Rodrigo Cienfuegos

Wave-Breaking Model for Boussinesq-Type Equations Including Roller Effects in the Mass Conservation Equation

We investigate the ability of a 1D fully nonlinear Boussinesq model including breaking to reproduce surf zone waves in terms of wave height and nonlinear intraphase properties such as asymmetry and skewness. An alternative approach for wave-breaking parameterization including roller effects through diffusive-type terms on both, the mass conservation and momentum equations is developed and validated on regular wave and solitary wave experiments as an attempt to improve wave height and left-right asymmetry estimates. The new approach is able to reproduce wave height decay, and intraphase nonlinear properties within the entire surf zone of spilling breakers without requiring temporal evolution of model parameters.

The 1 April 2014 Pisagua tsunami: Observations and modeling

On 1 April 2014, an earthquake with moment magnitude Mw 8.2 occurred off the coast of northern Chile, generating a tsunami that prompted evacuation along the Chilean coast. Here tsunami characteristics are analyzed through a combination of field data and numerical modeling. Despite the earthquake magnitude, the tsunami was moderate, with a relatively uniform distribution of runup, which peaked at 4.6 m. This is explained by a concentrated maximal slip at intermediate depth on the megathrust, resulting in a rapid decay of tsunami energy. The tsunami temporal evolution varied, with locations showing sustained tsunami energy, while others showed increased tsunami energy at different times after the earthquake. These are the result of the interaction of long period standing oscillations and trapped edge wave activity controlled by inner shelf slopes. Understanding these processes is relevant for the region, which still posses a significant tsunamigenic potential.

Energy Dissipation and Turbulent Production in Weak Hydraulic Jumps

The present experimental investigation focuses on energy dissipation and turbulence production in two undeveloped and a partially developed inflow weak hydraulic jumps, measured with micro-ADVs. For the undeveloped inflow jumps, the turbulence production is mostly confined in the shear layer located in the upper part of the water column. For the partially developed inflow jump, two peak turbulence production regions are observed, one in the upper shear layer and the second in the near-wall region. Moreover, the measured energy dissipation distribution in the jumps reveals a similar longitudinal decay of energy dissipation integrated over the flow sections and of maximum turbulence production values from the intermediate jump region toward its downstream section.

Video monitoring and field measurements of a rapidly evolving coastal system: the river mouth and sand spit of the Mataquito River in Chile

ABSTRACT Cienfuegos R., Villagran M. ,Aguilera J.C., Catalán P., Castelle B., Almar R,, 2014. Video monitoring and field measurements of a rapidly evolving coastal system: the river mouth and sand spit of the Mataquito River in Chile. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 639–644, ISSN 0749-0208. The understanding of morphological processes controlling the evolution of sand spit reformation after a tsunami impact is a challenging and interesting topic, especially in highly energetic and micro tidal environments. A field campaign performed during December 2012 at the Mataquito River mouth in Chile, allowed us to simultaneously monitor topo-bathymetry evolution, wave climate, tidal range, swash zone dynamics and upper beach face evolution over a portion of its sand spit. A video system was set up for a continuous and long-term monitoring of the evolution of the river mouth and sand spit. Primarily, in this work we focus on the application of a video-derived shoreline detection method to assess shoreline evolution and beach cusps migration at hourly scales. We test the method performance on short-term episodic migration of beach cusps recorded during the campaign. Beach face variations at a daily scale were observed, which can be attributed to the migration of beach cusps in the alongshore direction, and linked to wave forcing and alongshore sediment transport.

Perspectives on the Long-Term Equilibrium of a Wave Dominated Coastal Zone Affected by Tsunamis: The Case of Central Chile

ABSTRACT Catalán, P.A.; Cienfuegos, R., and Villagrán, M., 2014. Perspectives on the long-term equilibrium of a wave dominated coastal zone affected by tsunamis: The case of Central Chile. The capability to predict the long term evolution of coastal state parameters can be severely affected by neglecting major geomorphic forcings. Among these, the effect of tsunamis as been largely neglected along the Chilean coast. In this contribution, we present a qualitative and descriptive assessment of the sudden change induced by the tsunami on a coastal location in Central Chile, and the consequent recovery process. The latter is driven mostly by strong wave forcing, with a very fast recovery capactity. The necessity and consequences of including tsunamis in long term evaluations fo coastal morphology are briefly discussed.

Spatial evolution of turbulence characteristics in weak hydraulic jumps

This experimental investigation focuses on the turbulence features of weak hydraulic jumps in rectangular channels for two different approach flow lengths. The turbulent kinetic energy equation includes the turbulence production and dissipation terms, two advection and two turbulent transport terms and the pressure transport term, which could not be measured, however. For jumps with a limited approach flow length, the turbulence production is mostly confined to the shear layer, while for jumps with a longer approach flow length, an additional peak turbulence production region is observed at the near-wall region due to boundary layer separation. The turbulent energy is then transported by the mean flow both towards the free surface and into the downstream direction and is diffused by turbulent processes away from the energetic shear layer towards less energetic regions. Dissipation occurs mostly in the shear layer along the upstream portion of the jump and over most of the flow depth further downstream.

