Wind waves in the vicinity of Cape Town, South Africa, were measured by means of an N.I.O. (England) ship-borne wave recorder, in water depths varying from 12 - 140 metres. One dimensional frequency spectra were computed from the records, by power spectrum analysis, based on the method of Blackman and Tukey, using an I.B.M. 1130 Computer. Assumptions of normality and stationarity were tested. The Gaussian assumption of the waves was found to be acceptable for the waters off Cape Town. At the 5% critical level, using the chi-square test, 3 out of 23 records tested were found to be non-Gaussian. No significant difference between the Gaussian properties of the deep and the shallow stations was found. Tests for stationarity applied to 3 selected records showed 1 record as clearly non-stationary. However, this recording was obtained under fluctuating wind conditions. Comparison of the total variances of the power spectra obtained in shoaling water showed a systematic decrease of variance with depth. Normalised spectra did not show a systematic selective attenuation of the variances with frequency. Factors which might have caused the systematic reduction of the total variances with depth have been examined. The bottom friction factor for this coast was estimated. The mean value of the bottom friction is 0.22. This is higher than found by other workers.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/18125 |
| Date | January 1970 |
| Creators | Van Ieperen, Maarten Pieter |
| Contributors | Harris, T F W |
| Publisher | University of Cape Town, Faculty of Science, Department of Oceanography |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MSc |
| Format | application/pdf |
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