해저면에 복수열의 트렌치(핏)을 설치할때 발생하는 회절에 대하여 3차원 다방향불규칙파를 연구한것이다. 유체영역을 N개의 핏영역과 외부영역으로 구분하여 N+1영역으로 처리하였다. 내부영역은 프리에해석을 이용하고, 외부영역은 적분방정식을 이용하여 연계하여 솔류 ...

해저면에 복수열의 트렌치(핏)을 설치할때 발생하는 회절에 대하여 3차원 다방향불규칙파를 연구한것이다. 유체영역을 N개의 핏영역과 외부영역으로 구분하여 N+1영역으로 처리하였다. 내부영역은 프리에해석을 이용하고, 외부영역은 적분방정식을 이용하여 연계하여 솔류션을 얻었다. 이 결과를 활용하여 다방향 불규칙파랑이론에 입각하여 불규칙파랑으로서 Pit와 파랑과의 상호작용을 연구하였다. 불규칙파에 사용된 스펙트럼식은 Pierson-Moskowitz 공식을 사용하였다. 핏트설치에 따른 파라의 파고변화는 그 효과를 잘 나타내고 있다. 본 연구과제에서 활용할 수 있는 효과는 크게 두 부분으로 요약될 수 있다. 첫째, 항만운영에 있어서 pit에 의한 파랑의 회절이나 에너지 감소의 파랑제어를 통하여 항로운행중의 선박의 안정성확보 문제를 들 수 있다. 단주기 파랑에 의한 항내정온도의 향상 혹은 장주기파에 의한 항내부진동 문제에 대처할 수 있다. 따라서 장주기파에 의한 만내 부진동으로 하역률이 저하되는 경우에, pit설치에 의해 파랑제어를 통한 장주기파의 저감효과를 꾀할 수 있다. 둘째, 해저퇴적물을 제거하면서 오염된 토양을 복원할 수 있는 환경보전의 문제이다. 준설작업을 통해 야기될 수 있는 수질오염문제의 파악을 위하여, pit에 의해 3차원의 불규칙파랑의 상호작용의 해석에 의해 파랑장, 유속장 등의 해안수리학정보를 활용하여 오염물질, 부유물질의 추적, 퇴적 등의 추적에 사용할 수 있으며, 수질오염에 대처할 수 있다. 즉, 해저 퇴적물의 상당부분이 각종 오염물질을 내포하고 있으며 준설시 발생하는 해양수질오염의 문제를 대비하는 기초연구로서 활용할 수 있다.

A three-dimensional modeling of multidirectional random-wave diffraction by a group of rectangular submarine pits is presented in this paper. The fluid domain is divided into N interior regions representing the pit area and an overall exterior region ...

A three-dimensional modeling of multidirectional random-wave diffraction by a group of rectangular submarine pits is presented in this paper. The fluid domain is divided into N interior regions representing the pit area and an overall exterior region separated by the imaginary pit boundaries. In the interior region, the analytical expressions of the Fourier series expansion for velocity potentials in the pit regions have been derived with the unknown coefficients determined from a series of Green’s function based boundary integral equations. The boundary integral approach has also been applied to obtain the velocity potential and free-surface elevation in the exterior region. The Pierson-Moskowitz (P-M) frequency spectrum was selected for the random wave simulation using the superposition of solutions of a finite number of decomposed wave components. Numerical results for the cases of regular waves and random waves are presented to examine the influences of the pit geometry and incident wave condition on the overall wave field. The general diffraction pattern of alternate bands of increase and decrease of relative wave height in front of the pit system can be observed. It is found, in the shadow region, the relative wave height is reduced. As the number of pit increases, the effectiveness of reducing the relative wave height behind the multiple-pit system increases. However, the relative wave height within the pit area and in front of the leading pit shows increasing trend. It is noticed that under the random-wave condition, the level of increase and decrease of the relative wave height due to the existence of submarine pits is less pronounced than that observed from results in regular-wave condition.

A three-dimensional modeling of multidirectional random-wave diffraction by a group of rectangular submarine pits is presented in this paper. The fluid domain is divided into N interior regions representing the pit area and an overall exterior region ...

A three-dimensional modeling of multidirectional random-wave diffraction by a group of rectangular submarine pits is presented in this paper. The fluid domain is divided into N interior regions representing the pit area and an overall exterior region separated by the imaginary pit boundaries. In the interior region, the analytical expressions of the Fourier series expansion for velocity potentials in the pit regions have been derived with the unknown coefficients determined from a series of Green’s function based boundary integral equations. The boundary integral approach has also been applied to obtain the velocity potential and free-surface elevation in the exterior region. The Pierson-Moskowitz (P-M) frequency spectrum was selected for the random wave simulation using the superposition of solutions of a finite number of decomposed wave components. Numerical results for the cases of regular waves and random waves are presented to examine the influences of the pit geometry and incident wave condition on the overall wave field. The general diffraction pattern of alternate bands of increase and decrease of relative wave height in front of the pit system can be observed. It is found, in the shadow region, the relative wave height is reduced. As the number of pit increases, the effectiveness of reducing the relative wave height behind the multiple-pit system increases. However, the relative wave height within the pit area and in front of the leading pit shows increasing trend. It is noticed that under the random-wave condition, the level of increase and decrease of the relative wave height due to the existence of submarine pits is less pronounced than that observed from results in regular-wave condition.

A 3D boundary integral model has been developed to analyze the diffraction of multidirectional random waves by multiple rectangular submarine pits in water of uniform depth. The theoretical form of the model has been formulated by utilizing a general ...

A 3D boundary integral model has been developed to analyze the diffraction of multidirectional random waves by multiple rectangular submarine pits in water of uniform depth. The theoretical form of the model has been formulated by utilizing a general 3D Green function relevant to the 3D wave-structure interaction problem. To improve the accuracy of the interior solutions, the analytical expressions of velocity potential in the pit region have also been derived in terms of the Fourier series expansion with unknown coefficients to be determined.
Results for various pit geometries and incident wave conditions have been presented to illustrate the influence of pits on the wave field. The diffraction coefficients under the cases of regular waves and random waves are presented and compared. Generally, with the existence of the pits, a series of circular bands of wave diffraction pattern in front of the pit region can be clearly observed and in the shadow region, the reduction of the relative wave height can be achieved. For both cases of regular and random waves, the results indicate that the pit has major influence on the wave field in, in front of and behind the pit area. By increasing the number of pit (e.g., 3 pits), the relative wave height in the shadow region can be substantially reduced (e.g., up to 60% for the regular waves). However, major increase of the relative wave height within the pit area and in front of the leading pit can be observed. It is noticed that under the random-wave condition the level of increase and decrease of the relative wave height due to the existence of submarine pits is found to be less pronounced than that of regular waves. The present 3D numerical model may be extended to apply with confidence for many coastal engineering applications.