The free fall dynamics and the similarity criteria for gravity installed anchors in water

Abstract

For reduced-scaled model experiments of the gravity installed anchor (GIA), it is of great significance to extrapolate the model results to the prototype, highlighting the importance of exploring the similarity criteria. In the present work, the approach of computational fluid dynamics (CFD) is utilized to calculate the drag forces at different velocities of three typical GIAs, including the finless, T98 and OMNI-Max anchors, with which the relation expressions between the drag force and the velocity are fitted. The whole free fall process of GIAs in water can then be analyzed, and an analytical framework of the similarity criteria can be constructed. The structured-meshes are utilized to simulate the free fall process of reduced-scaled anchors, through which the similarity criteria are validated. Two case studies are performed to demonstrate various applications of the similarity criteria. By utilizing the similarity criteria developed, the whole dynamic falling process of GIAs in water can be obtained, not only from the reduced-scaled model test to the prototype anchor or the model anchor with a different scale, but also from the prototype test to the model anchors with any scales. This makes it possible to fully utilize precious and infrequent measured data from either prototype or model tests, and enlarges the knowledge of free fall properties of GIAs with any scales.