Giacomo Viccione

An Analytical Approximation for Continuous Flow Microwave Heating of Liquids

Both a numerical and an analytical models were developed to simulate temperature profiles in continuous laminar pipe flow during microwave heating. Fully developed velocity and thermally developing conditions were assumed. The numerical solution was obtained by first solving Maxwell equations and then by coupling them with the energy balance for the flowing fluid. On the other hand, the same problem was solved analytically under the simplifying assumption foreseeing uniform heat generation inside the pipe. With the aim of reducing computational efforts, numerical and analytical results were compared in order to investigate conditions for which the two models allowed to recover the same temperature patterns. Thus, it has been shown that suitable conditions can be found for which the simplified analytical model can lead to an easy way to predict the heat transfer through the pipe.

Simulating the fate of indigenous antibiotic resistant bacteria in a mild slope wastewater polluted stream

The fate of indigenous surface-water and wastewater antibiotic resistant bacteria in a mild slope stream simulated through a hydraulic channel was investigated in outdoor experiments. The effect of (i) natural (dark) decay, (ii) sunlight, (iii) cloudy cover, (iv) adsorption to the sediment, (v) hydraulic conditions, (vi) discharge of urban wastewater treatment plant (UWTP) effluent and (vii) bacterial species (presumptive Escherichia coli and enterococci) was evaluated. Half-life time (T1/2) of E. coli under sunlight was in the range 6.48-27.7min (initial bacterial concentration of 105CFU/mL) depending on hydraulic and sunlight conditions. E. coli inactivation was quite similar in sunny and cloudy day experiments in the early 2hr, despite of the light intensity gradient was in the range of 15-59W/m2; but subsequently the inactivation rate decreased in the cloudy day experiment (T1/2=23.0min) compared to sunny day (T1/2=17.4min). The adsorption of bacterial cells to the sediment (biofilm) increased in the first hour and then was quite stable for the remaining experimental time. Finally, when the discharge of an UWTP effluent in the stream was simulated, the proportion of indigenous antibiotic resistant E. coli and enterococci was found to increase as the exposure time increased, thus showing a higher resistance to solar inactivation compared to the respective total populations.

Simulating fluid-structure interaction with SPH

Fluid-structure interaction (FSI) is the condition according to which a fluid comes in contact and interacts with a structure. A simple application of the impulse-momentum theorem yields as a result the developing of pressure waves, propagating inside both media. The present work presents a critical assessment of the Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method to simulate the first stages of a 2D fluid impacting onto a rigid vertical wall. The effects on the results in terms of the sound speed c0, appearing inside the state equation, as well as of the velocity νa of the approaching fluid are here investigated.

Performance Study of E-Nose Measurement Chamber for Environmental Odour Monitoring

Offensive odours from industrial and sanitary environmental engineering plants can cause problems, such as sleep disorders, migraine and loss of appetite, also considering that they address the quality of life. Odour emission characterization is currently discussed in international literature as to determine its most feasible implementation. A method for continuous odour monitoring is based on the use of electronic noses. Electronic nose is an instrument which comprises an array of electronic chemical sensors with partial specificity and an appropriate pattern recognition system, capable of recognizing simple or complex odours. Aim of this work is to numerically analyze the performance of a sensor chamber in order to improve sensor response signals in terms of stability, reproducibility and response time. Comparative results are based on the location of four different diffusers. The numerical analysis was performed by a computational fluid dynamic (CFD) software in order to guarantee that all sensors are exposed to the same chemical sample under the same experimental conditions for the same time, reducing the presence of stagnant or recirculating regions.

A Laboratory Investigation of the Hydraulic Performance of String-Wound Filters

The present work focuses on the filtration of drinking water with string-wound filter cartridges. The presence of filtration devices may have consequences on networks operating under low pressures. Results consisting of pressure drop curves obtained from measures taken on a pilot plant located at the Laboratory of Environmental and Maritime Hydraulics (LIDAM), University of Salerno, are discussed.

Simulating Flows with SPH: Recent Developments and Applications

Fluid motion is often numerically reproduced by means of grid-based methods such as Finite Difference Methods (FDMs) and Finite Elements Methods (FEMs). However, these techniques exhibit difficulties, mainly related to the presence of time-dependent boundaries, large domain deformations or mesh generation. This chapter describes a relatively recent meshfree and pure Lagrangian technique, the Smoothed Particle Hydrodynamics (SPH) method, which overcomes the above mentioned limitations. Its original frame has been developed in 1977 by (Gingold and Monaghan, 1977) and independently by (Lucy, 1977) for astrophysical applications. Since then, a number of modifications to ensure completeness and accuracy have been yielded, in order to solve the main drawbacks of the primitive form of the method. Because a calculation is based on short-range particle interactions, it is essential to limit the computational costs related to the neighbourhood definition. Available searching algorithms are then presented and discussed. Finally, some practical applications are presented, primarily concerning free surface flows. The capability to easily handle large deformations is shown.

A numerical investigation of flow dynamics over a trapezoidal smooth open channel

The paper presents a numerical investigation of the flow dynamics in a laboratory flume. The adopted geometry consists of a U shaped trapezoidal smooth open channel with a fixed slope and unerodible bed. The branches, 3m of length each, are linked with a joint 1m long, realizing two 90 degrees bends. The system is fed upstream with a water discharge under critical conditions while a Cipolletti weir is set downstream to control flow profiles. Steady flow characteristics are deduced by means of three different softwares: a pure Lagrangian developed by the author, based on the Weakly Compressible Smoothed Particle hydrodynamics (WCSPH) technique, Flow3D® and HEC-RAS®. Depending on the specific boundary conditions being given, velocity profiles and water interfaces at certain cross sections are deducted by using the first two codes. Results are discussed then spatially averaged in terms of mean velocities and water depths respectively to make a comparison with the ones obtained with HEC-RAS, showing a satisfactory agreement.

An effective approach for designing circular pipes with the Colebrook-White formula

To designing pipe diameter, several flow resistance formulae are available in literature. Generally, these are relationships relating friction loss, relative roughness and Reynolds number. Here, an iterative procedure, based on the solution of a second order equation (standard approach), is presented. Then an effective and simple procedure (advanced approach) for designing circular pipes by means of the Colebrook-White transition formula is provided. Latter procedure is proven to be accurate in double precisionafter a limited number of iterative steps.