The Experts below are selected from a list of 2640 Experts worldwide ranked by ideXlab platform

Sébastien Fouques - One of the best experts on this subject based on the ideXlab platform.

  • Reliable and efficient injury assessment for free-fall Lifeboat occupants during water entry: Correlation study between Lifeboat acceleration indicators and simulated human injury responses
    Volume 4B: Structures Safety and Reliability, 2014
    Co-Authors: Jeroen Uittenbogaard, Svein-arne Reinholdtsen, Sébastien Fouques, Thomas Michel Sauder
    Abstract:

    The evacuation of personnel from an offshore installation in severe weather conditions is generally ensured by free-fall Lifeboats. During the water entry phase of the launch, the Lifeboat may be subject to large acceleration loads that may cause harmful acceleration-induced loads on the occupants. The present/common methodology for assessing the occupant safety of free-fall Lifeboats uses one single characteristic launch to perform injury risk analysis for a given free-fall Lifeboat launch condition that includes e.g. weather conditions, Lifeboat and host installation loading conditions. This paper describes an alternative methodology to fully assess the risk of injury for Lifeboat occupants during water entry by introducing a correlation model between acceleration load indicators and injury responses. The results are presented in terms of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.

  • influence of wave induced skid motions on the launch of free fall skid Lifeboats from floating hosts experimental and numerical investigations
    ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014
    Co-Authors: Neil Luxcey, Svein-arne Reinholdtsen, Sébastien Fouques, Wojciech Kauczynski, Thomas Michel Sauder, Geir Hovland
    Abstract:

    The evacuation of personnel from offshore installations in severe weather conditions is generally ensured by free-fall Lifeboats. Their performance can be assessed by means of numerical simulations to estimate accelerations loads on occupants, structural loads on the Lifeboat hull, as well as forward speed after water-exit. These parameters strongly depend on the water entry conditions of the Lifeboat, which in turn are very sensitive to the previous phases of the launch that starts on the skid. On floating production, storage and offloading (FPSO) vessels in the Norwegian Sea, Lifeboats are often installed on skids at the bow so that waves may induce large skid motions with typical extreme vertical amplitude of fifteen to twenty meters in a 100-year storm condition. Moreover, wave-induced motions may also cause trim and list of the skid, which initiates more complex six degrees-of-freedom trajectories during free-fall. In such conditions, a proper modelling of the Lifeboat trajectory on the moving skid is necessary in order to assess the performance of the Lifeboat with numerical simulations.This paper investigates the effects of the wave-induced skid motion on the launch of free-fall Lifeboats from floating hosts. The first part of the paper describes the six-degrees-of-freedom numerical skid model used in MARINTEK’s Lifeboat launch simulator VARUNA. The second part presents two model test campaigns aimed at validating the numerical skid model. The model test results are compared to those obtained from the numerical simulations. Finally, the importance of the skid motion on the Lifeboat trajectory is discussed.Copyright © 2014 by ASME

  • effect of wind loads on the performance of free fall Lifeboats
    ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014
    Co-Authors: Thomas Michel Sauder, Eloise Croonenborghs, Sébastien Fouques, Nabila Berchiche, Svein-arne Reinholdtsen
    Abstract:

    The paper presents a model describing the launch of free-fall Lifeboats from offshore structures in strong environmental wind.Six-degrees-of-freedom numerical simulations of the Lifeboat launch are performed using the free-fall Lifeboat simulator VARUNA with a complete set of wind coefficients for the Lifeboat. Those wind coefficients are obtained by CFD simulations validated against wind tunnel tests. The Lifeboat launch simulations are then verified against time-domain CFD simulations of the whole launch in air until water entry.It is shown by means of numerical simulations that wind-induced loads on the Lifeboat have a strong influence on its kinematics until water entry, and subsequently on the acceleration loads experienced by the occupants, on the structural loads on the Lifeboat, and on its forward speed after water exit.It is concluded that the effect of wind-induced loads on the Lifeboat performances should in general be investigated when establishing the operational limits for a given offshore installation.Copyright © 2014 by ASME

