A system of ordinary differential equations (ODE) is constructed for an air cushion vehicle (ACV). The system is simplified to an equation for the balance of the vertical forces and the equation for the adiabatic compression of the air in the cushion. Air pressure is constantly supplied into the system, but can leak out from underneath the edges of the cushion. A series of regular waves encounters the air cushion, causing a change in volume. Additionally, a computational analysis of the seakeeping of a Surface Effect Ship (SES) is performed using the commercial software WAMIT, which uses low-order, linear potential panel method. The model of the T-Craft consists of catamaran hulls, rigid end skirts, and the interface between the air cushion and the water surface. Beyond the six rigid body degrees of freedom of the T-Craft, additional modes are added for the motion of the interface panels. To verify the method used, the model is benchmarked using computational data for a small-scale barge model and experimental data for a T-Craft model. A comparison is performed for the T-Craft with and without its cushion. The solution for the nonlinear time-domain system is found numerically, and the stability of the system is studied by observing bifurcations with the incoming wave amplitude as the bifurcation parameter. The system experiences a period-doubling bifurcation, from a periodic orbit, to a subharmonic orbit, to a solution with multiple periods. Further increasing the wave amplitude increases the period doubling, eventually leading to chaotic behavior. As a result of the linear-potential simulations, significant differences are found in the seakeeping of the T-Craft when on and off the cushion. These differences are caused by the direct and indirect effects of the cushion (added aerodynamics and a decreased draft). The RAO's of the craft experience changes in amplitude and phase, which will affect the multi-body relative motions. The time-domain model shows very chaotic behaviour that is presented visually in a bifurcation diagram. These linear potential and time-domain methods illustrate the complexity and importance of modelling air-cushion effects.

A capacidade de prever os movimentos de uma plataforma de petróleo sujeita a ondas é bastante importante no contexto da engenharia naval e oceânica, já que esses movimentos terão diversas implicações no projeto deste sistema, com impactos diretos nos custos de produção e tempo de retorno do investimento. Esse trabalho apresenta os fundamentos teóricos sobre o problema de comportamento no mar de corpos flutuantes sujeitos a ondas de gravidades e um método numérico para solução do problema 2D no domínio do tempo. A hipótese básica adotada é a de escoamento potencial, que permitiu a utilização do método de elementos de contorno para descrever a região fluida. Optou-se pela utilização de fontes de Rankine como função de Green no desenvolvimento do método, o qual será abordado somente no contexto linear do problema matemático, delimitado através de um procedimento combinado entre expansão de Stokes e série de Taylor. As simulações são realizadas no domínio do tempo sendo, portanto, resolvido o problema de valor inicial com relação às equações do movimento e equações que descrevem a superfície-livre combinadas com dois problemas de valor de contorno, um para o potencial de velocidades e outro para o potencial de aceleração do escoamento. As equações integrais de contorno permitem transformar o sistema de equações diferenciais parciais da superfície livre num sistema de equações diferenciais ordinárias, as quais são resolvidas através do método de Runge-Kutta de 4a. ordem. As equações integrais são tratadas de forma singularizada e o método utilizado para discretizar as mesmas é de ordem baixa tanto para a função potencial quanto para a aproximação geométrica, sendo as integrações necessárias realizadas numericamente através de quadratura Gauss-Legendre. O algoritmo numérico é testado e validado através de comparações com soluções analíticas, numéricas e experimentais presentes na literatura, considerando os problemas de geração de ondas, cálculo de massa adicional e amortecimento potencial através de ensaios de oscilação forçada, testes de decaimento e, por último, resposta em ondas. Os resultados obtiveram boa concordância com aqueles adotados como paradigma. / The ability to predict the seakeeping characteristics of an offshore structure (such as an oil platform) is very important in offshore engineering since these motions have important consequences regarding its design and therefore its cost and payback period. This work presents the theoretical and numerical aspects concerning the evaluation of the 2D seakeeping problem under the potential flow hypothesis, which allows the use a Boundary Elements Method to describe the fluid region with Rankine sources as Green function. The linearized version of the mathematical problem is built by a combined Stokes expansion and Taylor series procedure and solved in time domain. The initial value problem concerning the motion and free surface equations are solved combined to the boundary value problems considering the velocity and acceleration flow potentials, which transform the partial differential equations of the free surface into ordinary differential equations, that are solved using the 4th order Runge-Kutta method. The integral equations are solved in its singularized version using a low order method both for the potential function and the geometrical approximation, with the terms of the linear system evaluated using Gauss Legendre quadrature. The numerical scheme is tested and validated considering analytical, numerical and experimental results obtained in the literature, concerning wave generation, added mass and potential damping evaluation, decay tests and response to waves. The results achieved good agreement with respect to those used as paradigm.

