RESPONSE STATISTICS CALCULATION FORMULA FOR IRREGULAR WAVE SPECTRUM

RESPONSE  STATISTICS

ØAverage height of the response (doubled amplitude)  , R_avg=2.5√(m_0 )

ØMaximum Height of the response, R_max=7.44√(m_0 )

ØRoot mean Square height of the response, R_rms=2√(2m_0 ) 

ØSignificant height of the response, R_s=4√(m_0 ) 

 

**where m0 is the area under the spectrum. 

MATLAB SCRIPT TO CHANGE TIME TO FREQUENCY DOMAIN

JUST COPY AND PASTE THE BELOW CODE


clc
clear all
close all

HS=5;
pcf=0.3;
cf1=0.1;
cf2=1.5;
n=100;

t=0:1:2000;

dt=t(2)-t(1);
dcf=(cf2-cf1)/(n-1);
omega=cf1:dcf:cf2;
nomega=length(omega);
cc=(5/16)*(HS^2);
sdeta=(cc)*((pcf^4)*(omega.^-5)).*(exp(-1.25*((pcf^4)*(omega.^-4))));

figure
plot(omega,sdeta,'k');
xlabel('\omega (rad/sec)')
ylabel('S_\eta_\eta (m^2sec)')
grid on


pheta=rand(nomega,1)*2*pi;
df=omega(2)-omega(1);
ns=length(sdeta);
w=omega;
tl=length(t);

for i=1:tl
    x1(i)=0;
    for j=1:n
         a1(j)=sqrt(2*sdeta(j)*df);
         x1(i)=x1(i)+a1(j)*cos(-w(j)*(t(i))+pheta(j));

    end
end

figure
plot(t,x1,'k')
xlabel('t (sec)')
ylabel('\eta (m)')
grid on

HYDRODYNAMIC ANALYSIS (RAO) OF SPAR PLATFORM IN ANSYS AQWA