Grid-Characteristic Method on Overlapping Curvilinear Meshes for Modeling Elastic Waves Scattering on Geological Fractures

Interest in computational methods for calculating wave scattering from fractured geological clusters is due to their application in processing and interpreting the data obtained during seismic prospecting of hydrocarbon and other mineral deposits. In real calculations, numerical methods on structured, regular (Cartesian) computational grids are used to conserve computational resources though these methods do not correctly model the scattering of elastic waves from fractures that are not co-directed to the coordinate axes. The use of computational methods on other types of grids requires an increase in computational resources, which is unacceptable for the subsequent solution of inverse problems. This article is devoted to a possible solution to this problem. We suggest a novel modification of a computational grid-characteristic method on overlapping curvilinear grids. In the proposed approach, a small overlapping curvilinear grid is placed around a fracture that smoothly merges into the surrounding Cartesian background mesh, which helps to avoid interpolation between the background and overlapping meshes. This work presents the results of testing this method, which showed its high accuracy. The disadvantages of the developed method include the limited types of fractured clusters for which this method can be applied since the overlapping meshes should not intersect. However, clusters of subvertical fractures are usually found in nature; therefore, the developed method is applicable in most cases

Grid-Characteristic Method on Overlapping Curvilinear Meshes for Modeling Elastic Waves Scattering on Geological Fractures

Interest in computational methods for calculating wave scattering from fractured geological clusters is due to their application in processing and interpreting the data obtained during seismic prospecting of hydrocarbon and other mineral deposits. In real calculations, numerical methods on structured, regular (Cartesian) computational grids are used to conserve computational resources though these methods do not correctly model the scattering of elastic waves from fractures that are not co-directed to the coordinate axes. The use of computational methods on other types of grids requires an increase in computational resources, which is unacceptable for the subsequent solution of inverse problems. This article is devoted to a possible solution to this problem. We suggest a novel modification of a computational grid-characteristic method on overlapping curvilinear grids. In the proposed approach, a small overlapping curvilinear grid is placed around a fracture that smoothly merges into the surrounding Cartesian background mesh, which helps to avoid interpolation between the background and overlapping meshes. This work presents the results of testing this method, which showed its high accuracy. The disadvantages of the developed method include the limited types of fractured clusters for which this method can be applied since the overlapping meshes should not intersect. However, clusters of subvertical fractures are usually found in nature; therefore, the developed method is applicable in most cases

Nematic Ordering of Polymers in Confined Geometry Applied to DNA Packaging in Viral Capsids.

A density functional theory of the spatial distribution and biaxial nematic order of polymers of arbitrary length and rigidity inside a spherical cavity is proposed. The local order of different chain segments is considered as an alignment to a spatially varying director field of cylindrical symmetry. The steric interactions are taken into account in the second virial approximation. Polymer density and orientational order distributions inside the spherically cavity are the principal results. It was found that short and flexible polymers were located at the center of the sphere and were orientationaly disordered. Upon increasing polymer length and/or polymer rigidity, the location of the polymer was continuously shifted toward the surface of the spherical cavity and the polymer segments became gradually more aligned. Parameters have been selected to model the behavior of genomes in spherical viral capsids

Non-equilibrium electron transport induced by terahertz radiation in the topological and trivial phases of Hg1−xCdxTe

Terahertz photoconductivity in heterostructures based on n-type Hg1−xCdxTe epitaxial films both in the topological phase (x 0.16, normal band structure) has been studied. We show that both the positive photoresponse in films with x 0.16 have no low-energy threshold. The observed non-threshold positive photoconductivity is discussed in terms of a qualitative model that takes into account a 3D potential well and 2D topological Dirac states coexisting in a smooth topological heterojunction