Christos antoniadis
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LABORATORY INVESTIGATION ON GRAVEL AND MIXED BEACHES DURING AN OBLIQUE WAVE ATTACK Christos Antoniadis
JOURNAL OF COASTAL DEVELOPMENT Vol 16, No 1 (2012): Volume 16, Number 1, Year 2012
Publisher : JOURNAL OF COASTAL DEVELOPMENT

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Abstract

An experimental investigation into the behavior of gravel and mixed (sand and gravel) beaches was carried out at the 3-D Wave Basin located at Franzius-Institute (Marienwerder) of University of Hannover, at a nominal scale of 1:1. The experiment aimed to provide full scale measurements of cross-shore processes on gravel and mixed beaches, during an oblique wave attack, with uniform slope and a trench. Measurements included sediment transport, cross-shore beach profiles and wave-induced currents, for regular and random wave tests, for both types of beaches. Analysis of both cross-shore and long-shore currents shown interesting behaviour for both gravel and mixed beach, especially at the trench. There were morphological differences between the two types of beach concerning the crest and the step formation, the onshore sediment movement, and the erosion below the SWL, concluding the general difference of their mobility.
NEW MODIFIED EQUATION OF LONGSHORE CURRENT VELOCITY AT THE BREAKING POINT (FOR MIXED AND GRAVEL BEACHES) Christos Antoniadis
JOURNAL OF COASTAL DEVELOPMENT Vol 16, No 2 (2013): VOLUME 16, NUMBER 2, YEAR 2013
Publisher : JOURNAL OF COASTAL DEVELOPMENT

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Abstract

Wave breaking is the dominant process in the dynamics of nearshore water movements resulting in sediment transport. The transformation of the subsequent particle motion from irrotational to rotational motion generates vorticity and turbulence and this affects the sediment transport. An improved understanding of the location of the breaker point and characteristics of the wave under these changing parameters is essential to our understanding of short and long-term morphological beach development. This paper reports a series of 3-dimensional physical model tests to measure longshore current data, generated by oblique wave attack, along gravel and mixed beaches with a uniform slope and a trench. The studies described in this paper aim to improve the Longuet-Higgins’s formulae which predicted the longshore current velocity at the breaking point.
NEW EMPIRICAL FORMULAE OF UNDERTOW VELOCITY ON MIXED AND GRAVEL BEACHES Christos antoniadis
JOURNAL OF COASTAL DEVELOPMENT Vol 16, No 2 (2013): VOLUME 16, NUMBER 2, YEAR 2013
Publisher : JOURNAL OF COASTAL DEVELOPMENT

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Abstract

This paper reports a series of 3-dimensional physical model tests to measure cross-shore current data, generated by oblique wave attack, along gravel and mixed beaches with a uniform slope and a trench. Coastal managers and coastal engineers are beginning to give attention to gravel and mixed beaches due to the fact that they are two of the most effective natural sea defences.There is a need, from a scientific and coastal management perspective to have a deeper understanding of how gravel and mixed beaches operate.The studies described in this paper aim to investigate the behaviour of the undertow velocity on mixed and gravel beaches. Existing formulae have been used to predict the experimental results and new equations for predicting the undertow velocity under these conditions are proposed. The new empirical formulae predict time- and depth-averaged undertow and are based on a nonlinear regression of a modification of the Grasmeijer’s and Ruessink’s model where the zones where divided based on the related distance of the point of interest and the breaking point. Verification with large-scale experiments showed that the new formulae predicted well the undertow velocities on mixed and gravel beach with trench and uniform slope.