Although South African ports are sheltered from swell waves, three of them – Cape Town, Ngqura and Saldanha – can and do experience what are called infra-gravity waves. These are a category of gravity waves, which are waves travelling along the surface of the sea (where it interfaced with the atmosphere, technically another ‘fluid’) and whose dynamics are dominated by the effects of gravity. Infra-gravity waves are distinguished by having periods of greater than 30 seconds. Researchers at the Council for Scientific and Industrial Research’s (CSIR’s) Coastal and Hydraulics Laboratory, in Stellenbosch, in the Western Cape province, also referred to infra-gravity waves as ‘long waves’. These waves, CSIR senior technologist Chris Troch explained, could create resonance in the waters of harbour basins. In turn, this resonance could cause severe ship motions (in moored vessels), which disrupted the loading and unloading of cargo. Read More Engineering News | Home