A multiphysics multiscale finite-element based nonlinear computational wave basin (CWB) model is ... more A multiphysics multiscale finite-element based nonlinear computational wave basin (CWB) model is developed using LS-DYNA. Its predictive capability is calibrated using a large-scale fluid-structure interaction experiment conducted in a 3-dimensional wave basin to determine wave impact on a cylindrical structure. This study focuses on evaluating CWB accuracy using two wave excitation conditions — plane and focused solitary waves — and two cylinder arrangements — single and multiple cylinders. Water surface elevation and water particle velocity are predicted numerically for the fluid domain, obtaining horizontal force, overturning moment, and dynamic pressure on the cylindrical structure and calibrated against experimental measurement. The CWB model predicts wave motion characteristics — water surface elevation and velocity, and integrated structural response — horizontal force and overturning moment, for the given wave conditions well. Computation time increases and the predictive ac...
which uses bulk density and optimum water content is also presented. Both methods give satisfacto... more which uses bulk density and optimum water content is also presented. Both methods give satisfactory results.
Earthquake Engineering & Structural Dynamics, 1984
The effects of transient foundation uplift on the earthquake response of flexible structures are ... more The effects of transient foundation uplift on the earthquake response of flexible structures are investigated. The structural idealization chosen in this study is relatively simple but it incorporates the most important features of foundation uplift. In its fixed base condition the structure itself is idealized as a single‐degree‐of‐freedom system attached to a rigid foundation mat which is flexibly supported. The flexibility and damping of the supporting soil are represented by a Winkler foundation with spring‐damper elements distributed over the entire width of the foundation. Based on the response spectra presented for several sets of system parameters, the effects of foundation‐mat uplift on the maximum response of structures are identified. The influence of earthquake intensity, structural slenderness ratio, ratio of foundation mass to structural mass, foundation flexibility and p‐δ effects on the response of uplifting structures is also investigated.
Earthquake Engineering & Structural Dynamics, 1980
This investigation deals with the rocking response of rigid blocks subjected to earthquake ground... more This investigation deals with the rocking response of rigid blocks subjected to earthquake ground motion. A numerical procedure and computer program are developed to solve the non‐linear equations of motion governing the rocking motion of rigid blocks on a rigid base subjected to horizontal and vertical ground motion.The response results presented show that the response of the block is very sensitive to small changes in its size and slenderness ratio and to the details of ground motion. Systematic trends are not apparent: The stability of a block subjected to a particular ground motion does not necessarily increase monotonically with increasing size or decreasing slenderness ratio. Overturning of a block by a ground motion of particular intensity does not imply that the block will necessarily overturn under the action of more intense ground motion.In contrast, systematic trends are observed when the problem is studied from a probabilistic point of view with the ground motion modelle...
A multiphysics multiscale finite-element based nonlinear computational wave basin (CWB) model is ... more A multiphysics multiscale finite-element based nonlinear computational wave basin (CWB) model is developed using LS-DYNA. Its predictive capability is calibrated using a large-scale fluid-structure interaction experiment conducted in a 3-dimensional wave basin to determine wave impact on a cylindrical structure. This study focuses on evaluating CWB accuracy using two wave excitation conditions — plane and focused solitary waves — and two cylinder arrangements — single and multiple cylinders. Water surface elevation and water particle velocity are predicted numerically for the fluid domain, obtaining horizontal force, overturning moment, and dynamic pressure on the cylindrical structure and calibrated against experimental measurement. The CWB model predicts wave motion characteristics — water surface elevation and velocity, and integrated structural response — horizontal force and overturning moment, for the given wave conditions well. Computation time increases and the predictive accuracy decreases as nonlinear fluid-structure interaction becomes increasingly complex. A study of computation settings for improving computation performance showed that a high-performance parallel-computing hardware platform is needed to model details of highly nonlinear physics of fluid flow including wave breaking and turbulence.
