Industrial Symbiosis for a Sustainable City: Technical, Economical and Organizational Issues

In this paper, we propose the adoption of industrial symbiosis approach within cities as a tool to improve their environmental sustainability. In particular, organic waste can be used to produce electric energy required by cities. In this way, a resource closed loop is generated, able to reduce the amount of waste disposed of in landfill and the energy purchased from outside the city. We develop a conceptual model that identifies symbiotic flows and processes that generate and receive them. We model these processes using the input-output approach. An efficiency measure of the symbiotic approach within urban areas has been proposed. Finally, we employ three case examples in order to show how the model works. As a result, we provide some useful managerial suggestions for policy makers about the implementation of industrial symbiosis within cities

Transient formation of the passive scalar spectrum at a turbulent interface

We consider the transport of a passive scalar through the turbulent-turbulent interface between two decaying isotropic turbulent flows with different kinetic energy. Although the concentration of a passive substance exhibits a complex behaviour that shows many phenomenological parallels with the turbulent velocity field, the statistical properties of passive scalar turbulence are in part decou­pled from those of the underlying velocity [1,2]. In our numerical experiment, the passive scalar is initially uniform in each of the two isotropic regions. The interaction of the two isotropic flows generates a high scalar variance region in the centre of the mixing layer and two intermittent scalar fronts arise at the margins of the mixing layer. The velocity field instead presents one front only which is placed in the part of the field where the kinetic energy is lower [3,4] or, in case the ener­gy is uniform but the correlation is varying, where the integral scale is lower [5]. In the central part of the mixing layer, between the two intermittent fronts, the spectrum of the scalar fluctuation shows a full range of scales just after one eddy turnover time (see figure below). Moreover, the scalar spectrum shows a more prominent inertial range region than the velocity spectrum - a wider range with a scaling exponent closer to -5/3 - a feature which has been observed also in ho­mogeneous flows at moderate Reynolds numbers, see [6,7]. This feature is preserved for about ten eddy turnover times, during which the scalar variance decays slower than the velocity fluctuatio

Energy and water vapor transport across a simplified cloud-clear air interface

We consider a simplified physics of the could interface where condensation, evaporation and radiation are neglected and momentum, thermal energy and water vapor transport is represented in terms of the Boussinesq model coupled to a passive scalar transport equation for the vapor. The interface is modeled as a layer separating two isotropic turbulent regions with different kinetic energy and vapor concentration. In particular, we focus on the small scale part of the inertial range as well as on the dissipative range of scales which are important to the micro-physics of warm clouds. We have numerically investigated stably stratified interfaces by locally perturbing at an initial instant the standard temperature lapse rate at the cloud interface and then observing the temporal evolution of the system. When the buoyancy term becomes of the same order of the inertial one, we observe a spatial redistribution of the kinetic energy which produce a concomitant pit of kinetic energy within the mixing layer. In this situation, the mixing layer contains two interfacial regions with opposite kinetic energy gradient, which in turn produces two intermittent sublayers in the velocity fluctuations field. This changes the structure of the field with respect to the corresponding non-stratified shearless mixing: the communication between the two turbulent region is weak, and the growth of the mixing layer stops. These results are discussed with respect to experimental results with and without stratification.Comment: 12 pages, 8 figure

Cumulative distribution of the stretching of vortical structures in isotropic turbulence

By using a Navier-Stokes isotropic turbulent field numerically simulated in the box with a discretization of 1024^3 [Biferale et al. (2005)], we show that the probability of having a stretching-tilting larger than twice the local enstrophy is very small. This probability decreases if we try to filter out the large scales, while it increases filtering out the small scales. This is basically due to the suppression of the compact structures (blobs)

A cohesive model to predict the loading bond capacity of concrete structures repaired/reinforced with HPFRC/UHPFRC and stressed to mixed mode

The risk of cracking/debonding of a cement overlay used to repair or strengthen an existing structure is still a key issue. Current bond test methods are not designed to measure the combined effect of peeling (mode I) and shear (mode.II) on the interface. A few existing models propose theoretical approaches to predict that, but they were fitted on specific cases and lack in generality. In addition, controversial opinions about the influence of both the moisture level of the substrate surface prior to the application of the overlay and properties of the latter on the loading bond capacity call for further investigations. In this work, a cohesive model is developed to predict the loading bond capacity of an existing concrete structure overlaid by a layer of HPFRC/UHPFRC. Different bond tests were specifically designed for calibrating the cohesive pa-rameters employed into the model, which also takes into account the type of the overlay used and the moisture conditioning level. An experimental cam-paign confirmed the reliability of the predictions of the proposed theoretical model