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Tetsushi Ueta - One of the best experts on this subject based on the ideXlab platform.

  • Melnikov integral formula for Beam Sea roll motion utilizing a non-Hamiltonian exact heteroclinic orbit: analytic extension and numerical validation
    Journal of Marine Science and Technology, 2014
    Co-Authors: Atsuo Maki, Naoya Umeda, Tetsushi Ueta
    Abstract:

    In the reSearch field of nonlinear dynamical system theory, it is well known that a homoclinic/heteroclinic point leads to unpredictable motions, such as chaos. Melnikov’s method enables us to judge whether the system has a homoclinic/heteroclinic orbit. Therefore, in order to assess a vessel's safety with respect to capsizing, Melnikov’s method has been applied for investigations of the chaos that appears in Beam Sea rolling. This is because chaos is closely related to capsizing incidents. In a previous paper (Maki et al. in J Mar Sci Technol 15:102–106, 2010 ), a formula to predict the capsizing boundary by applying Melnikov’s method to analytically obtain the non-Hamiltonian heteroclinic orbit was proposed. However, in that paper, only limited numerical investigation was carried out. Therefore, further comparative reSearch between the analytical and numerical results is conducted, with the result being that the formula is validated.

  • Melnikov integral formula for Beam Sea roll motion utilizing a non-Hamiltonian exact heteroclinic orbit
    Journal of Marine Science and Technology, 2010
    Co-Authors: Atsuo Maki, Naoya Umeda, Tetsushi Ueta
    Abstract:

    The chaos that appears in the ship roll equation in Beam Seas known as the escape equation has been intensively investigated because it is closely related to capsizing incidents. In particular, many applications of the Melnikov integral formula have been reported in the literature; however, in all the analytical works concerning the escape equation, the Melnikov integral is formulated utilizing a separatrix for the Hamiltonian part or a numerically obtained heteroclinic orbit for the non-Hamiltonian part of the original escape equation. To overcome such limitations, this article attempts to utilise an analytical expression for the non-Hamiltonian part. As a result, an analytical procedure is provided that makes use of a heteroclinic orbit of the non-Hamiltonian part within the framework of the Melnikov integral formula.

Atsuo Maki - One of the best experts on this subject based on the ideXlab platform.

  • characteristics of rolling with drift in regular Beam Sea for small hard chine craft at rest
    Ocean Engineering, 2019
    Co-Authors: Toru Katayama, Atsuo Maki, Mai Kankaku, Mina Adachi, Nobuo Nishiyama
    Abstract:

    Abstract The characteristics of rolling with drift in regular Beam Sea for a small hard-chine craft at rest is investigated experimentally, and modification of a strip method with Ikeda's roll damping prediction method for hard-chine boat (Ikeda et al., 1990) is proposed. From the comparison between calculated and measured RAO of rolling, it is confirmed that the calculation overestimates roll amplitude at the condition where wave encounter period is shorter than its roll natural period, especially. The reasons of overestimation are investigated and it is confirmed that the coupling viscous roll moment from swaying cannot be ignored for small hard-chine craft for shorter wave period than its roll natural period. Because the roll natural period is shorter than that of a conventional displacement type vessel and its resonant wavelength is short comparing with its breadth, therefore its swaying can't follow orbital motion of wave, then coupling viscous roll moment from swaying becomes significant. Moreover, as another reason of the overestimation, the estimation accuracy of wave exciting roll moment is investigated and it is recommended that the diffraction potential should be solved under strict satisfying the body boundary condition for short wave length (λ/B

  • non gaussian pdf of ship roll motion in irregular Beam Sea and wind conditions comparison between theory and experiment
    Ocean Engineering, 2019
    Co-Authors: Atsuo Maki, Naoya Umeda, Akihiko Matsuda, Hiroki Yoshizumi
    Abstract:

    Abstract Ship transverse stability in Beam Seas has long been a significant concern to naval architects. Estimating roll motion remains important for practical risk assessments. However, this problem is not simple, due to the nonlinear equations of motion. A theoretical method for estimating the roll response and capsizing probability has been proposed, but this method has only been correlated by Monte Carlo simulations. Therefore, in this study, model experiments for a subject ship, which exhibited a strong nonlinearity exhibited in the GZ curve, were conducted at National ReSearch Institute of Fisheries Engineering. The results from this study correlated the proposed theory.

