ABSTRACT:

This paper presents the experimental investigation of characteristics of impact pressure patterns. The irregular motion of motion platform was generated from narrow and moderate band width white noise. Two different filling ratios of 20%H and 70%H were tested. The pressure time histories along with flow field were analyzed depending on the location of the pressure sensors. The analysis revealed major types of impact which are either Wagner type or Bagnold type impact. The combination of these two impacts and other complex pressure pattern were also obtained. The impact pressure patterns and the corresponding flow fields are presented.

INTRODUCTION

The complex nature of the sloshing phenomenon in LNG (Liquefied Natural Gas) tank needs confirmation of the flow field by pressure measurement. It means that the practical estimation of the sloshing impact load is based on the pressure measurement. Therefore the analysis of pressure time history can be a very important issue in sloshing analysis. The test was done with irregular motion of the motion platform. It was intended to generate various impact patterns. Therefore it was decided to go with irregular motion. Three types of motions were generated. The irregular motions were generated from narrow band and two other moderate band white noises. The pressures were measured at 54 different locations. The flow field was recorded with video camera to incorporate with pressure time history. The two basic flow patterns in fluid impact are the Wagner type impact (Wagner, 1932) and Bagnold type impact (Bagnold, 1939). These two patterns were witnessed. The combination of these two flow patterns was also obtained. The recorded flow pattern revealed that the Bagnold type impact was caused by air pocket. The Wagner type impact was generated when the impact was due to pure hydrodynamic impact.

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