Introduction of an optimised dynamic installation anchor via model test and numerical analysis: Freefall in the water column

This paper introduces a novel shaped dynamically installed anchor (called ‘maverick anchor’) with optimised geometric components (tip, shaft, and fins). The performance of the maverick anchor in terms of hydrodynamic characteristics (terminal velocity, hydrodynamic drag, and directional stability) obtained through freefall drop tests in water and Computational Fluid Dynamics (CFD) analyse was compared with that of existing dynamically installed anchors used in offshore Brazil and in the Gulf of Mexico. Freefall drop tests on model anchors were performed in a 1.56 m depth water tank at UWA. Freefall motions of the anchors were filmed mounting two cameras, and subsequently quantified using Python code. In testings, geometric similarity was ensured between the model and prototype. CFD analyses were then carried out on the corresponding field scale anchors using Ansys/Fluent, fixing the anchor at a particular location, and flowing the water column with a velocity. Numerical analyses ensured similarity in Reynolds number. Results have confirmed that compared to the commercially used dynamically installed anchors, the maverick anchor can attain a higher terminal velocity, and the corresponding drag coefficient is lower due to smooth fluid flow along the anchor body. The verticality or lateral stability during the freefall was also promising. • An optimised dynamically installed anchor, named the maverick anchor, is introduced. • Scaled model tests and CFD simulations (field-scale) demonstrated that the maverick anchor exhibits a significantly lower drag coefficient, faster terminal velocity, and enhanced stability. • These improvements are attributed to the maverick anchor's unique geometric features, including its smaller size and streamlined design without abrupt transitions.