Hee Jong Choi - Academia.edu (original) (raw)
Papers by Hee Jong Choi
Journal of the Society of Naval Architects of Korea, 2007
Journal of the Korean Society of Marine Environment and Safety, 2013
The primary objective of the current work is to develop efficient numerical code to assess the re... more The primary objective of the current work is to develop efficient numerical code to assess the resistance performance of the twin hull form. Resistance performance for the two different twin hull forms with asymmetric and symmetric mono hull using developed code are evaluated. Numerical calculations and model tests have been compared to validate a developed code used in the current work. Comparison were carried out through sinkages of the bow and stern, trim angle and wave-making resistance. Comparative analysis regarding hydrodynamic characteristic of different twin hull forms is worthy of application in the hull form development stage.
Electronics, 2021
Visual understanding of the implied knowledge in line charts is an important task affecting many ... more Visual understanding of the implied knowledge in line charts is an important task affecting many downstream tasks in information retrieval. Despite common use, clearly defining the knowledge is difficult because of ambiguity, so most methods used in research implicitly learn the knowledge. When building a deep neural network, the integrated approach hides the properties of individual subtasks, which can hinder finding the optimal configurations for the understanding task in academia. In this paper, we propose a problem definition for explicitly understanding knowledge in a line chart and provide an algorithm for generating supervised data that are easy to share and scale-up. To introduce the properties of the definition and data, we set well-known and modified convolutional neural networks and evaluate their performance on real and synthetic datasets for qualitative and quantitative analyses. In the results, the knowledge is explicitly extracted and the generated synthetic data show...
Brodogradnja, 2016
The present study proposes an automatic hull form control algorithm to effectively control the hu... more The present study proposes an automatic hull form control algorithm to effectively control the hull form of a ship. A Gaussian distribution function is implemented in the proposed algorithm that automatically controls the hull form in conjunction with an optimization algorithm that is executed during the hull form optimization procedure. The hull form optimization algorithm adopts sequential quadratic programming for the optimizer, and the wave-making resistance is used as an objective function and is solved using the potential-based panel method. A high-speed passenger ship is selected as the target ship, and the results of a numerical analysis of the original hull are compared to those of the optimized hull obtained using the hull form optimization in order to verify the effectiveness of the hull-form optimization technique using the proposed automatic hull form control algorithm.
Journal of Navigation and Port Research, 2013
In this paper the developed prediction technique of wave-making resistance performance for a ship... more In this paper the developed prediction technique of wave-making resistance performance for a ship attached with a vertical blade had been verified. Numerical analysis program as a prediction technique had been developed using the Rankine source panel method and the vortex lattice method(VLM). The nonlinearity of the free surface conditions was fully taken into account using the iterative method and the trim and the sinkage of the ship were also considered in the numerical analysis program. Panel cutting method was applied to get hull surface panels. Numerical computations were carried out for a 4000TEU container carrier and the vertical blade was attached 6 different locations astern. To investigate the validity of the numerical analysis program the commercial viscous flow field analysis program FLUENT was used to obtain the viscous flow field around the ship and the model test was performed. The model test results were compared with the numerical analysis results.
Journal of Korean navigation and port research, 2012
A hull form design technique to enhance the wave-making resistance performance for a medium size ... more A hull form design technique to enhance the wave-making resistance performance for a medium size high speed Ro-Pax ship was studied introducing an optimization method and an automatic hull form modification method. SQP(sequential quadratic programming) was applied as the optimization algorithm and the geometry of hull surface was represented and modified using the NURBS(Non-Uniform Rational B-Spline). The wave-making resistance performance as an objective function in the optimization procedure was evaluated using the Rankine source panel method in which nonlinearity of the free surface boundary conditions and the trim and sinkage of the ship was fully taken into account. Using the Ro-Pax ship as a base hull, the hull-form optimization method was applied to obtain the hull shape that produced the lower wave-making resistance. To verify the validity of the hull-form optimization method, the numerical results was compared with the model test results.