  • Melnikov integral formula for Beam Sea roll motion utilizing a non-Hamiltonian exact heteroclinic orbit: analytic extension and numerical validation
    Journal of Marine Science and Technology, 2014
    Co-Authors: Atsuo Maki, Naoya Umeda, Tetsushi Ueta
    Abstract:

    In the reSearch field of nonlinear dynamical system theory, it is well known that a homoclinic/heteroclinic point leads to unpredictable motions, such as chaos. Melnikov’s method enables us to judge whether the system has a homoclinic/heteroclinic orbit. Therefore, in order to assess a vessel's safety with respect to capsizing, Melnikov’s method has been applied for investigations of the chaos that appears in Beam Sea rolling. This is because chaos is closely related to capsizing incidents. In a previous paper (Maki et al. in J Mar Sci Technol 15:102–106, 2010 ), a formula to predict the capsizing boundary by applying Melnikov’s method to analytically obtain the non-Hamiltonian heteroclinic orbit was proposed. However, in that paper, only limited numerical investigation was carried out. Therefore, further comparative reSearch between the analytical and numerical results is conducted, with the result being that the formula is validated.

  • Melnikov integral formula for Beam Sea roll motion utilizing a non-Hamiltonian exact heteroclinic orbit
    Journal of Marine Science and Technology, 2010
    Co-Authors: Atsuo Maki, Naoya Umeda, Tetsushi Ueta
    Abstract:

    The chaos that appears in the ship roll equation in Beam Seas known as the escape equation has been intensively investigated because it is closely related to capsizing incidents. In particular, many applications of the Melnikov integral formula have been reported in the literature; however, in all the analytical works concerning the escape equation, the Melnikov integral is formulated utilizing a separatrix for the Hamiltonian part or a numerically obtained heteroclinic orbit for the non-Hamiltonian part of the original escape equation. To overcome such limitations, this article attempts to utilise an analytical expression for the non-Hamiltonian part. As a result, an analytical procedure is provided that makes use of a heteroclinic orbit of the non-Hamiltonian part within the framework of the Melnikov integral formula.

Whyte Andrew - One of the best experts on this subject based on the ideXlab platform.

  • Downtime cost analysis of offloading operations under irregular waves in Malaysian waters
    'Techno-Press', 2020
    Co-Authors: Patel M.s., Liew M.s., Mustaffa Z., Abdurasheed A.s., Whyte Andrew
    Abstract:

    © 2020 Techno-Press, Ltd. The objective of this study was to evaluate the downtime cost of side-by-side offloading operations in Malaysian waters. With the help of a numerical time domain tool, the structure and cable response of moored FPSO vessel was simulated for heading and Beam Sea-states under irregular waves. The weather downtime was assessed by comparing the response under operational wave condition with the pre defined industrial safe offloading criteria. Additionally, two cases of cable failure were simulated for each Sea-state. The novel study on downtime cost was presented for three different location of Malaysia subcontinent for which the location specific wave scatter diagram facilitated to estimate the probability of occurrence of operational wave condition. It was concluded that an unpredictable increment in wave height by 0.5 m can significantly impact the production cost

  • A numerical study: Transitional hydrodynamic behaviour of a moored barge in different ultra-shallow water depths of Malaysia
    'Bentham Science Publishers Ltd.', 2020
    Co-Authors: Patel M.s., Azizan N., Liew, Mohd. Shahir, Mustaffa Zahiraniza, Ali M.o., Whyte Andrew
    Abstract:

    Background: Malaysia has most of its oil reservoirs in the South China Sea. The water depth ranges from 50 m to 200 m. The effects of ultra-shallow water are of prime importance in the exploration of marginal oil fields. Hence, there is an increasing demand for understanding the hydrodynamic behavior of FPSO in ultra-shallow water depths. Objective: A simulation study in both frequency-domain and time-domain analyses has been performed to understand the dynamic responses of a moored barge in varying shallow water depths. The objective of this study was to observe the transitional hydrodynamic behavior of the moored barge under varying shallow water depths. Methods: The moored barge was administered under regular and irregular waves. Operating conditions for irregular waves in terms of significant wave height and peak time period were incorporated from PETRONAS Technical Standards (PTS). The wave-body interactions and mooring effects have been numerically modelled using a commercial Computational Fluid Dynamics (CFD) and simulation software (ANSYS AQWA) successfully. In order to gain confidence in the simulation software, additional experimental validation was performed for a FPSO model. Results: Though the barge was primarily free to rotate in all Degrees Of Freedom (DOF), however, only three DOFs were considered for our study; viz, heave, roll and yaw respectively. The force spectral density, cable RAO’s in addition to the time series of cable forces, along with the effect of significant motions on the mooring cables behavior have been discussed. Conclusion: In irregular Beam Sea state, the significant motions in ultra-shallow water were greater than that for deep waters, this was primarily the main reason for higher cable responses in ultra-shallow water

