EXPRO-CFD: An Overview of European Research in CFD-Based Fluid Loading and Fluid Structure Interaction

Abstract

Abstract This paper provides an overview of ongoing research in the collaborative project EXPRO-CFD. This project is aimed at developing and validating co-simulation systems combining CFD with hydromechanics models for floating production systems, hence improving the accuracy of calculations of fluid loading and response, and reducing design uncertainties. The paper describes progress to date in developing computer modelling systems which couple together commercial computational fluid dynamics software, wave diffraction and hydromechanics tools (vessel dynamics incorporating risers and mooring systems). It provides an overview of the experimental programme carried out at MARIN and Ecole Centrale de Nantes and some typical results for a vertical cylinder and an FPSO in regular waves using PIV techniques for quantitative flow measurement. Preliminary results from CFD validation studies are provided, and reviewed. Results are also provided for fully coupled calculations of fluid loading and response to extreme events. The paper also contains conclusions on overcoming the various technical issues associated with performing fluid structure interactions calculations using CFD, and the areas where such methods might be used in the future with some confidence. Introduction EXPRO-CFD is a collaborative project aimed at making substantial improvements to techniques for the prediction of non-linear and extreme wave loads and responses of offshore floating production systems. The project is supported by the European Commission as part of its Fifth Framework programme Growth2000, and has been running for just over two years of its three year planned duration. The partnership consists of 13 organisations and research institutions from the UK, Norway, The Netherlands, France and Spain. It includes 2 oil companies (BP and Statoil), three design contractors (Aker, SBM and LMG Marin), three consultants (Atkins, Sirehna and CIMNE), one classification society (DNV), a model basin (MARIN) and three Universities (Imperial College London, University College London and Ecole Centrale de Nantes, who also have access to a model basin). The Coordinators of the project are Atkins. The key themes of EXPRO-CFD are integration, validation and delivery systems. Integration. A novel but pragmatic approach has been adopted to provide integrated hydrodynamic and fluid-structure interaction analysis systems. No new software tools have been developed. Instead, existing and reliable methods in diffraction, CFD and Finite Element analysis, have been adopted and the means to allow them to communicate or run in parallel investigated. This allows the integrity of existing software tools to be retained along with all of the built-in knowledge and experience gained in their development and application. Their integration however opens up many new capabilities, opportunities to clear away uncertainty and conservatism, and improvements in the prediction of design loads, but at significantly lower cost.