A.P.M. Vonk

Bio: A.P.M. Vonk is an academic researcher. The author has an hindex of 1, co-authored 2 publications receiving 3 citations.

A low-cost inshore wave direction indicator

Abstract: Although many attempts have been made in the past to measure the direction of propagation of ocean waves, a need for a simple, reliable solution to the problem has remained. The technique described here, intended for near-shore usage, makes use of a simple bottom-mounted flow direction indicator. The influence of rip and longshore currents on wave direction recordings is identified and a means of reducing these steady state current effects by a reduction in gauge sensitivity is presented, along with various possible recording and analysis techniques. Usefulness of the gauge is established as a simple engineering tool with certain limitations and examples are given of »'aire direction recordings related to meteorological data. A possible usage of the gauge FE an approximate sediment transport indicator is also proposed.

Gansbaai Fishing Harbour – The Design and Construction of a Breakwater on a Hostile Coast

Abstract: This paper describes the design and construction of a fishing harbour on a rocky coastline exposed to the prevailing south westerly swell of the South Atlantic and to severe westerly gales. Because of economic pressure the first phase of the development was undertaken without adequate knowledge of the wave regime or the topography of the sea-bed in the area and resulted in a virtually unusable harbour. The second phase of construction was therefore only embarked upon after extensive hydrographic surveys, wave recording and analyses, and probably the most exhaustive series of model tests ever undertaken for such a small project. These investigations and the good co-operation between research staff, engineers and contractors resulted in the elimination of most of the initial problems and the creation of a functional fishing harbour,

Design and Construction of Rubble Mound Breakwaters

Abstract: The principal function of a rubble mound breakwater is to protect a coastal area from excessive wave action. The dissipation of wave energy through absorbtion rather than reflection distinguishes rubble mound breakwaters from other types of fixed breakwater. A principal design objective is to determine the size and layout of the components of the cross-section. Designing and constructing a stable structure with acceptable energy absorbing characteristics continues to rely heavily on past experience and physical modelling. This paper outlines key design and construction issues, with particular regard to armour stability.

A proposal for wave energy conversion near cape town

Abstract: The South African wave energy program has been underway for several years and has included an analysis of the temporal and spatial distribution of wave energy along the full coast-line, determination of energy attenuation perpendicular to the coast-line at a site on the south western coast, and the development of a wave energy converter which is most suited to local conditions and requirements. The resource analysis has shown that the inshore power levels occurring along the south western coast are as promising as any elsewhere in the world. A bottom mounted, V-shaped wave energy conversion device driving an air turbine has been found to be most suited to prevailing conditions. The conversion characteristics of the device are presented, based on 1:100 scale three dimensional and 1:50 scale two dimensional model studies. Preliminary design studies of the proposed conversion system have underlined its potential viability as a cost effective supplementary source of power.