Journal of the Society of Naval Architects of Korea, 2009
The present study focused on evaluation for the performance of the Flow Control Flat Plate (FCFP)... more The present study focused on evaluation for the performance of the Flow Control Flat Plate (FCFP) attached in the stern side of the ship. The important function of this FCFP is to enhance the resistance performance through the decrease of stern sinkage and the propulsive performance by the adjustment of inflow velocities in the propeller plane. Two different hull forms were considered to identify the effects of the FCFP. The attachment position, the angle and the size of the FCFP were studied in this numerical simulation. In this paper, the roles of the FCFP were intended to analyze fully through the numerical interpretation.
Journal of the Society of Naval Architects of Korea, 2007
In the present study, stern form optimization has been carried out using computational fluid dyna... more In the present study, stern form optimization has been carried out using computational fluid dynamics (CFD) techniques. The viscous pressure drag has been minimized to optimize stern shape. Parametric modification function has been used to modify the shape of the hull. By the use of the parametric modification function and algebraic scheme to grid manipulation, the initial ship geometry was easily deformed according to change of design parameters. For purpose of illustration, KRISO 319K VLCC (KVLCC) is chosen for example ship to demonstrate stern form optimization. The numerical results indicate that the optimized hull yields a reduction in viscous resistance.
Journal of Korean navigation and port research, 2014
When a ship operates in a shallow water and channel, the hull sinkage and asymmetrical force gene... more When a ship operates in a shallow water and channel, the hull sinkage and asymmetrical force generated around the ship by the influence of sea bottom and bank walls are caused collision with sea bottom, other ships or the bank itself. Especially, the shipping company and pilots navigating the area of Europe and North America with many channels are deal with it as a important matter to prevent collision. In this paper, hydrodynamic force generated between the ship and bank using the numerical analysis for the safe navigation of ship, that is, sway force and yaw moment should be presumed qualitatively. It makes a program for fluid analysis of the shallow water and bank effect. Analyses are carried out for three kind of parameter, that is, ship' s speed, water depth and ship-bank distance for crude oil carriers. The numerical analysis results are compared with results of the experiments and the previous published papers.
International Journal of Naval Architecture and Ocean Engineering, 2011
Journal of Ocean Engineering and Technology, 2011
The Ranking source panel method was used to predict the flow phenomenon of a ship with a goose-ne... more The Ranking source panel method was used to predict the flow phenomenon of a ship with a goose-neck type bulbous bow penetrating the free surface. The non-linearity of the free surface boundary condition was fully satisfied using an iterative calculation method, and the raised panel method was adopted to obtain a more stable solution at each iteration step. The panel cutting method was applied to generate a hull calculation grid at each iteration step, including the first step. At that time, the nose of the goose-neck type bulbous bow was divided by the free surface and the free surface panel was modified at each iteration step using the variable free surface panel method. Numerical calculations were performed to investigate the validity and efficiency of the applied numerical algorithm using the 3600 TEU container carrier. The computed wave resistance coefficients were compared with the experimentally achieved residual resistance coefficients.
Journal of the Society of Naval Architects of Korea, 2009
In the paper the effect of a stern-plate attached to a ship was taken into account. The relations... more In the paper the effect of a stern-plate attached to a ship was taken into account. The relationship between the trim angle of a ship and the wave-resistance coefficient induced by the a stern-plate was studied using the potential flow analysis method. Numerical algorithm was described using the panel method and the vortex lattice method(VLM) to simulate the flow phenomena around a ship. The non-linearity of the free surface boundary conditions were considered using the iterative method and the IGE-GMRES(Incomplete Gaussian Elimination-The Generalized Minimal RESidual) algorithm was adopted to solve the linear equation at each iterative step. Numerical calculations were carried out to investigate the validity of the adopted algorithm using KCS(KRISO 3600 TEU Container) hull. Possible cases for attachment of the plate were checked. The results showed that the numerical algorithm could be physically appropriate. ※Keywords: Flow control plate(유동제어판), Vortex lattice method(와류격자법), Nonlinear free surface boundary conditions(비선형 자유수면 경계조건), Vortex generator(와류발생기)
Journal of Korean navigation and port research, 2006
Journal of Korean navigation and port research, 2005
Journal of Korean navigation and port research, 2006
Journal of the Society of Naval Architects of Korea, 2008
Journal of the Society of Naval Architects of Korea, 2006
Journal of the Society of Naval Architects of Korea, 2007
Journal of the Korean Society of Marine Environment and Safety, 2013
The primary objective of the current work is to develop efficient numerical code to assess the re... more The primary objective of the current work is to develop efficient numerical code to assess the resistance performance of the twin hull form. Resistance performance for the two different twin hull forms with asymmetric and symmetric mono hull using developed code are evaluated. Numerical calculations and model tests have been compared to validate a developed code used in the current work. Comparison were carried out through sinkages of the bow and stern, trim angle and wave-making resistance. Comparative analysis regarding hydrodynamic characteristic of different twin hull forms is worthy of application in the hull form development stage.
