Entrance and run angle variations of hull form preserving the prismatic coefficient

Son Eun-Young,오민재,Oh Se-Jin,김명수,김유철 대한조선학회 2023 International Journal of Naval Architecture and Oc Vol.15 No.-

There are several methods of hull form variation that can be used in initial ship design, such as offset variation, line variation, and hull form variable variation. Hull form variations are typically done manually, and different results can be obtained according to the designer's know-how. This study proposes a conversion method that uses the Free-Form Deformation method to vary the entrance angle and run angle among the variables that are capable of converting hull form. The Free-Form Deformation is a method for transforming shapes. The variation using Free-Form Deformation method has the advantage of allowing for smooth conversion of the overall shape of the object to be varied, so the local variation is smoothly controlled when a designer manually transforms. However, if the Free-Form Deformation method is used, the varied entrance angle and run angle of the bow and stern will be changed, as will the prismatic coefficient, which is a constraint. Therefore, to obtain the same prismatic coefficient from before the variation, a method of correcting the prismatic coefficient converted 1-CP variation while maintaining the entrance angle and run angle was proposed, and the result was verified. The proposed method can shorten the time needed to generate various hull form data to identify the optimal hull form. It will also help strengthen the competitiveness of small and medium-sized shipbuilders who lack hull form variation technology, as they can use the proposed method to obtain an optimal hull form.

Modeling of Profile Error and Application to a Low Reynolds Number Airfoil

Jaehun Lee,Joong Hun Bae,Kyoung Jin Jung 한국항공우주학회 2018 International Journal of Aeronautical and Space Sc Vol.19 No.4

This paper deals with the development of a computational environment to estimate the effect of the profile error. The profile error is one of the mismatches which refers to the smooth local difference between the designed and the manufactured shapes. Because there are no general criteria for the profile error, we developed the computational environment to evaluate the aerodynamic effect of the profile error. We used the computational fluid dynamic analysis to calculate aerodynamic performance and the shape deformation method called free-form deformation to model the profile error. We applied the computational environment to a typical low Reynolds number airfoil and we could derive a critical value of the profile error. Therefore, the current computational environment is useful in determining the effect of the profile error.

Torque Display Method for Free-Form Deformation with Haptic Device

Yoshimasa Tokuyama,R.P.C. Janaka Rajapakse,Yuji Nakazawa,Kouichi Konno 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

Haptic devices provide a powerful interface that allows users to use their sense of touch to interact with 3D shapes. Even though much research has been done on haptics-based design and sculpting, less effort has been spent on applications related to torque computing and to rque-based modeling. We have constructed a 3D shape modeling and modification system based on a haptic device, with acceptable interactivity to improve intuition. Bending and twisting formulations are widely used in physical modeling and sculpting. The use of to rque-based haptic interaction for deforming and editing 3D shapes has the potential to magnify artistic intuition and creativity of designers. In this paper, we propose a torque display method for free-form deformation(FFD) with haptic device. The combination of bending and twisting extends the editing capabilities of constructed shape deformation system by means of screw-motions.

Optimization Approach for a Catamaran Hull Using CAESES and STAR-CCM+

Zhang Yongxing,김동준 한국해양공학회 2020 韓國海洋工學會誌 Vol.34 No.4

This paper presents an optimization process for a catamaran hull form. The entire optimization process was managed using the CAD-CFD integration platform CAESES. The resistance of the demi-hull was simulated in calm water using the CFD solver STAR-CCM+, and an inviscid fluid model was used to reduce the computing time. The Free-Form Deformation (FFD) method was used to make local changes in the bulbous bow. For the optimization of the bulbous bow, the Non-dominated Sorting Genetic Algorithm (NSGA)-II was applied, and the optimization variables were the length, breadth, and angle between the bulbous bow and the base line. The Lackenby method was used for global variation of the bow of the hull. Nine hull forms were generated by moving the center of buoyancy while keeping the displacement constant. The optimum bow part was selected by comparing the resistance of the forms. After obtaining the optimum demi-hull, the distance between two demi-hulls was optimized. The results show that the proposed optimization sequence can be used to reduce the resistance of a catamaran in calm water.

Image Registration Method from LDCT Image Using FFD Algorithm

Chika Tanaka,Tohru Kamiya,Takatoshi Aoki 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10

In recent years, the number of lung cancer deaths has been increasing. In Japan, CT (Computed Tomography) equipment is used for its visual screening. However, there is a problem that seeing huge number of images taken by CT is a burden on the doctor. To overcome this problem, the CAD (Computer Aided Diagnosis) system is introduced on medical fields. In CT screening, LDCT (Low Dose Computed Tomography) screening is desirable considering radiation exposure. However, the image quality which is caused the lower the dose is another problem on the screening. A CAD system that enables accurate diagnosis even at low doses is needed. Therefore, in this paper, we propose a registration method for generating temporal subtraction images that can be applied to low-quality chest LDCT images. Our approach consists of two major components. Firstly, global matching based on the center of gravity is performed on the preprocessed images, and the region of interest (ROI) is set. Secondly, local matching by free-form deformation (FFD) based on B-Spline is performed on the ROI as final registration. In this paper, we apply our proposed method to LDCT images of 6 cases, and reduce 57.29% in the calculation time, 26.1% in the half value width, and 29.6% in the sum of histogram of temporal subtraction images comparing with the conventional method.

