used in combination with eld data and numerical simulations for studying both subjects. Existing parameterizations of velocity nonlinearities account only for the in uence of local wave parameters (e.g. wave height, wave length and water depth), which leads to considerable estimation errors, especially of the maximal values of nonlinearity. This work shows that the velocity nonlinearities depend also on non-local wave parameters: (i) o shore wave steepness, (ii) o shore spectral bandwidth and (iii) beach slope. A new parameterization is proposed, which reduces by about 50% the root-mean-square error relatively to former parameterizations. The experimental results in the light-weight-sediment wave ume demonstrate that wave conditions with the same short-wave energy, but di erent low-frequency modulation, shape di erent equilibrium beach pro les. The in uence of the infragravity waves on the sediment transport is con rmed and depends on two di erent mechanisms: (i) advection of the short-wave suspended sediment by the infragravity-waves, which is dependent on the infragravity-wave height and phasing with the short-wave groups and (ii) modulation of short-wave nonlinearities by infragravity-wave motion, both directly and indirectly, through waterdepth modulation. Changes in the beachface morphology induced by infragravity waves are connected to beach-pro le changes in the surf and inner-shoaling zones, highlighting the existent link between the di erent zones of the cross-shore beach pro le.
As não-linearidades das ondas de superfície são desde há algum tempo reconhecidas como um dos principais promotores do transporte sedimentar na zona costeira. Contudo, existem ainda erros signi cativos na estimativa do transporte devidos, entre outros, a uma imprecisa descrição das não-linearidades da velocidade do escoamento orbital. As ondas infragravíticas, que coexistem com as ondas curtas na zona costeira, são ondas de longo período (20-200 s) associadas aos grupos de ondas curtas. Os mecanismos de geração, propagação e dissipação destas ondas são actualmente razoavelmente bem compreendidos, mas a sua influência no transporte sedimentar ainda apresenta limitações. Com o objectivo de (i) melhorar as parameterizações existentes das não-linearidades da velocidade e (ii) investigar o papel das ondas infragrav íticas no transporte sedimentar, foram realizadas novas experiências em dois canais de ondas, um de fundo fi xo e outro de fundo móvel com sedimentos de baixa densidade. Os dados obtidos nos modelos físicos foram utilizados conjuntamente com dados de campo e de simulações numéricas para investigar ambos os temas. As parameterizações existentes para as não-linearidades da velocidade têm apenas em conta a influência de parâmetros locais de onda (e.g. altura de onda, comprimento de onda e profundidade de água), o que resulta em erros consideráveis nas estimativas, em particular dos valor máximos de não-linearidade. Este trabalho evidencia que a nãolinearidade da velocidade depende também de parâmetros que não são locais: (i) a declividade da onda ao largo, (ii) a largura da banda espectral ao largo e (iii) o declive da praia. Uma nova parameterização que reduz em cerca de 50% o erro dos resultados obtidos com as parameterizações existentes de proposta. Os resultados experimentais obtidos no canal de ondas com fundo móvel demonstram que climas de agitação marítima com a mesma energia de ondas curtas, mas com diferente modulação de baixa frequência, moldam perfís de praia diferentes. A influência das ondas infragravíticas no transporte sedimentar é posta em evidência e processa-se através de dois mecanismos distinctos: (i) advecção pelas ondas infragravíticas de sedimento colocado em suspensão pela acção das ondas curtas, a qual é dependente da altura das ondas infragravíticas e da sua fase relativamente aos grupos de ondas curtas e (ii) as ondas infragravíticas alteram as não-linearidades das ondas curtas, tanto directa como indirectamente, através da modulação da altura da coluna de água. As variações morfológicas da face da praia induzidas pelas ondas infragravíticas estão associadas a alterações do perfil de praia nas zonas de surf e de empolamento, evidenciando o elo existente entre as diferentes zonas do perfil transversal da praia.
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Rocha, Mariana Vieira Lima Matias da. "Observation et modélisation des ondes infra-gravitaires et des non-linéarités des vagues en milieu littoral." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAU043/document.