Electronics, 2021
Visual understanding of the implied knowledge in line charts is an important task affecting many ... more Visual understanding of the implied knowledge in line charts is an important task affecting many downstream tasks in information retrieval. Despite common use, clearly defining the knowledge is difficult because of ambiguity, so most methods used in research implicitly learn the knowledge. When building a deep neural network, the integrated approach hides the properties of individual subtasks, which can hinder finding the optimal configurations for the understanding task in academia. In this paper, we propose a problem definition for explicitly understanding knowledge in a line chart and provide an algorithm for generating supervised data that are easy to share and scale-up. To introduce the properties of the definition and data, we set well-known and modified convolutional neural networks and evaluate their performance on real and synthetic datasets for qualitative and quantitative analyses. In the results, the knowledge is explicitly extracted and the generated synthetic data show...
Brodogradnja, 2016
The present study proposes an automatic hull form control algorithm to effectively control the hu... more The present study proposes an automatic hull form control algorithm to effectively control the hull form of a ship. A Gaussian distribution function is implemented in the proposed algorithm that automatically controls the hull form in conjunction with an optimization algorithm that is executed during the hull form optimization procedure. The hull form optimization algorithm adopts sequential quadratic programming for the optimizer, and the wave-making resistance is used as an objective function and is solved using the potential-based panel method. A high-speed passenger ship is selected as the target ship, and the results of a numerical analysis of the original hull are compared to those of the optimized hull obtained using the hull form optimization in order to verify the effectiveness of the hull-form optimization technique using the proposed automatic hull form control algorithm.
Journal of Navigation and Port Research, 2013
In this paper the developed prediction technique of wave-making resistance performance for a ship... more In this paper the developed prediction technique of wave-making resistance performance for a ship attached with a vertical blade had been verified. Numerical analysis program as a prediction technique had been developed using the Rankine source panel method and the vortex lattice method(VLM). The nonlinearity of the free surface conditions was fully taken into account using the iterative method and the trim and the sinkage of the ship were also considered in the numerical analysis program. Panel cutting method was applied to get hull surface panels. Numerical computations were carried out for a 4000TEU container carrier and the vertical blade was attached 6 different locations astern. To investigate the validity of the numerical analysis program the commercial viscous flow field analysis program FLUENT was used to obtain the viscous flow field around the ship and the model test was performed. The model test results were compared with the numerical analysis results.
Journal of Korean navigation and port research, 2012
A hull form design technique to enhance the wave-making resistance performance for a medium size ... more A hull form design technique to enhance the wave-making resistance performance for a medium size high speed Ro-Pax ship was studied introducing an optimization method and an automatic hull form modification method. SQP(sequential quadratic programming) was applied as the optimization algorithm and the geometry of hull surface was represented and modified using the NURBS(Non-Uniform Rational B-Spline). The wave-making resistance performance as an objective function in the optimization procedure was evaluated using the Rankine source panel method in which nonlinearity of the free surface boundary conditions and the trim and sinkage of the ship was fully taken into account. Using the Ro-Pax ship as a base hull, the hull-form optimization method was applied to obtain the hull shape that produced the lower wave-making resistance. To verify the validity of the hull-form optimization method, the numerical results was compared with the model test results.
