NON LINEAR WAVES AND MORISON TYPE LOADING ON COASTAL STRUCTURES

Ένα μη γραμμικό μοντέλο διασπειρόμενων κυματισμών αναπτύσεται και εφαρμόζεται για τον υπολογισμό των υδροδυναμικών φορτίσεων των βυθισμένων παράκτιων κυλινδρικών κατασκευών. Το μοντέλο βασίζεται σε μία αναλυτική λύση της εξίσωσης Laplace και έχει τη μορφή των εξισώσεων Boussinesq. Η πρόβλεψη της οριζόντιας δύναμης, που υπολογίζεται με τη βοήθεια της εξίσωσης Μοrisοn, συγκρίνεται με πειραματικά δεδομένα και αναλυτικές λύσεις της μη γραμμικής θεωρίας κυματισμών. Επίσης εξετάζεται και η εφαρμογή της παραπάνω εξίσωσης στην περίπτωση φορτίσεων μεγάλων κυλίνδρων όπου θεωρητικά δεν ισχύει γιατί δεν περιγράφει τα αποτελέσματα της περίθλασης.A non linear dispersive wave model is developed and applied for the calculation ol hydrodynamic forces on circular cylinders. The model is based on an analytical solution of the Laplace equation and has the form of the Boussinesq equations. The prediction of the horizontal force, calculated from Morison equation, is compared with experimental data and analytical solutions oi non linear wave theory. The application of the above equation for large cylinders is also examined outside its theoretical range ot valisity where the diflraction eflects are significant

Nonlinear wave energy modelling in the surf zone

International audienceBreaking wave energy in the surf zone is modelled through the incorporation of the time dependent energy balance equation in a non linear dispersive wave propagation model. The energy equations solved simultaneously with the momentum and continuity equation. Turbulence effects and the non uniform horizontal velocity distribution due to breaking is introduced in both the energy and momentum equations. The dissipation term is a function of the velocity defect derived from a turbulent analysis. The resulting system predicts both wave characteristics (surface elevation and velocity) and the energy distribution inside surf zone. The model is validated against experimental data and analytical expressions

WAVE DYNAMICS IN THE ASSESSMENT OF IMPACT OF COASTAL WORKS ON COASTAL MORPHOLOGY

Η εργασία αυτή περιγράφει τη σύνθετη εφαρμογή υδροδυναμικών μαθηματικών μοντέλων για το σχεδιασμό των παράκτιων τεχνικών έργων και την εκτίμηση των επιπτώσεων τους στη μορφολογία ακτών. Παρουσιάζονται δύο κατηγορίες μοντέλων που έχουν τη δυνατότητα της προσομοίωσης των φαινομένων της γένεσης, ανάπτυξης και της διάδοσης των κυματισμών στη παράκτια ζώνη καθώς και της διάβρωσης και πρόσχωσης του θαλάσσιου πυθμένα. Τα μοντέλα αυτά εφαρμόζονται στην περίπτωση σχεδιαμού και μελέτης μιας σειράς εγκαρσίων στην ακτή βραχιόνων.This paper describes the application of computer hydrodynamic mathematical models tor the design of coastal works and their impact assessment in coastal morphology. Two types of models are presented, capable of simulating the growth, development and propagation oi waves in the coastal zone as well as the erosion and accretion of the sea bottom. These models are applied to a case study concerning a series ot jetties perpendicular to the coast

Resonant response of harbours to short-wave groups

A non-linear short-wave propagation model is used for the simulation of low-frequency waves induced by short-wave groups. The model is based on the higher order Boussinesq-type equations for the propagation of breaking and non-breaking waves in nearshore areas. The 2DH (two horizontal dimensions) Boussinesq model is used to calculate the resonant response of harbours due to bound waves generated by short-wave groups. The results are compared with experimental data available in the literature. In these experiments, bound long waves are generated by carrier bichromatic short waves, which form regular wave groups. The results of the model were found to be in good agreement with the experimental data. The 1DH Boussinesq model is applied in the surf zone to simulate surf beat generation by a time-varying breakpoint and the reflected long wave induced by bichromatic wave groups. A new breaking criterion is introduced, based on the relative trough Froude number. Model generation of the surf beat is also shown to be in good agreement with experimental data. </jats:p