The Explicit Simplified Interface Method for compressible multicomponent flows

This paper concerns the numerical approximation of the Euler equations for multicomponent flows. A numerical method is proposed to reduce spurious oscillations that classically occur around material interfaces. It is based on the "Explicit Simplified Interface Method" (ESIM), previously developed in the linear case of acoustics with stationary interfaces (2001, J. Comput. Phys. 168, pp.~227-248). This technique amounts to a higher order extension of the "Ghost Fluid Method" introduced in Euler multicomponent flows (1999, J. Comput. Phys. 152, pp. 457-492). The ESIM is coupled to sophisticated shock-capturing schemes for time-marching, and to level-sets for tracking material interfaces. Jump conditions satisfied by the exact solution and by its spatial derivative are incorporated in numerical schemes, ensuring a subcell resolution of material interfaces inside the meshing. Numerical experiments show the efficiency of the method for rich-structured flows.Comment: to be published in SIAM Journal of Scientific Computing (2005

A High-Resolution Penalization Method for large Mach number Flows in the presence of Obstacles

International audienceA penalization method is applied to model the interaction of large Mach number compressible flows with obstacles. A supplementary term is added to the compressible Navier-Stokes system, seeking to simulate the effect of the Brinkman-penalization technique used in incompressible flow simulations including obstacles. We present a computational study comparing numerical results obtained with this method to theoretical results and to simulations with Fluent software. Our work indicates that this technique can be very promising in applications to complex flows

A multiscale method applied to shallow water flow

A flux-limited second order scheme with the C-property is used to solve the one dimensional or two dimensional Saint-Venant system for shallow water flows with non-flat bottom and friction terms, as is introduced in [7] G. Haro, Numerical simulation of shallow water equations amd some physical models in image processing. Ph.D.Thesis, Departament of Technologies, Universitat Pompeu Fabra, Barcelona, 2005. High resolution at low cost can be obtained by applying a point-value multiresolution transform [2, 3, 9] in order to detect regions with singularities. The above method is applied in these regions, while a cheap polynomial interpolation is used in the smooth zones, thus lowering the computational cost

The PCHIP subdivision scheme

In this paper we propose and analyze a nonlinear subdivision scheme based on the monotononicity-preserving third order Hermite-type interpolatory technique implemented in the PCHIP package in Matlab. We prove the convergence and the stability of the PCHIP nonlinear subdivision process by employing a novel technique based on the study of the generalized Jacobian of the first difference scheme.MTM2011-2274

A family of non-oscillatory 6-point interpolatory subdivision schemes

In this paper we propose and analyze a new family of nonlinear subdivision schemes which can be considered non-oscillatory versions of the 6-point Deslauries-Dubuc (DD) interpolatory scheme, just as the Power p schemes are considered nonlinear non-oscillatory versions of the 4-point DD interpolatory scheme. Their design principle may be related to that of the Power p schemes and it is based on a weighted analog of the Power p mean. We prove that the new schemes reproduce exactly polynomials of degree three and stay ’close’ to the 6-point DD scheme in smooth regions. In addition, we prove that the first and second difference schemes are well defined for each member of the family, which allows us to give a simple proof of the uniform convergence of these schemes and also to study their stability as in [19, 22]. However our theoretical study of stability is not conclusive and we perform a series of numerical experiments that seem to point out that only a few members of the new family of schemes are stable. On the other hand, extensive numerical testing reveals that, for smooth data, the approximation order and the regularity of the limit function may be similar to that of the 6-point DD scheme and larger than what is obtained with the Power p schemes

Operadores de reconstrucción y esquemas de subdivisión asociados

Los esquemas de subdivisión son unas herramientas muy usadas en el diseño de curvas y superficies, y tienen también relación con otras aplicaciones interesantes en tratamiento digital de imágenes o en la resolución de ecuaciones diferenciales. Estos esquemas están basados en un conjunto de reglas, las cuales aplicadas recursivamente permiten un refinamiento sucesivo de un conjunto inicial de puntos llamado puntos de control. Una propiedad importante a verificar en estos esquemas es la de preservación de la convexidad y de la monotonía. Una manera de abordar estas cuestiones se basa en la estrecha relación entre esquemas de subdivisión y operadores de reconstrucción. Estos operadores de reconstrucción conectan datos discretos con un cierto espacio funcional, que dependerá de las aplicaciones en concreto. Nuestro objetivo es presentar ciertos operadores de reconstrucción y sus esquemas de subdivisión asociados, verificando si conservan la convexidad y la monotonía

