Hassan Abyn - Academia.edu (original) (raw)

Papers by Hassan Abyn

نشریه مهندسی دریا, Dec 1, 2022

Bulbous bow optimization for ship is one of the ways to increase the efficiency of the ship throu... more Bulbous bow optimization for ship is one of the ways to increase the efficiency of the ship through its hydrodynamic performance. In this study, with the aim of STAR-CCM +, the effects of changes in bulbous bow length for the KCS ship on hydrodynamic behaviour investigated. For this purpose, the leng3th of the bulbous bow was reduced by 5%, and increase 5%, 15% and 25% compared to the baseline, and then simulations were performed on three Froude numbers of 22/0, 26/0and 30/0. Their results of the simulations show that with reducing the bulbous bow length by 5%, the total resistance in the three Froud number increased, respectively, but increased the bulbous bow length the total resistance reduced. Also, with increasing Froude number, the effect of the bulbous bow length will be more influence in reducing the total resistance.

Applied Mechanics and Materials, Dec 1, 2013

The investigation of vortex-induced vibration on very short cylinders with two degrees of freedom... more The investigation of vortex-induced vibration on very short cylinders with two degrees of freedom has drawn the attention of a large number of researchers. Some investigations on such a problem are carried out in order to have a better understanding of the physics involved in vortex-induced motions of floating bodies such as offshore platforms. In this paper, experiments were carried out in a recirculating water channel over the range of Reynolds number 6000 o Re o70 000. Measured response amplitudes and frequencies of cylinders with two degrees of freedom, three different small mass ratios (m n ¼1.00; 2.62 and 4.36) and very low aspect ratios (0.3 r L/D r 2.0) were shown and the results were discussed in depth. Conversely to what would be expected for cylinders with very low aspect ratio, the results showed large motions in the transverse direction with maximum amplitudes around 1.5 diameters for cylinders with L/D ¼ 2.0, despite being smaller when the aspect ratio is reduced. Moreover, the response amplitudes presented high values around 0.4 diameters in the in-line direction. In fact, the large transverse motions were related to a strong coupling with the in-line responses, visibly identified in the plots of nondimensional frequency, as well as by the trajectories in the XY-plane, Lissajous figures, particularly in the case of m n ¼1.00 and L/D¼ 2.0, when 8-shape trajectories were clearly observed. The case of m n ¼ 1.00 deserves more attention because of its smaller amplitude compared to the cases with the same aspect ratio and a larger mass ratio. This counter-intuitive behavior seems to be related to the energy transferring process from the steady stream to the oscillatory hydroelastic system. Finally, it is noteworthy that the characteristic of the ''Strouhal-like'' number decreases when the aspect ratio decreases, as also observed in previous works available in the literature, most of them for stationary cylinders.

CRC Press eBooks, Oct 7, 2013

This paper proposed an empirical method to predict the minimum gap between two floating structure... more This paper proposed an empirical method to predict the minimum gap between two floating structures in tandem arrangement. The minimum distance is the shortest distance between two structures achieved due to surge motions induced by wave. This proposed empirical equation is created based on the experimental data between TLP and Semi-submersible. The experimental results indicate that the minimum gap length between TLP and Semi-submersible is highly depended on the structures' response. The empirical equation developed here is to estimate the minimal gap between structures in the functions of structures' response, wave height, wavelength and initial gap distance. Besides, this empirical method was shown well fixed with experimental results. The result showed that gap between structures changes in non-linear function to the wavelength. Finally, this suggested equation also can be used to define the safety of structures' arrangement in preliminary study.

CRC Press eBooks, Jun 21, 2016

This paper aims to present the effect of dynamic motion interaction between Round Shape FLNG and ... more This paper aims to present the effect of dynamic motion interaction between Round Shape FLNG and KVLCC2 to the RAO of the Round Shape FLNG. The research focuses on the effect of radiation waves generated from the motion of the floating structures and the propagated radiation wave outward to nearby influenced structures.To conduct this study, the Round ShapeFLNGandKVLCC2were arranged in parallel headsea arrangement to capture the strong radiation wave effect on the RAO of Round Shape FLNG. The proposed method was developed to estimate the RAO of Round Shape FLNG due to the radiation wave generated by the motion of nearby structures. Using this method, the wave force and hydrodynamic coefficient were calculated based on the diffraction potential theory and modified drag term of Morison. In addition, the dynamic motion interaction effect was estimated based on the Motion Dissipate Energy concept and Huygens Principle.To verify the proposed method, motion experiments in regular waves were conducted in selected conditions. Then, the results predicted by the proposed method were compared to the experiment results.