  • A numerical study: Transitional hydrodynamic behaviour of a moored barge in different ultra-shallow water depths of Malaysia
    'Bentham Science Publishers Ltd.', 2020
    Co-Authors: Patel M.s., Liew M.s., Mustaffa Z., Azizan N., Ali M.o., Whyte Andrew
    Abstract:

    © 2019 Patel et al. Background: Malaysia has most of its oil reservoirs in the South China Sea. The water depth ranges from 50 m to 200 m. The effects of ultra-shallow water are of prime importance in the exploration of marginal oil fields. Hence, there is an increasing demand for understanding the hydrodynamic behavior of FPSO in ultra-shallow water depths. Objective: A simulation study in both frequency-domain and time-domain analyses has been performed to understand the dynamic responses of a moored barge in varying shallow water depths. The objective of this study was to observe the transitional hydrodynamic behavior of the moored barge under varying shallow water depths. Methods: The moored barge was administered under regular and irregular waves. Operating conditions for irregular waves in terms of significant wave height and peak time period were incorporated from PETRONAS Technical Standards (PTS). The wave-body interactions and mooring effects have been numerically modelled using a commercial Computational Fluid Dynamics (CFD) and simulation software (ANSYS AQWA) successfully. In order to gain confidence in the simulation software, additional experimental validation was performed for a FPSO model. Results: Though the barge was primarily free to rotate in all Degrees Of Freedom (DOF), however, only three DOFs were considered for our study; viz, heave, roll and yaw respectively. The force spectral density, cable RAO’s in addition to the time series of cable forces, along with the effect of significant motions on the mooring cables behavior have been discussed. Conclusion: In irregular Beam Sea state, the significant motions in ultra-shallow water were greater than that for deep waters, this was primarily the main reason for higher cable responses in ultra-shallow water

Naoya Umeda - One of the best experts on this subject based on the ideXlab platform.

  • non gaussian pdf of ship roll motion in irregular Beam Sea and wind conditions comparison between theory and experiment
    Ocean Engineering, 2019
    Co-Authors: Atsuo Maki, Naoya Umeda, Akihiko Matsuda, Hiroki Yoshizumi
    Abstract:

    Abstract Ship transverse stability in Beam Seas has long been a significant concern to naval architects. Estimating roll motion remains important for practical risk assessments. However, this problem is not simple, due to the nonlinear equations of motion. A theoretical method for estimating the roll response and capsizing probability has been proposed, but this method has only been correlated by Monte Carlo simulations. Therefore, in this study, model experiments for a subject ship, which exhibited a strong nonlinearity exhibited in the GZ curve, were conducted at National ReSearch Institute of Fisheries Engineering. The results from this study correlated the proposed theory.

  • Melnikov integral formula for Beam Sea roll motion utilizing a non-Hamiltonian exact heteroclinic orbit: analytic extension and numerical validation
    Journal of Marine Science and Technology, 2014
    Co-Authors: Atsuo Maki, Naoya Umeda, Tetsushi Ueta
    Abstract:

    In the reSearch field of nonlinear dynamical system theory, it is well known that a homoclinic/heteroclinic point leads to unpredictable motions, such as chaos. Melnikov’s method enables us to judge whether the system has a homoclinic/heteroclinic orbit. Therefore, in order to assess a vessel's safety with respect to capsizing, Melnikov’s method has been applied for investigations of the chaos that appears in Beam Sea rolling. This is because chaos is closely related to capsizing incidents. In a previous paper (Maki et al. in J Mar Sci Technol 15:102–106, 2010 ), a formula to predict the capsizing boundary by applying Melnikov’s method to analytically obtain the non-Hamiltonian heteroclinic orbit was proposed. However, in that paper, only limited numerical investigation was carried out. Therefore, further comparative reSearch between the analytical and numerical results is conducted, with the result being that the formula is validated.

  • Melnikov integral formula for Beam Sea roll motion utilizing a non-Hamiltonian exact heteroclinic orbit
    Journal of Marine Science and Technology, 2010
    Co-Authors: Atsuo Maki, Naoya Umeda, Tetsushi Ueta
    Abstract:

    The chaos that appears in the ship roll equation in Beam Seas known as the escape equation has been intensively investigated because it is closely related to capsizing incidents. In particular, many applications of the Melnikov integral formula have been reported in the literature; however, in all the analytical works concerning the escape equation, the Melnikov integral is formulated utilizing a separatrix for the Hamiltonian part or a numerically obtained heteroclinic orbit for the non-Hamiltonian part of the original escape equation. To overcome such limitations, this article attempts to utilise an analytical expression for the non-Hamiltonian part. As a result, an analytical procedure is provided that makes use of a heteroclinic orbit of the non-Hamiltonian part within the framework of the Melnikov integral formula.

