ABSTRACT
In the present work, the impact that the longitudinal shape of channels has on the current produced in the flow of a magneto-hydrodynamic microgenerator (MHDMG) is studied. The goal is to find the micro-channel geometry via modeling to maximize the current output for low Reynolds and Mach regimes. To carry out this study, a 3D dynamic numerical tool relying on the finite volume method was handled with the open-source software OpenFOAM. It is the base model to study the impact of intricate geometries on the ability to produce energy. An additional steady-state 2D analytical model was also developed to check some basic modeling assumptions. Both models have been experimentally validated on the simplest flow system having a constant square cross-section throughout. The results produced by both models cross-check very well and compare favorably with respect to experimental data. Hence, using the validated numerical tool, three shapes have been further investigated, namely, progressive (linear decrease of the cross-section), arc (parabolic decrease of the cross-section), and wavy (sinusoidal shape). It was found that the arc channel provides the greatest current output for the same volumetric flow. It is therefore the preferred choice for developing high current gain and more efficient MHDMG used in micro-scaled actuators and sensors.
ABSTRACT
Experimental and numerical results are reported for the internal and external flow fields evolving in a bio-inspired snapping plunger. The experimental evidence underlines the nature of the dynamic-coupling between the processes taking place inside and outside the device. Two main structures dictate the properties of the external flow field: a strong jet which is followed by a vortex ring. Internally, complex patterns of cavitating structures are simultaneously produced in the chamber and the venturi-like conduit. We find the cavitation cycle to be suitably described by the Rayleigh-Plesset model and, thus, proceed to characterize the coupling of both fields in terms of the fluctuations of the velocity. All main parameters, as well as the energy released to the fluid during the collapse, are found to be within the same order-of-magnitude of previously known experimental results for isolated bubbles of comparable size.
Subject(s)
HydrodynamicsABSTRACT
The dataset presented in this article was collected in a laboratory flow circuit, which was designed to investigate high-viscosity flows. The data set is composed of 1200 s (equivalent to 12,000 samples) of mass flow and pressure measurements taken at five points along the pipeline. The first 300 s were recorded when the flow in the loop was composed only of glycerol. The remaining data were acquired when the flow was composed of a water-glycerol mixture. During the data acquisition, two extractions were produced. The research reported in [1] uses 160 s of the data provided here. This article explains in detail the experimental set-up and the principal instruments used for obtaining the dataset. The dataset is in the form of seven columns: Time, Mass Flow, Pressure 1, Pressure 2, Pressure 3, Pressure 4, Pressure 5, in supplementary Excel and Matlab files.
ABSTRACT
A creative low-cost and compact mechanical device that mimics the rapid closure of the pistol shrimp claw was used to conduct electrochemical experiments, in order to study the effects of hydrodynamic cavitation on the corrosion of aluminum and steel samples. Current-time curves show significant changes associated with local variations in dissolved O2 concentration, cavitation-induced erosion, and changes in the nature of the surface corrosion products.
ABSTRACT
A comparative experimental study of the velocity field and the strain field produced down-stream of biological and mechanical artificial valves is presented. In order to determine the spatial and temporal distributions of these fields, a phase-locked stereoscopic particle image velocimetry (or 3D-PIV) technique was implemented. Emphasis was placed on the identification of the fundamental differences between the extensional and the shear components of the strain tensor. The analysis of the characteristic flows reveal that the strains in every direction may reach high values at different times during the cardiac cycle. It was found that elevated strain levels persist throughout the cardiac cycle as a result of all these contributions. Finally, it is suggested that the frequency with which the strain variations occur at particular instants and locations could be associated to the cumulative damage process of the blood constituents and should be taken into account in the overall assessment of existing valve types, as well as in future design efforts.