  • human injury probability during water entry of free fall Lifeboats operational criteria based on long term simulations using hindcast data
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE OMAE2014-24074 4B, 2014
    Co-Authors: Sébastien Fouques, Svein-arne Reinholdtsen, Thomas Michel Sauder, Jeroen Uittenbogaard
    Abstract:

    The paper addresses the safety of occupants in free-fall Lifeboats launched from turret-moored floating production, storage and offloading (FPSO) vessels. It presents a methodology for assessing operational limits with respect to acceleration-induced loads experienced by the passengers during water entry. The probability of being injured is estimated by means of numerical simulations for several seat rows and in various sea states described in terms of significant wave height and mean wind velocity. Those results are therefore practical for on-site decisions regarding the use of the free-fall Lifeboats. The numerical simulations performed to estimate the 6-degrees of freedom (6-DOF) water entry accelerations in the Lifeboats are based on more than 50 years of hindcast metocean data. These consist of sea state parameters provided every third hour and including the significant wave height, the peak period and the direction of both wind-sea and swell as well as the direction and mean velocity of the wind. In a first step, the motion of the FPSO is computed for the whole time period covered by hindcast metocean data, using a state-of-the art numerical model validated against experimental data. The model includes nonlinear excitation forces, a dynamic positioning system with a realistic heading control strategy, mooring line forces as well as turret-hull coupling. The obtained FPSO motion is then used in Monte Carlo simulations of Lifeboat launches performed for selected time windows in the original metocean hindcast database corresponding to selected intervals of the significant wave height and mean wind velocity. In addition to the 6-DOF skid motion, the Lifeboat launch simulations account for the effects of wind and waves diffracted by the FPSO hull. Finally, a probabilistic model describing the joint-distribution of several injury types and water entry acceleration parameters computed through the launch simulations is used to evaluate the injury probability. The results are presented in term of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.

  • theoretical study of the water entry of a body in waves application to safety of occupants in free fall Lifeboats
    ASME 2009 28th International Conference on Ocean Offshore and Arctic Engineering, 2009
    Co-Authors: Thomas Michel Sauder, Sébastien Fouques
    Abstract:

    The safety of occupants in free-fall Lifeboats (FFL) during water impact is addressed. The first part of the paper describes a theoretical method developed to predict the trajectory in six degrees of freedom of a body entering water waves. Slamming forces and moments are computed, based on momentum conservation, long wave approximation and a von Karman type of approach. The added mass matrix of the body is evaluated for impact conditions by a boundary element method. The second part of the paper focuses on the application of the method to free-fall Lifeboats, which are used for emergency evacuation of oil platforms or ships. Acceleration loads on FFL occupants during water impact are dependent on numerous parameters, especially the hull shape, the mass distribution, the wave heading relative to the Lifeboat, and the impact point on the wave surface. Assessing operational limits of FFL by means of model tests only has therefore been costly and time consuming. This issue is addressed here by applying the theoretical method described in the first part. The model has been validated for FFL through extensive model testing in calm water and regular waves, and statistical estimates of acceleration levels for Lifeboat occupants, as well as acceleration time series were obtained that can be used as inputs to numerical human response models.© 2009 ASME

Thomas Michel Sauder - One of the best experts on this subject based on the ideXlab platform.

  • Reliable and efficient injury assessment for free-fall Lifeboat occupants during water entry: Correlation study between Lifeboat acceleration indicators and simulated human injury responses
    Volume 4B: Structures Safety and Reliability, 2014
    Co-Authors: Jeroen Uittenbogaard, Svein-arne Reinholdtsen, Sébastien Fouques, Thomas Michel Sauder
    Abstract:

    The evacuation of personnel from an offshore installation in severe weather conditions is generally ensured by free-fall Lifeboats. During the water entry phase of the launch, the Lifeboat may be subject to large acceleration loads that may cause harmful acceleration-induced loads on the occupants. The present/common methodology for assessing the occupant safety of free-fall Lifeboats uses one single characteristic launch to perform injury risk analysis for a given free-fall Lifeboat launch condition that includes e.g. weather conditions, Lifeboat and host installation loading conditions. This paper describes an alternative methodology to fully assess the risk of injury for Lifeboat occupants during water entry by introducing a correlation model between acceleration load indicators and injury responses. The results are presented in terms of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.

