Enrique Peña

Estimation of Drag Coefficient and Settling Velocity of the Cockle Cerastoderma edule Using Particle Image Velocimetry (PIV)

Abstract This paper presents the results of a hydrodynamic study of a cockle population from the Ullas estuary in Galicia (Spain). An analysis of the parameters has made it possible to determine the hydraulic characteristics of whole cockles during their threshold of movement and suspension. Dynamic analysis of the forces exerted on the submerged cockles led to a detailed characterization of a final population of 11 cockles, including their characteristic dimensions in addition to shell and body density. The friction angle between the existing sediment in the Ullas estuary and the cockle shells was also recorded. The particle image velocimetry (PIV) laser technique was successfully applied to obtain an accurate calculation of the threshold velocity fields. This experimental tool provides the means to experiment with various approaches of the velocity governing the onset of motion and to obtain a more detailed definition of the parameters involved. Applying the PIV technique, three drag entrainment coefficients were obtained with different velocity profiles. Using the depth-averaged velocity profile, a constant entrainment drag coefficient value of 0.43 was obtained for this cockle family, whereas the use of the upper tangential velocity on the cockle resulted in a value of 0.56 with a wider range of variation. This velocity may be considered a more intrinsic parameter of the movement of the cockle. The process of cockle sedimentation was also monitored, enabling us to ascertain the settling velocity and to calculate the settling drag coefficient. Both parameters present constant values in the group of cockles analyzed, with mean values of 0.36 m s−1 and 1.08, respectively. The settling drag coefficient was also calculated. A comparison of these two experimental values with other existing reports exhibited similar results, thus validating both the procedures used and the effect of the shape factor on the settling drag coefficient value.

Two-layer exchange flows over a dune: effect of large-scale bottom roughness

Graphical Abstract

Neural Network Overtopping Predictor Proof of Concept

Wave overtopping is a dangerous phenomenon. When it occurs in a commercial port environment, the best case scenario will be the disruption of activities and even this best case scenario has a negative financial repercussion.

Análisis regional de frecuencia de precipitaciones extremas en el Norte de Mozambique

Extreme precipitation events that occur over internal basins of Cabo Delgado (Northern Mozambique) often result in the occurrence of flood events with associated loss of life and infrastructure. This paper presents a study of regional frequency analysis of maximum daily precipitations based on the index flood procedure with estimated parameters by L-moments approach. Observed annual maximum daily precipitation series of 12 stations with records of more than 20 years were analyzed. The discordancy and heterogeneity measures based on the L-moments suggest that the region can be considered as homogeneous. Among the candidate distributions analyzed Monte Carlo simulations identified the Generalized Logistic distribution function as the best regional fit for the region. The achieved results will be useful in hydrologic and hydraulic studies related to floods and floodplain delineation in the region.