Page 119. CHAPTER 4 A METHODOLOGY FOR ANALYSIS AND DESIGN OF SENSITIVE NONLINEAR OCEAN SYSTEMS So... more Page 119. CHAPTER 4 A METHODOLOGY FOR ANALYSIS AND DESIGN OF SENSITIVE NONLINEAR OCEAN SYSTEMS Solomon CS Yim and Huan Lin Oregon State University, Corvallis, OR 97330 Abstract. A methodology ...
Journal of Computational Design and Engineering, Apr 10, 2023
In this manuscript, we propose a new effective method for eigenpair reanalysis of largescale fini... more In this manuscript, we propose a new effective method for eigenpair reanalysis of largescale finite element (FE) models. Our method utilizes the matrix block-partitioning algorithm in the Rayleigh-Ritz approach and expresses the Ritz basis matrix using thousands of block matrices of very small size. To avoid significant computational costs from the projection procedure, we derive a new formulation that uses tiny block computations instead of global matrix computations. Additionally, we present an algorithm that recognizes which blocks are changed in the modified FE model to achieve computational cost savings when computing new eigenpairs. Through selective updating for the recognized blocks, we can effectively construct the new Ritz basis matrix and the new reduced mass and stiffness matrices corresponding to the modified FE model. To demonstrate the performance of our proposed method, we solve several practical engineering problems and compare the results with those of the combined approximation (CA) method, the most well-known eigenpair reanalysis method, and ARPACK, an eigenvalue solver embedded in many numerical programs.
This study focuses on the computation and analysis of the energy content of a wave train and the ... more This study focuses on the computation and analysis of the energy content of a wave train and the influence of nonlinear components, such as nonlinear wave profile as in Stokes wave and phased locked breathers, on the content. To this end, an overview of a state-of-the-art nonlinear Fourier analysis tools for the nonlinear Schrödinger equation is presented. Experimental measurements from a set of performance tests of the directional wave basin at Oregon State University were analyzed using this tool and the energy contents, both from the linear spectrum and nonlinear spectrum, were calculated. The deviation of the energy content from linear analysis and its relationship to the level of nonlinearity of the wave train is investigated. The Benjamin-Feir parameter presents the degree of nonlinearity of the wave train. An increasing energy deviation was observed for increasing nonlinearity of the wave field. Spatial evolution of such behavior is also investigated. It was confirmed that the significant difference from the linear energy is due to increase in the nonlinear components and the more distance the wave train could travel (without substantial dissipation) the more erratic and more significant energy deviations were observed.
The First International Offshore and Polar Engineering Conference, 1991
The chaotic and stochastic dynamics of rocking response of free-standing offshore equipment subje... more The chaotic and stochastic dynamics of rocking response of free-standing offshore equipment subjected to horizontal base excitation are investigated using a realistic model taking into account the geometric nonlinearity (finite slenderness ratio) of the rocking systems. Additional important nonlinear effects including transition of governing equations of motion at impact, and abrupt reduction in angular velocity due to impact energy dissipation are examined. It has been demonstrated that the nonlinearities associated with the transition of governing equations at impact procedures complex responses. In addition to the anticipated harmonic and subharmonic periodic responses, two new types of steady state motions - quasi-periodic, and chaotic responses are also found. In this study, it is shown that although the excitations to the rocking systems are simple and purely deterministic, some stochastic characteristics of the chaotic rocking responses are detected using Poincare maps and amplitude probability densities. While the chaotic time histories have a periodic time dependency, thus non-stationary, time series consist of Poincare points are ergodic. Results indicate that chaotic response may be a strong link between deterministic and stochastic responses.
Load cell data of Ocean Sentinel (OS) mooring, OS locations data and environmental conditions dat... more Load cell data of Ocean Sentinel (OS) mooring, OS locations data and environmental conditions data (wave, wind, current) measured in the 2013 field test.
This paper presents a novel 1:7 scale point absorber wave energy converter (WEC), developed by Co... more This paper presents a novel 1:7 scale point absorber wave energy converter (WEC), developed by Columbia Power Technologies (COLUMBIA POWER). Four hydrodynamic modeling tools were employed in the scaled development and the optimization process of the WEC, including WAMIT, Garrad Hassan's GH WaveFarmer, OrcaFlex and ANSYS AQWA. The numerical analysis development is discussed, and the performance and mooring estimates at 1:7 scale and full scale are evaluated and optimized. The paper includes the development of the 1:7 scale physical model and the associated WEC field testing in Puget Sound, WA.