Journal of Applied Sciences, Dec 1, 2014

Brodogradnja, Jun 17, 2016

Drilling is carried out in deeper to deeper waters around the globe to meet growing demands for o... more Drilling is carried out in deeper to deeper waters around the globe to meet growing demands for oil and natural gas, and a number of multi body structures are deployed in various oil fields in the world. Investigation of hydrodynamic interaction of offshore structures is therefore worthwhile. Hydrodynamic interaction between floating offshore structures affects motion and relative motion especially during loading and offloading operations. Hydrodynamic interactions may lead to large motions of floating bodies that would cause damage to moorings and offloading systems and may collide with each other. This research work discusses experimental results of hydrodynamic interaction in surge, heave and pitch motion, relative motion and relative distance between a Tension Leg Platform (TLP) and semi-submersible (Tender Assisted Drilling) in regular waves. The experiment is conducted without tendon because of the depth limitation of the Towing Tank. However, in order to consider the contribution of mooring in linear direction, appropriate stiffness of horizontal springs have been used. The experiment was conducted for a full scale wave height of 3.77 m to 12.49 m for a separation distance of 21.7 m. From the analyses of the experimental and numerical results, it can be concluded that nonlinearity of the wave has an important effect on increasing the motion especially in the natural frequency region. Finally, a number of recommendations have been made for further study.

Page 1. Proceedings of MARTEC 2010 The International Conference on Marine Technology 11-12 Decemb... more Page 1. Proceedings of MARTEC 2010 The International Conference on Marine Technology 11-12 December 2010, BUET, Dhaka, Bangladesh 221 MOTION RESPONSES AND INCIDENT WAVE FORCES ON A MOORED SEMI SUBMERSIBLE IN REGULAR WAVES ...

$Research paper thumbnail of Comparison of floating structures motion prediction between diffraction, diffraction-viscous and diffraction-Morison methods$

CRC Press eBooks, Sep 30, 2014

This research is targeted to improve the accuracy of diffraction potential theory to predict semi... more This research is targeted to improve the accuracy of diffraction potential theory to predict semi-submersible heave motion response by considering the drag effect in the prediction. From both the numerical and experimental studies, it can be observed that the diffraction potential theory is not predicting well the semi-submersible heave motion response when the motion is dominated by damping. In this research, the viscous damping correction method and Morison equation drag correction method are applied to improve the motion response predicted by diffraction potential theory. This paper will briefly present the procedure to integrate the viscous damping correction method or Morison equation drag term correction method with the diffraction potential theory. The proposed numerical methods are applied in this research to simulate the semi-submersible heave motion response. After that, all simulation results are compared to the experimental result from tests at the same wave condition to validate the proposed numerical methods. From the comparison, it is concluded that Morison equation drag correction method is able to estimate the semi-submersible heave response in the damping dominated region and provides more reasonable motion tendency compare to other methods

Jurnal teknologi, Jul 25, 2016

In this paper a space-averaged Navier-Stokes approach was deployed to Modified Wavemaker Boundary... more In this paper a space-averaged Navier-Stokes approach was deployed to Modified Wavemaker Boundary condition for a numerical wave tank. The developed model is based on the smoothed particle hydrodynamic (SPH) method which is a pure Lagrangian approach and can handle large deformations of the free surface with high accuracy. In this study, the large eddy simulation (LES) turbulent model was coupled with the weakly compressible version of the smoothed particle hydrodynamics (WCSPH) method to Modified Wavemaker Boundary condition for a numerical wave tank. An absorbing wavemaker boundary condition was developed to absorb the second reflecting waves from the wavemaker. The capacity of absorbing secondary reflecting waves and incoming waves in absorbing wavemaker was validated through comparisons of the numerical results with general wavemaker.