Operationally, marine components and structures such as boiler in a Ship, are exposed to varying mechanically and thermally induced forces. High-frequency mechanical loading arises from the cyclic pressure, temperature transients, and six directional Rapid Amplitude Operator (RAOs). These types of loadings are mainly in the elastic region usually denoted as high cycle fatigue (HCF), most pronounced during the start-up, and the shut-down sequence of operation, which are responsible for an astronomically  reduction in Marine Boiler’s lifetime as compared to land boiler with same designed operating condition. Therefore, there is a need to determine the limitations of the engineering variables of the boiler with respect to Pressure, temperature, RAOs, and best locational point for the optimization of its designed lifetime during Operation. Detailed knowledge of this interaction between varying temperatures, RAOs and load cases is of considerable importance for precise lifetime calculations.  In order to understand and analyze the material behavior under contentious stress exposure, a general-purpose linear Finite Element (FE) code, LS-DYNA software is used as a pre-processor and solver during the simulation and data are post-processed using stress-based analysis method.

In this dissertation, an approach for determining parameters for a nonlinear Lagrangian mechanical system model of a submerged vessel maneuvering near waves is presented. The nonlinear model with determined parameters is capable of capturing nonlinear effects neglected by other linear models, and therefore can be applied to improve maneuvering performance and expand the operating envelope for submerged vessels operating in elevated sea states. To begin, a first principles Lagrangian nonlinear maneuvering (LNM) model for a surface-affected submerged vessel derived by using Lagrangian mechanics cite{BattistaPhD2018} is reformulated to allow the application of data from a medium fidelity potential flow code. In the reformulation process, the order of integration and differentiation in the integro-differential parameters are switched and partial derivatives of the Lagrangian function are computed with readily available data from the panel code solution. As a result, all model parameters can be computed individually using the panel code, wherein the need for additional numerical discretization is circumvented in the computation process through use of solutions already performed by the basic panel code, enabling higher accuracy and lower computational cost. Furthermore, incident wave effects are incorporated into the reformulated LNM model to yield a Lagrangian nonlinear maneuvering and seakeeping (LNMS) model. The LNMS model is numerically validated by confirming the proposed methods and by comparing steady and unsteady hydrodynamic force calculations from the LNMS model against panel code computations for various vessel motions in calm water and in plane progressive waves. Finally, methods for computing physically intuitive components of the model parameters, as well as methods for making approximations of the terms accounting for memory effects are presented, leading to a model formulation amenable to control design. By applying the methods proposed in this dissertation, each and every parameter of the Lagrangian mechanical system model of a submerged vessel maneuvering in waves can be obtained accurately and with computational efficiency by using a potential flow panel code. The resulting nonlinear motion model provides higher model fidelity than existing unified maneuvering and seakeeping models, especially in applications such as nonlinear control design and simulation. / Doctor of Philosophy / A unified maneuvering and seakeeping model for a submerged vessel maneuvering near waves describes