Data collection after the 2010 Maule earthquake in Chile

This article presents an overview of the different processes of data recollection and the analysis that took place during and after the emergency caused by the Mw 8.8 2010 Maule earthquake in central-south Chile. The article is not an exhaustive recollection of all of the processes and methodologies used; it rather points out some of the critical processes that took place with special emphasis in the earthquake characterization and building data. Although there are strong similarities in all of the different data recollection processes after the earthquake, the evidence shows that a rather disaggregate approach was used by the different stakeholders. Moreover, no common standards were implemented or used, and the resulting granularity and accuracy of the data was not comparable even for similar structures, which sometimes led to inadequate decisions. More centralized efforts were observed in resolving the emergency situations and getting the country back to normal operation, but the reconstruction process took different independent routes depending on several external factors and attitudes of individuals and communities. Several conclusions are presented that are lessons derived from this experience in dealing with a large amount of earthquake data. The most important being the true and immediate necessity of making all critical earthquake information available to anyone who seeks to study such data for a better understanding of the earthquake and its consequences. By looking at the information provided by all these data, we aim to finally improve seismic codes and engineering practice, which are important social goods.

Modeling Rapid Flood Propagation Over Natural Terrains Using a Well-Balanced Scheme

AbstractThe consequences of rapid and extreme flooding events, such as tsunamis, riverine flooding, and dam breaks show the necessity of developing efficient and accurate tools for studying these flow fields and devising appropriate mitigation plans for threatened sites. Two-dimensional simulations of these flows can provide information about the temporal evolution of water depth and velocities, but the accurate prediction of the arrival time of floods and the extent of inundated areas still poses a significant challenge for numerical models of rapid flows over rough and variable topographies. Careful numerical treatments are required to reproduce the sudden changes in velocities and water depths, evolving under strong nonlinear conditions that often lead to breaking waves or bores. In addition, new controlled experiments of flood propagation in complex geometries are also needed to provide data for testing the models and evaluating their performance in more realistic conditions. This work implements a ro...

On the use of the Radon transform to estimate longshore currents from video imagery

ABSTRACT Larnier, S., Almar, R., Cienfuegos, R., Lejay, A., 2014. On the use of the Radon transform to estimate longshore currents from video imagery. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 023–028, ISSN 0749-0208. In nearshore applications, the estimation of longshore currents is of primary importance since it controls the alongshore sediment transport and coastal evolution. Direct estimation of longshore currents using in-situ instruments is difficult and costly, especially under highly energetic wave climates. Low cost remote sensing systems based on video observations constitute a promising alternative when the drifting sea foam left after the passage of breaking waves is visible. In this paper we describe a method based on longshore timestacks that necessitates less data than approaches using the full video frames. Our approach uses the Radon transform applied on the time series derived from timestacks to produce an estimate of the longshore component of nearshore surface currents detected from the foam signature in video images. The Radon transform can be used to separate the wave crests from the drifting foam part. The identification of the longshore drift is enhanced with both a temporal and a spatial filters. The corresponding sinogram from the Radon transform is computed in order to find the angle of the alongshore drifting that is further converted into the longshore component of the surface currents. For the estimation of longshore currents, our approach is first tested using synthetic timestack examples created using anisotropic Gaussian random current fields. Comparisons between estimates derived by our algorithm and manual operator detection from videos are performed showing good agreement. These videos come from a field campaign conducted in the Mataquito River mouth area in the Maule region (Chile). Field test comparisons were also made against in situ current meter from the 2008 Truc Vert experiment in Aquitaine (France). It was taking place during an energetic event.

NONLINEAR SURF ZONE WAVE PROPERTIES AS ESTIMATED FROM BOUSSINESQ MODELLING: RANDOM WAVES AND COMPLEX BATHYMETRIES

The present work aims at investigating the ability of Boussinesq-type equations and breaking-wave parameterizations to reproduce nonlinear properties of surf zone waves. We compare results produced by two different breaking models : those proposed by Kennedy et al. (2000) and by Cienfuegos et al. (2005). Both breaking strategies are implemented in a fully nonlinear and weakly dispersive Boussinesq code (Cienfuegos et al., 2006a,b). In the first part we calibrate model parameters on the spilling regular wave experiment conducted by Ting and Kirby (1994). In the 2nd part, we apply the breaking Boussinesq models on a new laboratory experiment on random waves propagating over uneven bathymetries.