40 research outputs found
The new functionalities of www.aiia.it - technical note
No full textThe main funcniolaties of the renewed website of Italian Association of Agricultural Engineering, at the address www.aiia.it, are briefly described
Numerical and experimental analysis of vertical spray control patternators
No full textThe experimental vertical spray control walls have the purpose of picking up the liquid delivered by trained sprayer for providing the liquid distribution profile in height. Theoretically this should correspond to the ideal profile, which consists in a uniform distribution on the vegetation. If the profile is different from the ideal, a parameter setup is required on the sprayer. Nonetheless, some problems are hidden in the aforementioned statements: i) no wall measures exactly the distribution profile (i.e. the flow through the sections in the vertical plane, parallel to the direction of advancement of the sprayer). Compared to real profile, sensitive errors are introduced: the evaporation of the drops, the deviation of the air flows caused by the sensors panel themselves; by the possibility that the drops bounce on the wall panels, also due to the current of air that can push the liquid veil laterally or upwards, Moreover, everything varies depending on the geometry of the sensors, air velocity, air humidity; ii) no one knows what exactly is the optimal distribution profile. It is often considered as optimal a profile that reflects the amount of leaf area subtended by each section absorber: however, it is evident that the path of the droplets changes according to the sprayer typology (eg. radial-flow or horizontal flows). In this work a combined numerical-experimental approach is adopted, in order to assess some of the aforementioned issues: numerical data obtained by using computational fluid dynamics models are compared and validated with experimental data, in order to assess the reliability of numerical simulations in configurations which are difficult to analyze using an experimental setu
Enhancement and reversal heat transfer by competing modes in jet impingement
No full textA transient numerical analysis for fluid flow and heat transfer from a planar jet impingement on a finite thickness substrate is performed. A discrete heating boundary condition is applied to the substrate’s under side; by including the effect of buoyancy, some assisting or opposing mixed convection configuration can be modelled and regions of momentum dominated, buoyancy dominated and unstable flows can be monitored. For low volumetric flows and small temperature differences, different competitive heat transfer modes can be detected, as conduction may affect heat transfer away from the impact site in the initial times, and flow pattern is driven by the ruling convective mechanism, whether forced or natural. The related flow field and local heat transfer rate are investigated as a function of a variety of geometry configurations, material coupling and thermal-fluid driving factors, for the unitary value of the mixed convection
parameter Ri (transitional mixed convection).
Normalized heat transfer coefficients along the impinged substrate are reported by a parametric evaluation and may be employed to control the distribution of heat transfer at the given configuration. The inclusion of the conduction mechanism in the analysis confirms that the conjugate effect (heat transfer reversal) cannot be neglected during the initial exposition when an opposing cooling jet configuration is realized, for the largest investigated Re
2-D Transmitral Flows Simulation by Means of The Immersed Boundary Method On Unstructured Grids
No full textApplication of Constrained Optimization Techniques in Optimal Shape Design of a Freezer to Dosing Line Splitter for Ice Cream Production
No full textDesign of multiple branches splitting of equal mass flow rate in complex rheological flows like ice cream near melting point temperature can be a challenging task. Pulsations in flow rate due to air pumping process and small fluctuations in temperature affecting flow rheology can determine a consistent difference in internal pipe velocity distribution, resulting in a significant difference in the distribution of ice cream dosage. Computational sciences and engineering techniques have allowed a major change in the way products and equipment can be engineered, as a computational model simulating physical processes can be more easily obtained, rather than making prototypes and performing multiple experiments. Among such techniques, optimal shape design (OSD) represents an interesting approach. In OSD, the essential element with respect to classical numerical simulations in fixed geometrical configurations relays on the introduction a certain amount of geometrical degrees of freedom as a part of the unknowns. This implies that the geometry is not completely defined, but part of it is allowed to move dynamically in order to minimize or maximize an objective function. From a mathematical point of view, OSD is a branch of differentiable optimization and more precisely the application of optimal control for distributed systems. OSD is still today numerically difficult to implement, because it relies on a computer intensive activity and moreover because the concept of “optimal” is a compromise between shapes that are good with respect to several criteria. In this work, the applications of a multivariate constrained optimization algorithm is proposed in the case of a mechanical ice cream 1 to 5 splitting system, required to distribute in an evenly way from one freezer into five dosing valves. Results allowed to design a retro-fitting system on an existing production plant reducing the dosing error down to 3% on the average
Air Assisted Production of Alginate Beads Using Focusing Flow Microfluidic Devices: Numerical Modeling of Beads Formation
No full textAlginate micro-bead production represents an interesting technological application in many fields such as pharmaceutical, food, and cosmetics. Usually the studies of micro droplet or micro-bead creation in micro channels formed in different geometries and different techniques (mostly T channel or flow-focusing) have been the subject of many research studies using pure, well characterized solutions and do not take into account the behavior and interaction of food grade and natural products. The possibility of using air as focusing flow [2] in microfluidic devices to produce sodium alginate micro-bead introduce some advantages; for example, the utilization of different focusing fluids like oil frequently requires complicate production processes, introducing a barrier to the interaction of alginate solution with the calcium ions during gelification phase and requiring a posteriori filtering and washing procedure. Moreover, direct immersion of liquid alginate drops in a calcium chloride bath to induce gelification usually happens at relatively high speed, inducing a bead shape deformation due to inertial effects. As in microfluidics details really matter, the geometry of the device represents an important issue: small changes in geometrical configuration, like coaxial misalignment could results in major changes in the dynamics of droplet formation. In this work such effects are investigated using numerical analysis
2-D transmitral flows simulation by means of the immersed boundary method on unstructured grids
No full textSub-band IIR acoustic echo canceller
No full textIn teleconferencing systems the echo can be very long. A direct FIR implementation of the echo canceller often requires more than 2000 taps. One approach is to process the signal in sub-bands providing a separate FIR echo canceller for each band. We propose the use of an IIR filter in each sub-band adapted by a variant of the Steiglitz-McBride identification scheme instead of the classical adaptive FIR filters. Experimental results and computer simulations show that the proposed IIR sub-band echo canceller performs better then the equivalent FIR counterpart
Modeling in postharvest: A multiscale perspective
No full textThe development in plant physiology understanding together with the extension of mechanistic and hybrid models suggests that the use of models in the postharvest chain will always more extended in the next future. Modeling allows not only to verify experimental data under a unifying umbrella, but also to gain an insight in physical and biological process, to predict product characteristics and to optimize the postharvest chain at different scale levels. In this short review a multiscale point of view is presented.
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Analysis of Instantaneous IMU Acquisition for Safety Index Identification in Tractor Driving
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