Numerical Study of Environment Loads and Mooring Line Scope Effects to The Buoy Offset

Abstract

The Indonesian Buoy for Tsunami Early Warning System (INATEWS - Buoy) consists of a tsunami buoy, an ocean bottom unit (OBU), a satellite and a ground station. The changes of the water pressure due to the seismic motion prior to the tsunami event will be acquired by OBU and sent the reading to the tsunami buoy by acoustic signal. One of the conditions that affect the success of sending data from the OBU to the buoy is the distance between the two (offset). Several parameters that are considered to have an effect on the occurrence of offsets on the buoy are the magnitude of the environmental load around the buoy and the value of the scope mooring line used. Environmental loads that consist of current, wave and wind loads are analyzed. Analysis of each environmental load is carried out separately to determine the level of load sensitivity to the offset buoy. In addition, a buoy offset study was also carried out on several scope values from the mooring line to determine the change in the buoy offset. Offset prediction on buoys is calculated by numerical simulation. From this numerical simulation, it found that changes in environmental load, especially changes in current speed, significantly affect the offset value of the buoy that occurs. Likewise with the determination of the mooring line scope, where the smaller the scope value used in the mooring line system, the smaller the offset value that occurs. Finally, the designed mooring systems while applied at the selected operational buoy location, will have Safety Factor 3.61 and 4.57 for wire and nylon rope mooring line components, respectively.