A new split and recombine (SAR) passive micromixer, namely the H-C mixer, is presented. The performance of the micromixer is analyzed numerically at Reynolds numbers up to 100, varying the inlet flow-rate ratio. In order to validate the numerical model, tests for an inlet flow-rate ratio of 1 were carried out on the new H-C micromixer along with the established Tear-drop and Chain micromixers for comparison, and good correspondence was found between the differently obtained data. Contrary to the Tear-drop and Chain micromixers, the H-C micromixer exhibited a mixing efficiency greater than 90% independent of Reynolds numbers. In particular, no noticeable dependence on inlet flowrate ratio was observed. Furthermore, the pressure drop along the H-C mixer was found to be lower than those along the already known mixers.
ARTICLE HISTORY
The flow field inside an air-jet loom main nozzle is studied numerically, by means of a two-dimensional model implemented in the commercial computational fluid dynamics (CFD) code Fluent. In order to determine which physical model could allow a better prediction of the nozzle behavior, preliminary simulations were carried out on a basic geometry configuration, changing flow models and comparing results with available experimental data. Having done the model setup, simulations aimed at evaluating drag force on the weft yarn were performed on various geometry configurations; in particular, the influence of acceleration tube length, shape and size on drag force was evaluated. Results gave some guidelines for future prototyping and experimentation.
In this paper, a novel UGV (unmanned ground vehicle) for precision agriculture, named “Agri.q,” is presented. The Agri.q has a multiple degrees of freedom positioning mechanism and it is equipped with a robotic arm and vision sensors, which allow to challenge irregular terrains and to perform precision field operations with perception. In particular, the integration of a 7 DOFs (degrees of freedom) manipulator and a mobile frame results in a reconfigurable workspace, which opens to samples collection and inspection in non-structured environments. Moreover, Agri.q mounts an orientable landing platform for drones which is made of solar panels, enabling multi-robot strategies and solar power storage, with a view to sustainable energy. In fact, the device will assume a central role in a more complex automated system for agriculture, that includes the use of UAV (unmanned aerial vehicle) and UGV for coordinated field monitoring and servicing. The electronics of the device is also discussed, since Agri.q should be ready to send-receive data to move autonomously or to be remotely controlled by means of dedicated processing units and transmitter-receiver modules. This paper collects all these elements and shows the advances of the previous works, describing the design process of the mechatronic system and showing the realization phase, whose outcome is the physical prototype.
A numerical analysis on the feeding system of externally pressurized gas bearings, for the correction of the theoretical mass flow rate formula by means of a discharge coefficient, is presented. A flat aerostatic pad with a simple orifice-type feeding system was chosen as case on study, the authors having previously carried out experimental tests on such a prototype. Using the commercial CFD code Ansys Fluent ®, preliminary simulations were carried out on a pad's geometry using three different flow models. Having selected the flow model able to give the best prediction of the pad's behaviour in terms of pressure distribution along the air film, additional simulations were carried out on pads with two different diameters of the supply hole, varying the film thickness in a range from 9 to 14 μm.. A comparison between numerical and experimental results is presented. In addition, the effect of the flow intake used to perform experimental tests and of the shape of the orifice's external edge on pressure distribution is analysed.
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