Hydrodynamic modeling in the channel network of Venice

A combined framework of hydrodynamic models is presented that describes the water dynamics in the channel network of the city of Venice. The application of these hydrodynamic models is part of a larger project carried out by UNESCO that has the aim of describing the water quality of the channels in Venice. An existing 2-dimensional finite element model simulates the hydrodynamic features in the Venice Lagoon. The simulated data is then used as the boundary condition for the 1-dimensional hydrodynamic model of the inner channels of Venice. Inside the channel system the water elevation and the current velocities are computed. The simulated variables are calibrated and compared with data from field measurements that UNESCO has carried out during the years 1990-92 and during 1998. It was possible to use a constant friction parameter for all the channels in the network. Simulated water elevation shows an excellent agreement with the measured data, and also current velocities are generally reproduced quite faithfully. Some low-energy channels show major errors in the reproduction of the velocity speed. It is believed that changing bathymetry (silting-up of the channels) could be a cause of this phenomenon. The hydrodynamic data will eventually be used in the second part of the project where the water quality of the channel network will be investigated. For this purpose the hydrodynamic parameters simulated will be used by the water quality model as a boundary and initial condition in order to simulate the biological and chemical variables and to describe the ecological dynamics

On the correct surface stress for the prediction of the wind wave field and the storm surge in the Northern Adriatic Sea

This paper discusses which formulation of the surface stress over the sea determines the most accurate prediction of the wind wave field and storm surge in the Northern Adriatic Sea. The study shows that the results of the storm surge and wind wave models, when compared to the available observations, can be used for the validation of the surface stress and of the expression adopted for the ssr (sea surface roughness). The results are representative of short fetch and young wind sea conditions. The agreement between the results and the measurements shows the feasibility of the wind wave and storm surge predictions in the Adriatic Sea and supports the dependence of the ssr, and, therefore, of the surface stress, on the spectrum of the surface wave

Deep-sea reverse osmosis desalination for energy efficient low salinity enhanced oil recovery

The decrease in the oil discoveries fuels the development of innovative and more efficient extraction processes. It has been demonstrated that Enhanced Oil Recovery (EOR, or tertiary recovery technique) offers prospects for producing 30 to 60% of the oil originally trapped in the reservoir. Interestingly, oil extraction is significantly enhanced by the injection of low salinity water into oilfields, which is known as one of the EOR techniques. Surface Reverse Osmosis (SRO) plants have been adopted to provide the large and continuous amount of low salinity water for this EOR technique, especially in offshore sites. In this article, we outline an original solution for producing low salinity water for offshore EOR processes, and we demonstrate its energy convenience. In fact, the installation of reverse osmosis plants under the sea level (Deep-Sea Reverse Osmosis, DSRO) is found to have significant potential energy savings (up to 50%) with respect to traditional SRO ones. This convenience mainly arises from the non-ideality of reverse osmosis membranes and hydraulic machines, and it is especially evident - from both energy and technological point of view - when the permeate is kept pressurized at the outlet of the reverse osmosis elements. In perspective, DSRO may be a good alternative to improve the sustainability of low salinity EOR

DAS Over Multimode Fibers With Reduced Fading by Coherent Averaging of Spatial Modes

We investigate the performance of distributed acoustic sensing over multi-mode fibers based on heterodyne phase-sensitive optical time-domain reflectometry. We report a mathematical model describing the relation between phase variation and applied strain in the presence of multi-mode propagation that supports the feasibility of distributed acoustic measurements over multi-mode fibers. We also propose a novel coherent averaging method that achieves up to a three-fold reduction of the noise floor compared to state-of-the-art methods

Storm surge in the Adriatic Sea: observational and numerical diagnosis of an extreme event

International audienceStorm surge events occur in the Adriatic Sea, in particular during autumn and winter, often producing flooding in Venice. Sea levels are forecasted by numerical models, which require wind and pressure fields as input. Their performances depend crucially on the quality of those fields. The storm surge event on 16 November 2002 is analysed and simulated through a finite element hydrodynamic model of the Mediterranean Sea. Several runs were carried out, imposing different atmospheric forcings: wind fields from ECMWF analysis, high resolution winds from the limited area model LAMI and satellite observed winds from QuikSCAT (NASA). The performance of the hydrodynamic model in each case has been quantified. ECMWF fields are effective in reproducing the sea level in the northern Adriatic Sea, if the wind speed is enhanced by a suitable multiplying factor. High resolution winds from LAMI give promising results, permitting an accurate simulation of the sea level maxima. QuikSCAT satellite wind fields produce also encouraging results which claim, however, for further research

A comparison between modelled and observed atmospheric fields over the Adriatic and Tyrrhenian Seas

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