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Les non-linéarités des ondes de surface, qui se caractérisent par leur aspect dissymétrique, sont reconnues comme l'un des principaux moteurs du transport de sédiments en zone littorale. Cependant, l'estimation du transport reste imparfaite, en partie du fait d’une description inexacte des non-linéarités de la vitesse de l'écoulement orbital. Les ondes infra-gravitaires, qui coexistent avec les ondes courtes en zone littorale, sont des ondes de longue période (20-200 s) associés aux groupes d'ondes courtes. Les mécanismes de génération, propagation et dissipation de ces ondes sont maintenant relativement bien compris, mais leur effet sur le transport sédimentaire est encore mal connu. Afin (i) d’améliorer les paramétrisations existantes des non-linéarités de vitesse et (ii) d’étudier le rôle des ondes infra-gravitaires dans le transport sédimentaire, de nouvelles expériences ont été réalisées dans deux canaux à houle, l’un avec un fond fixe et l'autre avec un fond mobile constitué de sédiments de faible densité. Les données obtenues avec ces modèles physiques ont été utilisés conjointement à des données de terrain et des simulations numériques pour étudier les deux sujets.}TEXT{}{Les paramétrisations classiques pour les non-linéarités de vitesse prennent seulement en compte l'influence de paramètres locaux (la hauteur de vague, la longueur d'onde et la profondeur d’eau), ce qui entraîne des erreurs importantes dans les estimations, en particulier les valeurs maximales de non-linéarité. Ce travail montre que les non-linéarités de vitesse ont aussi une dépendance avec des paramètres qui ne sont pas locaux: (i) la cambrure de vague et (ii) la largeur de la bande spectrale au large, ainsi que (iii) la pente de la plage. Une nouvelle paramétrisation est proposée, qui réduit d’environ 50% l'erreur sur les résultats obtenus avec les paramétrisations existantes. Les résultats expérimentaux obtenus dans le canal à houle avec un fond mobile montrent que des conditions de vagues avec la même énergie d'ondes courtes, mais avec une modulation basse fréquence différente, modèlent des profils de plage différents. L'influence des ondes infra-gravitaires sur le transport sédimentaire est mis en évidence par deux mécanismes distincts: (i) l’advection par les ondes infra-gravitaires de sédiment mis en suspension par l'action des ondes courtes, qui dépend de la hauteur des ondes infra-gravitaires et de leur phase par rapport aux groupes d'ondes courtes et (ii) les ondes infra-gravitaires modifient les non-linéarités des ondes courtes, que ce soit directement ou indirectement, par modulation de la hauteur de la colonne d'eau. Les variations morphologiques du haut de plage induites par les ondes infra-gravitaires sont associées à des changements du profil de la plage dans les zones de déferlement et de levée, en mettant en évidence le lien entre les différentes régions du profil transversal de la plageWave nonlinearities have long been recognised as being among the main drivers of sediment transport in the coastal zone. However, there are still significant errors in the prediction of this transport associated, partially due to inaccurate predictions of the velocity nonlinearities. The infragravity waves, which coexist with the short waves in the coastal zone, are long-period waves (with 20-200 s) associated to the short-wave groups. Their generation, propagation and dissipation mechanisms are already reasonably well understood, but their influence on sediment transport is still very poorly characterised. In order to (i) improve current predictions of velocity nonlinearities and (ii) investigate the role of infragravity waves in sediment transport, new experiments were carried out both in a fixed-bed wave flume and in a light-weight-sediment wave flume. The physical-modelling data set is used in combination with field data and numerical simulations for studying both subjects. Existing parameterizations of velocity nonlinearities account only for the influence of local wave parameters (e.g. wave height, wave length and water depth), which leads to considerable estimation errors, especially of the maximal values of nonlinearity. This work shows that the velocity nonlinearities depend also on non-local wave parameters: (i) offshore wave steepness, (ii) offshore spectral bandwidth and (iii) beach slope. A new parameterization is proposed, which reduces by about 50% the root-mean-square error relatively to former parameterizations. The experimental results in the light-weight-sediment wave flume demonstrate that wave conditions with the same short-wave energy, but different low-frequency modulation, shape different equilibrium beach profiles. The influence of the infragravity waves on the sediment transport is confirmed and depends on two different mechanisms: (i) advection of the short-wave suspended sediment by the infragravity-waves, which is dependent on the infragravity-wave height and phasing with the short-wave groups and (ii) modulation of short-wave nonlinearities by infragravity-wave motion, both directly and indirectly, through water-depth modulation. Changes in the beachface morphology induced by infragravity waves are connected to beach-profile changes in the surf and inner-shoaling zones, highlighting the existent link between the different zones of the cross-shore beach profile
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Tran, Ngan. "The impact of hydrodynamic coupling on the performance of multi-mode wave energy converters." Thesis, 2021. https://hdl.handle.net/2440/135690.
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Recently, research interest has deepened in developing technologies that are capable of generating electricity from renewable sources. Ocean wave energy is one such source, and is gaining attention due to its high energy density and favourable variability properties compared to other sources such as solar and wind. Although many Wave Energy Converter (WEC) prototypes have been proposed over the years, there is still no convergence on the best design. An emerging subset of WEC designs are ‘multi-mode converters’, which are capable of absorbing power from multiple hydrodynamic modes. This allows them to generate more energy from incoming waves compared to most other WECs, which typically use only one Degree-of-Freedom (DOF) for power absorption. However, one of the key challenges in the design and control of multi-mode WECs is the strong coupling between hydrodynamic modes, which can potentially lead to sub-optimal performance. The effect of this coupling on the device performance may also be further exacerbated when nonlinear hydrodynamic effects are considered. This thesis is dedicated to building an understanding of the impact of nonlinear coupling between hydrodynamic modes on the power absorption efficacy of a submerged, multi-mode, point absorber WEC with a flat cylindrical geometry. From this, the project also intends to provide general recommendations regarding the control and design of multi-mode WECs for increased performance. Three specific research questions were investigated: (i) what is the effect of nonlinear hydrodynamic coupling forces, caused by the change in projected surface area with large pitch motions, on the performance of multi-mode WECs, (ii) how should the surge, heave and pitch hydrodynamic modes be tuned to enhance the performance of WECs subjected to nonlinear coupling forces and (iii) what design parameters can be implemented to passively tune the hydrodynamic modes in a nonlinear, under-actuated WEC device. To address these questions, various numerical models were developed and compared, ranging from low fidelity models in the frequency-domain based on linear hydrodynamic models, to a weakly nonlinear hydrodynamic code based on the weak-scatterer approximation. Initially, it was necessary to gain a fundamental understanding of the nonlinear hydrodynamic forces acting on a device forced to undergo large pitch motions and oscillate in multiple hydrodynamic modes simultaneously. To this end, initial investigations assumed a simple WEC system with fully idealised kinematic control, wherein the pitch and surge motions could be explicitly defined. It was found that simultaneous surge and pitch motions changed the radiation forces acting on the WEC, resulting in significant reductions to the maximum power that could be absorbed by the device. Different approaches for adjusting the dynamics and resonance behaviour of the multi-mode WEC through tuning of the hydrodynamic modes were then investigated. Under the effects of nonlinear coupling between hydrodynamic modes, tuning the surge, heave and pitch modes to the same natural frequency was demonstrated to result in significant reductions in power absorbed, especially when the pitch amplitude was high. Recommendations were therefore made to decouple these modes when developing multi-mode WECs in the case where the design does not limit large pitch amplitudes. From the models investigated, this tuning approach also demonstrated a potential for improving the broadband power absorption efficacy of the device in irregular waves. In the final stage of this project, the impact of nonlinear coupling in an under-actuated system was investigated. A sensitivity study was conducted to investigate the effect of adjusting the geometric design of a three-tethered WEC on the resonance behaviour of each hydrodynamic mode. It was concluded that for maximum power absorption, two out of three of the device’s planar rigid body modes should be utilised to harvest energy from incident waves. Furthermore, for this WEC geometry and design, these rigid body modes should contain predominantly surge and heave motions. Subharmonic excitations caused by nonlinear forces arising from the tether arrangement and hydrodynamic interactions were also found to significantly reduce the performance of the device compared to the predictions from linear theory. It was determined that the power absorbed by the device was most sensitive to the arrangement of the tethers, while adjusting parameters related to the mass distribution resulted in little benefit to the overall device performance.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2022
Book chapters on the topic "Hydrodynamic nonlinearities"
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Husser, Nicholas, and Stefano Brizzolara. "A Linear Model Analysis of the Unsteady Force Response of a Planing Hull Through Forced Vertical Plane Motion Simulations." In Progress in Marine Science and Technology. IOS Press, 2020. http://dx.doi.org/10.3233/pmst200039.
