Session: 08-07-01 Internal Flows & Fluid–Structure Interaction in Riser and Pipeline Systems

Submission Number: 175534

A Differential-Pressure-Based Approach for Two-Phase Fluid-Structure Interaction
Analysis (2-Fsi) Under Slug Flow Pattern: Toward Applications in Lazy-Wave Riser Systems 

The reliable prediction of fluid-structure interaction (FSI) in offshore lazy-wave risers (LWRs) remains a key challenge in engineering. Due to their particular geometry, LWRs transport multiphase flows under both upward and downward flow conditions, and along the system various flow patterns may occur, including slug flow, from the touchdown point (TDP) to the hang-off point (HOP) connected to the floating platform. However, the dynamic response of lazy-wave risers under multiphase flow conditions is not yet fully understood, and the development of robust simulation tools remains essential to ensure safe and efficient design and operation.

 

In this work, experimental tests and computational simulations were carried out to validate and provide input for Finite Element Method (FEM) models. The proposed methodology is based on the reconstruction of transient hydrodynamic loads from high-frequency differential pressure transducer measurements. These reconstructed loads are then applied to a FEM model of the structure, developed in Giraffe, an in-house FEM simulation code, to reproduce the structural response.

 

A dedicated experimental campaign was conducted with air–oil two-phase flow in a 2-inch I.D., 30-meter-long steel pipeline mounted on an inclinable platform system. The test line was instrumented with distributed accelerometers along the pipe and differential pressure transducers with high acquisition rates, enabling the capture of synchronized structural vibrations and unsteady flow signals. Tests were performed at different inclinations, covering both upward and downward flow conditions. The upward configuration represents conventional production scenarios, while the downward configuration is of particular interest for carbon capture and storage (CCS) operations.

 

For the FEM model, a generalized Hamilton’s principle for non-material volumes was implemented in Giraffe to model variable-mass systems and account for the effects of internal multiphase flow (particularly the slug flow pattern) on FSI analysis. The analysis focuses on assessing the ability of the proposed methodology to reproduce the transient structural responses induced by slug flow by comparing numerical FEM simulations with experimental acceleration data.

 

In addition to validating the methodology under controlled experimental conditions, this study positions the proposed framework as a foundation for future applications in lazy-wave risers operating in deepwater environments. By integrating experimental differential pressure measurements to FEM-based structural predictions, the approach bridges the gap between laboratory testing and offshore applications.

Presenting Author: Freddy Alejandro Portillo Morales University of São Paulo

Presenting Author Biography: Ph.D. in Mechanical Engineering from the Federal University of Uberlândia (2023), with emphasis on mathematical and computational modeling of fluid-structure interaction. His doctoral research focused on the application of hexahedral solid elements in industry-oriented simulations. He obtained his M.Sc. degree in Mechanical Engineering from the same institution (2019), where his work addressed the nitriding process by electrical discharges (EDM) in AA 2011 duralumin. He holds a B.Sc. in Mechanical Engineering from Universidad Francisco de Paula Santander, Colombia (2016), where he worked on the geometric characterization and 3D digitization of complex mechanical components such as turbocharger impellers.He has experience in numerical and computational simulation, with a focus on fluid-structure interaction (FSI), Computational Fluid Dynamics (CFD), Finite Element Method (FEM), and Flow-Induced Vibration (FIV). He received scholarships from CAPES and CNPq, participating in applied research projects in collaboration with Petrobras, including FSI studies in piping systems of a Fluid Catalytic Cracking Unit (FCCU) at REPLAN refinery and in tube banks of a recovery boiler at RECAP refinery. He is currently a postdoctoral researcher at the University of São Paulo, working at the Laboratory of Industrial Multiphase Flows (LEMI) on a research project in collaboration with ExxonMobil and Equinor.

Authors:

Freddy Alejandro Portillo Morales University of São Paulo
Gabriel M. B. Cruz University of São Paulo
Gabriel Vicentin Pereira Lapa University of São Paulo
Matheus Medeiros Donatoni University of São Paulo
Pedro Jose Miranda Lugo University of São Paulo
Cristhian Enrique Álvarez Pacheco University of São Paulo
Jorge Enrique Arrollo Caballero University of São Paulo
Ivan Carlos Perissini University of São Paulo
Leopoldo P. R. De Oliveira University of São Paulo
Alfredo Gay Neto University of São Paulo
Oscar Mauricio Hernandez Rodriguez University of São Paulo