mathematically the relationship between input values to the dynamical system, such as thrust from the propulsors, and output values from the system, such as the position and orientation of the vessel. This unified model has a wide range of applications, ranging from vessel hull form optimization in the early design phase to motion controller tuning after the vessel has been constructed. In order for a unified model to make accurate predictions, for instance, for a submerged vessel making a rapid turn near large waves, nonlinear effects have to be included in the model formulation. To that end, a nonlinear motion model for a marine craft affected by a free surface has been developed using Lagrangian mechanics. This dissertation describes an approach for determining the parameters of the nonlinear motion model using a potential flow panel code, which is originally designed to determine flow velocity of the fluid and pressure distribution over marine vessels. The nonlinear motion model is reformulated and the software implementation is modified to support parameter computations. In addition, the methods are numerically validated by comparing computations using the model against solutions output by the panel code. Compared to traditional parameter estimation approaches, the proposed methods allow for a more accurate and efficient determination of parameters of the nonlinear potential flow model for a submerged vessel operating near waves. The resulting Lagrangian nonlinear maneuvering and seakeeping (LNMS) model with determined parameters is able to capture critical nonlinear effects and has applications such as nonlinear control design, rapid design optimization and training simulator development.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008. / This study investigates practical passive methods to improve the seakeeping of a Hydrofoil Supported Catamaran (Hysucat). The Hysucat is a hybrid vessel combining hydrofoil efficiency with the stability of catamarans. The seakeeping of the Hysucat was initially investigated experimentally to determine what seakeeping improvements are inherent to the Hysucat design. The results showed that the seakeeping is improved by 5-30%. A passive suspension system for the main hydrofoil of the Hysucat was designed and tested. A concept development strategy was followed for the design of the suspension system as such a system had never been investigated previously. Detailed specifications for the design were developed and concepts that could satisfy the customer and engineering requirements were generated. Numerical simulation models for the Hysucat and the final concepts were derived assuming a simplified 2nd order system to describe the seakeeping dynamics of the demi-hulls. Unknown parameters were determined using parameter estimation techniques. Representative parameter values were calculated from multiple towing tank experiments. Theory describing the motion of a hydrofoil in an orbital velocity wave field was combined with the hull model to simulate the Hysucat as well as the suspension system concepts. The models indicated that the concept where the main hydrofoil was attached to a spring loaded arm, that was free to pivot in response to orbital waves, was the most feasible in damping out vertical transmitted accelerations. Experimental tests indicated that little improvement was achieved with the suspension system at low frequencies. At resonance the suspension system was effective in decreasing the heave of the vessel by up to 27%. The pitch and acceleration response results showed improvements at the higher encounter frequencies of up to 50%. The calm water resistance of the vessel increased by 10% over the Hysucat with rigidly attached hydrofoils; however was still 24% less than the hull without foils.