  • influence of wave induced skid motions on the launch of free fall skid Lifeboats from floating hosts experimental and numerical investigations
    ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014
    Co-Authors: Neil Luxcey, Svein-arne Reinholdtsen, Sébastien Fouques, Wojciech Kauczynski, Thomas Michel Sauder, Geir Hovland
    Abstract:

    The evacuation of personnel from offshore installations in severe weather conditions is generally ensured by free-fall Lifeboats. Their performance can be assessed by means of numerical simulations to estimate accelerations loads on occupants, structural loads on the Lifeboat hull, as well as forward speed after water-exit. These parameters strongly depend on the water entry conditions of the Lifeboat, which in turn are very sensitive to the previous phases of the launch that starts on the skid. On floating production, storage and offloading (FPSO) vessels in the Norwegian Sea, Lifeboats are often installed on skids at the bow so that waves may induce large skid motions with typical extreme vertical amplitude of fifteen to twenty meters in a 100-year storm condition. Moreover, wave-induced motions may also cause trim and list of the skid, which initiates more complex six degrees-of-freedom trajectories during free-fall. In such conditions, a proper modelling of the Lifeboat trajectory on the moving skid is necessary in order to assess the performance of the Lifeboat with numerical simulations.This paper investigates the effects of the wave-induced skid motion on the launch of free-fall Lifeboats from floating hosts. The first part of the paper describes the six-degrees-of-freedom numerical skid model used in MARINTEK’s Lifeboat launch simulator VARUNA. The second part presents two model test campaigns aimed at validating the numerical skid model. The model test results are compared to those obtained from the numerical simulations. Finally, the importance of the skid motion on the Lifeboat trajectory is discussed.Copyright © 2014 by ASME

  • effect of wind loads on the performance of free fall Lifeboats
    ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014
    Co-Authors: Thomas Michel Sauder, Eloise Croonenborghs, Sébastien Fouques, Nabila Berchiche, Svein-arne Reinholdtsen
    Abstract:

    The paper presents a model describing the launch of free-fall Lifeboats from offshore structures in strong environmental wind.Six-degrees-of-freedom numerical simulations of the Lifeboat launch are performed using the free-fall Lifeboat simulator VARUNA with a complete set of wind coefficients for the Lifeboat. Those wind coefficients are obtained by CFD simulations validated against wind tunnel tests. The Lifeboat launch simulations are then verified against time-domain CFD simulations of the whole launch in air until water entry.It is shown by means of numerical simulations that wind-induced loads on the Lifeboat have a strong influence on its kinematics until water entry, and subsequently on the acceleration loads experienced by the occupants, on the structural loads on the Lifeboat, and on its forward speed after water exit.It is concluded that the effect of wind-induced loads on the Lifeboat performances should in general be investigated when establishing the operational limits for a given offshore installation.Copyright © 2014 by ASME

  • human injury probability during water entry of free fall Lifeboats operational criteria based on long term simulations using hindcast data
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE OMAE2014-24074 4B, 2014
    Co-Authors: Sébastien Fouques, Svein-arne Reinholdtsen, Thomas Michel Sauder, Jeroen Uittenbogaard
    Abstract:

    The paper addresses the safety of occupants in free-fall Lifeboats launched from turret-moored floating production, storage and offloading (FPSO) vessels. It presents a methodology for assessing operational limits with respect to acceleration-induced loads experienced by the passengers during water entry. The probability of being injured is estimated by means of numerical simulations for several seat rows and in various sea states described in terms of significant wave height and mean wind velocity. Those results are therefore practical for on-site decisions regarding the use of the free-fall Lifeboats. The numerical simulations performed to estimate the 6-degrees of freedom (6-DOF) water entry accelerations in the Lifeboats are based on more than 50 years of hindcast metocean data. These consist of sea state parameters provided every third hour and including the significant wave height, the peak period and the direction of both wind-sea and swell as well as the direction and mean velocity of the wind. In a first step, the motion of the FPSO is computed for the whole time period covered by hindcast metocean data, using a state-of-the art numerical model validated against experimental data. The model includes nonlinear excitation forces, a dynamic positioning system with a realistic heading control strategy, mooring line forces as well as turret-hull coupling. The obtained FPSO motion is then used in Monte Carlo simulations of Lifeboat launches performed for selected time windows in the original metocean hindcast database corresponding to selected intervals of the significant wave height and mean wind velocity. In addition to the 6-DOF skid motion, the Lifeboat launch simulations account for the effects of wind and waves diffracted by the FPSO hull. Finally, a probabilistic model describing the joint-distribution of several injury types and water entry acceleration parameters computed through the launch simulations is used to evaluate the injury probability. The results are presented in term of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.

  • theoretical study of the water entry of a body in waves application to safety of occupants in free fall Lifeboats
    ASME 2009 28th International Conference on Ocean Offshore and Arctic Engineering, 2009
    Co-Authors: Thomas Michel Sauder, Sébastien Fouques
    Abstract:

    The safety of occupants in free-fall Lifeboats (FFL) during water impact is addressed. The first part of the paper describes a theoretical method developed to predict the trajectory in six degrees of freedom of a body entering water waves. Slamming forces and moments are computed, based on momentum conservation, long wave approximation and a von Karman type of approach. The added mass matrix of the body is evaluated for impact conditions by a boundary element method. The second part of the paper focuses on the application of the method to free-fall Lifeboats, which are used for emergency evacuation of oil platforms or ships. Acceleration loads on FFL occupants during water impact are dependent on numerous parameters, especially the hull shape, the mass distribution, the wave heading relative to the Lifeboat, and the impact point on the wave surface. Assessing operational limits of FFL by means of model tests only has therefore been costly and time consuming. This issue is addressed here by applying the theoretical method described in the first part. The model has been validated for FFL through extensive model testing in calm water and regular waves, and statistical estimates of acceleration levels for Lifeboat occupants, as well as acceleration time series were obtained that can be used as inputs to numerical human response models.© 2009 ASME

Svein-arne Reinholdtsen - One of the best experts on this subject based on the ideXlab platform.

  • Experimental validation of CFD simulations of free-fall Lifeboat launches in regular waves
    Ship Technology Research, 2015
    Co-Authors: Nabila Berchiche, Anders Östman, Ole Andreas Hermundstad, Svein-arne Reinholdtsen
    Abstract:

    This paper presents results from model tests and CFD simulations of Lifeboat launches in regular waves. To the authors’ knowledge, this is the first time CFD simulations of Lifeboat launches in waves have been validated. The predicted accelerations agreed well with the measured ones. The pitch velocity was slightly overestimated due to a slight difference in the geometric features at the bow between the CFD model and the physical model. The simulations provided in general accurate or conservative estimates of the local pressure at various locations on the hull except on one location on top of the canopy where the pressure was slightly under-predicted. Furthermore, it has been shown that to improve the predictions of the pressure loads on the aft wall of the Lifeboat, the compressibility of air has to be taken into account in the simulations in order to capture the behaviour of the air-pocket behind the Lifeboat.

  • Reliable and efficient injury assessment for free-fall Lifeboat occupants during water entry: Correlation study between Lifeboat acceleration indicators and simulated human injury responses
    Volume 4B: Structures Safety and Reliability, 2014
    Co-Authors: Jeroen Uittenbogaard, Svein-arne Reinholdtsen, Sébastien Fouques, Thomas Michel Sauder
    Abstract:

    The evacuation of personnel from an offshore installation in severe weather conditions is generally ensured by free-fall Lifeboats. During the water entry phase of the launch, the Lifeboat may be subject to large acceleration loads that may cause harmful acceleration-induced loads on the occupants. The present/common methodology for assessing the occupant safety of free-fall Lifeboats uses one single characteristic launch to perform injury risk analysis for a given free-fall Lifeboat launch condition that includes e.g. weather conditions, Lifeboat and host installation loading conditions. This paper describes an alternative methodology to fully assess the risk of injury for Lifeboat occupants during water entry by introducing a correlation model between acceleration load indicators and injury responses. The results are presented in terms of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.

