Recent developments in surface technology and the effect on roughness and drag
Candries, M. (1998). Recent developments in surface technology and the effect on roughness and drag. Ir Thesis. Universiteit Gent. Vakgroep Mechanische Constructie en Productie. Afdeling Maritieme Techniek: Gent. 96 pp.
Two different developments in surface technology are reviewed and investigated: the introduction of new antifouling paint types and advances made in the study of drag reduction methods. The problem of fouling is considered. Whereas macrofouling is largely presented, no paint system to date is able and likely to prevent the colonisation of a surface by micro-organisms. The rate and strength of adhesion of micro-organisms depends on the substrate's characteristics and has important consequences in the formulation of new paint systems. The introduction of new paint systems is hastened by legislative decisions to ban organotin containing paints. One completely different approach is to try to prevent the attachment of fouling organisms altogether instead of getting rid of settled organisms by the use of toxins. This concept leads to non-stick or foul-release coatings. The general increase in roughness and drag caused by the application of paint is considered and to investigate the effects of the chemically fundamentally different surface characteristics or non-stick coatings, flat plane towing experiments have been set up. A systematic and critical overview of different methods that modify or alter the properties of a surface in order to reduce drag, with an emphasis on skin friction drag, is presented on the basis of their suitability for marine applications. A conclusive evaluation in terms of techno-economic feasibility has not been made; some methods have great potential (e.g. polymer additives, air injection) but seem less applicable than others with smaller potential (e.g. riblets, compliant coatings), while other techniques are still in an early stage of development (e.g. EMTC) and it may well be that a combination of techniques will be most successful. However, one important conclusion is that biofouling is one of the greatest barriers to the application of a lasting combination of drag reduction techniques and a system with antifouling properties, presumably by integration with paint technology, therefore has to be sought.
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