Este trabalho apresenta uma abordagem numérica com base em ensaios experimentais previamente realizados, direcionada ao problema de ressonância do campo de ondas em operações de alívio lado a lado (side by side). Os efeitos dessas interferências hidrodinâmicas são responsáveis por alterar drasticamente o campo de ondas em regiões de confino, gerando amplificação nos movimentos de primeira ordem e trazendo risco à operação. Este fenômeno está presente em diversas áreas da exploração e produção offshore e vem sendo o principal objeto de estudo nos últimos anos, principalmente em operações de alívio lado a lado, nos quais existe uma grande preocupação de colisão, rompimento dos cabos e integridade estrutural das defensas, devido à proximidade dos cascos. Neste contexto, devido à complexidade do problema, a modelagem numérica utilizada para interpretar o fenômeno de ressonância em softwares comerciais deve ser realizada com cautela, sendo que a utilização direta desta ferramenta gera amplificações equivocadas da superfície ressonante uma vez que esta resolução tem como base a teoria potencial. As diferenças observadas durante a comparação entre ensaios numéricos e experimentais são causadas em virtude da negligência na avaliação da dissipação de parte da energia das ondas ressonantes provocadas devido aos efeitos como viscosidade, vorticidade e turbulência do escoamento. Com o objetivo de analisar corretamente este fenômeno por meio de ensaios numéricos, uma maneira consiste na inclusão de adaptações no modelo para atingir os resultados desejáveis. Estas adaptações consistem na implementação de métodos artificiais, tais como os chamados \"Modos Generalizados\" e \"Praias Numéricas\", aplicados à região entre as embarcações com o intuito de amortecer as elevações irrealistas da superfície. Sendo assim, este trabalho abordará o problema de ressonância de ondas, investigando o desempenho de duas ferramentas numéricas para a sua predição, o WAMIT (Wave Analysis Massachusetts Institute of Technology) e o TDRPM (Time Domain Rankine Painel Method). Os resultados serão comparados com dados obtidos em um conjunto de ensaios em escala reduzida, realizado previamente no laboratório Tanque de Provas Numérico da USP (TPN). Dessa forma, o estudo dos fenômenos de ressonância será discutido, principalmente, em seu aspecto numérico, visando à verificação do desempenho do WAMIT e do TDRPM. / This work presents a numerical study based on previously conducted experimental studies, focused on the problem of resonance of the wave field in operations involving multi-body. The hydrodynamic interferences effects are responsible for drastically changing the wave field in confine regions, generating amplification of first order movements and bringing operational risk. This phenomenon is present in several areas of offshore exploration and production and has been the main object of study in recent years, mainly in side-by-side offloading operations, in which there is a great concern due to the risk of mooring lines breaking, damages to the fenders and also collision. In this context, due to the complexity of the problem, the numerical modeling used to evaluate the resonance phenomenon in commercial software becomes unsuitable, generating erroneous amplifications of the resonant surface since it is based on the potential theory. The differences observed during the comparisons between numerical and experimental tests are caused by negligence in the evaluation of the dissipation of part of the resonant wave energy caused by viscosity, vorticity and flow turbulence effects. In order to correctly analyze this phenomenon through numerical tests, one way is to include adaptations on the model to achieve the desired results. These adaptations consist of the implementation of artificial methods, such as \"Generalized Modes\" and \"Numerical Damping Zones\", applied to the region between the vessels in order to damp the unrealistic elevations of the surface. Thus, this study will approach the problem of gap wave resonance, investigating the performance of two numerical tools for its prediction, WAMIT (Wave Analysis Massachusetts Institute of Technology) and TDRPM (Time Domain Rankin Panel Method). The results will be compared with data obtained from a set of small scale tests previously performed at the Numerical Test Tank of USP laboratory (TPN). Therefore, the study of resonance phenomena will be discussed, mainly, in its numerical aspect, in order to verify the performance of WAMIT and TDRPM.

