1,721,403 research outputs found
ABBA: A Celebration
Full text linkPromotional material and playbill insert for the January 28, 2006 performance of ABBA: A Celebration.https://opus.govst.edu/cpa_memorabilia/1042/thumbnail.jp
Dynamic tensorial eddy viscosity model: Effects of compressibility and of complex geometry
Full text linkA previous paper by Cimarelli et al. ["General formalism for a reduced description and modelling of momentum and energy transfer in turbulence,"J. Fluid Mech. 866, 865-896 (2019)] has shown that every decomposition of turbulent stresses is naturally approximated by a general form of tensorial eddy viscosity based on velocity increments. The generality of the formalism is such that it can also be used to give a reduced description of subgrid scalar fluxes. In the same work, this peculiar property of turbulent stresses and fluxes has been dynamically exploited to produce tensorial eddy viscosity models based on the second-order inertial properties of the grid element. The basic idea is that the anisotropic structure of the computational element directly impacts, although implicitly, the large resolved and small unresolved scale decomposition. In the present work, this new class of turbulence models is extended to compressible turbulence. A posteriori analysis of flow solutions in a compressible turbulent channel shows very promising results. The quality of the modeling approach is further assessed by addressing complex flow geometries, where the use of unstructured grids is demanded as in real world problems. Also in this case, a posteriori analysis of flow solutions in a periodic hill turbulent flow shows very good behavior. Overall, the generality of the formalism is found to allow for an accurate description of subgrid quantities in compressible conditions and in complex flows, independent of the discretization technique. Hence, we believe that the present class of turbulence closures is very promising for the applications typical of industry and geophysics
Dynamic Tensorial Eddy Viscosity and Turbulent Stresses
No full textIn the theoretical framework provided by an alternative decomposition of the turbulent stresses, a new formalism for their approximation and understanding has been proposed in [1] that spontaneously directs to a tensorial turbulent eddy viscosity. Based on this, new modelling approaches for LES, representing subgrid fluxes for momentum, energy and heat fluxes, based on the second order inertial properties of the grid element are developed. The new model has firstly tested in the case of typical LES benchmark for compressible flow, such as the turbulent channel flow. A numerical simulation of turbulent flows in a more complex geometry using unstructured meshes has been performed, exploiting the properties of the eddy viscosity model based on the inertial tensor of the numerical grid element. The analysis highlights the capability of the model to well reproduce the anisotropic character of the turbulent flows
Effect of Variable Density on Subgrid Scales
No full textVariable density flows are very common in nature, in technology and in industry. The numerical simulation of complex flows of applicative interest and with relevant variable density flows requires the truncation of turbulent scales of the resolved velocity field, in order to reduce the required computational resources
MARTA ABBA, A VAMP VIRTUOSA DO ÚLTIMO PIRANDELLO
No full textMARTA ABBA, A VAMP VIRTUOSA DO ÚLTIMO PIRANDELLO.
Analysis of the variation of costs for sewage sludge transport, recovery and disposal in Northern Italy: A recent survey (2015-2021)
Full text linkThe cost for the recovery/disposal of residues produced by wastewater treatment plants (WWTPs) represents a relevant aspect in the economics of WWTP management. We elaborated and applied a desk-based methodology to analyze tender processes and to investigate quantitatively and qualitatively the variability of unit costs for sewage sludge (EWC 190805) management in Northern Italy from 2015 to 2021. We conducted a qualitative survey for operators of the sector. Unit costs for sludge management increased over time. The unit cost was mostly affected by the type of sludge recovery/disposal being the cost for recovery in agriculture (direct or by composting) lower than incineration and landfilling. Other variables influencing the cost were the distance and discount offered by the contractor. Regulatory and judiciary events determined a sudden increase of sludge disposal costs in Italy between 2017 and 2019. Recovery in agriculture, when practicable, remains the preferable option. Results can orient and support the optimization of sludge management costs and be of interest for future studies at national or European level
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