ssc-367 - Ship Structure Committee

T: v.
Visually Observed Period, or Mean Period, or Apparent
Period
The visually observed period is the centroid of the S(u) spectrum.
The International Ship Structures Congress (ISSC) and some
environmental reporting agencies have adopted Tv as the period
visually estimated by observers.
Tv = 2~*(mo/m2) 4
Tz :
Average Zero-uncrossing period or Average Period
The average zero-uncrossing period is the average period between
successive zero up-crossings. The average period may be obtained
from a wave record with reasonable accuracy.
Tz
= 2n*(mo/mz) 4
Tc :
Crest Period
The crest period is the average period between successive crests.
The crest period may be taken from a wave record, but its accuracy is
dependent upon the resolution of the wave measurement and recording
equipment and the sampling rate.
Tc
= 2~*(mz/mq) %
T5:
Significant
Period
The significantperiod is the average period of the highest one-third
of the waves. Some environmental reporting agencies give the sea
characteristicsusing Ts and Hs, the significant wave height. There
are two equations relating Ts to Tp.
Ts = 0.8568*TP, Old
A-8