Esta tese apresenta o desenvolvimento de um método de elementos de contorno (BEM) no domínio do tempo baseado em fontes de Rankine para analise linear de comportamento no mar de sistemas oceânicos. O método e formulado por dois problemas de valor inicial de contorno definidos para os potenciais de velocidade e aceleração, sendo este ultimo utilizado para calcular de maneira acurada a derivada temporal do potencial de velocidades. Testes de verificação são realizados para a solução dos problemas de difração, radiação e de corpo livre para flutuar. Uma vez verificada, a ferramenta e aplicada em dois problemas multicorpos considerados no estado-da-arte em termos de modelagem hidrodinâmica utilizando BEM. O primeiro trata do problema envolvendo duas embarcações atracadas a contrabordo. Este é um caso no qual os códigos baseados na teoria de escoamento potencial são conhecidos por apresentarem dificuldades na determinação das soluções, tendendo a superestimar as elevações de onda no vão entre as embarcações e a apresentar problemas de convergência numérica associados a efeitos ressonantes de onda. O problema e tratado por meio do método de damping lid e a convergência das series temporais e investigada avaliando diferentes níveis de amortecimento. Os resultados são comparados com dados experimentais. O segundo problema se refere a analise de sistemas multicorpos com grandes deslocamentos relativos. Neste problema, ferramentas no domínio da frequência nao podem ser utilizadas, por considerarem apenas malhas fixas. Deste modo, o presente método e estendido para considerar um gerador de malhas de paineis e um algoritmo de interpolação de ordem alta no laco de tempo do código, possibilitando a mudança de posições relativas entre os corpos durante a simulação. Os resultados são comparados com dados de experimentos executados especificamente para fins de verificação do código, apresentando uma boa concordância. De acordo com o conhecimento do autor, esta e a primeira vez que certas questões relativas a modelagem numérica destes dois problemas multicorpos são relatadas na literatura especializada em hidrodinâmica computacional. / The development of a time domain boundary elements method (BEM) based on Rankine\'s sources for linear seakeeping analysis of offshore systems is here addressed. The method is formulated by means of two Initial Boundary Value Problems defined for the velocity and acceleration potentials, the latter being used to ensure an accurate calculation of the time derivatives of the velocity potential. Verification tests for solving the difraction, radiation and free floating problems are presented. Once verified, the code is applied for two complex multi-body problems considered to be in the state-of-the-art for hydrodynamic modelling using BEM. The first is the seakeeping problem of two ships arranged in side-by-side, a problem in which all potential flow codes are known to have a poor performance, tending to provide unrealistic high wave elevations in the gap between the vessels and to present numerical convergence problems associated to resonant effects. The problem is here addressed by means of a damping lid method and the convergence of the time series with different damping levels is investigated. Results are compared to data measured in an experimental campaign. The second problem refers to the analysis of multi-body systems composed of bodies undergoing large relative displacements. This is a case that cannot be properly analyzed by frequency domain codes, since they only consider fixed meshes. For this application, the present numerical method is extended to consider a panel mesh generator in the time loop of the code, enabling the change of body relative positions during the computations. Furthermore, a higher order interpolation algorithm designed to recover the solutions of a previous time-step was also implemented, enabling the calculations to progress with reasonable accuracy in time. The numerical results are compared to data of experimental tests designed and executed for verification of the code, and presented a very good agreement. To the author\'s knowledge, this is the first time that certain issues concerning the numerical modelling of these two complex multi-body problems are reported in the literature specialized in hydrodynamic computations.

The effects of winds and/or waves on ship motions, forces, moments, maneuverability and controllability are investigated with URANS computations. The air/water flow computations employ a semi-coupled approach in which water is not affected by air, but air is computed assuming the free surface as a moving immersed boundary. The exact potential solution of waves/wind problem is modified introducing a logarithmic blending in air, and imposed as boundary and initial conditions. The turbulent air flows over 2D water waves are studied to investigate the effects of waves on incoming wind flow. Ship airwake computations are performed with different wind speeds and directions for static drift and dynamic PMM in calm water, pitch and heave in regular waves, and 6DOF motions in irregular waves simulating hurricane CAMILLE. Ship airwake analyses show that the vortical structures evolve due to ship motions and affect the ship dynamics significantly. Strong hurricane head and following winds affect up to 28% the resistance and 7% the motions. Beam winds have most significant effects causing considerable roll motion and drift forces, affecting the controllability of the ship. A harmonic wave group single run seakeeping procedure is developed, validated and compared with regular wave and transient wave group procedures. The regular wave procedure requires multiple runs, whereas single run procedures obtain the RAOs for a range of frequencies at a fixed speed, assuming linear ship response. The transient wave group procedure provides continuous RAOs, while the harmonic wave group procedure obtains discrete transfer functions, but without focusing. Verification and validation studies are performed for transient wave group procedure. Validation is achieved at the average interval of 9.54 (%D). Comparisons of the procedures show that harmonic wave group is the most efficient, saving 75.8% on the computational cost compared to regular wave procedure. Error values from all procedures are similar at 4 (%D). Harmonic wave group procedure is validated for a wide range of Froude numbers, with satisfactory results. Deterministic wave groups are used for three sisters rogue waves modeling. A 6DOF ship simulation is demonstrated which shows total loss of controllability with extreme ship motions, accelerations and structural loads.

