Advancing the Industry Practice in Offshore Wind Load Estimation - An Overview of On-Going SNAME OC-8 Activities

In early 2014, the Society of Naval Architects and Marine Engineers (SNAME) OC-8 Panel was formed to address regulatory acceptance of wind tunnel testing for stability calculations of offshore floating production systems governed by the U.S. Code of Federal Regulations (CFR). Initially, this focused on updating the 1988 SNAME T&R Bulletin 5-4 "Guidelines for Wind Tunnel Testing" which has served as a de facto industry standard for nearly 25 years. The update was intended to leverage new technologies and lessons learned to improve the accuracy and repeatability of the results. As time progressed, the focus of the Panel broadened to encompass the empirical ‘building block’ method of wind load estimation (i.e., the basis of the CFR stability calculations) and computational fluid dynamics (CFD). The need to step back and objectively assess the relative accuracy and repeatability of these estimation methods was recognized in 2016. In response, SNAME OC-8 organized a ‘first-of-its-kind’ comparative wind load study to benchmark the relative accuracy and repeatability of available wind load estimation methods (i.e., empirical ‘building block’ methods, wind tunnel testing, and CFD) for a representative semi-submersible hull. The study resulted in two important outcomes: 1) U.S. regulatory authorities participated in the workshop and expressed support for acceptance of wind tunnel test results pending the publication of a new industry guideline which could assure accuracy/ repeatability, and 2) key stakeholders from operators, engineering companies, classification societies, and regulatory bodies expressed support for the development of a new industry design guideline to broadly address wind load estimation (including the use of CFD) through the engineering design spiral. The present paper summarizes the contributions of the SNAME OC-8 Panel since its inception. High- level findings/ take-aways from the 2017 comparative wind load study are discussed, and unanswered questions of importance are highlighted. The SNAME OC-8 Panel plans to deliver two new industry guidelines to improve the accuracy and repeatability of empirical ‘building block’, wind tunnel, and CFD wind load estimates; the on-going efforts of the Panel and its constituent subcommittees are further outlined in the latter portion of the paper.