Hydrodynamics of High-Speed Marine Vehicles

Faltinsen, Odd M.

doi:10.1017/cbo9780511546068

Cited by 251 publications

(255 citation statements)

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“…A correction is also present in the added-mass and convolution-integral term of equation (1). Indeed, within linear theory, β(τ) is a six-component vector equal toξ while here it is in general different and estimated in time from the body-boundary condition…”

Section: The Numerical Methodsmentioning

confidence: 99%

Can the water on deck influence the parametric roll of a FPSO? A numerical and experimental investigation

Greco

Lugni

Faltinsen

2014

European Journal of Mechanics - B/Fluids

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Parametric roll and water on deck are investigated numerically and experimentally for a FPSO ship in head-sea regular waves in the zone of the first fundamental resonance. On the numerical side, a weakly-nonlinear potential seakeeping solver based on the weak-scatterer theory is coupled within a Domain-Decomposition (DD) strategy with a shallowwater approximation for water-shipping events and with a local analytical solution for bottom-slamming prediction.The comparison against the model tests confirmed the capability of the numerical method in predicting occurrence and features of parametric roll and water-on-deck phenomena. The solver has then been used to complement the physical analysis by examining the roll instability occurrence with a refined step of the calm-water roll natural frequency-toexcitation frequency ratio, ω 4n0 /ω, around to 0.5. It is confirmed that the water shipping features are qualitatively and quantitatively affected by the parametric roll: the flow onto the deck becomes asymmetric and the water-on-deck occurrence becomes periodic with the roll-natural period, the level of green-water induced pressures increases. In some cases water shipping is even directly induced by large roll. In return the green-water loads affect the parametric instability by changing (both increasing and decreasing) the duration of the transient phase. This has been measured in terms of the variation of the time, t max , required to reach the largest peak in the roll envelope before occurrence of steady-state conditions. The water on deck mostly increases the steady-state roll amplitude, ξ 4a , with an amount up to about seven degrees for the examined cases. Two scaling laws have been proposed for the variations of t max and ξ 4a involving a modified steepness ǫ = (2A − f )/λ, with A and λ the incident-wave amplitude and wavelength, respectively, and with f the ship mean freeboard. The scaling laws α1(δ1) and γ1(δ1) , with α1 = −(∆t max /T ) · ǫ, γ1 = −10∆ξ 4a · ǫ, δ1 = 100(ω 4n0 /ω) 2 · ǫ and T the incident-wave period, appeared to be more suitable in the region where water shipping is more relevant for parametric roll. They are well approximated by polynomial curves which could be useful to estimate the variations of t max and ξ 4a due to water shipping for incident-wave parameters different from those examined here.

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Section: The Numerical Methodsmentioning

confidence: 99%

Can the water on deck influence the parametric roll of a FPSO? A numerical and experimental investigation

Greco

Lugni

Faltinsen

2014

European Journal of Mechanics - B/Fluids

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“…where  is the vessel speed,  is the submerged vessel length, and  is the acceleration of gravity (Faltinsen, 2005). According to Fossen (2005), the stated 3 DOF model is only valid for   ≤ 03, which corresponds to a speed of only 225  for the USV under consideration.…”

Section: Modeling Considerationsmentioning

confidence: 99%

Straight-Line Target Tracking for Unmanned Surface Vehicles

Breivik¹,

Hovstein²,

Fossen³

2008

MIC

173

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This paper considers the subject of straight-line target tracking for unmanned surface vehicles (USVs). Target-tracking represents motion control scenarios where no information about the target behavior is known in advance, i.e., the path that the target traverses is not defined apriori. Specifically, this work presents the design of a motion control system which enables an underactuated USV to track a target that moves in a straight line at high speed. The motion control system employs a guidance principle originally developed for interceptor missiles, as well as a novel velocity controller inspired by maneuverability and agility concepts found in fighter aircraft literature. The performance of the suggested design is illustrated through full-scale USV experiments in the Trondheimsfjord.

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“…Therefore, the ventilated length is shortest along the keel. It increases with speed and is connected with the height of the keel in the flow attachment area above the keel , before the step [1].…”

Section: Introductionmentioning

confidence: 99%