Esta tese apresenta o desenvolvimento de um método de elementos de contorno (BEM) no domínio do tempo baseado em fontes de Rankine para analise linear de comportamento no mar de sistemas oceânicos. O método e formulado por dois problemas de valor inicial de contorno definidos para os potenciais de velocidade e aceleração, sendo este ultimo utilizado para calcular de maneira acurada a derivada temporal do potencial de velocidades. Testes de verificação são realizados para a solução dos problemas de difração, radiação e de corpo livre para flutuar. Uma vez verificada, a ferramenta e aplicada em dois problemas multicorpos considerados no estado-da-arte em termos de modelagem hidrodinâmica utilizando BEM. O primeiro trata do problema envolvendo duas embarcações atracadas a contrabordo. Este é um caso no qual os códigos baseados na teoria de escoamento potencial são conhecidos por apresentarem dificuldades na determinação das soluções, tendendo a superestimar as elevações de onda no vão entre as embarcações e a apresentar problemas de convergência numérica associados a efeitos ressonantes de onda. O problema e tratado por meio do método de damping lid e a convergência das series temporais e investigada avaliando diferentes níveis de amortecimento. Os resultados são comparados com dados experimentais. O segundo problema se refere a analise de sistemas multicorpos com grandes deslocamentos relativos. Neste problema, ferramentas no domínio da frequência nao podem ser utilizadas, por considerarem apenas malhas fixas. Deste modo, o presente método e estendido para considerar um gerador de malhas de paineis e um algoritmo de interpolação de ordem alta no laco de tempo do código, possibilitando a mudança de posições relativas entre os corpos durante a simulação. Os resultados são comparados com dados de experimentos executados especificamente para fins de verificação do código, apresentando uma boa concordância. De acordo com o conhecimento do autor, esta e a primeira vez que certas questões relativas a modelagem numérica destes dois problemas multicorpos são relatadas na literatura especializada em hidrodinâmica computacional. / The development of a time domain boundary elements method (BEM) based on Rankine\'s sources for linear seakeeping analysis of offshore systems is here addressed. The method is formulated by means of two Initial Boundary Value Problems defined for the velocity and acceleration potentials, the latter being used to ensure an accurate calculation of the time derivatives of the velocity potential. Verification tests for solving the difraction, radiation and free floating problems are presented. Once verified, the code is applied for two complex multi-body problems considered to be in the state-of-the-art for hydrodynamic modelling using BEM. The first is the seakeeping problem of two ships arranged in side-by-side, a problem in which all potential flow codes are known to have a poor performance, tending to provide unrealistic high wave elevations in the gap between the vessels and to present numerical convergence problems associated to resonant effects. The problem is here addressed by means of a damping lid method and the convergence of the time series with different damping levels is investigated. Results are compared to data measured in an experimental campaign. The second problem refers to the analysis of multi-body systems composed of bodies undergoing large relative displacements. This is a case that cannot be properly analyzed by frequency domain codes, since they only consider fixed meshes. For this application, the present numerical method is extended to consider a panel mesh generator in the time loop of the code, enabling the change of body relative positions during the computations. Furthermore, a higher order interpolation algorithm designed to recover the solutions of a previous time-step was also implemented, enabling the calculations to progress with reasonable accuracy in time. The numerical results are compared to data of experimental tests designed and executed for verification of the code, and presented a very good agreement. To the author\'s knowledge, this is the first time that certain issues concerning the numerical modelling of these two complex multi-body problems are reported in the literature specialized in hydrodynamic computations.

