Session: 04-01-05 Flexible Pipes V

Submission Number: 181253

A Numerical Model for Contact Analysis of Non-Bonded Flexible Pipes With Accelerated Search Approach and Parallel Computation 

Non-bonded flexible pipes are multilayer structures comprising helically wound metal strips and extruded polymers, widely used offshore for production, injection, and control lines. In practice, the inner carcass and pressure armours are helically wound at angles close to 90° with profiled steel strips to withstand internal pressure and radial inward forces, whereas the tensile armours are laid at 30°–55° with rectangular or round shaped steel wires to carry tension and torque. When adjacent layers can slide, large deformations produce dense, path-dependent contact. The combination of multilayer anisotropy and pervasive contact yields pronounced geometric and interface nonlinearities, which produces significant challenges for both numerical modeling and solution.

In this paper, a new numerical model is established for non-bonded flexible pipe considering contact problems by achieving progress in the following aspects: (1) The basic numerical framework for contact analysis for flexible pipes is implemented based on an open-source 3-D large-deformation contact finite-element solver (Zuo et al.), which is capable to handle layer interactions of pipes and consider large deformations; (2) Motivated by the near-90° windings of carcass and pressure armor, we idealize the load-bearing core as a homogenized orthotropic cylindrical layer, while the overwrap tensile layer is modeled as isotropic linear elastic. (3) To reduce search cost of contact analysis, we introduce a geometry-aware broad phase: Each slave integration point first attempts a warm start by re-projecting the previous step’s master hit; if rejected by a small gap/penetration check, it queries nearby buckets on a periodic grid indexed by circumferential angle and axial position, and a Newton projection refines the closest point on each candidate face. If the bucket query yields no valid hit, we fall back to the original baseline contact-search routine. The bucket grid is rebuilt lazily only when accumulated motion exceeds a small fraction of the bucket size. (4) Parallel computation is used to further increase computational efficiency . Element and contact contributions are computed in parallel; each worker emits sparse triplets for stiffness and force that are merged once via a sort-and-group ordered reduction, eliminating write conflicts and reducing summation-order sensitivity.

Based on this model, we conduct bending benchmarks for two-layer pipes composed of an orthotropic core and an isotropic helical overwrap. The computed responses are identical to those from the open-source baseline, and comparisons against the commercial solvers Abaqus and FEBio show differences that are small and within engineering tolerance. Replacing the baseline exhaustive search with the proposed geometry-aware contact search delivers a speedup greater than fourfold; with the additional parallel triplet assembly, the total acceleration exceeds tenfold, substantially reducing wall-clock time. Overall, the method provides an efficient contact search algorithm for non-bonded flexible-pipe contact analysis.

Presenting Author: Yichao Lu State Key Laboratory of Structural Analysis, Optimization and CAE Software for Industrial Equipment

Presenting Author Biography: I am a graduate student at the State Key Laboratory of Structural Analysis, Optimization and CAE Software for Industrial Equipment, Dalian University of Technology.My research focuses on the structural mechanics and inter-layer contact behavior of unbonded flexible marine risers.My Email Address: yichaolu@mail.dlut.edu.cn.

Authors:

Yichao Lu State Key Laboratory of Structural Analysis, Optimization and CAE Software for Industrial Equipment
Chunhong Hu Offshore Oil Engineering Co., Ltd
Mo Zhai Offshore Oil Engineering Co., Ltd
Chunmei Yue Offshore Oil Engineering Co., Ltd
Hailong Lu State Key Laboratory of Structural Analysis, Optimization and CAE Software for Industrial Equipment
Jun Yan State Key Laboratory of Structural Analysis, Optimization and CAE Software for Industrial Equipment
Yiqian He State Key Laboratory of Structural Analysis, Optimization and CAE Software for Industrial Equipment