1MARINTEK
On the counting of maxima(short contribution)
Carl Trygve StansbergMARINTEK/CeSOS , Trondheim, Norway
CeSOS Workshop on Research Challenges in Probabilistic Load and Response Modelling,Trondheim, Norway, 24th March 2006
2MARINTEK
Consider a simplified quadratic model for slow-drift responses
y(t) = df HR(f) e j 2f t df0 N*(f-f0/2) N(f+f0/2)(i.e. a linearly filtered wave energy envelope)
HR(f) = {1/(C √[422 + (1-2)2])} e-j arctg[2/(1-)]
(linear oscillator)
(re: Stansberg (2000) – OMAE)
CeSOS Workshop on Research Challenges in Probabilistic Load and Response Modelling,Trondheim, Norway, 24th March 2006
3MARINTEK
CeSOS Workshop on Research Challenges in Probabilistic Load and Response Modelling,Trondheim, Norway, 24th March 2006
4MARINTEK
CeSOS Workshop on Research Challenges in Probabilistic Load and Response Modelling,Trondheim, Norway, 24th March 2006
5MARINTEK
CeSOS Workshop on Research Challenges in Probabilistic Load and Response Modelling,Trondheim, Norway, 24th March 2006
Number of slow-drift maxima in a given record N = Tduration / T:
T = ?
T = Tz T2?
May be OK for narrow-banded waves.Not necessarily OK for slow-drift maxima
Alternative:
N = Tduration /
where = correlation length of time signal, based on spectral bandwidth of response signal, e.g.:
6MARINTEK
CeSOS Workshop on Research Challenges in Probabilistic Load and Response Modelling,Trondheim, Norway, 24th March 2006
7MARINTEK
CeSOS Workshop on Research Challenges in Probabilistic Load and Response Modelling,Trondheim, Norway, 24th March 2006
8MARINTEK
CeSOS Workshop on Research Challenges in Probabilistic Load and Response Modelling,Trondheim, Norway, 24th March 2006
Correlatedmaxima
Reasonableagreement
”Hiddenmaxima”
9MARINTEK
CeSOS Workshop on Research Challenges in Probabilistic Load and Response Modelling,Trondheim, Norway, 24th March 2006
Number of slow-drift maxima in a given record N = Tduration / T:
T = ?
T = Tz T2?
May be OK for narrow-banded waves.Not necessarily OK for slow-drift maxima
Alternative:
N = Tduration /
where = correlation length of time signal, based on spectral bandwidth of response signal, e.g.:
