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The impact of climate change on agriculture is a major challenge for the food and water security of next decades. In the future, the Mediterranean area will be particularly exposed to water scarcity, which may lead to significant losses in agricultural yield. Climate projections show that many densely cultivated areas of Southern Europe will suffer decreases of precipitation intensity and frequency, with severe consequences in terms of irrigation requirements, i.e. the amount of water needed to meet the evapotranspirative demand of crops during dry periods. Therefore, the modelling of climate-driven crop water requirements and available water resources is essential to understand future criticalities for agriculture and to adopt proper adaptation strategies.In this study, the agricultural irrigation requirement was estimated by modeling the daily water balance in the soil, on the basis of evapotranspirative demand and precipitation, over the densely irrigated basin of Demonte, in South Piedmont (Italy). The volumes of irrigation required by local agriculture were calculated for 30 main crops, taking into account the local information of yearly distribution of crops. The available surface water in the basin was compared to the present irrigation requirements, using flow discharge data from the river that feeds the local network of irrigation channels. In order to analyze future scenarios, precipitation and temperature data from five EURO-CORDEX regional climate models were used to estimate the irrigation requirements and the available surface water for the 2035-2055 period, considering multiple RCP scenarios.Results show that the current available water resources are little enough to meet the irrigation requirements over the Demonte basin for the months of July and August, when most of the cereals reach the maximum growing phase. The climate-driven assessment for the future decades shows that the water required for irrigation will gradually exceed the threshold of available resources, with different degrees of severity depending on the RCP scenario. Moreover, future scenarios highlight a progressive increase in the temporal lag between the period of maximum irrigation requirements (July-August) and the high-flow regime period in the hydrographic network (April-June). As a consequence, most of the surface freshwater in the Demonte basin will not be available for agriculture during summer, when most of the irrigation will be required. Modeling the future scenarios of agricultural water needs and available resources is an important step to understand the future implications of climate change on food production. Moreover, this is a valuable instrument to support proper adaptation strategies, both in terms of agricultural and water management planning policies.

Since Howard (1833) first suggested that air temperatures recorded in urban areas are higher than in the surrounding countryside, there have been hundreds of studies of the Urban Heat Island (UHI) phenomenon, which is due to the different thermal properties between urbanized and natural lands, anthropogenic heat emissions, human-induced pollution and limited wind blowing among buildings. The impervious land cover type and the presence of sheltering constructions trap heat during the day and release it during the night, resulting in higher night-time temperatures. The UHI intensity is commonly computed as the difference between an urban and a rural measurement site and, therefore, the definition of station pairs is a crucial task for its evaluation. To this end, we propose a powerful method capable of highlighting the thermal pattern typical of each weather station: the Mean Temperature Difference (MTD) method. Principal Component Analysis (PCA) is adopted to cluster similar thermal behaviours, allowing an objective classification of the stations. The strength and novelty of this data-based approach, which employs hourly temperature measurements, lays in the fact that any preliminary assumption about the landscape characterizing each station (i.e. urban or rural) is not needed, making it less arbitrary and more objective than other methods. The application of the proposed method to the metropolitan area of Turin (Italy) shows that the joint use of MTD with PCA yields reliable and easily interpretable results, also in an area with complex morphology (orographic and hydrographic heterogeneity, different land uses, etc.). Once the best urban and rural pairs have been identified, the characteristics of the Urban Heat Island are shown, highlighting its seasonal and daily properties.

Rayleigh-Bénard convection with nonhomogeneous thermal boundaries (sinusoidal temperature patterns set in-phase at the top and bottom plates) is numerically studied in three- and two-dimensional domains. Two spatial convective scales occur: the one due to the self-organized clustering of plumes-which is known to appear in homogeneous conditions-and the scale induced by the boundary heterogeneities. The latter drives the convection patterning, both in 3D and 2D, when the wavelength of the perturbation is comparable with the self-organized one.

International audience; Electromagnetic attacks, which in fact exploit essentially the magnetic field generated by ICs, are commonly used by adversaries to retrieve secret information manipulated by integrated circuits. Due to the increasing resolution and effectiveness of EM equipment used to perform these attacks, it is becoming increasingly difficult to design secure circuits robust enough to resist these attacks. The contribution of this paper is threefold. First, it describes a simulation flow of the magnetic field radiated by ICs. The introduced flow is based on an industrial voltage drop tool: ANSYS RedHawk. Second, it introduces a methodology to localize the root cause of leakages in ICs as well as EM hotspots, i.e. positions above the IC surface where an adversary can place its probe to capture secrets. The latter contribution is based on the concept of noise to add which is introduced in this paper in order to overcome the absence of noise in simulations (noise which is omnipresent in practice) that limits their interpretability. Finally, the paper demonstrates the soundness of the proposed solution by confronting simulation results with measurements.

This work investigates how turbulence in open-channel flows is altered by the passage of surface waves by using experimental data collected with laboratory tests in a large-scale flume facility, wherein waves followed a current. Flow velocity data were measured with a laser Doppler anemometer and used to compute profiles of mean velocity and Reynolds stresses, and pre-multiplied spectra. The velocity signal containing contributions from the mean flow, wave motion and turbulence was decomposed using the empirical mode decomposition (EMD), which is considered a promising tool for the analysis of velocity time series measured in complex flows. A novel outer length scale ) appears. These longitudinal structures present in the wave-dominated flow region seem to share many features with Langumir-type cells.

This paper investigates the existence and scaling of the so-called large-scale and very-large-scale motions (LSMs and VLSMs) in non-uniform turbulent open-channel flows developing over a smooth bed in a laboratory flume. A laser Doppler anemometry system was employed to measure vertical profiles of longitudinal and bed-normal velocity statistics over a wide range of hydraulic conditions. Pre-multiplied spectra of the longitudinal velocity fluctuations revealed the existence of two peaks occurring at wavelengths consistent with those associated with LSMs and VLSMs as detected in the past literature pertaining to wall turbulence. However, contrary to so-called canonical wall flows (i.e. flat-plate boundary layers, pipe and closed-channel flows), the LSM and VLSM peaks observed in the open-channel flows investigated herein are detectable over a much larger extent of the wall-normal coordinate. Furthermore, the VLSM peak appears at von Karman numbers $Re_{\unicode[STIX]{x1D70F}}$ as low as 725, whereas in other wall flows much higher values are normally required. Finally, as conjectured by a recent study on uniform rough-bed open-channel flows, the present paper confirms that LSM wavelengths scale nicely with the flow depth, whereas the channel aspect ratio (i.e. the ratio between channel width and flow depth) is the non-dimensional parameter controlling the scaling of VLSM wavelengths. The intensity and wavelengths of the VLSM peaks were also observed to depend on the spanwise coordinate. This result suggests that VLSMs might be dynamically linked to secondary currents, as these are also known to vary in strength and size across the channel width.

We review developments in the field of boundary-layer flow over complex topography, focussing on the period from 1970 to the present day. The review follows two parallel strands: the impact of hills on flow in the atmospheric boundary layer and gravity-driven flows on hill slopes initiated by heating or cooling of the surface. For each strand we consider the understanding that has resulted from analytic theory before moving to more realistic numerical computation, initially using turbulence closure models and, more recently, eddy-resolving schemes. Next we review the field experiments and the physical models that have contributed to present understanding in both strands. For the period 1970–2000 with hindsight we can link major advances in theory and modelling to the key papers that announced them, but for the last two decades we have cast the net wider to ensure that we have not missed steps that eventually will be seen as critical. Two important new themes are given prominence in the 2000–2020 period. The first is flow over hills covered with tall plant canopies. The presence of a canopy changes the flow in important ways both when the flow is nearly neutral and also when it is stably stratified, forming a link between our two main strands. The second is the use of eddy-resolving models as vehicles to bring together hill flows and gravity-driven flows in a unified description of complex terrain meteorology.

A non-intrusive low-cost technique for monitoring the temporal and spatial evolution of the scour hole around bridge piers is presented. The setup for the application of the technique is simple, low-cost and non-intrusive. It couples a line laser source and commercial camera to get a fast and accurate measurement of the whole scour hole in the front and behind the bridge pier. A short campaign of measurements of the scour hole around a bridge pier in clear-water conditions is presented to provide a control test and to show how to apply the new method. Finally, the results are compared with two of the most used equations, for the time evolution of the maximum scour depth in clear-water conditions, to show the effectiveness of the proposed technique.

A rotary hydrostatic pressure machine (RHPM) is a hydropower converter for very low head applications (less than 2.5 m). An RHPM can be installed in straight canals, because its wheel can g...

The dispersion of heavy particles such as seeds within canopies is evaluated using Lagrangian stochastic trajectory models, laboratory, and field experiments. Inclusion of turbulent kinetic energy dissipation rate intermittency is shown to increase long-distance dispersal (LDD) by contributing to the intermittent ejection of particles to regions of high mean velocity outside the canopy volume. Model evaluation against controlled flume experiments, featuring a dense rod canopy, detailed flow measurements, and imaged trajectories of spherical particles, demonstrates that superimposing a terminal velocity on the fluid velocity is insufficient to determine the particle dispersal kernel. Modifying the trajectory model by adding dissipation intermittency is found to be significant for dispersal predictions along with the addition of inertial and crossing trajectories’ effects. Comparison with manual seed-release experiments in a forest using wind-dispersed seeds shows that the model captures most of the measured kernels when accepted uncertainties in plant area index and friction velocity are considered. Unlike the flume experiments, the model modifications for several wind-dispersed seeds have minor effects on short-distance dispersal. A large increase was predicted in LDD when including dissipation intermittency for the forest experiment. The main results suggest that fitting or calibrating models to the ‘main body’ of measured kernels may not offer extrapolating foresight to LDD predictions. As inertial effects were found mostly negligible in the field conditions here, the extended trajectory model requires specifying only the seed’s terminal velocity and a constant variance of the normalized dissipation rate. Therefore, the proposed modifications can be readily applied to classical trajectory models so as to improve LDD predictions.

Streamflow prediction in high-altitude scarcely-gauged catchments is essential for efficient water resources management and hydropower generation. Aim of this study is to estimate water resources availability (WRA) by the application of a standard rainfall-runoff model and to study its impact on mini-hydropower production with application to Mangla basin. The Mangla basin is a scarcely gauged catchment situated in the snow- and glacier-fed Himalayan and Pir Panjal Range. Daily streamflow forecasting has been performed by the application of a GIS (Geographic Information System) based hydrological modeling system (HEC-HMS) with observed and TRMM (Tropical Rainfall Measuring Mission) rainfall data to cover the ungauged part of the catchment. The obtained results suggest that HEC-HMS can efficiently reproduce daily streamflows in snow-fed glacierized catchments with Nash-Sutcliffe (NS) coefficients in the range 0.71–0.80. The WRA was estimated at the Mangla dam to analyze its impact on mini-hydropower generation at Upper Jhelum Canal (UJC). The gross mini-hydropower potential energy on the UJC was found to be 196 and 360 GWH for average and design discharge, respectively, demonstrated that mini-hydro power generation could be a significant addition for the energy sector of Pakistan.

Comenzando por el análisis del método gnoseológico sugerido por John Locke en su Essay concerning Human Understanding y a partir del estudio de contenidos psíquicos tales como placer/deseo y dolor/desasosiego, así como sobre su lugar en la taxonomía de ideas, intento aquí re-considerar la concepción Lockeana de consciencia y de consciencia de sí, buscando arrojar luz sobre algunos aspectos sin precedente, aspectos que parecen dejar lugar para una genuina ontología crítica de la persona humana. Estos resultados, aunque se distancian de la interpretación histórica-filosófica tradicional del pensamiento Lockeano (que se enfoca en Hume y subraya la relación genealógica entre Locke y el empirismo escocés), están en plena sintonía con las tesis tanto del Essay como de la correspondencia epistolar entre Locke y Stillingfleet. Es así que las reflexiones de Locke, por virtud a su naturaleza crítica-experimental, pueden ser bastante útiles para el interés actual en el realismo.Starting from the examination of the gnoseological method suggested by John Locke in his Essay concerning Human Understanding and from the study of the psychich contents such as pleasure/delight and pain/uneasiness and their place in the taxonomy of the ideas, I hereby aim to re-consider the Lockean conception of consciousness and self-consciousness, trying to bring some unprecedented aspects to light, aspects which seem to leave an opening for a genuine critical ontology of the human person. These outcomes, although distancing themselves from the traditional historico-philosophical interpretation of the Lockean thought (which focused on Hume and underlined the genealogical relationship between Locke and the Scottish empiricist), are in full consistency with the theses of both the Essay and the correspondence between Locke and Stillingfleet. Thus, Locke’s reflections, by virtue of their critico-experimental nature, can be rather useful for the present-day revival of realism.

Laser Doppler anemometery and laser-induced fluorescence techniques were used to explore the spatial structure of the flow within and above finite cavities created within porous and solid media. The cavities within these two configurations were identical in size and were intended to mimic flow disturbances created by finite gaps and forest clearing. Because flows over permeable boundaries differ from their solid counterparts, the study here addresses how these differences in boundary conditions produce differences in, (i) bulk flow properties including the mean vorticity within and adjacent to the gaps, (ii) second-order statistics such as the standard deviations and turbulent stresses, (iii) the relative importance of advective to turbulent stress terms across various regions within and above the gaps, and (iv) the local imbalance between ejections and sweeps and momentum transport efficiencies of updrafts and downdrafts. Both configurations exhibited a primary recirculation zone of comparable dimensions inside the gap. The mean vorticity spawned at the upstream corner of the gap was more intense for the solid configuration when compared to its porous counterpart. The free-shear layer spawned from the upstream corner-edge deeper into the gap for the porous configuration. The momentum flux at the interface within and above the gap was enhanced by a factor of 1.5–2.0 over its upstream value, and this enhancement zone was much broader in size for the porous configuration. For the turbulent transport terms in the longitudinal and vertical mean momentum balances, these transport terms were significant inside the gap for both boundary configurations when compared to their upstream counterpart. The effectiveness of using incomplete cumulant expansion methods to describe the momentum transport efficiencies, and the relative contributions of ejections and sweeps to turbulent stresses, especially in this zone, were also demonstrated. The flatness factor for both velocity components, often used as a measure of intermittency, was highest in the vicinity of the upstream corner in both configurations. However, immediately following the downstream corner, the flatness factor remained large for the porous configuration, in contrast to its solid configuration counterpart.

The scalar concentration fluctuations within a plane parallel-to-the-ground surface were measured inside a model canopy composed of densely arrayed rods using the laser-induced fluorescence technique. Two-dimensional scalar concentration spectra were computed and were shown to exhibit an approximate −3 power-law scaling at wavenumbers larger than those associated with wake production during quiescent instances when von Karman vortex streets dominated the flow. However, during instances when sweeps disrupted the flow, the spectral exponents increased above −3. The −3 power-law for these concentration fluctuation spectra measurements was shown to be consistent with a simplified spectral budget for locally homogeneous and isotropic turbulence augmented with a relaxation time scale similarity argument that assumed a constant enstrophy injection rate and wake generation mechanism. Hence, the origin of this −3 power-law scaling here differs from the well-known −3 power-law result for the so-called inertial diffusive range derived for the scalar concentration spectrum at small Prandtl numbers.

