A New Approach to Estimate Directional Spreading Parameters of a Cosine-2s Model

Shaosong Zhang Ocean Engineering Program, Civil Engineering Department, Texas A&M University, College Station, Texas

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Jun Zhang Ocean Engineering Program, Civil Engineering Department, Texas A&M University, College Station, Texas

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Abstract

For accurate and consistent estimates of the directional spreading parameter and mean wave direction of directional seas based on a cosine-2s directional spreading model, a new approach is proposed, employing a maximum likelihood method (MLM) to estimate the directional spreading function and then the angular Fourier coefficients. Because an MLM is more tolerant of errors in the estimated cross-spectrum than a directional Fourier transfer used in the conventional approach, the proposed approach is able to estimate the directional spreading parameter more accurately and consistently, which is examined and confirmed by applying the proposed approach and conventional approach, respectively, to the time series generated by numerical simulation and recorded in field measurements.

Corresponding author address: Dr. Jun Zhang, Ocean Engineering Program, Dept. of Civil Engineering, Texas A&M University, College Station, TX 77843-3136. Email: jun-zhang@tamu.edu

Abstract

For accurate and consistent estimates of the directional spreading parameter and mean wave direction of directional seas based on a cosine-2s directional spreading model, a new approach is proposed, employing a maximum likelihood method (MLM) to estimate the directional spreading function and then the angular Fourier coefficients. Because an MLM is more tolerant of errors in the estimated cross-spectrum than a directional Fourier transfer used in the conventional approach, the proposed approach is able to estimate the directional spreading parameter more accurately and consistently, which is examined and confirmed by applying the proposed approach and conventional approach, respectively, to the time series generated by numerical simulation and recorded in field measurements.

Corresponding author address: Dr. Jun Zhang, Ocean Engineering Program, Dept. of Civil Engineering, Texas A&M University, College Station, TX 77843-3136. Email: jun-zhang@tamu.edu

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