We present laboratory experiments of surface wave turbulence excited by paddles in the deep water regime. The free surface is seeded with buoyant particles that are advected and dispersed by the flow. Positions and velocities of the floaters are measured using particle tracking velocimetry. We study the statistics of velocity and acceleration of the particles, mean vertical displacements, single-particle horizontal dispersion, and the phenomenon of preferential concentration. Using a simple model together with the experimental data, we show that the time evolution of the particles has three characteristic processes that dominate the dynamics at different times: drag by surface waves at early times, trapping by short-lived horizontal eddies at intermediate times, and advection by a large-scale mean circulation at late times. arXiv:1901.09991v2 [physics.flu-dyn]
En este trabajo se presenta el desarrollo y la caracterización de un sistema de velocimetría por seguimiento de partículas para la medición lagrangiana de flujos. El sistema está basado en el uso conjunto de dos cámaras rápidas que observan sincronizadamente una región común del flujo a estudiar. Se describen en detalle el procedimiento de calibración conjunta del sistema de cámaras, la evaluación de los errores de medición y el procesado de las imágenes individuales para el cálculo de trayectorias de partículas en el espacio 3D. Enúltimo lugar, se discuten los resultados de la aplicación de este sistema al estudio de la dinámica de clústeres de partículas flotantes sobre la superficie libre de un campo de ondas turbulento. Palabras Clave: velocimetría, seguimiento de partículas, descripción lagrangiana de flujos. In this paper we present the development and characterization of a velocimetry system based on individual particle tracking, specially designed for the lagrangian description of fluid flows. This system is based on the joint use of two high-speed cameras which synchronically observe a common region on the flow under study. We describe in detail the joint calibration procedure of the system, as well as the processing of individual images for calculating particle trajectories in three-dimensional space. Lastly, results are shown concerning the application of this measuring system to the dynamics of buoyant particle clustering on the free surface of a turbulent wave field.
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