Head-on collision of two solitary waves and residual falling jet formation

The head-on collision of two equal and two unequal steep solitary waves is investigated numerically. The former case is equivalent to the reflection of one solitary wave by a vertical wall when viscosity is neglected. We have performed a series of numerical simulations based on a Boundary Integral Equation Method (BIEM) on finite depth to investigate during the collision the maximum runup, phase shift, wall residence time and acceleration field for arbitrary values of the non-linearity parameter a/h, where a is the amplitude of initial solitary waves and h the constant water depth. The initial solitary waves are calculated numerically from the fully nonlinear equations. The present work extends previous results on the runup and wall residence time calculation to the collision of very steep counter propagating solitary waves. Furthermore, a new phenomenon corresponding to the occurrence of a residual jet is found for wave amplitudes larger than a threshold value

Finite element modelling of heat transfer in avocados

Un modèle basé sur la méthode des éléments finis à deux dimensions a été développé pour prédire les distributions de température à l'intérieur d'avocats soumis à une préréfrigération à l'air. Ce modèle, conçu pour les fruits de forme assymétrique, prend en compte la chaleur due à la respiration, l'évaporation lors de la réfrigération due à la transpiration ainsi que la convection et les transferts de radiations à la surface des fruits. Ce modèle a été ensuite appliqué à des échantillons d'avocats en test de réfrigération, afin d'estimer le coefficient de convection à partir de données expérimentales (mesures de température à deux niveaux de localisation à l'intérieur du fruit). Un procédé d'optimisation basé sur la minimisation des différences entre les températures expérimentales et les températures calculées a été utilisé. Les coefficients de convection moyens obtenus pour les deux variétés (Fuerte, Hass) n'ont pas été trouvées significativement différentes (P=0.05). Les valeurs obtenues par l'utilisation du modéle des éléments finis ont été plus faibles que celles mesurées par une méthode analytique impliquant un modéle en aluminium en forme d'avoca

An experimental study of steep solitary wave reflection at a vertical wall

Until now very few experimental investigations have been conducted to study the reflection of steep solitary waves at a vertical wall whereas many theoretical analysis and numerical simulations were developed in the past. Theuse of experimental techniques to capture the waveform and associate phenomena during the short-time head-on collision of two solitary waves (or the reflection of a solitary wave by a vertical wall) is not an easy task. Solitary waves with amplitude a/h ≤ 0.556 are experimentally generated by a piston type wavemaker. We have used a high speed camera and our experimental results were compared with previous studies, including both theoretical investigations and numerical simulations. We found that previous theoretical results underestimate wave run-up characteristics (maximal run-up amplitude, attachment and detachment times, wall residence time), except the third-order result of Su & Mirie [1] who calculated maximal run-up which is in good agreement with experiments. Within the range of solitary wave amplitude considered experimentally, present measurements are in excellent agreement with numerical results of Cooker et al [2] and Chambarel et al [3]. Furthermore, for very steep solitary waves we found numerically the occurrence of a Rayleigh-Taylor instability on the top of the jet due the collision.A theoretical explanation of the existence of this instability is given

Optimisation de méthodes diélectriques pour l'hydrologie

National audienc

Peregrine's system revisited

43 pages, 91 references, 15 figures, 2 tables. Other author's papers can be downloaded at http://www.denys-dutykh.com/International audiencePeregrine's system revisited arXiv.org / halIn 1967 D. H. Peregrine proposed a Boussinesq-type model for long waves in shallow waters of varying depth. This prominent paper turned a new leaf in coastal hydrodynamics along with contributions by F. Serre, A. E. Green & P. M. Naghdi and many others since then. Several modern Boussinesq-type systems stem from these pioneering works. In the present work we revise the long wave model traditionally referred to as the Peregrine system. Namely, we propose a modification of the governing equations which is asymptotically similar to the initial model for weakly nonlinear waves, while preserving an additional symmetry of the complete water wave problem. This modification procedure is called the invariantization. We show that the improved system has well conditioned dispersive terms in the swash zone, hence allowing for efficient and stable run-up computations