Underwater parachute, an alternative installation method

Abstract

In the following thesis the concept of free-falling underwater parachute systems are investigated, as a substitute for traditional methods for installing subsea structures. Model size experimental research has been carried out at an indoor model basin, at Marinteknisk Senter, NTNU. Due to lack of previous work related to underwater parachute systems, the thesis main objective, was to build a foundation for better understanding the dynamic behavior of these systems. The main objectives were to investigate landing velocities, horizontal movement for better prediction of the landing position, and general observation of the parachutes behavior. Due to the complex hydrodynamics of these systems, the theoretical foundation used in the thesis is based on simple theory from marine- and aerodynamics.

A wide range of different configurations were tested during the basin experiments, with the intention of observing variations in their behavior. To capture and sample data from the experiment, an optical measurement system in form of underwater cameras were utilized.

The parachute systems showed to be very unpredictable with respect to horizontal movement. For forced asymmetry of the parachutes, gliding attitudes of strong stability and directional predictability were observed. For future applications, it is recommended to design parachutes with increased maneuverability and stability, as these attributes will be necessary to safely and efficient landing of subsea structures.