Quadratic Volterra 모델을 이용한자유지지 라이저의 동적 응답 시계열 예측
Time Series Prediction of Dynamic Response of a Free-standing Riser using Quadratic Volterra Model
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초록
Time series of the dynamic response of a slender marine structure was predicted using quadratic Volterra series. The wave-structureinteraction system was identified using the NARX(Nonlinear Autoregressive with Exogenous Input) technique, and the networkparameters were determined through the supervised training with the prepared datasets. The dataset used for the network training wasobtained by carrying out the nonlinear finite element analysis on the freely standing riser under random ocean waves of white noise. The nonlinearities involved in the analysis were both large deformation of the structure under consideration and the quadratic term ofrelative velocity between the water particle and structure in Morison formula. The linear and quadratic frequency response functions ofthe given system were extracted using the multi-tone harmonic probing method and the time series of response of the structure waspredicted using the quadratic Volterra series. In order to check the applicability of the method, the response of structure under therealistic ocean wave environment with given significant wave height and modal period was predicted and compared with the nonlineartime domain simulation results. It turned out that the predicted time series of the response of structure with quadratic Volterra seriessuccessfully captures the slowly varying response with reasonably good accuracy. It is expected that the method can be used inpredicting the response of the slender offshore structure exposed to the Morison type load without relying on the computationallyexpensive time domain analysis, especially for the screening purpose.
Abstract
Time series of the dynamic response of a slender marine structure was predicted using quadratic Volterra series. The wave-structureinteraction system was identified using the NARX(Nonlinear Autoregressive with Exogenous Input) technique, and the networkparameters were determined through the supervised training with the prepared datasets. The dataset used for the network training wasobtained by carrying out the nonlinear finite element analysis on the freely standing riser under random ocean waves of white noise. The nonlinearities involved in the analysis were both large deformation of the structure under consideration and the quadratic term ofrelative velocity between the water particle and structure in Morison formula. The linear and quadratic frequency response functions ofthe given system were extracted using the multi-tone harmonic probing method and the time series of response of the structure waspredicted using the quadratic Volterra series. In order to check the applicability of the method, the response of structure under therealistic ocean wave environment with given significant wave height and modal period was predicted and compared with the nonlineartime domain simulation results. It turned out that the predicted time series of the response of structure with quadratic Volterra seriessuccessfully captures the slowly varying response with reasonably good accuracy. It is expected that the method can be used inpredicting the response of the slender offshore structure exposed to the Morison type load without relying on the computationallyexpensive time domain analysis, especially for the screening purpose.
참고문헌 (18)
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