The 1356 Basel earthquake: an interdisciplinary revision

Within historical times one of the most damaging events in intra-plate Europe was the 1356 Basel earthquake. Given its significance for assessing regional seismic hazard in central Europe, an interdisciplinary project was launched in 2005 to re-explore this event. Our effort aimed to incorporate techniques from history, seismology, archaeology, paleoseismology and engineering. New and reinterpreted historical data from Basel and its surroundings plus archaeological findings on buildings that survived the event and still exist enabled this macroseismic assessment. Palaeoseismological studies combined with historical evidence provided additional data. For the surrounding areas, archaeology offers sparse information on some castles and churches, sometimes supported by historical records. A contemporary source allows some reconstruction of the stronger fore- and aftershocks. This expanded information base improves our sense of the event's damage and consequences. For the city of Basel, the relatively abundant archaeological data allowed us to assess statistically the macroseismic intensity at IX, although the pattern of damage was scattered. Data points for the expected area of damage around Basel are not distributed regularly. The absence of historical and archaeological findings for southern Germany might be due to archival problems; future investigation may improve this situation. Our results confirm that the Basel earthquake was the most destructive known for central Europe. Intensities up to VIII are found within a radius of about 30 km. Analysing the macroseismic field confirms our former assessment of the event and shows an epicenter located about 10 km south of Basel. The most probable range for the moment magnitude Mw is between 6.7 and 7.

Mediterranean diet and invasive breast cancer risk in the predimed trial

Trabajo presentado en el X Congreso Internacional de la Dieta Mediterránea, celebrado en Barcelona (España) del 02 al 03 de abril de 2014.[Introduction]: Rates of breast cancer incidence have been rising over the past 3 decades. Dietary factors may play a role in the risk of breast cancer. Some observational cohort studies have suggested that the Mediterranean diet may reduce the risk of breast cancer but no randomized controlled trial had investigated this issue. We aimed to evaluate the effect of two interventions with Mediterranean diet on the primary prevention of breast cancer in a randomized controlled trial. [Methods]: The PREDIMED study (Prevención con Dieta Mediterránea) is a randomized, singleblind, and controlled trial conducted in Spanish primary healthcare centres. Out of 4,282 women recruited (aged 60 to 80 years), 1,478 were assigned to a Mediterranean diet supplemented with extra-virgin olive oil, 1,288 to a Mediterranean diet supplemented with mixed nuts and 1,393 to a control diet (advice to reduce dietary fat). Primary analyses were performed on an intention-to-treat basis. Poisson regression analyses were used to assess the relationship between the nutritional intervention and the incidence of confirmed invasive breast cancer. [Results]: After a median of 4.3 years after randomization, participants in both Mediterranean diet groups (extra-virgin olive oil or nuts) had a 55% relative reduction (95%CI: 9% to 78%) in the risk of invasive breast cancer compared with participants assigned to a control group (with the recommendation to follow a low-fat diet). Observed rates (per 1000 person-years) were 1.14, 1.82 and 2.90 for the Mediterranean diet with extra-virgin olive oil group, the Mediterranean diet supplemented with nuts group and the control group, respectively. The multivariable-adjusted rate ratios versus the control group were 0.34 (95% CI: 0.14 to 0.83) for the Mediterranean diet with extra-virgin olive oil group, and 0.60 (95% CI: 0.26 to 1.35) for the Mediterranean diet supplemented with nuts group. [Conclusions]: This is the first large randomized trial assessing the role of a dietary pattern on breast cancer incidence. Our results suggest that an intervention promoting adherence to the Mediterranean dietary pattern, specially when it is supplemented with extra-virgin olive oil, may contribute to a substantial reduction in the incidence of invasive breast cancer risk in women 60 years and older. However, a longer follow-up of our participants is needed to obtain more precise estimates