CFD Analysis in Subsea and Marine Technology

Abstract

Abstract. Computational Fluid Dynamics (CFD) is established in design and analysis for a range of industries, but its use in Marine and Naval Hydrodynamics is behind the trend. This can be attributed to the complexity of modelling needs, including presence of free surface, irregular transient flows, fluid-structure coupling and presence of established modelling tools based on potential theory.In this paper, state-of-the-art of CFD in Naval Hydrodynamics, wave and offshore applications is given, with an update of recent advances, validation and computing requirements for typical simulation cases. IntroductionSince the beginning of the 21st century, Computational Fluid Dynamics (CFD) has become well established across the range of engineering applications. CFD results are well understood, expectations on accuracy in design studies can be satisfied. For example, automotive industry uses CFD to significantly reduce the use of experimental studies in aerodynamics, internal combustion engine design and exhaust gas after-treatment. Indeed, CFD studies are now regularly performed in applications which were never properly analysed experimentally, such as passenger compartment comfort, vehicle soiling and acoustics-related phenomena, where the design primarily relies on CFD results.Acceptance of CFD in marine engineering, naval hydrodynamics and evaluation of wave loads appears to be lagging behind the trend of other industries. This is partially due to the complexity of free surface flows, but mainly by the fact that the phenomena under consideration imply significantly higher computational requirements. For example, sea-keeping studies of ships in irregular waves or calculation of transfer functions for wave loading on floating structures still cannot be performed at acceptable speed. "Engineering time-scale" in product design requires turn-over time of 8-12 hours for simulations to be practically useful.An important factor in the acceptance of CFD is the presence of alternative simulation tools. Numerical models based on potential flow theory are widely accepted, fast and validated and have been in use for more than a decade. The potential flow assumption, whole adequate for a part of industrial needs, brings it own limitations, mainly due to the formulation, or failure to account for coupled/non-linear effects. The best example is the evaluation of added resistance in waves, which may provide adequate loading results on the hull, but cannot account for forward speed of the ship.The challenges for CFD modelling in naval hydrodynamics can be grouped as follows:

Ship resistance when operating in floating ice floes: A combined CFD&DEM approach

“…An alternative approach is to couple Computational Fluid Dynamics (CFD) with DEM, which allows for fully non-linear fluid solutions and is a very mature approach to model hydrodynamic problems [28].…”

“…An alternative approach is to couple Computational Fluid Dynamics (CFD) with DEM, which allows for fully non-linear fluid solutions and is one of the most mature approaches to model hydrodynamic problems [27]. CFD has been shown capable of simulating the motion of an ice floe in waves and has achieved good agreement with experiments when overwash occurs [28][29][30].…”

Launching of ships from horizontal berth by tipping tables – CFD simulation of wave generation

“…In this section, the numerical simulation setup and the numerical results are presented in detail. The goal of the simulation is to validate the Naval Hydro Pack [27,28,29,30,31,32,33,34,35], combined with the new overset fringe algorithm, on the sideways launching case. The primary validation item is the generated wave amplitude during the sideways launching where the numerical results are compared with the experimental data [11].…”

Fluid-structure interaction of a large ice sheet in waves

“…CFD has been widely applied to hydrodynamic problems (Jasak, 2017), e.g. using the open-source code, OpenFOAM (Jasak et al, 2007).…”