Séminaire

Titre :	Mario Ricchiuto (INRIA Bordeaux, équipe CARDAMOM). Bore propagation in channels with sloping banks: physical, numerical and asymptotic modelling.
Contact :	Jean-François Fritsch
Date :	23/09/2021
Lieu :	14h30, visioconférence

Abstract: Experience shows that bore propagation in estuaries and human-made channels undergoes two transitions. One is related to the occurrence of wave breaking, with the appearance of a turbulent bore across the whole section. The second transition separates two different undulating bore regimes: a Low Froude Number (LFN) regime involving very long waves and low steepness, and a High Froude Number (HFN) one involving higher frequency steep dispersive propagation. The origin, and even the existence, of the LFN waves is not very well known nor understood. In this talk we will briefly recall the above setting with several examples, and focus on the analysis of the LFN-HFN undular bore transition. The physical characteristics of the two regimes defining it are discussed and then studied by different means. Firstly, we present simulations based on a weakly dispersive depth-averaged model. We will briefly recall the main features of the model, as well as provide a few details concerning the challenges related to its numerical approximation, and the choices made here. We then discuss the results obtained on the LFN-HFN transition. An ansatz on the physical origin of the low steepness waves observed in the LFN regime is then presented and verified using an ad-hoc asymptotic model providing an excellent approximation of the wavelength measurements.