Maritime

FLOW-3D maritime

Modeling Moving Objects

FAVORTM is a unique, cartesian fixed-mesh method for handling geometry. This method allows for moving object dynamics to be modeled without the need for a moving/deforming mesh, reducing simulation runtimes while maintaining accuracy. The moving objects model gives the user the flexibility of tracking vessel motion using either an explicit or an implicit method. FLOW-3D‘s Immersed Boundary Method allows for highly accurate predictions of forces on fixed and moving objects. This simulation shows the complex, fully-coupled motion of an LNG tanker moving in waves. 

Mooring Lines, Springs & Ropes

Special objects in FLOW-3D (such as mooring lines and springs) when attached to other moving objects, allow engineers to accurately capture vessel dynamics during ship launches, floating barrier dynamics, buoys, wave energy converters, etc. In this ship launch example, a ship slides down a slipway and into the water. The motion of the ship is constrained by mooring lines, which prevents it from floating off downstream. Simulation courtesy of Eastern Shipbuilding.

Welding

With the addition of FLOW-3D WELD, welders in the shipbuilding industry can minimize welding defects such as porosity, significantly increasing the quality of their hulls while optimizing production times.

Offshore Structures

Loads on marine offshore structures are largely determined by the detail of wave structure interactions in random sea states. FLOW-3D allows users to model non-linear interactions between floating structures under a variety of wave types and sea spectra, including JONSWAP, Pierson Moskowitz, and custom wave energy profiles.  FLOW-3D provides green water (water on deck) presence analysis, impact loads, and fully non-linear wave propagation analysis, as well and structure response in wave – structure – mooring systems. In addition to fixed pile structures, FLOW-3D can be used to simulate the forces on floating structures, such as the dock shown here. The movement of the dock is stabilized using the mooring lines model, and the dynamics of the dock as a result of a steadily increasing water level can be seen in this video.

Simulating Wave Impacts on Offshore Platforms

The calm-water air gap under offshore platform decks is a critical design parameter and is determined by the required minimum air gap in extreme design conditions. FLOW-3D can be used to effectively in the prediction of air gap and wave impact loads on offshore platforms, tension leg platforms and semi-submersibles. By modeling problems at full scale in the numerical environment, FLOW-3D allows engineers to by-pass the often delicate scaling issues associated with reduced-scale model physical basin testing.

Planing Hulls & Ship Motion

Flow around the hulls of ships is an important focus for naval architects. Many aspects of the flow past the hull need to be examined, including the resistance (drag), stern boundary layer, streamwise vortices, and velocity field at the propeller plane. FLOW-3D‘s Moving Objects Model allows naval architects to model the behavior of hulls in displacement, semi planing or planing regimes, as well as the transients of hulls accelerating onto the plane. FLOW-3D‘s natural strengths modeling free surfaces allows engineers to accurately predict the pressure field acting on a hull even in large amplitude wave or high speed regimes, where slamming forces too can be evaluated.

The hydro-dynamic response of a planing hull is analyzed in three distinct regimes that are demonstrated in this series of simulations. The first simulation shows the ‘rise to the plane’ stage during which the motor yacht accelerates until the hydrodynamic forcing is sufficient to effectively lift the yacht above the water. The second simulation shows the yacht cruising on flat water at 40 knots, and the third simulation shows the response of yacht at high speeds with an incoming wave field.

Sloshing & Slamming

The accelerations and loads induced by internal sloshing motions on global seagoing vessels such as LNG carriers are an important factor in safety design of such vessels. Ships can experience significant internal forcing due to such wave sloshing dynamics, where cargo tanks may experience additional loads on their containment system and supporting structures. FLOW-3D‘s non-inertial reference frame model allows complex motion parameters to be prescribed in order to accurately track fluid motion in a container. FLOW-3D accurately predicts liquid cargo and propellant motion in fuel tanks. Slamming analysis as well as “green water” (water covering the deck as a result of wave spray or hull over-topping) is a common application of FLOW-3D where FLOW-3D‘s TruVOF approach to these problems provides unique capabilities for engineers in the maritime engineering industry.

This simulation shows the complex, fully-coupled motion of an LNG tanker moving in waves, as captured by FLOW-3D. The sloshing of fluid in the tanks affects the dynamics of the vessel, which contains bilge keels and a bulbous bow to help it maintain stability in incident waves. Notice also that the fluid sloshing in the tanks has a phase shift from the motion of the ship, as expected. The moving object model, the density evaluation model and the wave generation boundary conditions in FLOW-3D can assist maritime engineers in analyzing similar problems.

Maritime Case Studies

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