Inferring the vertical variation of the mean turbulent kinetic energy dissipation rate (e) inside dense canopies remains a basic research problem to be confronted. Using detailed laser Doppler anemometry (LDA) measurements collected within a densely arrayed rod canopy, traditional and newly proposed methods to infer e profiles are compared. The traditional methods for estimating e at a given layer include isotropic relationships applied to the viscous dissipation scales that are resolved by LDA measurements, higher order structure function methods, and residuals of the turbulent kinetic energy budget in which production and transport terms are all independently inferred. The newly proposed method extends earlier approaches based on zero-crossing statistics, which were shown to be promising in a number of laboratory flows. The extension to account for an arbitrary threshold (hereafter referred to as the level-crossing method) instead of zero-crossing minimizes the effects of instrument noise on the inferred e. While none of the e methods employed here can be titled as ‘measured’, these methods differ in their underlying assumptions and simplifications. Above the canopy, where a balance between production and dissipation rate of turbulent kinetic energy is expected, the agreement among all the methods is reasonably good. In the lower-to-middle layers of the canopy, all the methods agree except for those based on a structure-function inference of e. This departure can be attributed to the lack of a well-defined inertial subrange in these layers. In the upper canopy layers, the disagreements between the methods are largest. Even the higher order structure-function methods disagree with each other when e is inferred from third- and fifth-order moments. However, for all layers within the canopy, the proposed zero- and threshold-crossing methods agree well with estimates of e derived from the isotropic relationship applied to the viscous dissipation range. Finally, the advantages of introducing thresholds to minimize two types of instrument noises, additive and multiplicative, are briefly discussed.

Virtually all reviews dealing with aerosol-sized particle deposition onto forested ecosystems stress the significance of topographic variations, yet only a handful of studies considered the effects of these variations on the deposition velocity (Vd ). Here, the interplay between the foliage collection mechanisms within a dense canopy for different particle sizes and the flow dynamics for a neutrally stratified boundary layer on a gentle and repeating cosine hill are considered. In particular, how topography alters the spatial structure of Vd and its two constitutive components, particle fluxes and particle mean concentration within and immediately above the canopy, is examined in reference to a uniform flat-terrain case. A two-dimensional and particle-size resolving model based on first-order closure principles that explicitly accounts for (i) the flow dynamics, including the two advective terms, (ii) the spatial variation in turbulent viscosity, and (iii) the three foliage collection mechanisms that include Brownian diffusion, turbo-phoresis, and inertial impaction is developed and used. The model calculations suggest that, individually, the advective terms can be large just above the canopy and comparable to the canopy collection mechanisms in magnitude but tend to be opposite to each other in sign. Moreover, these two advective terms are not precisely out of phase with each other, and hence, do not readily cancel each other upon averaging across the hill wavelength. For the larger aerosol-sized particles, differences between flat-terrain and hill-averaged Vd can be significant, especially in the layers just above the canopy. We also found that the hill-induced variations in turbulent shear stress, which are out-of-phase

To investigate how velocity variances and spectra are modified by the simultaneous action of topography and canopy, two flume experiments were carried out on a train of gentle cosine hills differing in surface cover. The first experiment was conducted above a bare surface while the second experiment was conducted within and above a densely arrayed rod canopy. The velocity variances and spectra from these two experiments were compared in the middle, inner, and near-surface layers. In the middle layer, and for the canopy surface, longitudinal and vertical velocity variances (\({\sigma_u^2,\sigma_w^2}\)) were in phase with the hill-induced spatial mean velocity perturbation (Δu) around the so-called background state (taken here as the longitudinal mean at a given height) as predicted by rapid distortion theory (RDT). However, for the bare surface case, \({\sigma_u^2 }\) and \({\sigma_w^2 }\) remained out of phase with Δu by about L/2, where L is the hill half-length. In the canopy layer, wake production was a significant source of turbulent energy for \({\sigma_w^2 }\) , and its action was to re-align velocity variances with Δu in those layers, a mechanism completely absent for the bare surface case. Such a lower ‘boundary condition’ resulted in longitudinal variations of \({\sigma_w^2}\) to be nearly in phase with Δu above the canopy surface. In the inner and middle layers, the spectral distortions by the hill remained significant for the background state of the bare surface case but not for the canopy surface case. In particular, in the inner and middle layers of the bare surface case, the effective exponents derived from the locally measured power spectra diverged from their expected − 5/3 value for inertial subrange scales. These departures spatially correlated with the hill surface. However, for the canopy surface case, the spectral exponents were near − 5/3 above the canopy though the minor differences from − 5/3 were also correlated with the hill surface. Inside the canopy, wake production and energy short-circuiting resulted in significant departures from − 5/3. These departures from − 5/3 also appeared correlated with the hill surface through the wake production contribution and its alignment with Δu. Moreover, scales commensurate with Von Karman street vorticies well described wake production scales inside the canopy, confirming the important role of the mean flow in producing wakes. The spectra inside the canopy on the lee side of the hill, where a negative mean flow delineated a recirculation zone, suggested that the wake production scales there were ‘broader’ when compared to their counterpart outside the recirculation zone. Inside the recirculation zone, there was significantly more energy at higher frequencies when compared to regions outside the recirculation zone.

The choice of the Kolmogorov constant (C0) in Lagrangian Stochastic Models (LSMs) for canopy flows remains a subject of debate and uncertainty. This uncertainty stems from the fact that canopy flows are highly dissipative, lack a well-defined inertial subrange (ISR) in their energy cascade, and in the deeper layers of the canopy, the attenuation of turbulence can amplify finite Reynolds number effects on C0. From the analysis here, it was shown that C0 inside dense canopies is reduced relative to its value in the atmospheric surface layer (ASL) primarily due to wake production (a factor of 5), followed by finite Reynolds number effects (a factor of 1.5 at most). The short-circuiting of the energy cascade tends to increase C0 though not enough to compensate for the other two reductions. These results are qualitatively consistent with theoretical predictions of a reduced C0 with an increased anisotropy and localized acceleration when referenced to a homogeneous isotropic stationary turbulence. Simplified scaling arguments were proposed for each of these three effects and tested using flume experiments. The fact that C0 may vary nonlinearly inside canopies complicates inverse estimates of C0 that use fitting Lagrangian dispersion models (LDMs) to mean concentration measurements. The C0 values inferred from such an approach were shown to be sensitive to the source location (especially inside the canopy) and concentration sampling points. On a positive note, the fact that C0 may vary within the canopy does not require any revisions to the well-mixed condition because LDM are not sensitive to gradients in C0. A phenomenological model that accounts for the vertical variation in C0 as a function of the most elementary flow variables, the mean velocity and canopy adjustment length scale, is proposed but its general applicability remains to be tested.

