파랑중 슬로싱을 동반한 바아지의 운동특성과 PIV를 이용한 압력장 해석에 관한 연구

Abstract

In many cases, the size of the vessel has been increased to improve the loading efficiency of the vessel in relation to the LNG handling and storage. Therefore, ensuring the stability of the cargo hold to store the LNG has been considered as an important matter. Especially, the sloshing, which is the fluid impact load on the hull structure, has become an emerging problem. However, the current GTT and many classes has been using different evaluation methods based on their own concepts and evaluation process as well as the technical examination methods. Thus, it is necessary to conduct an experimental study regarding the sloshing phenomenon and it is also important that the accumulation of the results.

Prediction of the pressure on the sloshing phenomenon is complicated phenomenon. Therefore, it is important to examine the exact movement of the fluid in the hydrodynamic viewpoint and to identify the physical phenomenon associated with the change of various conditions. Hence, the only way to derive a reliable result for now is to conduct an experimental study.

Many previous studies measured an impact pressure in the sloshing tank using a pressure sensor. This is a method for measuring only the pressure value at a certain point(point peak pressure) in the interior of the tank.

The primary purpose of the study is to provide a way to measure the pressure field in the total flow field in the noncontact method using the PIV technique. A beam structure was prepared for the development of noncontact pressure field analysis techniques for this purpose and a pressure sensor was attached on the side of the beam structure. When the incident waves hit the beam structure, the pressure value was measured using a pressure sensor in real time. At the same time the surrounding fluid in the beam structure was measured using a PIV technique. Through comparison of two different measurement methods were used to verify the validity of the noncontact pressure field analysis techniques using the PIV technique.

Based on the experiment results using the PIV technique, this study analyzed the pressure field including both the inside fluid flow of the sloshing tank and the surrounding fluid flow of the barge shaped model. This analysis is for the pressure of the total flow field.

The secondary purpose of this study was to figure out the movement characteristics of the FPSO accompanied by the sloshing in the waves using a 2-D wave tank. Also the researcher examined how the sloshing in the tank affects on the motion of the experimental model.

This experiment was performed with a simplified barge shaped model for FPSO. Tank sloshing phenomenon is mainly influenced by the greatest of the structure according to rolling in the beam sea. Therefore, the conditions of the incident waves were set in this papers as a beam sea.

Model experiments were performed based on a change in the fluid height in the tank loading (0%, 10%, 30%, 50%, 80%) and a change of the incident wave period(0.7sec~1.8sec). Factors of the change mentioned above were examined how the factors affect the movement and sloshing phenomenon of the structure.

In this study, the results were compared the contact-type pressure value measured by the pressure sensor and the noncontact-type pressure value measured by the PIV technique.

In addition, this study measured the movement of the experimental model(roll, heave) and the PIV experiment was performed to measure the inside flow of the sloshing tank and the surrounding flow of the experimental model at the same time.

A diode laser, a high speed camera, a wave height meter, a 4-motion instrumentation, and a wave maker were synchronized and used for the study.