Exploiting the limit of BEM solvers in moonpool type floaters

Abstract

Solvers based on Boundary Element Method (BEM) are fast and they have proven to provide accurate results in a wide range of applications. On the other hand, computational fluid dynamics (CFD) solvers are high-fidelity tools able to account for viscous effects. However, they are computationally demanding. In the present work, the limitations of BEM solvers are exploited considering the case study of a moonpool type floater in which the viscous effects near the sharp edges of the body (vortex shedding) are not negligible. The BEM results are compared with the results from an unsteady Reynolds averaged Navier-Stokes (URANS) CFD solver and experimental data, while viscous corrections of the BEM method are assessed.

Hydrodynamics of Moonpool-Type Floaters: A Theoretical and a CFD Formulation

“…Regarding the vertical excitation force in Figure 10, the comparison between the methodologies was fair, with the CFD simulations predicting smaller peak loads and shifted towards the lower frequencies. This has also been noted in [29]. Nevertheless, the qualitative comparison for both the total force and the individual body forces was considered to be in good agreement.…”

“…A grid consisting of 5 million cells was employed with symmetry conditions (half of the moonpool is modelled). Since the moonpool was considered fixed and the waves were essentially in the linear region, the flow is assumed laminar [29,44].…”

“…In this section, a brief description of the CFD modelling applied to the present bodies' configurations is presented. For a more detailed review of the solver's methodology, the reader may refer to [29,33]. In the previous mentioned publications, a series of test cases have been examined, including a moonpool configuration excited by incident waves that prove the liability of the solver in this type of simulations.…”

“…Recently, in [28] a viscous damping model for energy losses of a 2D fluid response in a moonpool due to wall friction and flow separation was proposed. Furthermore, the limitations of boundary element method solvers when viscous effects near floater's sharp edges were taken into account and were exploited in [29] in the case of a moonpool type floater.…”

Multiscale interactions of liquid, bubbles and solid phases in ultrasonic fields revealed by multiphysics modelling and ultrafast X-ray imaging

“…Klaseboer et al [21] also simulated an underwater exploding bubble and its interaction with a flat plate numerically using the FEM and boundary-element method (BEM). However, the FEM and BEM methods have inherent limitations when simulating high viscous fluids, vortices and tracking the evolution of interfacial boundary [22] . In particular, those modelling and simulation work generally lack calibration and validation by experiments.…”