Numerical simulation and prediction of short duration hydrodynamic impact loading on a generic we... more Numerical simulation and prediction of short duration hydrodynamic impact loading on a generic wedge impacting a water free-surface is investigated. The fluid field is modeled using a finite element (FE) based arbitrary Lagrangian-Eulerian (ALE) formulation and the structure is modeled using a standard Lagrangian FE approximation. Validation of the numerical method against experimental test data and closed form analytical solutions shows that the ALE-FE/FE continuum approach captures the impact behavior accurately. A detailed sensitivity analysis is conducted to study the role of air compressibility, deadrise angle, and impact velocity in estimation of maximum impact pressures. The pressure field is found to be insensitive to air compressibility effect for a wide range of impact velocities and deadrise angles. A semi-analytical prediction model is developed for estimation of maximum impact pressures that correlates deadrise angle, impact velocity, and a nonlinear interaction term th...
29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 4, 2010
ABSTRACT A numerical study on the dynamic response of a generic rigid water-landing object (WLO) ... more ABSTRACT A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during water impact is presented in this paper. The effect of this impact is often prominent in the design phase of the re-entry project, to determine the maximum force it is subjected to, for material strength determination to ensure structural and equipment integrity, human safety and comfort. The predictive capability of the explicit finite-element arbitrary Lagrangian-Eulerian (ALE) and smoothed particle hydrodynamics (SPH) methods of a state-of-the-art nonlinear dynamic finite-element code for simulation of coupled dynamic fluid structure interaction (FSI) responses of the splashdown event of a WLO were evaluated. The numerical predictions are first validated with experimental data for the maximum impact accelerations and then used to supplement experimental drop tests to establish trends over a wide range of conditions including variations in vertical velocity, entry angle and object weight. The results show that the fully coupled FSI models can capture the water-impact response accurately for all range of drop tests considered and the impact accelerations are practically linearly with the increase in the height of the drop. The reliability of the maximum impact accelerations was calibrated with approximate classical von Karman and Wagner closed-form solutions.
Physical and numerical large-scale wave basin (LSWB) modeling offluid-structure interaction (FSI)... more Physical and numerical large-scale wave basin (LSWB) modeling offluid-structure interaction (FSI) and wave impact phenomena are examined in this study. In particular, the role of numerical mode ling and simulation in designand analysis of physical LS WB FSI andwave impact experiments using a numerical wave basin (NWB) modeling approach is examined. Physical characteristics and testing capabilities of are presentative LSWBare first described. Selectedphysical FSI and wave impactexperiments pertaining to civil, energy and naval engineering disciplines conducted at the LSWB and the accompanying NWBFSI modeling and simulations of these challenging phenomenaare presented. An effort to further improvetheNWBFSI softwarewith highly nonlinear wave impact modeling capabilities to facilitate physical FSI experiment design and testing, and details of an on-goingNWBdevelopment and validation processesare delineated.It is demonstrated that the NWBFSI software is useful in facilitating the design of complex, highly nonlinear FSI and wave impactexperiments. Conversely, the resulting measured data from the FSI and wave impact experiments can be used to validate and identify further modeling improvement needs of the NWBFSI and wave impactsoftware.
29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 4, 2010
The dynamics of a generic rigid water-landing object (WLO) during water impact is presented in th... more The dynamics of a generic rigid water-landing object (WLO) during water impact is presented in this paper. Tests from a range of drop heights were performed in a wave basin using a 1/6th-Froude scale model of a practical prototype using different drop mechanisms to determine the water impact and contact effects. The first experimental case involved dropping the WLO by using a rope and pulley arrangement, while the second case employed an electromagnetic release to drop the object. Hydrodynamic parameters including peak acceleration, touchdown pressure and maximum impact/contact force were measured using the two different drop mechanisms. The WLO was assumed as rigid, so the experimental results could be correlated with von Karman and Wagner closed form solutions and the maximum accelerations predicted are bounded by these classical analytical solutions. The major purpose of this study are to use the experiments to determine trends that occur when the object is dropped from successiv...