Patel M.s. - One of the best experts on this subject based on the ideXlab platform.

  • Downtime cost analysis of offloading operations under irregular waves in Malaysian waters
    'Techno-Press', 2020
    Co-Authors: Patel M.s., Liew M.s., Mustaffa Z., Abdurasheed A.s., Whyte Andrew
    Abstract:

    © 2020 Techno-Press, Ltd. The objective of this study was to evaluate the downtime cost of side-by-side offloading operations in Malaysian waters. With the help of a numerical time domain tool, the structure and cable response of moored FPSO vessel was simulated for heading and Beam Sea-states under irregular waves. The weather downtime was assessed by comparing the response under operational wave condition with the pre defined industrial safe offloading criteria. Additionally, two cases of cable failure were simulated for each Sea-state. The novel study on downtime cost was presented for three different location of Malaysia subcontinent for which the location specific wave scatter diagram facilitated to estimate the probability of occurrence of operational wave condition. It was concluded that an unpredictable increment in wave height by 0.5 m can significantly impact the production cost

  • A numerical study: Transitional hydrodynamic behaviour of a moored barge in different ultra-shallow water depths of Malaysia
    'Bentham Science Publishers Ltd.', 2020
    Co-Authors: Patel M.s., Azizan N., Liew, Mohd. Shahir, Mustaffa Zahiraniza, Ali M.o., Whyte Andrew
    Abstract:

    Background: Malaysia has most of its oil reservoirs in the South China Sea. The water depth ranges from 50 m to 200 m. The effects of ultra-shallow water are of prime importance in the exploration of marginal oil fields. Hence, there is an increasing demand for understanding the hydrodynamic behavior of FPSO in ultra-shallow water depths. Objective: A simulation study in both frequency-domain and time-domain analyses has been performed to understand the dynamic responses of a moored barge in varying shallow water depths. The objective of this study was to observe the transitional hydrodynamic behavior of the moored barge under varying shallow water depths. Methods: The moored barge was administered under regular and irregular waves. Operating conditions for irregular waves in terms of significant wave height and peak time period were incorporated from PETRONAS Technical Standards (PTS). The wave-body interactions and mooring effects have been numerically modelled using a commercial Computational Fluid Dynamics (CFD) and simulation software (ANSYS AQWA) successfully. In order to gain confidence in the simulation software, additional experimental validation was performed for a FPSO model. Results: Though the barge was primarily free to rotate in all Degrees Of Freedom (DOF), however, only three DOFs were considered for our study; viz, heave, roll and yaw respectively. The force spectral density, cable RAO’s in addition to the time series of cable forces, along with the effect of significant motions on the mooring cables behavior have been discussed. Conclusion: In irregular Beam Sea state, the significant motions in ultra-shallow water were greater than that for deep waters, this was primarily the main reason for higher cable responses in ultra-shallow water

  • A numerical study: Transitional hydrodynamic behaviour of a moored barge in different ultra-shallow water depths of Malaysia
    'Bentham Science Publishers Ltd.', 2020
    Co-Authors: Patel M.s., Liew M.s., Mustaffa Z., Azizan N., Ali M.o., Whyte Andrew
    Abstract:

    © 2019 Patel et al. Background: Malaysia has most of its oil reservoirs in the South China Sea. The water depth ranges from 50 m to 200 m. The effects of ultra-shallow water are of prime importance in the exploration of marginal oil fields. Hence, there is an increasing demand for understanding the hydrodynamic behavior of FPSO in ultra-shallow water depths. Objective: A simulation study in both frequency-domain and time-domain analyses has been performed to understand the dynamic responses of a moored barge in varying shallow water depths. The objective of this study was to observe the transitional hydrodynamic behavior of the moored barge under varying shallow water depths. Methods: The moored barge was administered under regular and irregular waves. Operating conditions for irregular waves in terms of significant wave height and peak time period were incorporated from PETRONAS Technical Standards (PTS). The wave-body interactions and mooring effects have been numerically modelled using a commercial Computational Fluid Dynamics (CFD) and simulation software (ANSYS AQWA) successfully. In order to gain confidence in the simulation software, additional experimental validation was performed for a FPSO model. Results: Though the barge was primarily free to rotate in all Degrees Of Freedom (DOF), however, only three DOFs were considered for our study; viz, heave, roll and yaw respectively. The force spectral density, cable RAO’s in addition to the time series of cable forces, along with the effect of significant motions on the mooring cables behavior have been discussed. Conclusion: In irregular Beam Sea state, the significant motions in ultra-shallow water were greater than that for deep waters, this was primarily the main reason for higher cable responses in ultra-shallow water