Validation of the Naval Hydro CFD software pack for focused wave loading on a fixed FPSO is presented in this paper. Naval Hydro is based on Finite Volume CFD software called foam-extend-4.0, and it is specialised for large-scale, two-phase surface flows encountered in naval hydrodynamics. Simulations are performed using SWENSE method (Spectral Wave Explicit Navier-Stokes Equations) for solution decomposition, while implicit relaxation zones are employed for wave initialisation and damping. Numerical results are submitted to a blind comparison with experimental results within the CCP-WSI Blind Test Workshop. Six cases are considered altogether where different incident waves and incident angles are considered. Pressure loads and free surface elevation are considered in this work.
Static naval objects such as Floating Production Storage and Offloading (FPSO) vessels are often exposed to severe weather conditions, where the operationality, life span, and structural integrity may be endangered. There is an ongoing effort in the scientific community aimed at the development, validation and certification of computational methods for predicting wave-body interaction. Finite Volume (FV) based Computational Fluid Dynamics (CFD) methods comprise one of the largest and most popular groups of computational methods for various problems, including naval hydrodynamics, and are more increasingly subjected to rigorous verification and validation in order to assure and promote their accuracy and applicability in modern marine industry. This paper presents a part of such an undertaking within the CCP-WSI Blind Test Workshop, where numerical results submitted by participants are compared to experimental measurements.
In this work Naval Hydro software pack is used to conduct simulations of focused wave loading on a static FPSO model. Naval Hydro pack is based on open-source, FV based CFD software called foam-extend-4.0, and it is specialised for large-scale, two phase flows with rigid body motion and wave generation. The discontinuities across the interface are taken into account with the Ghost Fluid Method (GFM) Vukčević, Jasak, and Gatin 2017, which imposes the free surface boundary conditions within the FV framework. For efficient wave propagation, SWENSE method Vukčević, Jasak, and Malenica 2016a; Vukčević, Jasak, and Malenica 2016b is employed, which is a solution decomposition approach where the flow field is decomposed into the incident portion arising from the potential wave theory, and diffracted component caused by inherent nonlinearities of Navier-Stokes equations. Surface waves are initialised and damped by using implicit relaxation zones Jasak et al. 2015, which are placed at the inlet and outlet of the computational domain, gradually blending the fully nonlinear CFD solution to the target incident wave field. The wave field is initialised with the NewWave theory Tromans et al. 1991.