Journal of Offshore Mechanics and Arctic Engineering, 2013
An experimental study of the dynamics of a generic rigid body during water impact and an equivale... more An experimental study of the dynamics of a generic rigid body during water impact and an equivalent-radius approximate analytical procedure is developed and calibrated in this study. The experimental tests in a wave basin covered a range of drop heights using a 1/6th-scale model of a practical water-landing object prototype for two drop mechanisms to determine the water impact and contact effects. The first mechanism involved a rope and pulley arrangement, while the second mechanism employed an electromagnetic release to drop the rigid body. Hydrodynamic parameters including peak acceleration and touchdown pressure were measured and the maximum impact/contact force was estimated for various entry speeds (corresponding to various drop heights) and weights of the rigid body. Results from the tests show that the impact acceleration and touchdown pressure increases approximately linearly with increasing drop height and the data provides conditions that keep impact accelerations under sp...
Journal of Offshore Mechanics and Arctic Engineering, 2014
A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during wa... more A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during water impact is presented in this paper. The effect of this impact is often prominent in the design phase of the re-entry project to determine the maximum force for material strength determination to ensure structural and equipment integrity, human safety and comfort. The predictive capability of the explicit finite-element (FE) arbitrary Lagrangian-Eulerian (ALE) and smoothed particle hydrodynamics (SPH) methods of a state-of-the-art nonlinear dynamic finite-element code for simulation of coupled dynamic fluid structure interaction (FSI) responses of the splashdown event of a WLO were evaluated. The numerical predictions are first validated with experimental data for maximum impact accelerations and then used to supplement experimental drop tests to establish trends over a wide range of conditions including variations in vertical velocity, entry angle, and object weight. The numerical res...
A multiphysics multiscale finite-element based nonlinear computational wave basin (CWB) model is ... more A multiphysics multiscale finite-element based nonlinear computational wave basin (CWB) model is developed using LS-DYNA. Its predictive capability is calibrated using a large-scale fluid-structure interaction experiment conducted in a 3-dimensional wave basin to determine wave impact on a cylindrical structure. This study focuses on evaluating CWB accuracy using two wave excitation conditions — plane and focused solitary waves — and two cylinder arrangements — single and multiple cylinders. Water surface elevation and water particle velocity are predicted numerically for the fluid domain, obtaining horizontal force, overturning moment, and dynamic pressure on the cylindrical structure and calibrated against experimental measurement. The CWB model predicts wave motion characteristics — water surface elevation and velocity, and integrated structural response — horizontal force and overturning moment, for the given wave conditions well. Computation time increases and the predictive ac...
which uses bulk density and optimum water content is also presented. Both methods give satisfacto... more which uses bulk density and optimum water content is also presented. Both methods give satisfactory results.
Earthquake Engineering & Structural Dynamics, 1984
The effects of transient foundation uplift on the earthquake response of flexible structures are ... more The effects of transient foundation uplift on the earthquake response of flexible structures are investigated. The structural idealization chosen in this study is relatively simple but it incorporates the most important features of foundation uplift. In its fixed base condition the structure itself is idealized as a single‐degree‐of‐freedom system attached to a rigid foundation mat which is flexibly supported. The flexibility and damping of the supporting soil are represented by a Winkler foundation with spring‐damper elements distributed over the entire width of the foundation. Based on the response spectra presented for several sets of system parameters, the effects of foundation‐mat uplift on the maximum response of structures are identified. The influence of earthquake intensity, structural slenderness ratio, ratio of foundation mass to structural mass, foundation flexibility and p‐δ effects on the response of uplifting structures is also investigated.
