Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Investigating the Parameters of a Spar Model Platform Through Still Water Decay Tests Using Low-Cost IMU Readings
Submission Author:
Aline Leal de Lima Gontarski , PR , France
Co-Authors:
Aline Leal de Lima Gontarski, André Fujarra
Presenter: Aline Leal de Lima Gontarski
doi://10.26678/ABCM.COBEM2023.COB2023-1089
Abstract
Offshore structures as platforms for gas production or wind turbines undergo flow-induced motions (FIM) since they are exposed to wind forces, currents and waves, leading to considerable motion amplitudes. FIM refers to the motion of a structure caused by the fluid flow forces acting on it. Vortex-induced motion (VIM), on the other hand, is a specific type of FIM that is caused by the vortices shedding in the fluid flow. This phenomenon generates unsteady forces on the structure that leads it to oscillate mainly in cross-flow and in-line directions. To reduce movement during platform operation, the design phase must take into account the natural frequencies of the structure. Water decay tests are usually used to determine the parameters of the structure in this environment. In this work, an scaled platform model was built to conduct still water decay tests using a low-cost inertial measurement unit (IMU) to record data. The model was built based on tests that had already been conducted by the authors at University of Tokyo (UTokyo), to evaluate the VIM response of the platform. The objective is to investigate the behavior of the platform and to validate the precision of data acquisition from two Inertial Measurement Units (IMUs). The process of converting acceleration and rotation rates into displacement in a specific frame using a low-cost IMU can potentially lower the cost of laboratory dynamic analysis. The experimental setup and calibration method are detailed in the work. A data treatment process employing Kalman filter and intrinsic mode functions (IMF) is described, followed by the signal analysis to find natural frequencies and displacement time history. The results are analyzed and discussed, comparing them to an optical tracking system. The results highlight the potential of IMUs as a reliable and cost-effective tool for collecting data in still water decay tests. Overall, this study contributes to the understanding of the behavior of spar platforms design and provides expertise to built and carry out model tests for such structures.
Keywords
VIM, platform model, still water decay test, inertial sensors, IMU