Free-form 소자의 기계적 변형 및 신뢰성 평가 기술 개발

전은채(E. c. Jeon),곽지윤(J. Y. Kwak),서동현(D. H. Seo) 한국기계가공학회 2021 한국기계가공학회 춘추계학술대회 논문집 Vol.2021 No.12

전단변형을 고려한 일축대칭 박벽 곡선보의 면외 좌굴 및 자유진동에 대한 엄밀해 연구

민병철 ( Byoung-cheol Min ) 한국고등직업교육학회 2004 한국고등직업교육학회논문집 Vol.5 No.3

For out-of-plane buckling and free vibration analyses of thin-walled curved beams with non-symmetric cross sections in account for shear deformation, an improved formulation is proposed. Firstly the displacement field is introduced considering the second order terms of semi tangential rotations. Next an elastic strain energy is newly derived by using transformation equations of displacement parameters and stress resultants and considering shear deformation effects due to shear forces and restrained warping torsion. And then the potential energy due to initial stress resultants is consistently derived with accurate evaluation of Wagner effect. In order to illustrate the accuracy and the reliability of this study, closed-form and numerical solutions for instability and natural frequencies of the structure are cross-checked with each others and compared with results by available references. Furthermore, the parametric studies for shear deformation and curvature effect are performed on out-of-plane behaviors of curved beams.

Space Deformation of Parametric Surface Based on Extension Function

Wang, Xiaoping,Ye, Zhenglin,Meng, Yaqin,Li, Hongda Society for Computational Design and Engineering 2002 International Journal of CAD/CAM Vol.1 No.1

In this paper, a new technique of space deformation for parametric surfaces with so-called extension function (EF) is presented. Firstly, a special extension function is introduced. Then an operator matrix is constructed on the basis of EF. Finally the deformation of a surface is achieved through multiplying the equation of the surface by an operator matrix or adding the multiplication of some vector and the operator matrix to the equation. Interactively modifying control parameters, ideal deformation effect can be got. The implementation shows that the method is simple, intuitive and easy to control. It can be used in such fields as geometric modeling and computer animation.

아이폰 5 기반의 실시간 3D 변형 물체 모델링에 관한 연구

전재홍,이승현,홍민 한국지식정보기술학회 2013 한국지식정보기술학회 논문지 Vol.8 No.5

Since the smart device hardware related technology has been rapidly developed and it can provide fast processing speed recently, the interest of real-time representation for 3D deformable objects has been focused in various fields of developing applications for smart device. To present the method for implementation of robust and fast dynamic simulations based on iPhone 5, this paper analysis the possible representation number of deformable objects and complexity of objects which can be computed in real-time by test of various 3D deformable objects. The implemented physically-based FFD-AABB algorithm utilized the 2-level bounding sphere based approach provides fast collision detection and handling using the shape analysis of 3D deformable objects. In addition, to evaluate the performance of implemented algorithm we perform the free falling simulation test from the predefined height with various shapes of 3D deformable objects. Therefore, this paper presents the 2-level bounding sphere based modeling of objects using the shape analysis for fast collision detection and provides the guideline of 3D deformable object modeling for real-time simulation with iPhone 5.

조영 전후의 폐 CT 영상 정합을 위한 특징 기반의 비강체 정합 기법

이현준,홍영택,심학준,권동진,윤일동,이상욱,김남국,서준범,Lee, Hyun-Joon,Hong, Young-Taek,Shim, Hack-Joon,Kwon, Dong-Jin,Yun, Il-Dong,Lee, Sang-Uk,Kim, Nam-Kug,Seo, Joon-Beom 대한의용생체공학회 2011 의공학회지 Vol.32 No.3

In this paper, a feature-based registration technique is proposed for pre-contrast and post-contrast lung CT images. It utilizes three dimensional(3-D) features with their descriptors and estimates feature correspondences by nearest neighborhood matching in the feature space. We design a transformation model between the input image pairs using a free form deformation(FFD) which is based on B-splines. Registration is achieved by minimizing an energy function incorporating the smoothness of FFD and the correspondence information through a non-linear gradient conjugate method. To deal with outliers in feature matching, our energy model integrates a robust estimator which discards outliers effectively by iteratively reducing a radius of confidence in the minimization process. Performance evaluation was carried out in terms of accuracy and efficiency using seven pairs of lung CT images of clinical practice. For a quantitative assessment, a radiologist specialized in thorax manually placed landmarks on each CT image pair. In comparative evaluation to a conventional feature-based registration method, our algorithm showed improved performances in both accuracy and efficiency.