Earthquake Engineering & Structural Dynamics, 1980
This investigation deals with the rocking response of rigid blocks subjected to earthquake ground... more This investigation deals with the rocking response of rigid blocks subjected to earthquake ground motion. A numerical procedure and computer program are developed to solve the non‐linear equations of motion governing the rocking motion of rigid blocks on a rigid base subjected to horizontal and vertical ground motion.The response results presented show that the response of the block is very sensitive to small changes in its size and slenderness ratio and to the details of ground motion. Systematic trends are not apparent: The stability of a block subjected to a particular ground motion does not necessarily increase monotonically with increasing size or decreasing slenderness ratio. Overturning of a block by a ground motion of particular intensity does not imply that the block will necessarily overturn under the action of more intense ground motion.In contrast, systematic trends are observed when the problem is studied from a probabilistic point of view with the ground motion modelle...
A multiphysics multiscale finite-element based nonlinear computational wave basin (CWB) model is ... more A multiphysics multiscale finite-element based nonlinear computational wave basin (CWB) model is developed using LS-DYNA. Its predictive capability is calibrated using a large-scale fluid-structure interaction experiment conducted in a 3-dimensional wave basin to determine wave impact on a cylindrical structure. This study focuses on evaluating CWB accuracy using two wave excitation conditions — plane and focused solitary waves — and two cylinder arrangements — single and multiple cylinders. Water surface elevation and water particle velocity are predicted numerically for the fluid domain, obtaining horizontal force, overturning moment, and dynamic pressure on the cylindrical structure and calibrated against experimental measurement. The CWB model predicts wave motion characteristics — water surface elevation and velocity, and integrated structural response — horizontal force and overturning moment, for the given wave conditions well. Computation time increases and the predictive accuracy decreases as nonlinear fluid-structure interaction becomes increasingly complex. A study of computation settings for improving computation performance showed that a high-performance parallel-computing hardware platform is needed to model details of highly nonlinear physics of fluid flow including wave breaking and turbulence.
Page 119. CHAPTER 4 A METHODOLOGY FOR ANALYSIS AND DESIGN OF SENSITIVE NONLINEAR OCEAN SYSTEMS So... more Page 119. CHAPTER 4 A METHODOLOGY FOR ANALYSIS AND DESIGN OF SENSITIVE NONLINEAR OCEAN SYSTEMS Solomon CS Yim and Huan Lin Oregon State University, Corvallis, OR 97330 Abstract. A methodology ...
Journal of Computational Design and Engineering, Apr 10, 2023
In this manuscript, we propose a new effective method for eigenpair reanalysis of largescale fini... more In this manuscript, we propose a new effective method for eigenpair reanalysis of largescale finite element (FE) models. Our method utilizes the matrix block-partitioning algorithm in the Rayleigh-Ritz approach and expresses the Ritz basis matrix using thousands of block matrices of very small size. To avoid significant computational costs from the projection procedure, we derive a new formulation that uses tiny block computations instead of global matrix computations. Additionally, we present an algorithm that recognizes which blocks are changed in the modified FE model to achieve computational cost savings when computing new eigenpairs. Through selective updating for the recognized blocks, we can effectively construct the new Ritz basis matrix and the new reduced mass and stiffness matrices corresponding to the modified FE model. To demonstrate the performance of our proposed method, we solve several practical engineering problems and compare the results with those of the combined approximation (CA) method, the most well-known eigenpair reanalysis method, and ARPACK, an eigenvalue solver embedded in many numerical programs.
This study focuses on the computation and analysis of the energy content of a wave train and the ... more This study focuses on the computation and analysis of the energy content of a wave train and the influence of nonlinear components, such as nonlinear wave profile as in Stokes wave and phased locked breathers, on the content. To this end, an overview of a state-of-the-art nonlinear Fourier analysis tools for the nonlinear Schrödinger equation is presented. Experimental measurements from a set of performance tests of the directional wave basin at Oregon State University were analyzed using this tool and the energy contents, both from the linear spectrum and nonlinear spectrum, were calculated. The deviation of the energy content from linear analysis and its relationship to the level of nonlinearity of the wave train is investigated. The Benjamin-Feir parameter presents the degree of nonlinearity of the wave train. An increasing energy deviation was observed for increasing nonlinearity of the wave field. Spatial evolution of such behavior is also investigated. It was confirmed that the significant difference from the linear energy is due to increase in the nonlinear components and the more distance the wave train could travel (without substantial dissipation) the more erratic and more significant energy deviations were observed.
