Numerical Assessment of Similitude Parameters and Dimensional Analysis for Water Entry Problems

The prediction of impulsive loads deriving from the sudden impact of a solid body on the water surface is of fundamental importance for a wide range of engineering applications. The study of hull-slamming phenomena largely relies on laboratory scale experimental investigations and on simplified analytical models. The aim of this paper is to quantitatively assess the interplay between the relevant nondimensional parameters for the water entry of a two-dimensional body, evidencing the similitude conditions that allow the transition from scaled experiments to real size applications. This assessment is performed through the numerical study of the hydrodynamics induced by the water impact of a two-dimensional wedge. The fluid flow is considered incompressible. First of all numerical simulations are validated by comparison with experimental data from the literature and with the Wagner seminal theory. Afterwards, a thorough computational study is performed by systematically varying all the relevant parameters, such as the nondimensional entry velocity and acceleration. We conclude by evidencing some design prescriptions that should be adopted in order to facilitate the transition of laboratory scale experiments to real scale applications

Life-cycle cost analysis of bridges subjected to fatigue damage

AbstractLife-cycle cost analysis (LCCA) is a decision-making tool particularly useful for the design of bridges as it predicts lifetime expenses and supports the inspections management and the maintenance activities. LCCA allows to consider uncertainties on loads, resistances, degradation and on the numerical modelling and structural response analysis. It also permits to consider different limit states and different types of damage in a unified framework. Among the types of damages that can occur to steel and steel-concrete composite bridges, fatigue is one of the most dangerous ones, as it may lead to sudden and fragile rupture, even at operational traffic levels. In this context, the present paper proposes a framework for LCCA based on the use of the Pacific Earthquake Engineering Research (PEER) equation which is for the first time utilized for fragility and cost analysis of bridges subjected to fatigue, highlighting the possibility of treating the problem of fatigue damage estimation with an approach similar to the one currently adopted for damage induced by other hazards, like earthquake and wind. To this aim, a damage index computed through the Palmgren-Miner's rule is adopted as engineering demand parameter. The framework is applied to a composite steel-reinforced concrete multi-span roadway bridge by evaluating the fatigue limit state from different traffic load models, i.e. a Technical Code-based model and a model based on results of Weigh in Motion monitoring system. The evolution over time of the probability of failure and the life-cycle costs due to fatigue damage induced by heavy traffic loads are investigated for different probability distributions of the engineering demand parameter and for different fragility models. The comparison between the fatigue failure probabilities and the life-cycle costs obtained with the two traffic models, encourages the adoption of traffic monitoring systems for a correct damage estimation

new efficiency opportunities arising from intelligent real time control tools applications the case of compressed air systems energy efficiency in production and use

Abstract Most of the production facilities in Europe make use of compressed air to drive equipment for manufacturing and Compressed Air Systems (CAS) account for about 10% of the total electrical energy consumption of European industries. Therefore, reducing CAS energy consumption is a crucial task to meet the European goals of improving energy efficiency and reducing environmental impact of the industrial sector. This work is part of a wider research activity aimed at developing a strategy to optimize the energy use in CAS. In particular, this paper shows the importance of monitoring energy consumption and control energy use in compressed air generation, to enable energy saving practices, enhance the outcomes of energy management projects, and to guide industries in energy management. We propose a novel procedure in which measured data are compared to a baseline obtained through mathematical modelling (i.e. regression functions) to enable faults detection and energy accounting, through the use of control charts (i.e. variations' control and the Cumulative Sums). The effectiveness of the proposed methodology is demonstrated in a case study, namely the compressed air system of a pharmaceutical manufacturing plant

Analysis of a Fuel Cell Combined Heat and Power Plant Under Realistic Smart Management Scenarios

Proton exchange membrane fuel cells are a promising and mature technology for combined heat and power plants. High efficiency (in particular for small size devices), practically zero pollutant emissions, noiseless operation and fast response to transient demand make these energy systems excellent prime movers for residential and commercial application. Nevertheless, due to large capital costs, their utilization and commercialization are still limited to demonstrative projects. In this scenario we are working on a research project, called AutoRe, which utilizes an automotive derivative fuel cell for a cogeneration plant to create a synergy between two non competitive industries (automotive and stationary plants) and to realize a significant economy of scale that will drastically cut the costs of fuel cell based cogenerative plants. In this paper we perform a thorough techno-economic analysis of the AutoRe (AUTomotive deRivative Energy system) power plant. A number of realistic energy management scenarios are constructed by varying the energy demand, the climatic condition, the energy cost, and the efficiency of the surrounding energy system. The control strategy is determined on an hourly basis, by minimizing the cost or the primary energy consumption through a graph based methodology. The resulting global parameters are compared to a reference scenario where electricity is acquired from the grid and heat is locally produced through a natural gas boiler. We consider 5 different building types (Office, Apartment district, Clinic, Hotel, Supermarket), 5 different climatic conditions (Hot, Cooling Based, Moderate, Heating based, Cold), and 2 differ- ent surrounding energy systems (USA and Europe). The results show that overall the proposed plant is economically sustainable and effective in reducing the energy costs and the primary energy consumption. Nevertheless, the building type and the energy prices impact on the return on investment, while the climatic condition affects the relative cost and energy variations. In the US scenario the management based on cost and primary energy minimization exhibits similar patterns. On the contrary, in Europe cost minimization might increase the primary energy consumption with respect to the reference scenario.This project has received funding from the Fuel Cells and Hydrogen Joint Undertaking under grant agreement N◦ 671396. This Joint Undertaking receives support from the European U- nion’s Horizon 2020 research and innovation programme and United Kingdom, Germany, Greece, Croatia, Italy, Switzerland, Norway. Swiss partners are funded by the State Secretariat for Education, Research and Innovation of the Swiss Confederation