On the Natural Keulegan–Carpenter Number for Subsea Industrial Modulus Installation

Abstract

Abstract The behavior of subsea equipment has been widely studied by companies to minimize risks during subsea installation, which brings huge costs to the operation. The prediction of equipment motions typically is accomplished by utilizing either commercial software or recommended practices from Classification Societies to comply with the minimum requirements for launching operations. This article analyzes subsea installation in time and frequency domains using experimental, numerical, and analytical approaches. Experiments have been carried out at Instituto de Pesquisas Tecnológicas (IPT) to investigate the dependency of drag and added mass coefficients on Keulegan–Carpenter (KC) number and at Laboratory of Waves and Currents (LOC-COPPE/UFRJ) to study equipment and cable responses on the installation. A numerical model is made in orcaflex® for determining the transmissibility of displacement and force in function of frequency ratio, and the time series of manifold responses. Linearized models from DNV (DNV-GL, 2017, “Recommended Practice (DNVGL-RP-N103) – Modelling and Analysis of Marine Operations.”) and the so-called natural KC (proposed in the present article) are taken in the investigation and compared to previous methodologies. The natural KC approach arises as an innovative way of investigating subsea equipment as the literature only provides parametric analysis considering an arbitrary KC value (i.e., Pestana et al., 2021, “Subsea Manifold Installation: Operational Windows Estimation Based on Hydrodynamic Model Testing,” Ocean. Eng., 219, p. 108364). The analyses notice a good agreement among experiments, orcaflex® model, and natural KC model, whereas the curves found by the DNV method usually overpredict the response of subsea equipment, especially around resonance region.