Porous Medium Typology Influence on the Scaling Laws of Confined Aquifer Characteristic Parameters

An accurate measurement campaign, carried out on a confined porous aquifer, expressly reproduced in laboratory, allowed the determining of hydraulic conductivity values by performing a series of slug tests. This was done for four porous medium configurations with dierent granulometric compositions. At the scale considered, intermediate between those of the laboratory and the field, the scalar behaviors of the hydraulic conductivity and the eective porosity was verified, determining the respective scaling laws. Moreover, assuming the eective porosity as scale parameter, the scaling laws of the hydraulic conductivity were determined for the dierent injection volumes of the slug test, determining a new relationship, valid for coarse-grained porous media. The results obtained allow the influence that the dierences among the characteristics of the porous media considered exerted on the scaling laws obtained to be highlighted. Finally, a comparison was made with the results obtained in a previous investigation carried out at the field scale

Characteristics of free and submerged hydraulic jumps over different macroroughnesses

AbstractThe present study deals with numerical simulations of the free and submerged hydraulic jumps over different shapes of roughness in various roughness arrangements and different Froude number conditions. The models were studied using three roughness shapes, i.e. triangular, square and semi-oval for 0.2 < T/I < 0.5, where T and I are height and distance of roughness, respectively. The results showed that the numerical model is fairly well able to simulate the free and submerged jump characteristics. The effect of roughness plays a role in the reduction of the relative maximum velocity which is greater in the submerged jump. The thickness of the boundary layer for both free and submerged jumps decreases with increasing the distance between the roughnesses. Triangular macroroughness has a significant effect on the length of the jump and shortest length with respect to the other shapes. The reduction in the submerged depth ratio and tailwater depth ratio depends mainly on the space of the roughnesses. The highest shear stress and energy loss in both jumps occur in a triangular macroroughness (TR) with T/I = 0.50 compared to other ratios and modes. The numerical results were compared with previous studies and relationships with good correlation coefficients were presented for the mentioned parameters

Numerical Simulations of the Flow Field of a Submerged Hydraulic Jump over Triangular Macroroughnesses

The submerged hydraulic jump is a sudden change from the supercritical to subcritical flow, specified by strong turbulence, air entrainment and energy loss. Despite recent studies, hydraulic jump characteristics in smooth and rough beds, the turbulence, the mean velocity and the flow patterns in the cavity region of a submerged hydraulic jump in the rough beds, especially in the case of triangular macroroughnesses, are not completely understood. The objective of this paper was to numerically investigate via the FLOW-3D model the effects of triangular macroroughnesses on the characteristics of submerged jump, including the longitudinal profile of streamlines, flow patterns in the cavity region, horizontal velocity profiles, streamwise velocity distribution, thickness of the inner layer, bed shear stress coefficient, Turbulent Kinetic Energy (TKE) and energy loss, in different macroroughness arrangements and various inlet Froude numbers (1.7 < Fr1 < 9.3). To verify the accuracy and reliability of the present numerical simulations, literature experimental data were considered

a multi node approach to simulate thin coastal structures in the sph context

We propose an improvement in modeling solid boundary conditions for 2D weakly-compressible Smoothed Particle Hydrodynamics (SPH) simulations for cases in which the thickness of the body is small compared to the desired particle size and the fluid surrounds the body from more than one side. Specifically, the fixed ghost particles technique developed by Marrone et al. (2011), based on interpolation nodes located within the fluid domain, is here extended to a multi-node approach. The fluid domain is thus divided into various sub-areas and an interpolation node for the considered solid particle is associated to every sub-area. Consequently, the solid particles present an array of values interpolated at different sub-areas for the same physical quantity. When a fluid particle located in a specific region interacts with a multi-node fixed ghost particle, the last assumes the field values interpolated in the reference area through the associated node. The present modeling allows to adopt a coarser spatial resolution to model the same physical problem, resulting in a reduction of the computational cost. The proposed solid boundary treatment is applied to horizontal decks and perforated wall-caisson breakwaters subjected to regular waves. In this context, an automatic hybrid diffusive formulation is introduced in order to prevent shock waves during water impacts and preserve the hydrostatic pressure. The formulation is obtained by defining a variable parameter detecting the occurrence of relevant density gradients induced by fluid impacts, resulting in an automatic switch between the two formulations