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The prediction of planing hull motions and accelerations in a seaway is of paramount importance to the design of high-speed craft to ensure comfort and, in extreme cases, the survivability of passengers and crew. The traditional approaches to predicting the motions and accelerations of a displacement vessel generally are not applicable, because the non-linear effects are more significant on planing hulls than displacement ships. No standard practice for predicting motions or accelerations of planing hulls currently exists, nor does a nonlinear model of the hydrodynamic forces that can be derived by simulation. In this study, captive and virtual planar motion mechanism (VPMM) simulations, using an Unsteady RANSE finite volume solver with volume of fluid approach, are performed on the Generic Prismatic Planing Hull (GPPH) to calculate the linearized added mass, damping, and restoring coefficients in heave and pitch. The linearized added mass and damping coefficients are compared to a simplified theory developed by Faltinsen [6], which combines the method of Savitsky [12] and 2D+t strip theory. The non-linearities in all coefficients will be investigated with respect to both motion amplitude and frequency. Nonlinear contributions to the force response are discussed through comparison of the force response predicted by the linear model and force response measured during simulation. Components of the planing hull dynamics that contribute to nonlinearities in the force response are isolated and discussed.
Conference papers on the topic "Hydrodynamic nonlinearities"
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Krasavin, Alexey, Pavel Ginzburg, and Anatoly V. Zayats. "Nonlinearities in plasmonic nanostructures: hydrodynamic description (Conference Presentation)." In Nanostructured Thin Films XI, edited by Tom G. Mackay and Akhlesh Lakhtakia. SPIE, 2018. http://dx.doi.org/10.1117/12.2323248.
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Zanganeh, Hossein, and Narakorn Srinil. "Two-Dimensional Coupled Vortex-Induced Vibration of Circular Cylinder: Prediction and Extraction of Hydrodynamics Properties." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10240.
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An advanced model for predicting a two-dimensional coupled cross-flow and in-line vortex-induced vibration (VIV) of a flexibly-mounted circular cylinder in a uniform flow is proposed and investigated. Attention is placed on a systematic extraction of variable hydrodynamics properties associated with a bi-directional fluid-structure interaction system. The governing equations of motion are based on double Duffing-van der Pol (structural-wake) oscillators with the two structural equations containing cubic and quadratic nonlinear terms. The cubic nonlinearities capture the geometrical coupling of cross-flow/in-line displacements excited by hydrodynamic lift/drag forces whereas the quadratic nonlinearities allow fluid-structure interactions. The combined analytical and numerical solutions of the proposed model are established. By varying flow velocities in numerical simulations, the derived low-order model qualitatively captures several key VIV characteristics of coupled in-line/cross-flow oscillations. By making use of a newly-derived empirical formula, the predicted maximum cross-flow/in-line VIV amplitudes and associated lock-in ranges compare well with several experimental results for cylinders with low/high mass or damping ratios. Moreover, such important hydrodynamic properties as VIV-induced mean drag, added mass, excitation and damping terms can be systematically determined via the proposed model and compared well with some experimental results in the literature.
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Xu, Yuwang, Ole Øiseth, and Torgeir Moan. "Time Domain Modelling of Frequency Dependent Wind and Wave Forces on a Three-Span Suspension Bridge With Two Floating Pylons Using State Space Models." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62721.
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Floating suspension bridges, one of several new designs to make it possible to cross deep and wide fjords, consist of three spans and supported by two tension leg platforms and two fixed traditional concrete pylons. Geometric nonlinearities, nonlinear aerodynamic and hydrodynamic forces and nonlinear mooring systems can become of high importance. Time domain methods are commonly applied when nonlinearities need to be considered. The main challenge in time domain simulation of the floating suspension bridge is the modelling of frequency-dependent aerodynamic self-excited forces and hydrodynamic radiation forces. This paper shows how rational functions fitted to aerodynamic derivatives and hydrodynamic added mass and potential damping can be converted to state space models to transform the frequency-dependent forces to time-domain. A user element is implemented in the software ABAQUS to be able to include the self-excited forces in the dynamic analysis. The element is developed as a one node element that is included in the nodes along the girder and the tension leg platforms. The responses of the floating suspension bridge under turbulent wind forces and first-order wave excitation forces are calculated in a comprehensive case study and compared with results obtained using a multi-mode frequency domain approach to illustrate the performance of the presented time-domain methodology.
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Bretl, James, Kathleen Edwards, Mike Mekhiche, and Hizkyas Dufera. "Results From an Integrated Tool for Marine System Hydrodynamic and Control Modeling." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-42187.
