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Your search keyword '"Fuhrmann, J."' showing total 4 results
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4 results on '"Fuhrmann, J."'

1. A personal discussion on conservation, and how to formulate it

Author

Franck, Emmanuel, Fuhrmann, Jürgen, Michel-Dansac, Victor, Navoret, Laurent, Franck, E ( Emmanuel ), Fuhrmann, J ( Jürgen ), Michel-Dansac, V ( Victor ), Navoret, L ( Laurent ), Abgrall, Remi; https://orcid.org/0000-0002-5553-7476, Franck, Emmanuel, Fuhrmann, Jürgen, Michel-Dansac, Victor, Navoret, Laurent, Franck, E ( Emmanuel ), Fuhrmann, J ( Jürgen ), Michel-Dansac, V ( Victor ), Navoret, L ( Laurent ), and Abgrall, Remi; https://orcid.org/0000-0002-5553-7476

Abstract

Since the celebrated theorem of Lax and Wendroff, we know a necessary condition that any numerical scheme for hyperbolic problem should satisfy: it should be written in flux form. A variant can also be formulated for the entropy. Even though some schemes, as for example those using continuous finite element, do not formally cast into this framework, it is a very convenient one. In this paper, we revisit this, introduce a different notion of local conservation which contains the previous one in one space dimension, and explore its consequences. This gives a more flexible framework that allows to get, systematically, entropy stable schemes, entropy dissipative ones, or accommodate more constraints. In particular, we can show that continuous finite element method can be rewritten in the finite volume framework, and all the quantities involved are explicitly computable. We end by presenting the only counter example we are aware of, i.e a scheme that seems not to be rewritten as a finite volume scheme.

Published
2023

2. Numerical dissipation and dispersion of the homogeneous and complete flux schemes

Author

Thije Boonkkamp, ten, J.H.M., Anthonissen, M.J.H., Fuhrmann, J., Ohlberger, M., Rohde, C., and Scientific Computing

Subjects
Physics, Finite volume method, Classical mechanics, Advection, Homogeneous, Dispersion (optics), Numerical dispersion, Flux, Mechanics, Numerical diffusion, Dissipation
Abstract

We analyse numerical dissipation and dispersion of the homogeneous flux (HF) and complete flux (CF) schemes, finite volume methods introduced in [4]. To that purpose we derive the modified equation of both schemes . We show that the HF scheme suffers from numerical diffusion for dominant advection, which is effectively removed in the CF scheme. The latter scheme, however, is prone to numerical dispersion. We validate both schemes for a model problem.

Published
2014

3. A new discretization method for the convective terms in the incompressible Navier-Stokes equations

Author

Kumar, Nikhil, Thije Boonkkamp, ten, J.H.M., Koren, B., Fuhrmann, J., Ohlberger, M., Rohde, C., Scientific Computing, and Center for Analysis, Scientific Computing & Appl.

Subjects
Convection, Physics::Fluid Dynamics, Finite volume method, Discretization, Interface (Java), Mathematical analysis, Compressibility, Mathematics::Analysis of PDEs, Boundary value problem, Navier–Stokes equations, Pressure gradient, Mathematics
Abstract

In this contribution we present the use of local one-dimensional boundary value problems (BVPs) to compute the interface velocities in the convective terms of the incompressible Navier-Stokes equations. This technique provides us with a better estimate for the interface velocities than linear interpolants.

Published
2014

4. Detection of Enterobius vermicularis in greater Berlin, 2007-2017: seasonality and increased frequency of detection.

Author

Friesen J, Bergmann C, Neuber R, Fuhrmann J, Wenzel T, Durst A, Müller M, and Ignatius R

Subjects
Adolescent, Adult, Aged, Animals, Berlin epidemiology, Cellulose, Child, Child, Preschool, Enterobiasis diagnosis, Female, Humans, Infant, Male, Middle Aged, Retrospective Studies, Sex Factors, Young Adult, Anal Canal parasitology, Enterobiasis epidemiology, Enterobius isolation & purification, Seasons
Abstract

The pinworm (Enterobius vermicularis) causes mostly mild infections characterised by nocturnal anal pruritus, mainly in children. Still, the infection is stigmatising and sleep disturbances may lead to lack of concentration. For Germany, no epidemiological data are available. Laboratory data of all patients for whom detection of E. vermicularis by cellulose tape test had been requested between 2007 and November 2017 were analysed retrospectively. E. vermicularis was detected in 971/5578 (17.4%) samples collected from 3991 patients. The detection rate increased significantly within the period of investigation. It was higher in male than in female patients (20.0 vs. 15.4%). Children 4 to 10 years old and, if also examined, their relatives were most frequently affected. Control investigations at an interval of at least 1 month, which could indicate insufficient therapy or re-infection, were performed in 90/714 patients (12.6%). While parasite detection in children < 6 years was evenly distributed throughout the year, in older patients, it peaked between October and December. In conclusion, in the area of investigation, the frequency of E. vermicularis is higher in males than in females and is subject to a hitherto undescribed seasonality. The causes of the increased frequency of parasite detection warrant further investigations.

Published
2019
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