Ocean Ultrasonic Shear and Compression Viscosities

[EN]A comprehensive description of ocean molecular flow and deformation is provided with the help of hydrodynamic and ultrasonic principles. Hydrodynamic computation of true or natural viscosities shows that ocean shear viscosity (?G), compression viscosity (?K), and extensional viscosity (?E) are interrelated. There are no experimental methods available for the in situ measurement of these viscosities. Sound absorption coefficients (? obs) allow to know the ultrasonic shear (?UG), compression (?UK), and longitudinal (?L) viscosities, which decrease with increasing frequency and increase with increasing temperature, the flow activation energies having nearly equivalent values; pressure (depth) increase/decrease them at low/high frequencies. The viscosities ?* UG, ?* UK, ?* L are approached at about 1000 KHz. They decrease with temperature and pressure, and increase with salinity. The ?*UG becomes equal to the true shear viscosity ? G at the viscosity ratio ? = ?UK / ?UG = 0.

Short-term variability of picoplankton across wind-shear region south of Gran Canaria

Máster en Oceanografía

Short-term variability of picoplankton across the wind-shear region south of Gran Canaria

[EN]We have studied the short-term variability -at temporal scale of days and spatial scale of 5 km- of the hydrographic field, organic and inorganic nutrients, chlorophyll and picoplanktonic abundances, across a 40 Km section crossing a frontal system south of Gran Canaria, where anticyclonic eddies in early-stages of formation and convergent fronts have been widely reported in the past. Each cruise consisted in a 3-4 daily-repeated section, and was carried out at the same period of the year (May) during two consecutive years (2011 and 2012). The main goal of our study was to analyze the picoplankton response to short-term variability at scales not considered in regular oceanographic samplings, even in regions with complex hydrographic fields.

Structure-soil-structure interaction effects on the dynamic response of piled structures under obliquely-incident seismic shear waves.

[EN] This work studies the structure-soil-structure interaction (SSSI) effects on the dynamic response of nearby piled structures under obliquely-incident shear waves. For this purpose, a three-dimensional, frequency-domain, coupled boundary element-finite (BEM-FEM) model is used to analyse the response of configuration of three buildings aligned parallel to the horizontal component of the wave propagation direction.