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While wave energy converters (WECs) offer the potential of renewable energy from ocean waves, a central challenge for developers is the ability to investigate candidate geometries and control systems prior to expensive wave tank tests or field deployment. If WEC behavior and power output can be simulated numerically, results can be analyzed to determine if a candidate development direction should be pursued. This paper describes the validation of a tool used at Ocean Power Technologies (OPT) to refine the design of its PowerBuoy® product. The tool, Simulink Target for OrcaFlex Runtime Model (STORM), was developed by OPT with support from MathWorks. STORM takes advantage of the ability of (a) OrcaFlex to represent the interaction of complex geometries with a realistic marine environment and (b) Simulink to represent the behavior of the device’s Power Takeoff (PTO) under different control functions, including the digital nature of real-time control. Optimal control of WECs is an active area of research within the industry. STORM provides the tools necessary to implement and evaluate various control architectures while exposing them to realistic physical constraints and nonlinearities.
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Marino, E., C. Lugni, L. Manuel, H. Nguyen, and C. Borri. "Simulation of Nonlinear Waves on Offshore Wind Turbines and Associated Fatigue Load Assessment." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24623.
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By using a global simulation framework that employs a domain-decomposition strategy for computational efficiency, this study investigates the effects of fully nonlinear (FNL) waves on the fatigue loads exerted on the support structure (monopile) of a fixed-bottom offshore wind turbine. A comparison is made with more conventional linear wave hydrodynamics. The FNL numerical wave solver is invoked only on specific sub-domains where nonlinearities are detected; thus, only locally in space and time, a linear wave solution is replaced by the FNL results as input to the Morison equation used for the hydrodynamic loads. The accuracy and efficiency of this strategy allows long timedomain simulations where strongly nonlinear free-surface phenomena, like imminent breaking waves, are accounted for in the prediction of structural loads. The unsteady nonlinear free-surface problem governing the propagation of gravity waves is formulated using potential theory and a higher-order boundary element method (HOBEM) is used to discretize Laplace’s equation. The FNL solver is employed and associated hydrodynamic loads are predicted in conjunction with aerodynamic loads on the rotor of a 5-MW wind turbine using the NREL open-source software, FAST. We assess fatigue loads by means of both time- and frequency-domain methods. This study shows that the use of linear theory-based hydrodynamics can lead to significant underestimation of fatigue loads and damage.
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Taguchi, Masakazu, and Masashi Kashiwagi. "Experimental Study on a Relation Between Nonlinear Hydrodynamic Forces and Wave-Induced Ship Motions." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95555.
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Abstract Nowadays, in maritime industries, container ships increase in size and they have large flares, which may induce nonlinear wave loads in large-amplitude waves. It is also well known that hydrodynamic forces acting on a ship and resulting ship motions show nonlinearities at some range of wave frequencies. Therefore, we should investigate not only correct estimation of wave loads and ship motions, but also nonlinear ship-motion characteristics in large-amplitude waves. However, it is not that clear which nonlinear hydrodynamic force terms are dominating for the nonlinearity in the ship motions. Although the linear equations of motion have been used, they should be modified to incorporate at least the most important nonlinear hydrodynamic forces and to establish a practical calculation method taking account of only the indispensable nonlinear terms. In this research, we did extensive experimental measurement of hydrodynamic forces and wave-induced ship motions, with which we aim to understand what are practically important nonlinear terms, and to derive practical nonlinear ship motion equations through numerical computation and comparison with experimental data.
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Hara, Kensuke, and Masahiro Watanabe. "Simulation and Measurement of a Nonlinear Hydrodynamic Sloshing Force on a Rectangular Tank With Shallow Water Depth." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45770.
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This paper deals with a hydrodynamic sloshing force on a rectangular tank. In particular, we focus on a contribution of the nonlinear sloshing in shallow water depth to the hydrodynamic force. It is well known that the water wave in shallow water depth shows the characteristic behaviors such as the solitary wave by inherent nonlinearities. Therefore, the effect of nonlinearity is crucial for the estimation of the hydrodynamic sloshing force. Although these behaviors arises from the typical feature of the sloshing in shallow water depth, the theoretical analysis is essentially difficult because a lot of higher order nonlinear terms and eigenmodes have to be taken into account for accurate numerical predictions. Consequently, it yields complicated algebraic procedures. This study presents a formulation based on the Hamiltonian dynamics. In addition, the Dirichlet-Neumann operators (DNO) developed by Craig and Sulem was introduced to obtain an asymptotic description for the kinematic boundary condition of the liquid surface. The proposed approach facilitates the consideration of the nonlinearity for the formulation. Moreover, experiments were conducted to measure time histories of the wave height and the nonlinear fluid force due to the sloshing in a rectangular tank subjected to a horizontal excitation. As the results of frequency analyses for the time histories of the hydrodynamic force, many frequency spectra with the odd multiple of the dominant frequency were observed. These features were also obtained by the theoretical predictions by the proposed method.
