Benchmark Study of Numerical Approaches for Wave-Current Interaction Problem of Offshore Floaters

2016 ◽  
Author(s):  
Zhiyuan Pan ◽  
Torgeir Vada ◽  
Styrk Finne ◽  
Arne Nestegård ◽  
Jan Roger Hoff ◽  
...  
Keyword(s):  
Free Surface Elevation ◽  
Benchmark Study ◽  
Validity Range ◽  
Current Interaction ◽  
Numerical Performance ◽  
Wave Drift Forces ◽  
Interaction Problem ◽  
A Current ◽  
Drift Forces ◽  
Numerical Approaches

The influence from a current on the relative motions and wave drift forces for moored floater can be quite significant. In this paper, a benchmark study is carried out for three programs, MULDIF, WADAM and WASIM, with the focus on their capability on handling the wave-current interaction problem. A semi-submersible model Troll B and a tanker model KVLCC2 are used for this study. The motions, free surface elevation at specified off-body points and mean drift forces are calculated by the programs in different current or forward speed conditions. Analysis results are compared and discussed, with the aim to evaluate the numerical performance of each programs and their validity range in terms of current speed.

Simulation of Low Frequency Motions in Severe Seastates Accounting for Wave-Current Interaction Effects

2017 ◽  
Author(s):  
Babak Ommani ◽  
Nuno Fonseca ◽  
Carl Trygve Stansberg
Keyword(s):  
Test Data ◽  
Time Domain ◽  
Low Frequency ◽  
Interaction Effects ◽  
Force Coefficients ◽  
Wave Drift ◽  
Current Interaction ◽  
Drift Force ◽  
Wave Drift Forces ◽  
Drift Forces

Today’s industry practice assumes wave drift forces on floating structures can be computed from zero current wave drift force coefficients for the stationary floater, while simplified correction models introduce current effects and slow drift velocity effects. The paper presents an alternative approach which overcomes some of the limitations of today’s procedures. The method, to be applied together with a time domain solution of the low frequency motions, is based on pre-calculation of mean wave drift force coefficients for a range of current velocities. During the low frequency motions simulation, the wave drift forces induced by the irregular waves are computed from the mean drift coefficients corresponding to instantaneous relative velocity resulting from the current and the low frequency velocities. A simple interpolation model, based on a quasi-steady assumption, is applied to obtain the drift forces in time-domain. Since calculation of the wave drift forces on Semi-submersibles in severe sea states with fully consistent methods is out of reach, a semi-empirical model is applied to correct the potential flow wave drift force coefficients. This model takes into account viscous effects, that are important in high seastates, and wave-current interaction effects. The paper compares the wave drift forces and the related low frequency motions computed by the proposed method, with results applying “standard” methods and with model test data. The test data was obtained in the scope of the EXWAVE JIP, with model tests designed to investigate wave drift forces in severe seastates and assess the wave-current interaction effects.

scholarly journals A CANDIDATE FOR EXACT CONTINUUM DUAL THEORY FOR SCALAR QED3

1993 ◽  
Vol 08 (14) ◽  
pp. 1343-1355 ◽  
Author(s):  
A. KOVNER ◽  
P. KURZEPA ◽  
B. ROSENSTEIN
Keyword(s):  
Fixed Point ◽  
Higgs Model ◽  
Magnetic Vortex ◽  
Dual Theory ◽  
Scalar Theory ◽  
Massive Vector ◽  
Vortex Model ◽  
Current Interaction ◽  
Vector Theory ◽  
A Current

We discuss a possible exact equivalence of the Abelian Higgs model and a scalar theory of a magnetic vortex field in 2 + 1 dimensions. The vortex model has a current-current interaction and can be viewed as a strong coupling limit of a massive vector theory. The fixed point structure of the theory is discussed and mapped into fixed points of the Higgs model.

Time-Domain Hydrodynamic Model for Mooring Analysis of a Spread Moored Fpso With Calibration of Wave Drift Forces

2021 ◽  
Author(s):  
Min Zhang ◽  
Junrong Wang ◽  
Junfeng Du ◽  
Nuno Miguel Magalhaes Duque Da Fonseca ◽  
Galin Tahchiev ◽  
...  
Keyword(s):  
Time Domain ◽  
Hydrodynamic Model ◽  
Wave Drift ◽  
Wave Drift Forces ◽  
Drift Forces

Tow Forces for Emergency Towing of Containerships

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Vladimir Shigunov ◽  
Thomas E. Schellin
Keyword(s):  
Wave Height ◽  
Current Speed ◽  
Sea Waves ◽  
Wave Direction ◽  
Equilibrium Equations ◽  
Significant Wave ◽  
Wind Speeds ◽  
Time Average ◽  
Wave Drift Forces ◽  
Drift Forces

For a series of five containerships of differing capacities (707, 3400, 5300, 14,000, and 18,000 TEU), systematic computations were performed to estimate the tow force required in an emergency. Time-average ship positions with respect to the given waves, wind, and current directions and the corresponding time-average forces were considered. Current speed was considered to include also towing speed. Directionally aligned as well as not aligned wind and waves were investigated. Wave height, wind speed, and wave and wind direction relative to current direction were systematically varied. Wind speeds based on the Beaufort wind force scale corresponded to significant wave heights for a fully arisen sea. Waves were assumed to be irregular short-crested seaways described by a Joint North Sea Wave Observation Project (JONSWAP) spectrum with peak parameter 3.3 and cosine squared directional spreading. For each combination of current speed, wave direction, significant wave height, and peak wave period, the required tow force and the associated drift angle were calculated. Tow force calculations were based on the solution of equilibrium equations in the horizontal plane. A Reynolds-Averaged Navier–Stokes (RANS) solver obtained current and wind forces and moments; and a Rankine source-patch method, drift forces and moments in waves. Tow forces accounted for steady (calm-water) hydrodynamic forces and moments, constant wind forces and moments, and time-average wave drift forces and moments. Rudder and propeller forces and towline forces were neglected.

On Approximations of the Wave Drift Forces Acting on Semi-Submersible Platforms With Heave Plates

2016 ◽  
Author(s):  
Bernard Molin ◽  
Jean-Baptiste Lacaze
Keyword(s):  
Wave Field ◽  
Scattered Wave ◽  
Diffraction Radiation ◽  
Morison Equation ◽  
Wave Drift ◽  
Horizontal Wave ◽  
Heave Plate ◽  
Drift Force ◽  
Wave Drift Forces ◽  
Drift Forces

The horizontal wave drift force acting on a vertical floating column, without then with a heave plate, is considered. Computations are performed with a diffraction-radiation code and through the Morison and Rainey equations. Focus is on wave frequencies around the heave resonance where the drift force may be significant, even though the scattered wave-field being weak. It is found that the Morison equation overpredicts the drift force while Rainey equations perform rather well.

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