Author(s): Jose Anta Alvarez; Enrique Pena Gonzalez; Jeronimo Puertas Agudo; Victor Vazquez Alvarez
Linked Author(s): Jose Anta Álvarez, Enrique Peña González, Jerónimo Puertas Agudo
Keywords: Environmental effects; Hydrodynamics; Shells; Granular sediments; Lasers; Experimental design; Calibration
Abstract: This article presents the factors and limit conditions of the cockle´s threshold movement in the Ulla´s Estuary. The migration of these bivalves generates an important social and economic impact in this 39 kilometres long estuary in which the principal economic activity is based on the shellfish’s collection. The laser technology Particle Image Velocimetry (PIV) has been applied in a laboratory channel to analyse with detail the hydrodynamic and the velocity profiles of a group of cockles of different sizes. This experimental tool allows determining accurately the shear forces which provoke the beginning of the movement in the cockles. By other side, a theoretical study and different tests in the threshold movement have been made to achieve a detailed description of the parameters which influence that point. In particular, the density of the cockle’s body and shells, the volume and submerged weight, and the friction angle between the sediment and the cockle. The developed experimental methodology has allowed estimating the values of the drag coefficient of these bivalves, comparing them with other existing studies (Thompson and Amos, 2002). The use of the PIV laser technology allows a better knowledge of the cockle’s hydrodynamic behaviour in the threshold point of equilibrium, and its potential influence in the surroundings of the river mouths.
Year: 2005