Ochi Hubble Wave |
 
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Ochi Hubble Wave |
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Ochi and Hubble (1976) developed a six parameter wave spectrum model consisting of two parts, one for the lower frequency components of the wave energy and the other covering the higher frequency components. Each component is expressed in terms of three parameters and the total spectrum is written as a linear combination of the two. This means that double peaks present in a wave energy density can be modelled, representing for example a (low frequency) swell along with (high frequency) wind-generated waves. The spectrum represents almost all stages of development of a sea in a storm. The Ochi-Hubble spectrum is based on the following formulation:
(1)
where the modal frequency, w0j, is related to the periods (peak and mean zero up-crossing) by the following equation:
(2)
and:
•HS1 is the significant wave height for the lower frequency components
•TP1 is the peak period for the lower frequency components
•TZ1 is the mean zero up-crossing period for the lower frequency components
•λ1 is the shape factor for the lower frequency components
•HS2 is the significant wave height for the higher frequency components
•TP2 is the peak period for the higher frequency components
•TZ2 is the mean zero up-crossing period for the higher frequency components
•λ2 is the shape factor for the higher frequency components
•*WAVE-OCHI-HUBBLE is used to specify an Ochi-Hubble random sea wave spectrum or spectra.