Investigation of finite-volume methods to capture shocks and turbulence spectra in compressible flows

The aim of the present paper is to provide a comparison between several finite-volume methods of different numerical accuracy: second-order Godunov method with PPM interpolation and high-order finite-volume WENO method. The results show that while on a smooth problem the high-order method perform better than the second-order one, when the solution contains a shock all the methods collapse to first-order accuracy. In the context of the decay of compressible homogeneous isotropic turbulence with shocklets, the actual overall order of accuracy of the methods reduces to second-order, despite the use of fifth-order reconstruction schemes at cell interfaces. Most important, results in terms of turbulent spectra are similar regardless of the numerical methods employed, except that the PPM method fails to provide an accurate representation in the high-frequency range of the spectra. It is found that this specific issue comes from the slope-limiting procedure and a novel hybrid PPM/WENO method is developed that has the ability to capture the turbulent spectra with the accuracy of a high-order method, but at the cost of the second-order Godunov method. Overall, it is shown that virtually the same physical solution can be obtained much faster by refining a simulation with the second-order method and carefully chosen numerical procedures, rather than running a coarse high-order simulation. Our results demonstrate the importance of evaluating the accuracy of a numerical method in terms of its actual spectral dissipation and dispersion properties on mixed smooth/shock cases, rather than by the theoretical formal order of convergence rate.Comment: This paper was previously composed of 2 parts, and this submission was part 1. It is now replaced by the combined pape

Genomics - from Neanderthals to high-throughput sequencing

A report on 'The Biology of Genomes' meeting, Cold Spring Harbor, USA, 10-14 May 2006

Sediment and associated radionuclide dynamics within the Ribble Estuary, North West England.

Intertidal environments represent a spatially complex and dynamic system, rendering point sampling geographically and temporally isolated within the context of the entire estuarine system. Airborne remote sensing has the potential to place these spatially isolated sampling points into a quantitative spatial context. Furthermore it provides a valuable data source for quantifying processes within estuarine zones and can supply calibration and validation information for hydrodynamic models. This study focuses on the Ribble Estuary, Lancashire, England which is accumulating elevated radionuclide concentrations derived from authorized industrial discharges from BNFL Sellafield and Westinghouse Springfields. An image mixture modeling approach was used on Airborne Thematic Mapper (ATM) data to derive accurate estimates of intertidal clay, in comparison to concurrent field sampling (r2=0.828) and radionuclide concentrations (r2= 0.822). Data processed for 2003 was compared with similar data from May 1997 (Rainey 1999; Rainey et aL., 2000; 2003) to investigate spatial changes in intertidal clay and 137Cs contamination. These results compared with field sampling data demonstrates considerable reduction (c.52%) in the activity concentrations, which is primarily attributed to processes of sediment dilution. Calibrated Compact Airborne Spectrographic Imager (CASI) imagery combined with concomitant ground reference data, was used to characterize the suspended sediment concentrations and the total suspended load over each flight line. Two sets of time series image data were compared to assess the spatial and temporal changes in suspended sediment and associated radionuclide transportation within the estuarine environment. In conjunction with total volumetric estimates generated from a two-dimensional vertically resolving hydrodynamic model, this data then allowed estimation of the total flux of suspended sediment and radionuclide over the flood and ebb tidal cycle to a reasonable precision (40%). To establish whether these flux estimates are realistic, the results are compared with time series field based observations collected from monthly observations over a two year cycle. The results provide a unique quantitative insight into the understanding of contaminant and sediment transport within this estuarine environment and the environmental processes controlling them. The contribution of field data with the intertidal and flood-ebb tide imagery has provided an enhanced understanding of the interactions of tides and fluvial flow on the spatial distribution of sediments within the Ribble Estuary. It could also be possible to apply the calibrated clay intertidal maps to other heavy metal pollutants that have a high affinity with fine-grained clay particles i.e. Pb, Zn, Cu, Al in estuarine sediments

On the numerical accuracy in finite-volume methods to accurately capture turbulence in compressible flows

The goal of the present paper is to understand the impact of numerical schemes for the reconstruction of data at cell faces in finite-volume methods, and to assess their interaction with the quadrature rule used to compute the average over the cell volume. Here, third-, fifth- and seventh-order WENO-Z schemes are investigated. On a problem with a smooth solution, the theoretical order of convergence rate for each method is retrieved, and changing the order of the reconstruction at cell faces does not impact the results, whereas for a shock-driven problem all the methods collapse to first-order. Study of the decay of compressible homogeneous isotropic turbulence reveals that using a high-order quadrature rule to compute the average over a finite volume cell does not improve the spectral accuracy and that all methods present a second-order convergence rate. However the choice of the numerical method to reconstruct data at cell faces is found to be critical to correctly capture turbulent spectra. In the context of simulations with finite-volume methods of practical flows encountered in engineering applications, it becomes apparent that an efficient strategy is to perform the average integration with a low-order quadrature rule on a fine mesh resolution, whereas high-order schemes should be used to reconstruct data at cell faces.Comment: arXiv admin note: text overlap with arXiv:1902.0666

Interculturality in the Primary EFL Classroom: Increasing Tolerance through (Inter) Cultural Awareness

Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Didáctica do Inglês,Os alunos de inglês como língua estrangeira aprendem as regras e convenções da língua para facilitar o seu percurso até se tornarem utilizadores competentes da língua inglesa. Este processo é justificado pelo facto de o inglês ser amplamente reconhecido como a língua mais utilizada na comunicação intercultural e comércio internacional. Este texto vai argumentar que o inglês, como língua estrangeira, é uma ferramenta essêncial na economia moderna. Portanto, pode ser usada para ampliar os horizontes tanto filosóficos como intelectuais dos alunos de inglês como língua estrangeira pois utiliza completamente as competências adquiridas através da promoção de princípios fundamentais da educação para a cidadania. Os conceitos de capital cultural, capital linguístico e facilidade linguística de Bourdieu farão parte dos fundamentos da discussão acerca da importância e utilidade social de adquirir competências linguísticas adcionais (ex: a língua inglesa). Focado principalmente no aumento da consciência de outras culturas entre alunos de inglês como língua estrangeira, especialmente de culturas de países onde a língua oficial é o inglês. O objectivo deste texto é identificar e reduzir a intolerância dentro da abordagem inter-cultural, sendo que especial atenção vai ser dada ao racismo

My Thoughts Are You

https://digitalcommons.library.umaine.edu/mmb-vp/4429/thumbnail.jp