Hydrodynamic Structure with Scour Hole Downstream of Bed Sills

Flow Field around a Vertical Cylinder in Presence of Long Waves: An Experimental Study

Long waves caused by storm surges or river floods can significantly impact marine and fluvial structures such as bridge piers. Apart from the forces that they generate on the structure, they also contribute to the formation of turbulent eddies downstream of the obstacle. This is relevant, as in this way they can affect both an erodible bottom and the ecosystem. The present study describes a medium-scale experiment, in which the propagation of two different long waves released on a steady current is investigated in the presence of a bottom-mounted rigid emergent cylinder. Velocity measurements were acquired by a Particle Image Velocimetry (PIV) system, providing instantaneous flow velocity vectors on selected 2D planes. For each experimental condition, the time-varying velocity field near the cylinder was examined in selected vertical and horizontal planes. First, we tested which analytical theory or approximated method can best represent the experimental waves. After this, we estimated the horizontal maps of velocity and vorticity downstream of the obstacle and finally processed the velocity signals by means of a wavelet-based technique, to derive the length scales of turbulent eddies. In such a way, we specifically derived how the spreading of coherent turbulent structures downstream of the cylinder depends on the features of the flume, cylinder, and wave.

Coastal vulnerability analysis to support strategies for tackling COVID-19 infection

The recent COVID-19 pandemic has constrained world governments to impose measures of restraint and social distancing which also involves coastal areas. One of the most affected activities is tourism due to travel restrictions imposed by precautionary measures. This is also reflected in the recreative use of the coastal strip. Consequently, beaches and coastal stretches of small municipalities can potentially become contagious outbreaks of COVID-19 if adequate control and management measures are not promptly implemented. During the 20th century, several factors, both natural and human induced, caused alterations to coastal processes and consequently to the services they were providing. Coastal environments are very vulnerable and sensitive to change. This raises the need for careful assessment prior to any intervention or strategy involving the coastal system. Several literature studies have been focused both in the past and in recent years on examining the main factors affecting coastal vulnerability highlighting critical issues and shortcomings. The present paper, addressing all critical issues from literature review, illustrates a consistent methodology to support coastal management which combines both physical and socio-economic aspects and provides for the quantification of two different coastal vulnerability indices. The approach adopted has led to a distinction of different coastal peculiarities and a mapping of risk levels providing, in addition, the basis for the implementation of strategies risks related to COVID-19. The methodology proposed can be a useful reference in several areas, in demonstrating its effectiveness it has been applied with respect to a coastal area in southern Italy.

Influence of Scour Development on Turbulent Flow Field in Front of a Bridge Pier

This study concerns the turbulent flow field influenced by the scour development around a bridge pier. The scour hole evolution as well as the temporal variation of scour depth around the pier were firstly analyzed. Subsequently, the flow fields in front of the pier at different instants during the scour process were measured using particle image velocimetry (PIV). It shows that the scour depth at the pier front exceeds that of the pier side at the later scouring stage. The temporal development of scour depth can be well predicted by a simple practical engineering model based on an exponential function with a change in the two adjustable coefficients. The flow field indicates that with the development of scour hole, the downward flow in front of the pier becomes more prominent, meanwhile the flow becomes more turbulent. The variation tendency for both velocities and turbulence intensities along the streamwise direction in front the pier shows similarity. The Reynolds shear stress generally increases with developing scour hole, and the region with large value enlarges and moves upstream of the scour hole.

On the Need for an Integrated Large-Scale Methodology of Coastal Management: A Methodological Proposal

Sustainable management of coastal areas involves dealing with problems such as coastal erosion, rapid growth in the rate of urbanization, tourism, environmental degradation associated with industrial and urban activities. Besides consideration is provided for the effects of climate change, whose scenarios also have significant consequences on coastal systems that are already extremely vulnerable and prone to many human pressures. Over the years, several international and national studies have been conducted to deepen the coastal processes. To date—despite considerable efforts—there are still problems. Two relevant priorities emerge: managing coastal risks and ensuring sustainable coastal management. In response to the above-mentioned challenges, it is worthwhile to elaborate an integrated methodology that, basing on the collection, analysis and evaluation of data, may provide an effective guideline for the successful implementation of each action, while providing timely and targeted information for the adoption of governance strategies concerning the prevention and management of marine-coastal risks. In the present study, considering what emerged in the major research projects on the coastal field during the last decades, a methodological proposal is outlined to pursue the principles of the integrated coastal zona management (ICZM) and join the managing coastal risks with sustainable uses focusing on the implementation scale.