Jurnal teknologi, May 27, 2015

Drilling and production of oil by semi submersible take place in many locations throughout the wo... more Drilling and production of oil by semi submersible take place in many locations throughout the world. Generally, floating structures play an important role in exploring the oil and gas from the sea. The force and motion prediction of offshore structures may be carried out using time domain or frequency domain models or model tests. In this paper the frequency domain analysis used because it is the simplified and linearized form of the equations of motion. The time domain analysis, unlike frequency domain models, is adequate to deal with non-linearities such as viscous damping and mooring forces, but it requires sophisticated solution techniques and it is expensive to employ. In this paper, the wave exciting forces of a free floating semi-submersible were carried out using 3D source distribution method within the scope of the linear wave theory. The results obtained from computations were also compared with the results obtained using commercial software MOSES and WAMIT.

Ships and Offshore Structures, Jul 12, 2020

ABSTRACT Numerical simulations are performed to study the interaction between propeller and hull ... more ABSTRACT Numerical simulations are performed to study the interaction between propeller and hull for two planing vessels: a hard-chine and a tunnelled craft. The numerical model used for reproduction of the problem is validated by comparing the obtained results against published data, showing that a morphing technique is more reliable compared to an overset one. It is demonstrated that propellers strongly affect the performance of a vessel by increasing trim angle and decreasing resistance, which are caused by a noticeable pressure reduction occurring near propellers. These changes are more significant for the case of a tunnelled hull since hydrodynamic pressure acting on the bottom of this vessel is larger compared to a hard-chine craft. While resistance of hulls is seen to be influenced by variation in the position of the propellers at early-planing mode, trim angle is seen to be insensitive to the position of propellers at all speeds.

Jurnal teknologi, 2014

Stability of the mobile floating harbor is an important criterion to avoid an accident in port op... more Stability of the mobile floating harbor is an important criterion to avoid an accident in port operation during lifting, loading, and uploading container. The stability of a mobile floating harbor which completed with a container crane was analyzed by study the structure's rolling amplitude at several sea conditions. Factors considered in the study as follows: size and height of crane and the location of the container during loading and unloading. The mobile floating harbor was constructed using a semisubmersible model on a scale of 1:70 with a specified gantry crane with maximum outreach length 65 meters (Actual size). Using the model, inclining test, swing and oscillating tests was carried out to obtain hydrostatic particulars. By using the experimental result, the roll amplitude for several sea conditions was simulated using the Morison equation. The simulation results showed that the highest roll amplitude occurs when the crane for mobile floating harbor loaded with container in any sea condition.

Jurnal teknologi, 2014

Generally, floating structures play an important role for exploring the oil and gas from the sea.... more Generally, floating structures play an important role for exploring the oil and gas from the sea. The force and motion prediction of offshore structures may be carried out by using time domain or frequency domain or model tests. In this paper the frequency domain analysis used because it is the simplified and linearized form of the equations of motion. Mostly in numerical calculations the number of meshes plays an important role in the accuracy of results, time of calculation and facing to computer memory limitations. The 3D source distribution panel method is shown to be sensitive to mesh near the resonance frequencies of the floating body. So, it is important to establish best practices and determine the mesh requirements for a given level of accuracy. The results obtained from numerical commercial software HydroSTAR (Hstar) on semi submersible prove it.

نشریه مهندسی دریا, Dec 1, 2022

Applied Ocean Research, 2005

The hydrodynamic interaction and mechanical coupling effects of two floating platforms connected ... more The hydrodynamic interaction and mechanical coupling effects of two floating platforms connected by elastic lines are investigated by using a time-domain multi-hull/mooring/riser coupled dynamics analysis program. Particular attention is paid to the contribution of off-diagonal hydrodynamic interaction terms on the relative motions during side-by-side offloading operation. In this regard, the exact method (CMM: combined matrix method) including all the vessel and line dynamics, and the 12 × 12 hydrodynamic coefficients in a combined matrix is developed. The performance of two typical approximation methods (NHI/No Hydrodynamic Interaction: iteration method between two vessels without considering hydrodynamic interaction effects; SMM/Separated Matrix Method: iteration method between two vessels with partially considering hydrodynamic interaction effects, i.e. ignoring off-diagonal cross-coupling terms in the 12 × 12 hydrodynamic coefficient matrix) is also tested for the same side-by-side offloading operation in two different environmental conditions. The numerical examples show that there exists significant discrepancy at sway and roll modes between the exact and the approximation methods, which means that the cross-coupling (off-diagonal block) terms of the full hydrodynamic coefficient matrix play an important role in the case of side-by-side offloading operation. Therefore, such approximation methods should be used with care. The fender reaction forces, which exhibit large force with contact but no force without contact, are also numerically modeled in the present time-domain simulation study.

