Ocean Ultrasonic Shear and Compression Viscosities

摘要

A comprehensive description of ocean molecular flow and deformation is provided with the help ofhydrodynamic and ultrasonic principles. Hydrodynamic computation of true or natural viscosities shows that ocean shearviscosity (ηG), compression viscosity (ηK), and extensional viscosity (ηE) are interrelated. There are no experimentalmethods available for the in situ measurement of these viscosities. Sound absorption coefficients (α obs) allow to know theultrasonic shear (ηUG), compression (ηUK), and longitudinal (ηL) viscosities, which decrease with increasing frequency andincrease with increasing temperature, the flow activation energies having nearly equivalent values; pressure (depth)increase/decrease them at low/high frequencies. The viscosities η*UG, η*UK, η*L are approached at about 1000 KHz. Theydecrease with temperature and pressure, and increase with salinity. The η*UG becomes equal to the true shear viscosity η Gat the viscosity ratio δ = ηUK / ηUG = 0.