A numerical extension of White's theory of P-wave attenuation to non-isothermal poroelastic media.

Mesoscopic P-wave attenuation in layered, partially saturated thermo-poroelastic media is analyzed by combining the theories of Biot poroelasticity and Lord-Shulman thermoelasticity (BLS). The attenuation is quantified by estimating the quality factor Q. The mesoscopic attenuation effect, commonly referred to as wave-induced fluid flow (WIFF), is the process that converts fast compressional and shear waves into slow diffusive Biot waves at mesoscopic heterogeneities larger than the pore scale, but much smaller than the dominant wavelengths.

Finite-element numerical simulations of seismic attenuation in finely layered rocks.

P-wave conversion to slow diffusion (Biot) modes at mesoscopic (small-scale) inhomogeneities in porous media is believed to be the most important attenuation mechanisms at seismic frequencies. This study considers three periodic thin layers saturated with gas, oil, and water, respectively, a realistic scenario in hydrocarbon reservoirs, and perform finite-element numerical simulations to obtain the wave velocities and quality factors along the direction perpendicular to layering. The results are validated by comparison to the Norris-Cavallini analytical solution, constituting a cross-check for both theory and numerical simulations.

A Simulation of a COVID-19 Epidemic Based on a Deterministic SEIR Model.

An epidemic disease caused by a new coronavirus has spread in Northern Italy with a strong contagion rate. We implement an SEIR model to compute the infected population and the number of casualties of this epidemic. The example may ideally regard the situation in the Italian Region of Lombardy, where the epidemic started on February 24, but by no means attempts to perform a rigorous case study in view of the lack of suitable data and the uncertainty of the different parameters, namely, the variation of the degree of home isolation and social distancing as a function of time, the initial number of exposed individuals and infected people, the incubation and infectious periods, and the fatality rate.

A model for wave propagation in a porous solid saturated by a three-phase fluid.

This paper presents a model to describe the propagation of waves in a poroelastic medium saturated by a three-phase viscous, compressible fluid. Two capillary relations between the three fluid phases are included in the model by introducing Lagrange multipliers in the principle of virtual complementary work. This approach generalizes that of Biot for single-phase fluids and allows to determine the strain energy density, identify the generalized strains and stresses, and derive the constitutive relations of the system.

A parametric analysis of waves propagating in a porous solid saturated by a three-phase fluid.

This paper presents an analysis of a model for the propagation of waves in a poroelastic solid saturated by a three-phase viscous, compressible fluid. The constitutive relations and the equations of motion are stated first. Then a plane wave analysis determines the phase velocities and attenuation coefficients of the four compressional waves and one shear wave that propagate in this type of medium.

Reflection and transmission coefficients of a single layer in poroelastic media.

Wave propagation in poroelastic media is a subject that finds applications in many fields of research, from geophysics of the solid Earth to material science. In geophysics, seismic methods are based on the reflection and transmission of waves at interfaces or layers. It is a relevant canonical problem, which has not been solved in explicit form, i.