$Research paper thumbnail of Linearized Morison Drag for Improvement Semi-Submersible Heave Response Prediction by Diffraction Potential$

This research is targeted to improve the semi-submersible heave response prediction by using diff... more This research is targeted to improve the semi-submersible heave response prediction by using diffraction potential theory by involving drag effect in the calculation. The comparison to the experimental result was observed that heave motion tendency predicted by the diffraction potential theory is no agreed with motion experimental result when the heave motion is dominated by damping. In this research, the viscous damping and drag force for heave motion is calculated from the drag term of Morison equation. The nonlinear drag term in Morison equation is linearized by Fourier series linearization method and then inserted into the motion equation to correct the inadequate of diffraction potential theory. The proposed numerical method is also applied to simulate the semi-submersible motion response to obtain the heave motion tendency predicted by this numerical method. In comparison to the experimental result which tested at the same wave condition obtained that the diffraction potential...

Maritime Technology and Engineering III, 2016

$Research paper thumbnail of Motion Responses of Ship Shape Floating Structure using Diffraction Potential$

This paper reviewed the capability of the proposed programming coded based on diffraction potenti... more This paper reviewed the capability of the proposed programming coded based on diffraction potential theory to predict a ship shape floating structure’s motion response.This paper briefly presents the procedure to apply the diffraction potential theory to simulate the ship shape floating structure’s motion response. As case study, the proposed programming code was applied to prediction motion responses of ship shape floating structure in surging, heaving, pitching, swaying, rolling and yawing directions.Results of simulation were compared with ANSYS AQWA software as bench mark. It found that the simulation results by the proposed programming code are similar with the ANSYS one.

نشریه مهندسی دریا, Dec 1, 2022

Applied Mechanics and Materials, Dec 1, 2013

CRC Press eBooks, Oct 7, 2013

CRC Press eBooks, Jun 21, 2016

Journal of Applied Sciences, Dec 1, 2014

Brodogradnja, Jun 17, 2016

$Research paper thumbnail of Comparison of floating structures motion prediction between diffraction, diffraction-viscous and diffraction-Morison methods$

CRC Press eBooks, Sep 30, 2014

Jurnal teknologi, Jul 25, 2016

Jurnal teknologi, May 27, 2015

Ships and Offshore Structures, Jul 12, 2020

Jurnal teknologi, 2014

نشریه مهندسی دریا, Dec 1, 2022

Applied Ocean Research, 2005

$Research paper thumbnail of Linearized Morison Drag for Improvement Semi-Submersible Heave Response Prediction by Diffraction Potential$

Maritime Technology and Engineering III, 2016

$Research paper thumbnail of Motion Responses of Ship Shape Floating Structure using Diffraction Potential$

$Research paper thumbnail of Comparison of Floating Structures Motion Prediction between Diffraction, Diffraction-Viscous and Diffraction-Morison method$

Maritime Technology and Engineering, 2014

This research is targeted to improve the accuracy of diffraction potential theory to predict semi... more This research is targeted to improve the accuracy of diffraction potential theory to predict semi-submersible heave motion response by considering the drag effect in the prediction. From both the numerical and experi-mental studies, it can observe that the diffraction potential theory is not well predicting the semi-submersible heave motion response when the motion is dominated by damping. In this research, the viscous damping correc-tion method and Morison equation drag correction method are applied in purpose to improve the motion re-sponse predicted by diffraction potential theory. This paper will briefly present the procedure to integrate the viscous damping correction method or Morison equation drag term correction method with diffraction potential theory. The proposed numerical methods are applied in this research to simulate the semi-submersible heave mo-tion response. After that, all simulation results are compared to the experimental result which tested at the same wave condition to validate the proposed numerical methods. From the comparison, it is obtained that Morison equation drag correction method is able to estimate the semi-submersible heave response in damping dominated region and provide more reasonable motion tendency compare to other methods.