WALOWA (wave loads on walls) : large-scale experiments in the delta flume

Overtopping wave loads on vertical structures on top of a dike have been investigated in several small scale experiments in the past. A large-scale validation for a mild foreshore situation is still missing. Hence the WALOWA experimental campaign was carried out to address this topic. In the present paper the objectives of the WALOWA project are outlined in detail, the model and measurement set-up described and the test program presented. Furthermore, preliminary results featuring a single 1000 irregular waves test of the test program are highlighted. This includes the study of the mild and sandy foreshore evolution by comparing profiles before and after the test execution. The profile measurements are obtained with a mechanical profiler. The wave parameters offshore and at the dike toe are numerically simulated using a SWASH model. The numerical results are validated against the measurements. Finally, the force and pressure time series of the waves impacting against the wall are processed and filtered. The load cell measurements and the time series of integrated pressures are compared to each other and for each impact event the maximum force is derived.Hydraulic Structures and Flood RiskEnvironmental Fluid Mechanic

Trend Detection of Wave Parameters along the Italian Seas

In this paper, trend detection of wave parameters such as significant wave height, energy period, and wave power along the Italian seas was carried out. To this purpose, wave time series in the period 1979–2018 taken from the global atmospheric reanalysis ERA-Interim by European Center for Medium-Range Weather Forecasts (ECMWF) were considered. Choosing a significance level equal to 90%, the use of the Mann–Kendall test allowed estimating ongoing trends on the mean values evaluated at yearly and seasonal scale. Furthermore, the assessment of the magnitude of the increase/decrease of the wave parameters was performed through the Theil–Sen estimator. The obtained results underlined that the mean values of the considered wave parameters were characterized by a high occurrence of positive trends in the different Italian seas. The findings of this study could have implications for studies of coastal flooding, shoreline variations, and port operations, and for the assessment of the performances of Wave Energy Converters

Post-buckling behaviour of transversely stiffened plate girders

Dottorato di Ricerca in Meccanica Computazionale CICLO XIX SSD,a.a.2007Many investigations have been carried out to date into the behaviour of transversely stiffened web panels in bending and shear and many different theories have been proposed. Different code rules have been developed based on these theories. The British steel bridge code, BS 5400 Part 3, based its design rules for transverse stiffeners on the work of Rockey, while early drafts of Eurocode prEN 1993-1-5 were based on the work of Höglund. The former's tension field theory places a much greater demand on stiffener strength than does the latter's rotated stress field theory. Due to a lack of European agreement, EN 1993-1-5 was modified late on its drafting to include a stiffener force criterion more closely aligned to that in BS 5400 Part 3. The rules for stiffener design in EN 1993-1-5 are thus no longer consistent with the rotated stress field theory and lead to a greater axial force acting in the stiffener. The rules for the design of the web panels themselves in shear however remain based on Höglund's rotated stress field theory, creating an inconsistency. Recent investigations have suggested that the rules in BS 5400 Part 3 and, to a lesser extent, in the current version of EN 1993-1-5 can be unduly pessimistic. This thesis investigates the behaviour of transversely stiffened plate girders in bending and shear using non-linear finite element analyses. It considers slender symmetrical steel girders with and without axial force and also steel-concrete composite plate girders (which are therefore asymmetric). It discusses the observed web post-buckling behaviour, compares it with the predictions of other current theories and recommends modified design rules. It includes investigation into whether a stiffness-only approach to stiffener design can be justified, rather than a combined stiffness and force approach. The shear-moment interaction behaviour of the girders as a whole are also investigated aUniversità della Calabri