Correct energy evolution of stabilized formulations: The relation between VMS, SUPG and GLS via dynamic orthogonal small-scales and isogeometric analysis. II: The incompressible Navier-Stokes equations

This paper presents the construction of a correct-energy stabilized finite element method for the incompressible Navier-Stokes equations. The framework of the methodology and the correct-energy concept have been developed in the convective--diffusive context in the preceding paper [M.F.P. ten Eikelder, I. Akkerman, Correct energy evolution of stabilized formulations: The relation between VMS, SUPG and GLS via dynamic orthogonal small-scales and isogeometric analysis. I: The convective--diffusive context, Comput. Methods Appl. Mech. Engrg. 331 (2018) 259--280]. The current work extends ideas of the preceding paper to build a stabilized method within the variational multiscale (VMS) setting which displays correct-energy behavior. Similar to the convection--diffusion case, a key ingredient is the proper dynamic and orthogonal behavior of the small-scales. This is demanded for correct energy behavior and links the VMS framework to the streamline-upwind Petrov-Galerkin (SUPG) and the Galerkin/least-squares method (GLS). The presented method is a Galerkin/least-squares formulation with dynamic divergence-free small-scales (GLSDD). It is locally mass-conservative for both the large- and small-scales separately. In addition, it locally conserves linear and angular momentum. The computations require and employ NURBS-based isogeometric analysis for the spatial discretization. The resulting formulation numerically shows improved energy behavior for turbulent flows comparing with the original VMS method.Comment: Update to postprint versio

On the mechanical behaviour of a butt jointed thermoplastic composite under bending

In the present work, the mechanical behavior of a recently developed novel butt jointed thermoplastic composite was investigated under bending conditions. The laminated skin and the web were made of carbon fiber (AS4) and polyetherketoneketone (PEKK). The butt joint (filler) was injection molded from 20% short carbon fiber filled with PEKK thermoplastic. The skin and web were co-consolidated together with the butt joint in the form of a hybrid T-shaped structure. A three point bending (3 PB) set-up was used to investigate the mechanical response of the hybrid composite. The crack initiation and propagation mechanisms for the filler and the delamination at the skin-filler interface were captured using a high speed camera. It was found from the experimental observations that the crack initiated in the filler and then propagated towards the skin-filler interface. A numerical model was also developed using the finite element method in ABAQUS including the crack initiation and growth in the filler together with the delamination at the skin-filler interface. For this purpose the virtual crack closure technique (VCCT) was employed for the crack growth in the filler and the traction separation law was applied at the skin-filler interface using a cohesive surface. The residual stresses and deformations coming from the co-consolidation process were predicted by applying a thermal load and taken into account in the quasi-static analysis. A good agreement was found between the predicted and measured force-displacement curves. The developed numerical model was further employed to address the crack initiation and growth in the filler and delamination at the skin-filler interface using the mix mode effective fracture energies. A linear elastic behavior was found in the structure until the crack initiation in the filler

A space-time framework for periodic flows with applications to hydrofoils

In this paper we propose a space-time framework for the computation of periodic flows. We employ the isogeometric analysis framework to achieve higher-order smoothness in both space and time. The discretization is performed using residual-based variational multiscale modelling and weak boundary conditions are adopted to enhance the accuracy near the moving boundaries of the computational domain. We show conservation properties and present a conservative method for force extraction. We apply our framework to the computation of a heaving and pitching hydrofoil. Numerical results display very accurate results on course meshes

eHealth in TB clinical management

BACKGROUND: The constant expansion of internet and mobile technologies has created new opportunities in the field of eHealth, or the digital delivery of healthcare services. This TB meta-analysis aims to examine eHealth and its impact on TB clinical management in order to formulate recommendations for further development.METHODS: A systematic search was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses framework in PubMed and Embase of articles published up to April 2021. Screening, extraction and quality assessment were performed by two independent researchers. Studies evaluating an internet and/or mobile-based eHealth intervention with an impact on TB clinical management were included. Outcomes were organised following the five domains described in the WHO "Recommendations on Digital Interventions for Health System Strengthening" guideline.RESULTS: Search strategy yielded 3,873 studies, and 89 full texts were finally included. eHealth tended to enhance screening, diagnosis and treatment indicators, while being cost-effective and acceptable to users. The main challenges concern hardware malfunction and software misuse.CONCLUSION: This study offers a broad overview of the innovative field of eHealth applications in TB. Different studies implementing eHealth solutions consistently reported on benefits, but also on specific challenges. eHealth is a promising field of research and could enhance clinical management of TB.</p

Beschreibung einer Vorrichtung zur Beförderung einer Flüssigkeit aus Unterdruckgefäßen in ein Medium mit Überdruck

Patentbeschreibung einer Vorrichtung, mit der Flüssigkeiten aus Unterdruckgefäßen in ein Medium mit Überdruck befördert werden können und die darauf beruht, daß die in Reihe angeordneten Aufnahmegefäße einerseits im Vakuum, andererseits mit Normaldruck arbeite