Resolving every detail of the three-dimensional canopy morphology and its underlying topography remains untenable when modeling high Reynolds number geophysical flows. How to represent the effects of such a complex morphological variability and any concomittant topographic variability into one-dimensional bulk flow representation remains a fundamental challenge to be confronted in canopy turbulence research. Theoretically, planar averaging to the scale of interest should be applied to the time-averaged mean momentum balance; however, such averaging gives rise to covariance or dispersive terms produced by spatial correlations of time-averaged quantities that remain ‘unclosed’ or require parameterization. When the averaging scale is commensurate with few canopy heights, these covariances can be labeled as ‘micro-dispersive’ stresses. When averaging is intended to eliminate low-wavenumber topographic variations, we refer to these covariances as ‘macro-dispersive’ terms. Two flume experiments were used to explore the magnitude and sign of both micro- and macro-dispersive fluxes relative to their conventional Reynolds stresses counterparts: a rod-canopy with variable roughness density and a dense rod canopy situated on gentle hilly terrain. When compared to the conventional momentum flux, the micro-dispersive fluxes in the lowest layers of sparse canopies can be significant (∼50%). For dense canopies, the dispersive terms remain negligible when compared to the conventional momentum fluxes throughout. For the macro-dispersive fluxes, model calculations suggest that these terms can be neglected relative to the Reynolds stresses for a deep canopy situated on a narrow hill. For the region in which topographic variations can interact with the pressure, both model calculations and flume experiments suggest that the macro-dispersive fluxes cannot be neglected, and their value can be 20% of the typical Reynolds stresses.

Wave power represents a highly promising field in the broader area of green energy and it is currently the subject of increasing research and investments. The wave energy converter (WEC) under study in this paper is a 1:8 scaled prototype of the ISWEC, a device able to harvest sea energy exploiting the inertial effect of a gyroscope. The aim of this work is to validate the numerical simulation model of the device against the results of a wave tank test campaign carried out in INSEAN facilities in Rome. In the first part of the paper the ISWEC dynamic and hydrodynamic governing laws are outlined and implemented in a numerical model. A detailed description of the 1:8 scaled prototype characteristics is provided together with the experimental setup for the tank tests. A wide range of theoretical operating conditions are considered in order to test the system dynamics as well as its control strategy, and it is discussed how different control strategies influence the system behavior and its energy production. In the last part the experimental results are compared with the output of the numerical model, which gives a good prediction of the device behavior.

Lo spaventoso sisma di Lisbona, verificatosi il 1° novembre 1755, non comportò solo incalcolabili devastazioni sul piano socio-economico, ma andò a colpire profondamente tanto l’immaginario popolare (minandone le certezze quotidiane), quanto i savants dell’Europa settecentesca, stimolando un’intensa riflessione (che coprì l’intero spettro dei punti di vista, da quello teologico, a quello scientifico). Il giovane Kant è chiaro exemplum dell’interesse suscitato dall’eccezionale fenomeno tellurico presso gli illuministi: tra il gennaio e l’aprile del 1756, egli dette alle stampe tre brevi saggi interamente dedicati alla descrizione scientifica del terremoto portoghese, saggi che si inseriscono nel contesto degli studi del pensatore di Königsberg riguardanti la filosofia della natura e, nello specifico, l’età, l’origine e la costituzione della terra (oggetto dei saggi del 1754 e del 1755). Con il presente lavoro, si intende portare all’attenzione del lettore quella che pare essere una precisa evoluzione della concezione dell’utilità del terremoto, nel passaggio dal periodo pre-critico a quello critico, in particolare nella Kritik der Urteilskraft (1790). Qui l’Autore pare escludere il terremoto dall’elenco degli eventi naturali catastrofici la cui esperienza, “se ci troviamo al sicuro”, genera nell’uomo il concetto di sublime dinamico (KU, AA 05: 261). Quali sono le ragioni per cui il terremoto non trova spazio in questo discorso? Il sisma perde cioè i caratteri di catastrofe agli occhi di Kant, oppure è giudicato così terrificante da togliere ogni razionalità all’uomo e impedire ogni spiraglio interpretativo?