  • influence of wave induced skid motions on the launch of free fall skid Lifeboats from floating hosts experimental and numerical investigations
    ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014
    Co-Authors: Neil Luxcey, Svein-arne Reinholdtsen, Sébastien Fouques, Wojciech Kauczynski, Thomas Michel Sauder, Geir Hovland
    Abstract:

    The evacuation of personnel from offshore installations in severe weather conditions is generally ensured by free-fall Lifeboats. Their performance can be assessed by means of numerical simulations to estimate accelerations loads on occupants, structural loads on the Lifeboat hull, as well as forward speed after water-exit. These parameters strongly depend on the water entry conditions of the Lifeboat, which in turn are very sensitive to the previous phases of the launch that starts on the skid. On floating production, storage and offloading (FPSO) vessels in the Norwegian Sea, Lifeboats are often installed on skids at the bow so that waves may induce large skid motions with typical extreme vertical amplitude of fifteen to twenty meters in a 100-year storm condition. Moreover, wave-induced motions may also cause trim and list of the skid, which initiates more complex six degrees-of-freedom trajectories during free-fall. In such conditions, a proper modelling of the Lifeboat trajectory on the moving skid is necessary in order to assess the performance of the Lifeboat with numerical simulations.This paper investigates the effects of the wave-induced skid motion on the launch of free-fall Lifeboats from floating hosts. The first part of the paper describes the six-degrees-of-freedom numerical skid model used in MARINTEK’s Lifeboat launch simulator VARUNA. The second part presents two model test campaigns aimed at validating the numerical skid model. The model test results are compared to those obtained from the numerical simulations. Finally, the importance of the skid motion on the Lifeboat trajectory is discussed.Copyright © 2014 by ASME

  • effect of wind loads on the performance of free fall Lifeboats
    ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014
    Co-Authors: Thomas Michel Sauder, Eloise Croonenborghs, Sébastien Fouques, Nabila Berchiche, Svein-arne Reinholdtsen
    Abstract:

    The paper presents a model describing the launch of free-fall Lifeboats from offshore structures in strong environmental wind.Six-degrees-of-freedom numerical simulations of the Lifeboat launch are performed using the free-fall Lifeboat simulator VARUNA with a complete set of wind coefficients for the Lifeboat. Those wind coefficients are obtained by CFD simulations validated against wind tunnel tests. The Lifeboat launch simulations are then verified against time-domain CFD simulations of the whole launch in air until water entry.It is shown by means of numerical simulations that wind-induced loads on the Lifeboat have a strong influence on its kinematics until water entry, and subsequently on the acceleration loads experienced by the occupants, on the structural loads on the Lifeboat, and on its forward speed after water exit.It is concluded that the effect of wind-induced loads on the Lifeboat performances should in general be investigated when establishing the operational limits for a given offshore installation.Copyright © 2014 by ASME

  • human injury probability during water entry of free fall Lifeboats operational criteria based on long term simulations using hindcast data
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE OMAE2014-24074 4B, 2014
    Co-Authors: Sébastien Fouques, Svein-arne Reinholdtsen, Thomas Michel Sauder, Jeroen Uittenbogaard
    Abstract:

