A Chebyshev collocation method for solving two-phase flow stability problems

This paper describes a Chebyshev collocation method for solving the eigenvalue problem that governs the stability of parallel two-phase flow. The method is based on the expansion of the eigenfunctions in terms of Chebyshev polynomials, point collocation, and the subsequent solution of the resulting generalized eigenvalue problem with the QZ-algorithm. We concentrate on the question how to handle difficulties that arise when these ¿standard¿ techniques are applied to the stability problem of a thin film of liquid that is sheared by a gas. After discussing this specific problem in detail, it is argued that the method of solution can readily be applied to other two-phase flow configurations as well

Recommendations for antibacterial therapy in adults with COVID-19-an evidence based guideline

Scope: The Dutch Working Party on Antibiotic Policy constituted a multidisciplinary expert committee to provide evidence-based recommendation for the use of antibacterial therapy in hospitalized adults with a respiratory infection and suspected or proven 2019 Coronavirus disease (COVID-19).Methods: We performed a literature search to answer four key questions. The committee graded the evidence and developed recommendations by using Grading of Recommendations Assessment, Development, and Evaluation methodology.Questions addressed by the guideline and Recommendations: We assessed evidence on the risk of bacterial infections in hospitalized COVID-19 patients, the associated bacterial pathogens, how to diagnose bacterial infections and how to treat bacterial infections. Bacterial co-infection upon admission was reported in 3.5% of COVID-19 patients, while bacterial secondary infections during hospitalization occurred up to 15%. No or very low quality evidence was found to answer the other key clinical questions. Although the evidence base on bacterial infections in COVID-19 is currently limited, available evidence supports restrictive antibiotic use from an antibiotic stewardship perspective, especially upon admission. To support restrictive antibiotic use, maximum efforts should be undertaken to obtain sputum and blood culture samples as well as pneumococcal urinary antigen testing. We suggest to stop antibiotics in patients who started antibiotic treatment upon admission when representative cultures as well as urinary antigen tests show no signs of involvement of bacterial pathogens after 48 hours. For patients with secondary bacterial respiratory infection we recommend to follow other guideline recommendations on antibacterial treatment for patients with hospital-acquired and ventilator-associated pneumonia. An antibiotic treatment duration of five days in patients with COVID-19 and suspected bacterial respiratory infection is recommended upon improvement of signs, symptoms and inflammatory markers. Larger, prospective studies about the epidemiology of bacterial infections in COVID-19 are urgently needed to confirm our conclusions and ultimately prevent unnecessary antibiotic use during the COVID-19 pandemic. (C) 2020 The Author(s). Published by Elsevier Ltd on behalf of European Society of Clinical Microbiology and Infectious Diseases.Immunogenetics and cellular immunology of bacterial infectious disease

Neutrino oscillation studies with IceCube-DeepCore

AbstractIceCube, a gigaton-scale neutrino detector located at the South Pole, was primarily designed to search for astrophysical neutrinos with energies of PeV and higher. This goal has been achieved with the detection of the highest energy neutrinos to date. At the other end of the energy spectrum, the DeepCore extension lowers the energy threshold of the detector to approximately 10 GeV and opens the door for oscillation studies using atmospheric neutrinos. An analysis of the disappearance of these neutrinos has been completed, with the results produced being complementary with dedicated oscillation experiments. Following a review of the detector principle and performance, the method used to make these calculations, as well as the results, is detailed. Finally, the future prospects of IceCube-DeepCore and the next generation of neutrino experiments at the South Pole (IceCube-Gen2, specifically the PINGU sub-detector) are briefly discussed

Electromagnetic effects in cylindrical pipe flow

Mechanical Maritime and Materials Engineerin

Direct numerical simulation of turbulent pipe flow at high Reynolds numbers: Extended abstract

With todays supercomputers we are able to simulate flows with moderate to high Reynolds numbers. These flows show features that are not present in simulations with lower Reynolds numbers. Recently we have finished a fully resolved direct numerical simulation of a turbulent pipe flow with a bulk Reynolds number of 76,000 on a computational domain which is 18 pipe diameters long. During the conference we will present results from this simulation, such as velocity statistics, pre-multiplied energy spectra and auto correlations.Process and EnergyEnergy Technolog

Direct numerical simulation of turbulent pipe at high Reynolds numbers, velocity statistics and large scale motions

In recent years there has been a considerable research effort dedicated to turbulent pipe flow. Topics of interest are, amongst others, the scaling of near wall turbulent statistics and the existence of very large scale turbulent structures at higher Reynolds numbers. These structures have been observed experimentally in boundary layers, Hutchins & Marusic (2007) and pipes, Monty et al. (2007). Recently these structures have also been observed in moderate Reynolds number direct numerical simulations of channel and boundary layer flows. In this paper we will report on the simulation of turbulent pipe flow at bulk Reynolds numbers of 24600, 37500, and 75,000. The numerical grid (up to 7.6e9 grid nodes) is comparable to the grid used by Jimenez & Hoyas (2008) and should be sufficiently fine to resolve all scales. At high Reynolds numbers we observe some evidence of the aforementioned long scale structures.Energy Technolog

Catch-up growth after prolonged hypothyroidism

Contains fulltext : 23474___.PDF (publisher's version ) (Open Access

The use of immersed boundary methods for the calculation of flow around objects

This article discusses the use of immersed boundary methods for the flow around objects. Treated are the reasons for their use, their benefits compared to other methods, their importance, and possible further developments.Mechanical, Maritime and Materials Engineerin

An experimental study on friction reducing polymers in turbulent pipe flow

An experimental study was conducted to search the reduction of friction in fully developed turbulent pipe flow using different types of polyacrylamides as friction reducing polymers. Pressure drop measurements determined the friction reduction. Three different polymer types Superfloc A110, Superfloc A130 and Superfloc A150 were used to examine the effect of polymer concentration, Reynolds number and polymer type on friction reduction. The Darcy friction factor was obtained for each polymer type at the polymer concentration ranging from 0 to 500 wppm and a Reynolds number range of 10000-80000. It was observed that friction factor decreased with increment in polymer concentration and Reynolds number for each polymer. Higher molecular weight polymers are more effective at reducing friction. With increasing concentration of polymer, the measured data approaches the Virk asymptote, which represents the maximum friction reduction limit by the polymers. The percentage of friction reduction increased with increasing concentration of polymer up to 100 wppm for each polymer type and then began to decrease for polymer concentrations higher than 100 wppm. An empirical formula was obtained to calculate the Darcy friction factor as a function of Reynolds number and polymer concentration for Superfloc A110.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Marine and Transport Technolog