The turbulent flow inside dense canopies is characterized by wake production and short-circuiting of the energy cascade. How these processes affect passive scalar con- centration variability in general and their spectral properties in particular remains a vexing problem. Progress on this problem is frustrated by the shortage of high resolution spatial concentration measurements, and by the lack of simplified analytical models that connect spectral modulations in the turbulent kinetic energy (TKE) cascade to scalar spectra. Here, we report the first planar two-dimensional scalar concentration spectra (φcc) inside tall cano- pies derived from flow visualization experiments. These experiments were conducted within the deeper layers of a model canopy composed of densely arrayed cylinders welded to the bottom of a large recirculating water channel. We found that in the spectral region experi- encing wake production, the φcc exhibits directional scaling power laws. In the longitudinal direction (x), or the direction experiencing the largest drag force, the φcc(kx ) was steeper than k −5/3

Modeling scalar transport within canopies remains a vexing research problem in eco-hydrology and eco-hydraulics. Canopy turbulence is inhomogeneous, non-Gaussian, and highly dissipative, thereby posing unique challenges to three-dimensional Lagrangian Dispersion Models (LDM). Standard LDM approaches usually satisfy the well-mixed condition and account for turbulence inhomogeneity but not for its non-Gaussian statistics and enhanced dissipation. While numerous studies evaluated the importance of the former (with mixed results), few studies to date considered the latter. In this paper we present new data and explore: (1) the skill of LDM in reproducing mean scalar concentration distributions within dense and rigid canopies for source releases near the canopy top and near the ground, and (2) the extent to which these estimates are sensitive to the formulation of the mean turbulent kinetic energy dissipation rate (ϵ) profile. Toward this end, Laser Induced Florescence (LIF) and Laser Doppler Anemometry (LDA) were used to measure scalar concentration and Eulerian flow statistics within a dense model canopy in a rectangular flume. It is shown that LDM concentration predictions are sensitive to how ϵ is estimated. Good agreement between measured and modelled mean concentration distributions were obtained when ϵ was estimated from the mean squared longitudinal velocity gradients and isotropic turbulence principles. However, when ϵ was estimated from the widely used scaling arguments that employ a constant Lagrangian time scale (Tl) and a specified vertical velocity variance ( σ w 2 ) profile, the predicted concentrations diverged significantly from the LIF measurements. Better agreement was obtained when a constant mixing length scale was used with the σ w 2 profile.

Topography influences many aspects of forest-atmosphere carbon exchange; yet only a small number of studies have considered the role of topography on the structure of turbulence within and above vegetation and its effect on canopy photosynthesis and the measurement of net ecosystem exchange of CO2 (Nee) using flux towers. Here, we focus on the interplay between radiative transfer, flow dynamics for neutral stratification, and ecophysiological controls on CO2 sources and sinks within a canopy on a gentle cosine hill. We examine how topography alters the forest-atmosphere CO2 exchange rate when compared to uniform flat terrain using a newly developed first-order closure model that explicitly accounts for the flow dynamics, radiative transfer, and nonlinear eco physiological processes within a plant canopy. We show that variation in radiation and airflow due to topography causes only a minor departure in horizontally averaged and vertically integrated photosynthesis from their flat terrain values. However, topography perturbs the airflow and concentration fields in and above plant canopies, leading to significant horizontal and vertical advection of CO2. Advection terms in the conservation equation may be neglected in flow over homogeneous, flat terrain, and then Nee = Fc, the vertical turbulent flux of CO2. Model results suggest that vertical and horizontal advection terms are generally of opposite sign and of the same order as the biological sources and sinks. We show that, close to the hilltop, Fc departs by a factor of three compared to its flat terrain counterpart and that the horizontally averaged Fc-at canopy top differs by more than 20% compared to the flat-terrain case.

Second-order closure models for the canopy sublayer (CSL) employ aset of closure schemes developed for `free-air' flow equations andthen add extra terms to account for canopy related processes. Muchof the current research thrust in CSL closure has focused on thesecanopy modifications. Instead of offering new closure formulationshere, we propose a new mixing length model that accounts for basicenergetic modes within the CSL. Detailed flume experiments withcylindrical rods in dense arrays to represent a rigid canopy areconducted to test the closure model. We show that when this lengthscale model is combined with standard second-order closureschemes, first and second moments, triple velocity correlations,the mean turbulent kinetic energy dissipation rate, and the wakeproduction are all well reproduced within the CSL provided thedrag coefficient (CD) is well parameterized. The maintheoretical novelty here is the analytical linkage betweengradient-diffusion closure schemes for the triple velocitycorrelation and non-local momentum transfer via cumulant expansionmethods. We showed that second-order closure models reproducereasonably well the relative importance of ejections and sweeps onmomentum transfer despite their local closure approximations.Hence, it is demonstrated that for simple canopy morphology (e.g.,cylindrical rods) with well-defined length scales, standard closureschemes can reproduce key flow statistics without much revision.When all these results are taken together, it appears that thepredictive skills of second-order closure models are not limitedby closure formulations; rather, they are limited by our abilityto independently connect the drag coefficient and the effectivemixing length to the canopy roughness density. With rapidadvancements in laser altimetry, the canopy roughness densitydistribution will become available for many terrestrialecosystems. Quantifying the sheltering effect, the homogeneity andisotropy of the drag coefficient, and more importantly, thecanonical mixing length, for such variable roughness density isstill lacking.

