Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 30578
Time Domain and Frequency Domain Analyses of Measured Metocean Data for Malaysian Waters

Authors: Mohd Shahir Liew, Duong Vannak, Guo Zheng Yew


Data of wave height and wind speed were collected from three existing oil fields in South China Sea – offshore Peninsular Malaysia, Sarawak and Sabah regions. Extreme values and other significant data were employed for analysis. The data were recorded from 1999 until 2008. The results show that offshore structures are susceptible to unacceptable motions initiated by wind and waves with worst structural impacts caused by extreme wave heights. To protect offshore structures from damage, there is a need to quantify descriptive statistics and determine spectra envelope of wind speed and wave height, and to ascertain the frequency content of each spectrum for offshore structures in the South China Sea shallow waters using measured time series. The results indicate that the process is nonstationary; it is converted to stationary process by first differencing the time series. For descriptive statistical analysis, both wind speed and wave height have significant influence on the offshore structure during the northeast monsoon with high mean wind speed of 13.5195 knots ( = 6.3566 knots) and the high mean wave height of 2.3597 m ( = 0.8690 m). Through observation of the spectra, there is no clear dominant peak and the peaks fluctuate randomly. Each wind speed spectrum and wave height spectrum has its individual identifiable pattern. The wind speed spectrum tends to grow gradually at the lower frequency range and increasing till it doubles at the higher frequency range with the mean peak frequency range of 0.4104 Hz to 0.4721 Hz, while the wave height tends to grow drastically at the low frequency range, which then fluctuates and decreases slightly at the high frequency range with the mean peak frequency range of 0.2911 Hz to 0.3425 Hz.

Keywords: Wind, Offshore Engineering, wave, Time series, Descriptive statistics, Metocean, Autospectral Density Function

Digital Object Identifier (DOI):

Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 3246


[1] Toshio Atsut, Shoji Toma and Kawasaki, 1976, "Fatigue Design of an Offshore Structure", Offshore Technology Conference, Houston, Texas, 3-6 May 1976.
[2] Peter S. Tromans and Luc Vanderschuren, “Response based design of floaters”.
[3] Rizwan Sheikh, “Kebabangan Northern Hub - Metocean Design and Operation Criteria”, 2010.
[4] Datta, Bisuddhan, “Design lower shallow – water offshore platform cost”, Vol.87, No.22, 1989, pp: 85-88.
[5] Institute of Marine Engineering, Science & Technology, “METOCEAN Awareness Course”. 2011.
[6] Metocean, “The International Association of Oil & Gas producers (OGP)”
[7] Haring, J.B. Bole and R.A. Stacy, “Application of directional wind and wave statistics”.Techinp, “Wave and Wind Directionality – Applications to the design of structures”, 1982, pp.545-573.
[8] Chakrabati, S.K., “Hydrodynamics of Offshore Structures.” Computational Mechanics Publications, Southampton, Boston. 2011, pp.86-90, 105-127.
[9] Walter H.Michel, “Sea Spectra Revisited”. Marine Technology, vol.36, No.4, winter. “Applied Mechanics and Materials”, 1999, pp. 211-227.
[10] Georg Lindgren and Igor Rychlik, 1997, “The Relation between Wave Length and Wave Period Distributions in Random Gaussian Waves”. Proc. of the Seventh International Offshore and Polar Engineering Conference, Honolulu, USA, May 25-30, 1970.
[11] Donald G., “Childers, Probability and Random Processs using MATLAB with application to continuous and Discrete Time Systems”, 1997, pp. 208-218, 300-303, 236-237.
[12] M.J. Robets, “Correlation, Energy Spectral Density and Power Spectral Density”, Chapter 8, 2005.
[13] T. Veerarajan, “Probability, Statistics and Random Processes”, 2nd Edition, 2003, pp. 372-375.
[14] Patrick F. Dunn, “Autocorrelation”, 2005.
[15] Bowerman B.L., O’Connell R. “Forecasting and Time Series – an applied approach”, 3rd Edition, 1993, pp.436-450.
[16] Edmund M. Glaser and Daniel S. Ruchkin, “Power Spectra and Covariance Function”, Principle of Neurobiological Signal Analysis. Chp.3. 1976, pp. 113-176.
[17] N. Yahaya, “Offshore Structures: General Introduction”
[18] Paul C. Liu, “Normalized and Equilibrium Spectra of Wind Wave in Lake Michigan”, 1971.
[19] Bruce Ravel, “Normalization”, Center for Advanced Radiation Sources, 2008.
[20] Robert L. Burr, “Interpretation of Normalized Spectral Heart Rate Variability Indices in Sleep”, 2007.
[21] Bio-Rad Laboratories, Inc. Philadelphia, USA, “Search Strategies for IR Spectra – Normalization and Euclidean Distance vs. First Derivative Algoritm”, 2008.
[22] O.P. Torset and O.A. Olsen, “The need of direction for structure design”, Techinp “Wave and Wind Directionality – Applications to the design of structures”, 1982, pp.365-377.
[23] JetStream, "Origin of Wind", 2008.
[24] Teledyne RD Instruments, “Waves Primer: Wave Measurements and the RDI ADCP Waves Array Technique”.