Este trabalho apresenta uma abordagem numérica com base em ensaios experimentais previamente realizados, direcionada ao problema de ressonância do campo de ondas em operações de alívio lado a lado (side by side). Os efeitos dessas interferências hidrodinâmicas são responsáveis por alterar drasticamente o campo de ondas em regiões de confino, gerando amplificação nos movimentos de primeira ordem e trazendo risco à operação. Este fenômeno está presente em diversas áreas da exploração e produção offshore e vem sendo o principal objeto de estudo nos últimos anos, principalmente em operações de alívio lado a lado, nos quais existe uma grande preocupação de colisão, rompimento dos cabos e integridade estrutural das defensas, devido à proximidade dos cascos. Neste contexto, devido à complexidade do problema, a modelagem numérica utilizada para interpretar o fenômeno de ressonância em softwares comerciais deve ser realizada com cautela, sendo que a utilização direta desta ferramenta gera amplificações equivocadas da superfície ressonante uma vez que esta resolução tem como base a teoria potencial. As diferenças observadas durante a comparação entre ensaios numéricos e experimentais são causadas em virtude da negligência na avaliação da dissipação de parte da energia das ondas ressonantes provocadas devido aos efeitos como viscosidade, vorticidade e turbulência do escoamento. Com o objetivo de analisar corretamente este fenômeno por meio de ensaios numéricos, uma maneira consiste na inclusão de adaptações no modelo para atingir os resultados desejáveis. Estas adaptações consistem na implementação de métodos artificiais, tais como os chamados \"Modos Generalizados\" e \"Praias Numéricas\", aplicados à região entre as embarcações com o intuito de amortecer as elevações irrealistas da superfície. Sendo assim, este trabalho abordará o problema de ressonância de ondas, investigando o desempenho de duas ferramentas numéricas para a sua predição, o WAMIT (Wave Analysis Massachusetts Institute of Technology) e o TDRPM (Time Domain Rankine Painel Method). Os resultados serão comparados com dados obtidos em um conjunto de ensaios em escala reduzida, realizado previamente no laboratório Tanque de Provas Numérico da USP (TPN). Dessa forma, o estudo dos fenômenos de ressonância será discutido, principalmente, em seu aspecto numérico, visando à verificação do desempenho do WAMIT e do TDRPM. / This work presents a numerical study based on previously conducted experimental studies, focused on the problem of resonance of the wave field in operations involving multi-body. The hydrodynamic interferences effects are responsible for drastically changing the wave field in confine regions, generating amplification of first order movements and bringing operational risk. This phenomenon is present in several areas of offshore exploration and production and has been the main object of study in recent years, mainly in side-by-side offloading operations, in which there is a great concern due to the risk of mooring lines breaking, damages to the fenders and also collision. In this context, due to the complexity of the problem, the numerical modeling used to evaluate the resonance phenomenon in commercial software becomes unsuitable, generating erroneous amplifications of the resonant surface since it is based on the potential theory. The differences observed during the comparisons between numerical and experimental tests are caused by negligence in the evaluation of the dissipation of part of the resonant wave energy caused by viscosity, vorticity and flow turbulence effects. In order to correctly analyze this phenomenon through numerical tests, one way is to include adaptations on the model to achieve the desired results. These adaptations consist of the implementation of artificial methods, such as \"Generalized Modes\" and \"Numerical Damping Zones\", applied to the region between the vessels in order to damp the unrealistic elevations of the surface. Thus, this study will approach the problem of gap wave resonance, investigating the performance of two numerical tools for its prediction, WAMIT (Wave Analysis Massachusetts Institute of Technology) and TDRPM (Time Domain Rankin Panel Method). The results will be compared with data obtained from a set of small scale tests previously performed at the Numerical Test Tank of USP laboratory (TPN). Therefore, the study of resonance phenomena will be discussed, mainly, in its numerical aspect, in order to verify the performance of WAMIT and TDRPM.