Confronting Grand Challenges in environmental fluid mechanics

Environmental fluid mechanics underlies a wealth of natural, industrial and, by extension, societal challenges. In the coming decades, as we strive towards a more sustainable planet, there are a wide range of grand challenge problems that need to be tackled, ranging from fundamental advances in understanding and modeling of stratified turbulence and consequent mixing, to applied studies of pollution transport in the ocean, atmosphere and urban environments. A workshop was organized in the Les Houches School of Physics in France in January 2019 with the objective of gathering leading figures in the field to produce a road map for the scientific community. Five subject areas were addressed: multiphase flow, stratified flow, ocean transport, atmospheric and urban transport, and weather and climate prediction. This article summarizes the discussions and outcomes of the meeting, with the intent of providing a resource for the community going forward

Confronting Grand Challenges in Environmental Fluid Dynamics

Environmental fluid dynamics underlies a wealth of natural, industrial and, by extension, societal challenges. In the coming decades, as we strive towards a more sustainable planet, there are a wide range of grand challenge problems that need to be tackled, ranging from fundamental advances in understanding and modeling of stratified turbulence and consequent mixing, to applied studies of pollution transport in the ocean, atmosphere and urban environments. A workshop was organized in the Les Houches School of Physics in France in January 2019 with the objective of gathering leading figures in the field to produce a road map for the scientific community. Five subject areas were addressed: multiphase flow, stratified flow, ocean transport, atmospheric and urban transport, and weather and climate prediction. This article summarizes the discussions and outcomes of the meeting, with the intent of providing a resource for the community going forward

The restorative role of annexin A1 at the blood–brain barrier

Annexin A1 is a potent anti-inflammatory molecule that has been extensively studied in the peripheral immune system, but has not as yet been exploited as a therapeutic target/agent. In the last decade, we have undertaken the study of this molecule in the central nervous system (CNS), focusing particularly on the primary interface between the peripheral body and CNS: the blood–brain barrier. In this review, we provide an overview of the role of this molecule in the brain, with a particular emphasis on its functions in the endothelium of the blood–brain barrier, and the protective actions the molecule may exert in neuroinflammatory, neurovascular and metabolic disease. We focus on the possible new therapeutic avenues opened up by an increased understanding of the role of annexin A1 in the CNS vasculature, and its potential for repairing blood–brain barrier damage in disease and aging

Sticks and carrots for reducing property-level risks from floods: an EU-US comparative perspective

In discussing legal and policy frameworks for flood risk management, the attention is often put on increasing resilience in public spaces. In terms of private properties, discussions are geared toward enhancing the adaptive capacity of future developments. This paper focuses on the instruments associated with resilience of existing privately owned residential buildings mainly from the perspective of post-flood policies and compensation regimes. The paper scrutinizes the relevant legal and policy landscapes in the United States, the European Union and two Member States – the UK and the Netherlands. The goal is to provide mutual lessons learned between the EU, its Member States, and the US and to set forth generally applicable recommendations for improving post-flood policies for existing buildings

RAMS sensitivity to grid spacing and grid aspect ratio in Large-Eddy Simulations of the dry neutral Atmospheric Boundary Layer

Large Eddy Simulation (LES) is being established as a commonplace modeling tool in many areas of research interested in reproducing Atmospheric Boundary Layer (ABL) turbulence. LES results can however be highly dependent on the combination of the numerical schemes, subgrid scale model and computational grid, and their impact on simulations should be examined. The present work focuses on assessing the impact of grid spacing on LES of an idealized neutral ABL realized with the Regional Atmospheric Modeling System (RAMS), a commonly employed mesoscale model. To this aim, nine simulations with varying grid resolutions and otherwise identical setups have been performed. The grids are obtained combining three different horizontal (64, 32, 16 m) and vertical (16, 8, 4 m) spacings, covering a domain of 4096 × 4096 × 1024 m. Results are post-processed in terms of mean profiles of momentum flux, horizontal velocity and velocity variances, as well as velocity spectra and instantaneous snapshots of velocity fields. The analysis reveals that the turbulent flow can be simulated satisfactorily by employing a computational grid with a sufficiently fine horizontal spacing and an aspect ratio that alleviates potential adverse effects of the combination of RAMS numerics and subgrid model on the solution. Based on the present results, a horizontal spacing smaller than around 30 m is suggested for the examined regime, and an aspect ratio of 4 is recommended, while both larger and smaller values should be avoided. When using different aspect ratios RAMS LESs of the neutral ABL were found to be affected by an excessive dissipation of turbulence kinetic energy

Comparison of High-Resolution Pressure Peaks in Closed and Open-Section Wind Tunnels

Wind tunnel testing represents an established technique for the assessment of wind-induced pressure on cladding systems. Nonetheless, some physical events, such as the strong negative peaks of pressure that occur on a building’s lateral facades, are not fully understood. These events can be catastrophic for cladding systems, which motivates their further investigation. The objective of the present work is to study the nature of extreme suction events, by comparing high-resolution pressure tap measurements on a high-rise building collected at two different facilities: the closed-circuit wind tunnel of Politecnico di Milano, and the open-circuit Wall of Wind facility at Florida International University. We first compare the statistics of the two atmospheric boundary layers, and subsequently present results for the mean and root mean square pressure distributions and negative peak pressure events. The experiments provide consistent results, and they both exhibit two types of negative peak pressure events: one is characterized by an extremely short duration and spatial extension, while the other impacts a larger portion of the facade