Decomposition of the mechanical stress tensor: from the compressible Navier–Stokes equation to a turbulent potential flow model

We frame the mechanical stress tensor decomposition in a general procedure which involves the Helmholtz-Hodge decomposition. We highlight the impact of the mechanical stress tensor decomposition on the Navier-Stokes equation, with emphasis on the dissipation function. For fluids with low compressibility, we draw some insights on the Reynolds Averaged Navier-Stokes equations, and on the Reynolds stress tensor decomposition. We derive a turbulent potential flow model, and investigate the transition from viscous potential flow to turbulent potential flow. Under low Mach number approximation, we apply the turbulent potential flow model to one-dimensional propagation of large amplitude pressure waves in liquid-filled pipe

Modeling of low Mach number unsteady turbulent pipe flows

Under adiabatic conditions, and neglecting temperature variations due to entropy production, we present a set of Reynolds Averaged Navier-Stokes (RANS) equations for fluids of low compressibility, i.e., fluids in the liquid state. In the low Mach number limit, we specialize the RANS equations to the one-dimensional unsteady pipe flow, and we deduce the dimensionless number that plays a predominant role in the flow behavior. We reduce the system of equations to a linear damped wave equation, and use its analytical solution to investigate the propagation of large amplitude pressure waves in liquid-filled pipes (water hammer phenomenon). We test the model reliability by comparing the analytical solution of the proposed model against experimental data available in the literature

Classical irreversible thermodynamics versus extended irreversible thermodynamics: the role of the continuity equation

This brief note focuses on a simple fluid, i.e., a homogeneous, chemically inert, and electrically neutral fluid, for which, in the linear non-equilibrium regime, the thermodynamic state is expressed by a relation between pressure, temperature, and density. The approach based on the elementary scales is used to check the validity range of both the classical irreversible thermodynamics and the extended irreversible thermodynamics. The achieved result reveals that the classical irreversible thermodynamics fails in providing arm adequate response when the mechanical solicitations exceed limit values

Beach drainage system: a comprehensive review of a controversial soft-engineering method

The beach drainage can be included among the soft engineering methods aimed to counteract the shoreline retreat related to the sediment redistribution along the beach profile. The idea that the groundwater table plays a role in the mobilization of the sediment grains underlies the application of the beach drainage system (BDS) as a tool able to modify the natural dynamics of groundwater table at sandy beaches. Indeed, BDS consists of a series of alongshore buried drains aimed to lower the groundwater table. Due to the drainage, the thickening of the layer of dry sand makes the solid grains less prone to be mobilized by the action of the waves at the swash zone, where interaction phenomena between the percolating and the incoming water lens take place. This tool had a troubled history. Its first applications were encouraging. Since then, controversial performances of both experimental and prototype scale experiences have been observed around the world. This paper aims to present an up-to-date full review of the studies and experiments carried out so far, in order to provide the reader with a complete perspective on its strength and weakness as well as open challenges to be faced in the near future

MRI and Clinical Biomarkers Overlap between Glaucoma and Alzheimer’s Disease

glaucoma is the leading cause of blindness worldwide. It is classically associated with structural and functional changes in the optic nerve head and retinal nerve fiber layer, but the damage is not limited to the eye. The involvement of the central visual pathways and disruption of brain network organization have been reported using advanced neuroimaging techniques. the brain structural changes at the level of the areas implied in processing visual information could justify the discrepancy between signs and symptoms and underlie the analogy of this disease with neurodegenerative dementias, such as alzheimer’s disease, and with the complex group of pathologies commonly referred to as “disconnection syndromes.” this review aims to summarize the current state of the art on the use of advanced neuroimaging techniques in glaucoma and alzheimer’s disease, highlighting the emerging biomarkers shared by both diseases

Explaining factors leading to community acceptance of wind energy. Results of an expert assessment

The present article deals with two key drivers of social acceptance of wind energy: procedural justice and distributional justice. It is based on a comparative expert assessment carried out in the frame of the Horizon 2020 project WinWind covering six European countries. The focus of the paper is on procedural and financial participation of citizens and local stakeholders in wind energy projects. The first part covers institutional arrangements for public engagement in two areas of the decision-making process-wind turbine zoning/siting in spatial plans and authorization procedures. Here, three levels of public involvement-information, consultation and participation-were analyzed. The second part examines active and financial participation of citizens and local stakeholders. Here, we distinguish between two different modes of governance: institutionalized forms of public governance and voluntary forms of corporate governance. The outcomes suggest that concrete paths to the social acceptance of wind energy are fostered via appropriate institutional spaces for public engagement. Furthermore, missing opportunities for active and passive financial participation can have strong negative consequences for community acceptance