International Journal of Civil and Structural Engineering Research ISSN 2348-7607 (Online) Vol. 9, Issue 2, pp: (83-91), Month: October 2021 - March 2022, Available at: www.researchpublish.com
Prediction of oceanographic data using LSTM network: A case study for FSRU in Arabian Sea A. Basu1, A.A. Purohit2, K.A. Chavan3 1
Scientist-C, 2Scientist-E, 3Research Assistant
1,2,3
Central Water and Power Research Station, Pune, India
Abstract: Information on site specific measured oceanographic data such as wind generated waves, currents is seldom available and plays an important role in offering solution to various coastal engineering problems. Due to unanticipated difficulties during field measurement campaigns, it has been observed that measured data for some specific duration is missing or lost. In such circumstances, data driven methods are essential to predict the missing data and its use to calibrate the physical model and to offer engineering solution to the project. Present study investigates the applicability of one of the popular recently developed artificial intelligence (AI) model named as long short-term memory (LSTM) in predicting current data in a macro tide dominated Thane creek and the significant wave height (Hs) for Floating Storage & Regasification Unit (FSRU) structure. The results indicate that LSTM networks formed based on data of 7/15 days of current/tide, can predict current data for 8/10 days with root mean square error (RMSE) of 0.091 and 0.09 respectively. Study also reveals that for location in Thane creek, LSTM prepared on the basis of 8 days of Hs data is able to predict Hs for 33 hours with RMSE value of 0.14. Based on the predicted data, current data is used to calibrate the physical tidal model to determine flow conditions for proposed FSRU in Thane creek and also operable condition (Hs). The study reveals that FSRU needs to be aligned at 33° N and hence LSTM network was found to be useful in design of waterfront structures. Keywords: Artificial intelligence, current, LSTM, oceanographic data, significant wave height.
I. INTRODUCTION The importance of measured oceanographic data such as wind generated waves, currents, tides, suspended sediment concentration, salinity etc. plays an important role for understanding various nearshore coastal processes such as coastal erosion/accretions, shoreline changes; determination of design/operational conditions for coastal structures; in planning schedule for safe navigation of ships; in assessing the trajectory of movement of dredged materials/oil spills; in validation/calibration of physical/numerical models on tidal/wave hydrodynamics, sedimentation/wave transformation etc. Presently various organisations such as Indian National Centre for Ocean Information Services (INCOIS) deployed buoys all over the Indian Ocean to measure different metocean parameters and the organisations like European Centre for Medium Range Weather Forecasts (ECMWF), National Oceanic and Atmospheric Administration (NOAA) forecast various metocean parameters at various grid resolutions all over the globe. However, the collection of site specific measured metocean data even although a costly affair and involves high risk of human life, measuring instruments; is still inevitable in solving various site specific coastal engineering problems. Due to the various difficulties during the field measurement campaign, many times it has been observed that the collected field data for some specific duration is either missing or is lost and, in such scenario, to predict the missing data, data driven methods are essential to predict the missing data and its use to calibrate physical/numerical model will offer engineering solution to the project. The development of Floating Storage and Regasification Unit (FSRU) near the entrance of Thane creek, Mumbai for availing storage facility for LNG (1,70,000 cum) and berthing of LNG tanker was under consideration. In order to provide design basis for this waterfront facility in macro tidal region (tidal range of 5 m), its alignment needs to be finalised in such a way that irrespective of phase of tide (flood/ebb), flow direction at berth of LNG tanker/FSRU should remain parallel to the prevailing flow direction to minimise the undesirable forces on mooring ropes and also to determine operational
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