Journal of the Society of Naval Architects of Korea, 2009
The present study focused on evaluation for the performance of the Flow Control Flat Plate (FCFP)... more The present study focused on evaluation for the performance of the Flow Control Flat Plate (FCFP) attached in the stern side of the ship. The important function of this FCFP is to enhance the resistance performance through the decrease of stern sinkage and the propulsive performance by the adjustment of inflow velocities in the propeller plane. Two different hull forms were considered to identify the effects of the FCFP. The attachment position, the angle and the size of the FCFP were studied in this numerical simulation. In this paper, the roles of the FCFP were intended to analyze fully through the numerical interpretation.
Journal of the Society of Naval Architects of Korea, 2007
In the present study, stern form optimization has been carried out using computational fluid dyna... more In the present study, stern form optimization has been carried out using computational fluid dynamics (CFD) techniques. The viscous pressure drag has been minimized to optimize stern shape. Parametric modification function has been used to modify the shape of the hull. By the use of the parametric modification function and algebraic scheme to grid manipulation, the initial ship geometry was easily deformed according to change of design parameters. For purpose of illustration, KRISO 319K VLCC (KVLCC) is chosen for example ship to demonstrate stern form optimization. The numerical results indicate that the optimized hull yields a reduction in viscous resistance.
Journal of Korean navigation and port research, 2014
When a ship operates in a shallow water and channel, the hull sinkage and asymmetrical force gene... more When a ship operates in a shallow water and channel, the hull sinkage and asymmetrical force generated around the ship by the influence of sea bottom and bank walls are caused collision with sea bottom, other ships or the bank itself. Especially, the shipping company and pilots navigating the area of Europe and North America with many channels are deal with it as a important matter to prevent collision. In this paper, hydrodynamic force generated between the ship and bank using the numerical analysis for the safe navigation of ship, that is, sway force and yaw moment should be presumed qualitatively. It makes a program for fluid analysis of the shallow water and bank effect. Analyses are carried out for three kind of parameter, that is, ship' s speed, water depth and ship-bank distance for crude oil carriers. The numerical analysis results are compared with results of the experiments and the previous published papers.
International Journal of Naval Architecture and Ocean Engineering, 2011
Journal of Ocean Engineering and Technology, 2011
The Ranking source panel method was used to predict the flow phenomenon of a ship with a goose-ne... more The Ranking source panel method was used to predict the flow phenomenon of a ship with a goose-neck type bulbous bow penetrating the free surface. The non-linearity of the free surface boundary condition was fully satisfied using an iterative calculation method, and the raised panel method was adopted to obtain a more stable solution at each iteration step. The panel cutting method was applied to generate a hull calculation grid at each iteration step, including the first step. At that time, the nose of the goose-neck type bulbous bow was divided by the free surface and the free surface panel was modified at each iteration step using the variable free surface panel method. Numerical calculations were performed to investigate the validity and efficiency of the applied numerical algorithm using the 3600 TEU container carrier. The computed wave resistance coefficients were compared with the experimentally achieved residual resistance coefficients.
Journal of the Society of Naval Architects of Korea, 2009
In the paper the effect of a stern-plate attached to a ship was taken into account. The relations... more In the paper the effect of a stern-plate attached to a ship was taken into account. The relationship between the trim angle of a ship and the wave-resistance coefficient induced by the a stern-plate was studied using the potential flow analysis method. Numerical algorithm was described using the panel method and the vortex lattice method(VLM) to simulate the flow phenomena around a ship. The non-linearity of the free surface boundary conditions were considered using the iterative method and the IGE-GMRES(Incomplete Gaussian Elimination-The Generalized Minimal RESidual) algorithm was adopted to solve the linear equation at each iterative step. Numerical calculations were carried out to investigate the validity of the adopted algorithm using KCS(KRISO 3600 TEU Container) hull. Possible cases for attachment of the plate were checked. The results showed that the numerical algorithm could be physically appropriate. ※Keywords: Flow control plate(유동제어판), Vortex lattice method(와류격자법), Nonlinear free surface boundary conditions(비선형 자유수면 경계조건), Vortex generator(와류발생기)
Journal of Korean navigation and port research, 2006
Journal of Korean navigation and port research, 2005
Journal of Korean navigation and port research, 2006
Journal of the Society of Naval Architects of Korea, 2008
Journal of the Society of Naval Architects of Korea, 2006