Adaptive ANCF method described by arbitrary Lagrange-Euler formulation with application in variable-length underwater tethered systems moving in limited spaces

Abstract

The nonlinear effect of the variable-length cable may dominate the design of Remotely Operated Vehicles (ROVs) due to the interaction between the flexible cable and surroundings, especially when moving in limited spaces. This paper develops a novel adaptive Absolute Nodal Coordinate Formulation (ANCF) described by Arbitrary Lagrange-Euler (ALE) formulation to investigate the nonlinear dynamics of variable-length underwater tethered systems going across obstacles. The adaptive element techniques are adopted to efficiently simulate the moving contact. Fine meshes are generated autonomously to capture the detailed contact behaviors in contact areas while coarse meshes emerge in non-contact areas, thus significantly reducing DOFs and contact pairs. Additionally, the precontact searching algorithm based on the axis-aligned bounding box (AABB) is employed for the acceleration of the contact detection, which is crucial when element number increases as the mass flow. Combined with the experimental records and analytical solutions in two numerical examples, the accuracy and efficiency of the proposed methodology are further assessed by a comprehensive comparison among the fine, coarse, and adaptive mesh results. The numerical algorithm provides an efficient means for developing a feed-forward controller to compensate the nonlinear cable effects on ROVs when moving in limited space.