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Barcarolo, Daniel, Olivia Thilleul, David le Touzé, Erwan Jacquin, Igor de Vries, and Mamoun Naciri. "Aframax in Numerical Wave Tank: From Classic Decay Test to the Ship Moored in Irregular Waves." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54844.
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The prediction of ship motions in extreme seastates is very complex as it involves strong nonlinearities. It deals with high motions of the ship and implies strong mooring system loads. These seastates are usually modeled in tank tests but an alternative in the near future could be CFD computations. In this article, all required steps to setup and verify the hydrodynamic and numerical model are performed. The setup of the hydrodynamic and numerical model enable us to show that CFD computations of motion RAOS and pitch decay tests provide results in agreement with diffraction-radiation results. Wave only simulations enable us to verify that irregular waves are accurately modelled in the CFD domain. Since the wavemaker motion used in tank tests to generate irregular waves is not available, a process of linear back propagation is set up from the wave elevation on a wave probe in tank tests. High Order Spectral (HOS) simulations are performed to reproduce the seastate measured in tank tests. Finally, a test was performed to model the ship motions in irregular extreme waves with ICARE solver coupled to the computed HOS wave field through Spectral Wave Explicit Navier Stokes Equations (SWENSE).
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Ganesan Thirunaavukarasu, Shivaji, Debabrata Sen, and Yogendra Parihar. "Steep Wave Effects on Wave Induced Vertical Bending Moment Using a 3D Numerical Wave Tank." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61161.
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This paper presents a detail comparative study on wave induced vertical bending moment (VBM) between linear and approximate nonlinear calculations using a 3D numerical wave tank (NWT) method. The developed numerical approach is in time domain where the ambient incident waves can be defined by any suitable wave theory. Certain justifying approximations employed in the solution of the interaction hydrodynamics (diffraction and radiation) enabling the NWT to generate stable long duration time histories of all parameters of interest. This is an extension of our earlier works towards the development of a practical NWT based solution for wave-structure interactions [1]. After a brief outline of the implemented numerical details, a comprehensive validation and verification of vertical shear force (VSF) and bending moment RAOs computed using the linearized version of the NWT against the usual linear results of strip theory and 3D panel codes are presented. Next we undertake the comparative study between the fully linear and approximate nonlinear versions of the present code for different incident wave steepness. In the approximate nonlinear formulation, the ambient incident wave is defined by the full nonlinear numerical wave model based on Fourier approximation method which can generate very steep steady periodic nonlinear waves up to the near wave breaking limit. The nonlinearities associated with the incident Froude Krylov and hydrostatic restoring forces/moments are exact up to the instantaneous wetted surface at the displaced location, but the hydrodynamic diffraction and radiation effects are linearized around the mean wetted surface. The standard S175 container hull is considered for the comparative studies because of its geometric nonlinearities. Numerical simulations are performed for four different wave lengths with increasing wave steepness. It is observed that the computed wave induced VBM amidships from the approximate nonlinear results can be almost 30% higher compared to the results from a purely linear solution, which can be a critical issue from the safety point. Significant higher harmonics are also observed in the approximate nonlinear results which at some times may be responsible for exciting the undesirable whipping/springing responses.
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Turk, Anton, Jasna Prpić-Oršić, and Carlos Guedes Soares. "Parametric Rolling Simulations of Container Ships." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-11344.
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A hybrid nonlinear time domain seakeeping analysis is applied to the study of a container ship advancing at different headings and encounter frequencies. A time-domain nonlinear strip theory in six degrees-of-freedom has been extended to predict ship motions by solving the unsteady hydrodynamic problem in the frequency domain and the equations of motion in the time domain which allows introducing nonlinearities in the linear model. The code is used to make parametric roll predictions for various speeds and headings and the results are summarized in a very intuitive 2D and 3D polar plots showing the full range of the parametric rolling realizations. The method developed is fairly accurate, robust, very computationally efficient, and can predict nonlinear ship motions. It is well suited to be used as a tool in ship design or as part of a path optimization model.