    The paper addresses the safety of occupants in free-fall Lifeboats launched from turret-moored floating production, storage and offloading (FPSO) vessels. It presents a methodology for assessing operational limits with respect to acceleration-induced loads experienced by the passengers during water entry. The probability of being injured is estimated by means of numerical simulations for several seat rows and in various sea states described in terms of significant wave height and mean wind velocity. Those results are therefore practical for on-site decisions regarding the use of the free-fall Lifeboats. The numerical simulations performed to estimate the 6-degrees of freedom (6-DOF) water entry accelerations in the Lifeboats are based on more than 50 years of hindcast metocean data. These consist of sea state parameters provided every third hour and including the significant wave height, the peak period and the direction of both wind-sea and swell as well as the direction and mean velocity of the wind. In a first step, the motion of the FPSO is computed for the whole time period covered by hindcast metocean data, using a state-of-the art numerical model validated against experimental data. The model includes nonlinear excitation forces, a dynamic positioning system with a realistic heading control strategy, mooring line forces as well as turret-hull coupling. The obtained FPSO motion is then used in Monte Carlo simulations of Lifeboat launches performed for selected time windows in the original metocean hindcast database corresponding to selected intervals of the significant wave height and mean wind velocity. In addition to the 6-DOF skid motion, the Lifeboat launch simulations account for the effects of wind and waves diffracted by the FPSO hull. Finally, a probabilistic model describing the joint-distribution of several injury types and water entry acceleration parameters computed through the launch simulations is used to evaluate the injury probability. The results are presented in term of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.

Makoto Arai - One of the best experts on this subject based on the ideXlab platform.

  • Water Entry Simulation of Free-fall Lifeboat
    Journal of the Society of Naval Architects of Japan, 2009
    Co-Authors: Makoto Arai, M. Reaz H. Khondoker, Yoshiyuki Inoue
    Abstract:

    Free-fall Lifeboats provide significant advances in the maritime lifesaving systems. Much of the danger associated with conventional Lifeboat systems can be eliminated by this new evacuation method if the boat is launched selecting suitable launching parameters. A primary consideration in the freefall Lifeboat system is the acceleration field to which the occupants are subjected during water entry. The international regulation, therefore, requires that a Lifeboat for free-fall launching shall be capable of ensuring protection against harmful accelerations when it is launched with its full complement of persons and equipment from at least the maximum designed height.When the Lifeboat enters the water, the acceleration forces exerted upon the boat due to impact are very high. According to the basic study upon the human body response, tolerance level for acceleration is different for each axis of the human body. Therefore, the safe seats in a free-fall Lifeboat are usually reclined relative to the axes of the Lifeboat to reduce the effect of high accelerations. In this paper, the authors introduce a new and probably the simplest concept to evaluate the acceleration field of the free -fall Lifeboat and apply it to the analysis of the safe seat orientation for the occupants. The results have been compared with those of the SRSS acceleration criteria and the dynamic response criteria, both of which are recommended by the IMO, and good agreement has been found.

  • new launching concept for free fall Lifeboats and validation by model experiments and numerical simulations
    Journal of ship and ocean technology, 2002
    Co-Authors: Makoto Arai
    Abstract:

    A new concept for launching free-fall Lifeboats, proposed by Yokohama National University is described in this paper. It has been pointed out that, using the conventional single-skid free-fall system, the potential for dangerous Lifeboat motions (in which the Lifeboat moves backward or jerks on the surface after entering the water) increases with the fall height of the Lifeboat. One of the principal causes of this undesirable motion is vertical rotation of the Lifeboat during its restricted fall at the edge of the launching skid. Thus a new "double-skid"launching concept is proposed to effectively eliminate the rotation of the Lifeboat at the skid end and to enable the Lifeboat to move smoothly after entering the water. In order to evaluate the performance of the proposed method, a series of model experiments and numerical simulations is carried out in which two Lifeboat models with overall lengths of 1 meter and 6 meters are used. The effects of design parameters such as skid angle and skid height are investigated, and an example of the implementation of this new system at the stern of a large merchant ship is illustrated.

