No abstract

Finite deformation contact of flexible solids embedded in fluid flows occurs in a wide range of engineering scenarios. We propose a novel three-dimensional finite element approach in order to tackle this problem class. The proposed method consists of a dual mortar contact formulation, which is algorithmically integrated into an eXtended finite element method (XFEM) fluid-structure interaction approach. The combined XFEM fluid-structure-contact interaction method (FSCI) allows to compute contact of arbitrarily moving and deforming structures embedded in an arbitrary flow field. In this paper, the fluid is described by instationary incompressible Navier-Stokes equations. An exact fluid-structure interface representation permits to capture flow patterns around contacting structures very accurately as well as to simulate dry contact between structures. No restrictions arise for the structural and the contact formulation. We derive a linearized monolithic system of equations, which contains the fluid formulation, the structural formulation, the contact formulation as well as the coupling conditions at the fluid-structure interface. The linearized system may be solved either by partitioned or by monolithic fluid-structure coupling algorithms. Two numerical examples are presented to illustrate the capability of the proposed fluid-structure-contact interaction approach.Keywords Finite deformation contact · Contact of solids in fluid · EXtended finite element method · Fluid-structure interaction · Dual mortar contact approach · Partitioned and monolithic fluid-structure coupling

Three-dimensional higher-order eXtended finite element method (XFEM)-computations still pose challenging computational geometry problems especially for moving interfaces. This paper provides a method for the localization of a higher-order interface finite element (FE) mesh in an underlying three-dimensional higher-order FE mesh. Additionally, it demonstrates, how a subtetrahedralization of an intersected element can be obtained, which preserves the possibly curved interface and allows therefore exact numerical integration.The proposed interface algorithm collects initially a set of possibly intersecting elements by comparing their 'eXtended axis-aligned bounding boxes'. The intersection method is applied to a highly reduced number of intersection candidates. The resulting linearized interface is used as input for an elementwise constrained Delaunay tetrahedralization, which computes an appropriate subdivision for each intersected element. The curved interface is recovered from the linearized interface in the last step. The output comprises triangular integration cells representing the interface and tetrahedral integration cells for each intersected element.Application of the interface algorithm currently concentrates on fluid-structure interaction problems on low-order and higher-order FE meshes, which may be composed of any arbitrary element types such as hexahedra, tetrahedra, wedges, etc. Nevertheless, other XFEM-problems with explicitly given interfaces or discontinuities may be tackled in addition. Multiple structures and interfaces per intersected element can be handled without any additional difficulties. Several parallelization strategies exist depending on the desired domain decomposition approach. Numerical test cases including various geometrical exceptions demonstrate the accuracy, robustness and efficiency of the interface handling.

A series of 15 patients with Peters' anomaly observed from 1987-1991 and a patient showing Wolf-Hirschhorn syndrome were studied retrospectively. Combined ocular anomalies were: microphthalmos (9x), myopia (4x), aniridia (2x), cataract (2x). Five of the patients had combined general anomalies: mental retardation, deafness, cardiac malformation (ASD II), and luxatio coxae. In two of them chromosomal anomalies were found: 4p minus syndrome, mosaic trisomy 9. After comparison of these data with those known from the literature the author confirms that Peters' anomaly is a morphologic finding rather than a distinct entity. Treatment depends on individual histopathologic findings and on the psychophysical development of the child.

A male infant is reported with congenital dyskeratosis and pancytopenia Zinsser-Engman-Cole. The bone marrow pathology showed similarities to Fanconi anaemia. Ophthalmological complications were vitreous haemorrhage, haemorrhagic cataracta complicata and glaucoma. Spontaneous and diepoxybutane-induced chromosomal fragility was within the range of normal cells but was elevated through induction with 4-nitroquinoline-oxide. These findings are contrasted with those of Fanconi anaemia.