A Comparative Study of LSTM and TCN Models for Semi-submersible Platform Wave Runup Prediction

Wave runup prediction is necessary for the offshore structure designs and early warnings. Data-driven methods based on machine learning have inspired reduced-order solutions for wave-structure interaction problems. This study provides the quantification of deep learning algorithms' potential for wave runup prediction. Two prominent deep learning models were utilized to predict the wave runups along the fore column of semi-submersible under head seas. The long short-term memory (LSTM) and the temporal convolutional networks (TCN) were comprehensively compared based on the datasets from a model test carried out in the deep ocean basin. The LSTM and TCN model structures were optimized to compare prediction accuracy and computational complexity reasonably. The results reveal that: (1) both developed TCN and LSTM models had satisfied prediction accuracy of over 90 %. Their predictions were extended to 10 seconds into the future with accuracies over 80 % and 45 %, respectively. (2) With the noise-extended datasets, the LSTM model was robust to noises, while the TCN model showed better prediction performance on the extreme wave runup events. (3) The incident wave and dominant rotation provided the major information for wave runup prediction. TCN and LSTM models' prediction accuracies were 91.5 % and 89.3 % based on the simplified input tensors composed of incident wave and pitch. The comparison showed the great potential of TCN model to predict the nonlinear wave runup with less time and memory costs. The input tensors design and optimization based on physical understanding also play a significant role in the prediction performance.