  • A comparative study on the behaviour of free-fall Lifeboat launching from a skid and from a hook
    Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2000
    Co-Authors: M. Reaz H. Khondoker, Makoto Arai
    Abstract:

    There are two commonly used launching methods of free-fall Lifeboats: from a skid and from a hook. A free-fall Lifeboat, whether it is released from a skid or from a hook, experiences tremendous impact when it enters the water. This impact force, together with other hydrostatic and hydrodynamic forces and moments, affects the motions and accelerations of the boat considerably. In this paper, a comparative study on the behaviours of the skid and hook launching of free-fall Lifeboats has been presented. Numerical simulation for different launching methods has been used as a tool to obtain trajectories of the Lifeboat for different launching conditions. Also polar diagrams of accelerations are drawn using the data computed for the same conditions. Dynamic response criteria have been used in order to evaluate the risk of injury to the occupants during water entry of the Lifeboat.

  • a new launching concept for free fall Lifeboats
    Major hazards offshore. Conference, 2000
    Co-Authors: Makoto Arai
    Abstract:

    Free-fall Lifeboat is a newly developed evacuation system suitable for use in large merchant ships and offshore structures. Although its efficient launching performance, the motion of the boat after water entry can become a dangerous one if the launching conditions such as fall-height, launch-skid angle are not appropriate. In this paper, detailed studies on the boat motion and exerted acceleration on hull structure, by using a series of model experiments and a numerical method developed by our group, are described. Specific characteristics of the system become clear by those studies. The authors, thus, propose a new launching method that improves the motion of the free-fall Lifeboat launched from the conventional skid. Remarkable improvement of the Lifeboat motion after water entry is illustrated. Results of a large-scale model experiment with 6 m long GFRP Lifeboat model will be shown to validate the behaviours of our proposed new launching method.

  • double skid method for launching free fall Lifeboats
    Journal of the Society of Naval Architects of Japan, 1999
    Co-Authors: Makoto Arai, Kazushige Okazaki, Shinichi Kamimura
    Abstract:

    This paper describes a new concept for launching free-fall Lifeboats proposed by Yokohama National University. Using the conventional single-skid free-fall system, as the fall height of the Lifeboat increases, the potential for increasing incidence of dangerous Lifeboat motions, in which the Lifeboat moves backward or stumbles on the surface after entering the water, has been pointed out. One of the principal causes of this undesirable motion is rotation of the Lifeboat during its restricted fall at the edge of the launching skid. Thus a new “double- skid” launching concept is proposed to effectively eliminate the rotation of the Lifeboat at the skid end and to enable the Lifeboat to move smoothly after entering the water. In order to confirm the performance of the proposed method a series of numerical simulations and model experiments are carried out in which two Lifeboat models with overall lengths of 1 meter and 6 meters are used. The effects of design parameters such as skid angle, skid height, etc., are investigated and an example of the implementation of this new system at the stern of a large merchant ship is illustrated.

M. Reaz H. Khondoker - One of the best experts on this subject based on the ideXlab platform.

  • Water Entry Simulation of Free-fall Lifeboat
    Journal of the Society of Naval Architects of Japan, 2009
    Co-Authors: Makoto Arai, M. Reaz H. Khondoker, Yoshiyuki Inoue
    Abstract:

    Free-fall Lifeboats provide significant advances in the maritime lifesaving systems. Much of the danger associated with conventional Lifeboat systems can be eliminated by this new evacuation method if the boat is launched selecting suitable launching parameters. A primary consideration in the freefall Lifeboat system is the acceleration field to which the occupants are subjected during water entry. The international regulation, therefore, requires that a Lifeboat for free-fall launching shall be capable of ensuring protection against harmful accelerations when it is launched with its full complement of persons and equipment from at least the maximum designed height.When the Lifeboat enters the water, the acceleration forces exerted upon the boat due to impact are very high. According to the basic study upon the human body response, tolerance level for acceleration is different for each axis of the human body. Therefore, the safe seats in a free-fall Lifeboat are usually reclined relative to the axes of the Lifeboat to reduce the effect of high accelerations. In this paper, the authors introduce a new and probably the simplest concept to evaluate the acceleration field of the free -fall Lifeboat and apply it to the analysis of the safe seat orientation for the occupants. The results have been compared with those of the SRSS acceleration criteria and the dynamic response criteria, both of which are recommended by the IMO, and good agreement has been found.

