The paper addresses response of subsea components subject to internal intermittent slug flows. The proposed work pursues experiments already published last year (OMAE2020-18620) and focuses on the way to numerically model such complex coupled physics for both rigid spool and steel lazy wave riser.
The first part of the paper relies on the coupling approach already presented in OTC-29306 and OMAE2020-18620 mixing (i) Finite Element solver to predict the mechanical behavior of the system and (ii) a Unit Cell solver to recover the intermittent slug flow. It accounts for both (i) the complexity of the slug flow properties at the spool inlet and (ii) their variability along the system. This approach is successfully compared to the experimental (large scale) results already published. This preliminary step validates the ability of the proposed numerical model to recover real-life behavior and underlines some limitations resulting from the Industry Best Practices use.
The second part of the paper extends the applicability of the proposed coupling philosophy to a steel lazy wave riser where a classical Flow Assurance software (e.g. Olga) is considered for the characterization of the intermittent flow and then coupled with a mechanical solver. This one-way coupling accounts for the slugging variability along the riser length and consequently exhibits a finer granularity of the mechanical behavior of the riser. This modelling is then compared to the industry best practices to open a discussion on the observed differences.