Time-domain Green functions for diffuse light in two adjoining turbid half-spaces

2007 ◽  
Vol 46 (10) ◽  
pp. 1641 ◽  
Author(s):  
Margarita L. Shendeleva
Keyword(s):  
Time Domain ◽  
Green Functions ◽  
Diffuse Light

Development of a Time Domain Boundary Element Method for the Seakeeping Behavior of a Cruise Ship Under Combined Strong Wind and Extreme Irregular Beam Seas

2014 ◽  
Author(s):  
G. D. Gkikas ◽  
F. van Walree
Keyword(s):  
Free Surface ◽  
Time Domain ◽  
Model Tests ◽  
The Body ◽  
Computational Method ◽  
Green Functions ◽  
Strong Wind ◽  
Cruise Ship ◽  
Time Step ◽  
Beam Seas

A computational method for the seakeeping behavior of a cruise ship at zero speed and under severe wind and oblique wave loads is presented. The proposed methodology is a time-domain panel method where the transient Green functions used for the estimation and implementation of the free surface effects on the vessel’s motions are estimated assuming constant low lateral speed, instead of the common practice zero speed influence functions. For the evaluation of the overall hydrodynamic forces, the so called “blended approach” is followed in the sense that the induced hydrodynamic pressures due to the scattering and radiation phenomena are calculated over the linearized position of the body, ignoring any displacements with respect to its mean position, while the hydrostatic and non-linear Froude-Krylov forces are considered at the actual body location and taking into account the free surface elevation at each time step. For the validation of the proposed methodology, heave and roll motions, the drift velocity as well as lateral accelerations of the vessel were investigated for two cases of severe beam seas combined with a constant strong wind load and the results were compared against experimental model tests. The model tests were performed to investigate the vessel’s behavior under extreme weather conditions. The low lateral speed Green functions were estimated for a speed similar to the one that the vessel was expected to drift, an estimation based on the model tests, as well as for the case where the input speed corresponded to the half of the expected speed. Good agreement was presented for both cases, showing that accurate and computationally efficient numerical simulations of the vessel’s motions under severe wind and wave excitations can be obtained by using low lateral speed transient Green functions.

An Efficient Time-Frequency Domain Solution Procedure for the Analysis of Offshore System

2011 ◽  
Author(s):  
F. N. Correˆa ◽  
B. P. Jacob
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Added Mass ◽  
Solution Procedure ◽  
Green Functions ◽  
Time Frequency ◽  
Green Approach ◽  
Linear Behaviour ◽  
Approach Method ◽  
External Loads

This work presents a formulation review of a hybrid time-frequency domain Green approach method (HTF-GA) for the solution of offshore systems. A step-by-step time domain solution procedure is established, based on the convolution between the Green functions of the problem and the vector of external loads. The Green functions are implicitly calculated in the frequency-domain. The accuracy is significantly improved when compared with traditional direct integration methods, or with other methods based on the Green approach. This method is able to deal with non-linear behaviour and implicity consider the frequency dependence of added mass and potential damping, encountered in offshore systems problems.

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