Computing Retardation Function from Radiation Coefficients

Calculation of retardation function and infinite-frequency added mass using frequency domain coefficients using Ogilvie’s formulae.

function [K, Ainf]=radiation_IRF(w, A, B, T)% 
% Inputs :
% - w   : Frequency vector
% - A   : Added mass coefficient
% - B   : Damping coefficient
% - T   : Time vector
%
% Outputs :
% - K   : Retardation function K
% - Ainf : Added mass at infinite frequency
%

nt=length(T);
T=reshape(T,[nt,1]);
nw=length(w);
K=zeros(nt,1);
for k = 1:nt;
    K(k) = (2/pi)*trapz(w,B.*(cos(w*T(k))));
end
CM=zeros(nw,1);
Ainf=0;
for k=1:nw
    CM(k) = trapz(T,K.*sin(w(k)*T));
    CM(k)=A(k)+CM(k)/w(k);
    Ainf=Ainf+CM(k);
end;
Ainf=Ainf/nw;



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