Dispersive flux terms are formed when the time-averaged meanmomentum equation is spatially averaged within the canopy volume.These fluxes represent a contribution to momentum transfer arisingfrom spatial correlations of the time-averaged velocity componentswithin a horizontal plane embedded in the canopy sublayer (CSL).Their relative importance to CSL momentum transfer is commonlyneglected in model calculations and in nearly all fieldmeasurement interpretations. Recent wind-tunnel studies suggestthat these fluxes may be important in the lower layers of thecanopy; however, no one study considered their importance acrossall regions of the canopy and for a wide range of canopy roughnessdensities. Using detailed laser Doppler anemometry measurementsconducted in a model canopy composed of cylinders within a largeflume, we demonstrate that the dispersive fluxes are onlysignificant (i.e., >10%) for sparse canopies. These fluxes arein the same direction as the turbulent flux in the lower layers ofthe canopy but in the opposite direction near the canopy top. Fordense canopies, we show that the dispersive fluxes are

The canonical form of atmospheric flows near theland surface, in the absence of a canopy, resembles a rough-wallboundary layer. However, in the presence of an extensive and densecanopy, the flow within and just above the foliage behaves as aperturbed mixing layer. To date, no analogous formulation existsfor intermediate canopy densities. Using detailed laser Dopplervelocity measurements conducted in an open channel over a widerange of canopy densities, a phenomenological model that describesthe structure of turbulence within the canopy sublayer (CSL) isdeveloped. The model decomposes the space within the CSL intothree distinct zones: the deep zone in which the flow field isshown to be dominated by vortices connected with vonKarman vortex streets, butperiodically interrupted by strong sweep events whose features areinfluenced by canopy density. The second zone, which is near thecanopy top, is a superposition of attached eddies andKelvin–Helmholtz waves produced by inflectional instability in themean longitudinal velocity profile. Here, the relative importanceof the mixing layer and attached eddies are shown to vary withcanopy density through a coefficient α. We show that therelative enhancement of turbulent diffusivity over its surface-layer value near the canopy top depends on the magnitude ofα. In the uppermost zone, the flow follows the classicalsurface-layer similarity theory. Finally, we demonstrate that thecombination of this newly proposed length scale and first-orderclosure models can accurately reproduce measured mean velocity andReynolds stresses for a wide range of roughness densities. Withrecent advancement in remote sensing of canopy morphology, thismodel offers a promising physically based approach to connect theland surface and the atmosphere without resorting to empiricalmomentum roughness lengths.

Energy spectra and structure functions of the streamwise and wall-normal turbulent velocity components in an open channel flow are experimentally investigated as a function of the distance from the wall. Both smooth- and rough-wall conditions are considered, with special attention to the zone close to the wall. In the core region, the small-scale turbulent flow field is always characterized by a high level of isotropy, while a strong anisotropy is found at small scales in the near-wall region. In the smooth-wall case, the extent of the scaling range increases as the wall is approached, but with exponents which are different from the classical ones. In the rough-wall case, the roughness strongly interacts with turbulence, destroying the scaling regions at small scales through the imposition of its characteristic scales. A lower level of intermittency and anisotropy is also observed at the small scales for rough-wall conditions. Energy spectra and structure functions suggest a connection of these behaviors with the turbulent energy directly injected into the flow by the roughness elements. The integral structure functions show that roughness effects exceed the sole modification of local shear and reveal the direct impact of wakes and vortices generated by the roughness in the near-wall region.

The aim of this work is to study the propagation of dam-break waves along a hillslope by mean of a physical model (basically i.e. a 3 x 4 m2 plane set downstream of a reservoir) build up in the Hydraulic Laboratory of the Politecnico di Torino. We want to recreate the water surface, to assess the shape of the flooded area and the arrival time of the wave front. The measurement facility is a high resolution CMOS camera. We measure the water height by linking the intensity of the pixels in the acquired images to the real water depth. Preliminary quantitative results are given for the 0°downstream-slope scenario and qualitative results are presented for the case of downstream inclined plane.

Wave power is one of the most rich and promising sources of renewable energy for the future. Approximately 2000 TWh/year can be produced through the exploitation of the wave energy potential. In the past four decades, hundreds of Wave Energy Converters have been proposed and studied, but so far a conclusive architecture to harvest wave power has not been identified. Many engineering problems are still to be solved; these include survivability, durability, and effective power capture in a variable wave climate. Reacting body devices use the inertia of a large mass to generate the reaction needed from the power take off (PTO). Heretically, in the case of a simple inertial mass, optimal control adjusts the dynamic parameters of the PTO, such as the spring constant and energy absorbing damping, to maximize energy absorption. The ISWEC (Inertial Sea Wave Energy Converter) uses a gyroscope to create an internal inertial reaction that is able to harvest wave power without exposing mechanical parts to the harsh o...

Connections between the spatial and temporal statistics of turbulent flow, and their possible convergence to ensemble statistics as assumed by the ergodic hypothesis, are explored for passive scalars within a rod canopy. While complete ergodicity is not expected to apply over all the spatial domain within such heterogeneous flows, the fact that canopy turbulence exhibits self-similar characteristics at a given depth within the canopy encourages a discussion on necessary conditions for an ‘operational’ ergodicity framework. Flows between roughness elements such as within canopies exhibit features that distinguish them from their well-studied classical boundary-layer counterparts. These differences are commonly attributed to short-circuiting of the energy cascade and the prevalence of intermittent von Karman vortex streets in the deeper layers of the canopy. Using laser-induced fluorescence measurements at two different depths within a rod canopy situated in a large flume, the spatio-temporal statistical properties and concomitant necessary conditions for ergodicity of passive scalar turbulence statistics are evaluated. First, the integral time and length scales are analyzed and their corresponding maximum values are used to guide the construction of an ensemble of independent realizations from repeated spatio-temporal concentration measurements. As a statistical analysis for an operational ergodicity check, a Kolmogorov–Smirnov test on the distributions of temporal and spatial concentration series against the ensemble was conducted. The outcome of this test reveals that ergodicity is reasonably valid over the entire domain except close to the rod elements where wake-induced inhomogeneities and damped turbulence prevail. The spatial concentration statistics within a grid-cell (square domain formed by four corner rods) appear to be less ergodic than their temporal counterparts, which is not surprising given the periodicity and persistence of von Karman vortices in the flow field. Also, a local advection velocity of dominant eddies is inferred using lagged cross-correlations of scalar concentration time series at different spatial locations. The computed probability density function of this advection velocity agrees well with the laser Doppler anemometry measurements for the same rod canopy.