  • A comparative study on the behaviour of free-fall Lifeboat launching from a skid and from a hook
    Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2000
    Co-Authors: M. Reaz H. Khondoker, Makoto Arai
    Abstract:

    There are two commonly used launching methods of free-fall Lifeboats: from a skid and from a hook. A free-fall Lifeboat, whether it is released from a skid or from a hook, experiences tremendous impact when it enters the water. This impact force, together with other hydrostatic and hydrodynamic forces and moments, affects the motions and accelerations of the boat considerably. In this paper, a comparative study on the behaviours of the skid and hook launching of free-fall Lifeboats has been presented. Numerical simulation for different launching methods has been used as a tool to obtain trajectories of the Lifeboat for different launching conditions. Also polar diagrams of accelerations are drawn using the data computed for the same conditions. Dynamic response criteria have been used in order to evaluate the risk of injury to the occupants during water entry of the Lifeboat.

  • Evaluation of optimum conditions of launching a free-fall Lifeboat
    International shipbuilding progress, 1999
    Co-Authors: M. Reaz H. Khondoker
    Abstract:

    This paper presents a study on the behaviour of a free-fall Lifeboat during water entry and exit corresponding to varying launching parameters. The motion of these Lifeboats are considerably influenced by the length and inclination of launch skid, falling angle and effective guide rail length. Attempt is made in this study to identify the optimum launching conditions which will enhance the safety of the boat and also of its occupants. The motion of the Lifeboat has first been categorized on the basis of the horizontal velocity and headway at the first phase of water exit. The range of various parameter combination corresponding to these categories have also been evaluated. The values of the falling angle were then evaluated for the Lifeboat model resulting in zero horizontal velocity at water exit for different skid lengths and falling heights. The optimum values of falling angle and falling height for safe water travel of the Lifeboat have been evaluated for a particular skid length. A criteria for safety of the occupants based on the effects of acceleration is also incorporated in the study. The influence of effective guide rail length on motion of the Lifeboat and safety of the passengers has also been investigated. It is found that at a skid length ratio of 0.5, the motion is expected to be the safest one for effective guide rail length ratio of 0.3.

  • Effects of Launching Parameters on the Performance of a Free‐Fall Lifeboat
    Naval Engineers Journal, 1998
    Co-Authors: M. Reaz H. Khondoker
    Abstract:

    The use of free-fall Lifeboats as a lifesaving aid is increasing rapidly in the ocean environment. However, knowledge and information regarding the performance of these Lifeboats during water entry and surfacing are yet very much limited. A study has been carried out to investigate the motion and attitude of the Lifeboat after water entry and surfacing with respect to various launching parameters. The motion has been categorized on the basis of the advance speed and headway at the first phase of surfacing of the Lifeboat. Numerical study has also been carried out to evaluate the effects of launching parameters on the motion characteristics and horizontal velocity at surfacing. Moreover, a suitable falling angle range has been established for the Lifeboat model based on zero horizontal velocity at surfacing corresponding to different skid lengths and falling heights. Finally, safe water travel conditions based on launching parameters have been evaluated considering the motion characteristics and the effects of accelerations on the occupants of free-fall Lifeboats.

  • Effect of guide rail on the motion and acceleration of a free-fall Lifeboat
    Indian Journal of Engineering and Materials Sciences, 1998
    Co-Authors: M. Reaz H. Khondoker, G. M. Khalil
    Abstract:

    The aim of this paper is to study the effect of guide rail on the motion and acceleration of a free-fall Lifeboat. Since the effect of friction between guide rail and launch skid on its behaviour is insignificant, only those attributed to the changes in the guide rail length are discussed here. From the numerical simulation, trajectories of the falling Lifeboat have been computed for different values of guide rail length and time histories of accelerations in different positions and directions are obtained for the same falling conditions. Moreover, relationship among quantitative values of skid length and fall height has been established based on the horizontal velocity at water exit of the Lifeboat. It is seen that guide rail length has considerable effect on the motion and acceleration of a free-fall Lifeboat.