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This work describes the main hydraulic features of vortex dropshafts along with some examples of their mis-designs and consequent malfunction. Laboratory experiments were conducted to test the hydraulic performance of subcritical vortex intakes using supercritical approach flow design basis. The purposes of these drop structures are to: (i) convey the storm runoff towards the sea through the existing sewer system located at lower elevations and (ii) by-pass insufficient sewers. The proper operation of these structures is crucial to prevent flooding and to guarantee the urban safety. This issue is particularly relevant for the sewer system of Naples (Italy), which is strongly constrained by its hilly landscape. Several drop structures were realized to connect the modern urban drainage system to the early sewer mains located at the sea level. This work intends to highlight practical issues to enhance the existing vortex dropshafts, with possible applications to other cases similar to the Neapolitan context. [ABSTRACT FROM PUBLISHER]

The OBREC is an overtopping structure which is integrated into a traditional rubble-mound breakwater to convert wave energy into electricity. The relatively simple geometry of this overtopping device, with a single frontal ramp and a reservoir, makes the technology suitable to be fully combined also with existing structures. OBREC has been deeply investigated over the last years with physical and numerical model tests, and it is still under development with the ongoing monitoring activities at full-scale in real environments focusing on the wave-OBREC interaction. A comprehensive review of the research studies during the last ten years is here presented. The paper contains some unpublished details on OBREC geometry and power take-off strategy. A special attention is also directed to the description of the full-scale prototype of OBREC at Naples harbour, where an experimental campaign is still continuing. • Innovative rubble mound breakwater for wave energy production. • Physical and numerical model tests. • Formulae for preliminary design. • Full-scale prototype. [ABSTRACT FROM AUTHOR]