The First International Offshore and Polar Engineering Conference, 1991
The chaotic and stochastic dynamics of rocking response of free-standing offshore equipment subje... more The chaotic and stochastic dynamics of rocking response of free-standing offshore equipment subjected to horizontal base excitation are investigated using a realistic model taking into account the geometric nonlinearity (finite slenderness ratio) of the rocking systems. Additional important nonlinear effects including transition of governing equations of motion at impact, and abrupt reduction in angular velocity due to impact energy dissipation are examined. It has been demonstrated that the nonlinearities associated with the transition of governing equations at impact procedures complex responses. In addition to the anticipated harmonic and subharmonic periodic responses, two new types of steady state motions - quasi-periodic, and chaotic responses are also found. In this study, it is shown that although the excitations to the rocking systems are simple and purely deterministic, some stochastic characteristics of the chaotic rocking responses are detected using Poincare maps and amplitude probability densities. While the chaotic time histories have a periodic time dependency, thus non-stationary, time series consist of Poincare points are ergodic. Results indicate that chaotic response may be a strong link between deterministic and stochastic responses.
Load cell data of Ocean Sentinel (OS) mooring, OS locations data and environmental conditions dat... more Load cell data of Ocean Sentinel (OS) mooring, OS locations data and environmental conditions data (wave, wind, current) measured in the 2013 field test.
This paper presents a novel 1:7 scale point absorber wave energy converter (WEC), developed by Co... more This paper presents a novel 1:7 scale point absorber wave energy converter (WEC), developed by Columbia Power Technologies (COLUMBIA POWER). Four hydrodynamic modeling tools were employed in the scaled development and the optimization process of the WEC, including WAMIT, Garrad Hassan's GH WaveFarmer, OrcaFlex and ANSYS AQWA. The numerical analysis development is discussed, and the performance and mooring estimates at 1:7 scale and full scale are evaluated and optimized. The paper includes the development of the 1:7 scale physical model and the associated WEC field testing in Puget Sound, WA.
Numerical simulation and prediction of short duration hydrodynamic impact loading on a generic we... more Numerical simulation and prediction of short duration hydrodynamic impact loading on a generic wedge impacting a water free-surface is investigated. The fluid field is modeled using a finite element (FE) based arbitrary Lagrangian-Eulerian (ALE) formulation and the structure is modeled using a standard Lagrangian FE approximation. Validation of the numerical method against experimental test data and closed form analytical solutions shows that the ALE-FE/FE continuum approach captures the impact behavior accurately. A detailed sensitivity analysis is conducted to study the role of air compressibility, deadrise angle, and impact velocity in estimation of maximum impact pressures. The pressure field is found to be insensitive to air compressibility effect for a wide range of impact velocities and deadrise angles. A semi-analytical prediction model is developed for estimation of maximum impact pressures that correlates deadrise angle, impact velocity, and a nonlinear interaction term th...
29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 4, 2010
ABSTRACT A numerical study on the dynamic response of a generic rigid water-landing object (WLO) ... more ABSTRACT A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during water impact is presented in this paper. The effect of this impact is often prominent in the design phase of the re-entry project, to determine the maximum force it is subjected to, for material strength determination to ensure structural and equipment integrity, human safety and comfort. The predictive capability of the explicit finite-element arbitrary Lagrangian-Eulerian (ALE) and smoothed particle hydrodynamics (SPH) methods of a state-of-the-art nonlinear dynamic finite-element code for simulation of coupled dynamic fluid structure interaction (FSI) responses of the splashdown event of a WLO were evaluated. The numerical predictions are first validated with experimental data for the maximum impact accelerations and then used to supplement experimental drop tests to establish trends over a wide range of conditions including variations in vertical velocity, entry angle and object weight. The results show that the fully coupled FSI models can capture the water-impact response accurately for all range of drop tests considered and the impact accelerations are practically linearly with the increase in the height of the drop. The reliability of the maximum impact accelerations was calibrated with approximate classical von Karman and Wagner closed-form solutions.