A new experimental technique for the investigation of near-wall turbulence using laser Doppler anemometry is presented, which allows an accurate measurement of the flow field very close to the wall, with good resolution and a high data rate. Such a technique is tested in a fully developed turbulent flow (with Reynolds numbers between 4,300 and 67,000) by carrying out a careful statistical analysis of the streamwise and wall-normal velocity components within the near-wall region, at distances from the wall ranging from approximately y+ = 1 to y+ = 100. The velocity profiles, Reynolds stresses and higher-order moments of the two-dimensional boundary layer are presented. The results, which are in agreement with the most recent data in the literature, testify the validity of the proposed experimental solution. Moreover, the accuracy of the results allows the friction velocity to be calculated as the intercept at the wall of the best linear fit of the total stress profile; in this way, an unambiguous examination of the normalized statistics is possible.

The exchange of scalars between the biosphere and the atmosphere has direct bearing on a large number of problems such as climate change, air and water quality, agricultural management and food security, landscape ecology, and decision making for environmental compliances and policy formulation. Near the canopy-atmosphere interface, turbulent fluctuations in scalar concentrations exhibit complex dynamic behaviour that shows some parallels with the transporting turbulent velocity field. However, the statistical properties of scalar turbulence within and just above the canopy can also be partly decoupled from those of the transporting velocity. Here, a unifying framework is proposed that accounts for vertical variations in scalar sources and sinks within the canopy volume, the lack of equilibrium between production and dissipation terms in second-order scalar budget equations, the rapid changes in turbulent kinetic energy dissipation rate inside canopies, the relative importance of ejections and sweeps, the role of thermal stratification, and the 'near-field' effects of the scalar source on gradient-diffusion theories. Ways in which these same phenomena modify the scalar spectra and scalar-vertical velocity co-spectra within the inertial subrange above the canopy and at scales finer than the wake generation region within the canopy are presented. Finally, the origin of organized eddy structure connected with surface renewal that leads to scalar ramps is briefly discussed. The work draws upon a large number of flume, wind tunnel, and field experiments, and offers novel theoretical scaling arguments as to how coherency in the flow field impacts scalar spectra and scalar-velocity co-spectra at scales smaller than the shear production scales.

In the past four decades, hundreds of Wave Energy Converters (WECs) have been proposed and studied, but so far a final architecture to harvest wave power has not been identified. Many engineering problems are still to be solved, like survivability, durability and effective power capture in a variable wave climate. ISWEC (Inertial Sea Wave Energy Converter) is a system using the gyroscope to extract power. The goal of this paper is to identify an optimal control strategy in order to maximize wave power exploitation of ISWEC. Here we present a new adaptive control technique and the results deriving from its application to an ISWEC device with rated power of 60kW. ISEWC with the new control strategy are finally applied to the test case of Alghero, and the results in terms of power potential and yearly productivity are shown.

The design process of a device for energy harvesting from sea waves is a complex task, which involves many different stages ranging from the initial mathematical models to an extensive field testing. Scale models are a crucial tool to asses the real world device performance and to validate the mathematical models used in the design process. This paper describes the first laboratory campaign of the scale model of an Inertial Sea Wave Energy Converter (ISWEC). The experiments were carried out in the wave tank of INSEAN (The Italian ship model basin, Rome) between February and April 2012. ISWEC uses a gyroscope to create an internal inertial reaction able to harvest wave power without exposing mechanical parts to the harsh oceanic environment. As for other WECs, the theoretically optimal control of ISWEC should be able to adjust the dynamic parameters of the PTO, such as the spring constant and energy absorbing damping, to maximize the energy absorption. The aim of this manuscript is to explore the effect of PTO control parameters on energy production for a given incoming wave

A streamfunction-vorticity formulation is used to explore the extent to which turbulent and turbulently inviscid solutions to the mean momentum balance explain the mean flow across forest edges and within cavities situated inside dense forested canopies. The turbulent solution is based on the mean momentum balance where first-order closure principles are used to model turbulent stresses. The turbulently inviscid solution retains all the key terms in the mean momentum balance but for the turbulent stress gradients. Both exit and entry versions of the forest edge problem are explored. The turbulent solution is found to describe sufficiently the bulk spatial patterns of the mean flow near the edge including signatures of different length scales reported in canopy transition studies. Next, the 'clearing inside canopy' or the so-called 'cavity' problem is solved for the inviscid and turbulent solutions and then compared against flume experiments. The inviscid solution describes the bulk flow dynamics in much of the zones within the cavity. In particular, the solution can capture the correct position of the bulk recirculation zone within the cavity, although with a weaker magnitude. The inviscid solution cannot capture the large vertical heterogeneity in the mean velocity above the canopy, as expected. These features are better captured via the first-order closure representation of the turbulent solution. Given the ability of this vorticity formulation to capture the mean pressure variations and the mean advective