Physical and numerical large-scale wave basin (LSWB) modeling offluid-structure interaction (FSI)... more Physical and numerical large-scale wave basin (LSWB) modeling offluid-structure interaction (FSI) and wave impact phenomena are examined in this study. In particular, the role of numerical mode ling and simulation in designand analysis of physical LS WB FSI andwave impact experiments using a numerical wave basin (NWB) modeling approach is examined. Physical characteristics and testing capabilities of are presentative LSWBare first described. Selectedphysical FSI and wave impactexperiments pertaining to civil, energy and naval engineering disciplines conducted at the LSWB and the accompanying NWBFSI modeling and simulations of these challenging phenomenaare presented. An effort to further improvetheNWBFSI softwarewith highly nonlinear wave impact modeling capabilities to facilitate physical FSI experiment design and testing, and details of an on-goingNWBdevelopment and validation processesare delineated.It is demonstrated that the NWBFSI software is useful in facilitating the design of complex, highly nonlinear FSI and wave impactexperiments. Conversely, the resulting measured data from the FSI and wave impact experiments can be used to validate and identify further modeling improvement needs of the NWBFSI and wave impactsoftware.
29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 4, 2010
The dynamics of a generic rigid water-landing object (WLO) during water impact is presented in th... more The dynamics of a generic rigid water-landing object (WLO) during water impact is presented in this paper. Tests from a range of drop heights were performed in a wave basin using a 1/6th-Froude scale model of a practical prototype using different drop mechanisms to determine the water impact and contact effects. The first experimental case involved dropping the WLO by using a rope and pulley arrangement, while the second case employed an electromagnetic release to drop the object. Hydrodynamic parameters including peak acceleration, touchdown pressure and maximum impact/contact force were measured using the two different drop mechanisms. The WLO was assumed as rigid, so the experimental results could be correlated with von Karman and Wagner closed form solutions and the maximum accelerations predicted are bounded by these classical analytical solutions. The major purpose of this study are to use the experiments to determine trends that occur when the object is dropped from successiv...
Journal of Offshore Mechanics and Arctic Engineering, 2013
An experimental study of the dynamics of a generic rigid body during water impact and an equivale... more An experimental study of the dynamics of a generic rigid body during water impact and an equivalent-radius approximate analytical procedure is developed and calibrated in this study. The experimental tests in a wave basin covered a range of drop heights using a 1/6th-scale model of a practical water-landing object prototype for two drop mechanisms to determine the water impact and contact effects. The first mechanism involved a rope and pulley arrangement, while the second mechanism employed an electromagnetic release to drop the rigid body. Hydrodynamic parameters including peak acceleration and touchdown pressure were measured and the maximum impact/contact force was estimated for various entry speeds (corresponding to various drop heights) and weights of the rigid body. Results from the tests show that the impact acceleration and touchdown pressure increases approximately linearly with increasing drop height and the data provides conditions that keep impact accelerations under sp...
Journal of Offshore Mechanics and Arctic Engineering, 2014
A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during wa... more A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during water impact is presented in this paper. The effect of this impact is often prominent in the design phase of the re-entry project to determine the maximum force for material strength determination to ensure structural and equipment integrity, human safety and comfort. The predictive capability of the explicit finite-element (FE) arbitrary Lagrangian-Eulerian (ALE) and smoothed particle hydrodynamics (SPH) methods of a state-of-the-art nonlinear dynamic finite-element code for simulation of coupled dynamic fluid structure interaction (FSI) responses of the splashdown event of a WLO were evaluated. The numerical predictions are first validated with experimental data for maximum impact accelerations and then used to supplement experimental drop tests to establish trends over a wide range of conditions including variations in vertical velocity, entry angle, and object weight. The numerical res...
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