Numerical Analysis of Gravitational Vortex Chamber

A rotating mass of fluid is known as vortex and the motion of the rotating mass of fluid is known as vortex motion. Vorticity is the circulation per unit area. In this research simulation of a vortex chamber is to be carried out in ANSYS CFD taking water as fluid domain for generating a water vortex that is capable enough to move a turbine for electricity generation. The CAD modelling of the setup was set down and simulation was done in fine mesh by taking suitable wall function in the model of a cylindrical chamber along with a rectangular channel with a contraction portion at the end of it where good amount of vortex generation was acquired by observing velocity and pressure by setting different parameters. The results shows the pressure and velocity contours with 3D velocity streamline flow and the curve of the velocity and pressure curve shows the decrease of pressure and increase of velocity from inlet to outlet that leads to a decent vortex generation.

3D Printed Brachytherapy Jig for Reference Air Kerma Rate Calibration

3D printing in modern radiotherapy provides creative autonomy which can be a valuable tool for use in brachytherapy source calibration. Radiotherapy centres may verify their brachytherapy source strength with a calibrated Farmer chamber. For this purpose, a jig was designed, 3D printed and commissioned for in-air source strength calibration. Measurements on four afterloaders with varied equipment and environments were completed. A full uncertainty budget was developed and measurements with the in-air jig were consistently within 3% of the certificate source strength. By creating a jig that is able to be customised to multiple catheter sizes and cylindrical chamber designs, centres can be provided with the option of independently checking their source strength with ease and for little cost.

FEATURES OF SOUND GENERATION BY THE JET-DRIVEN HELMHOLTZ OSCILLATOR

Experimental studies the model of a jet-driven Helmholtz oscillator has been carried out. The oscillator is a cylindrical chamber, closed on the sides by two covers with inlet and outlet holes. The oscillator was excited by a stream of airflow. The influence of the geometric dimensions of the chamber and the openings in the covers on the amplitude of pressure fluctuations was studied and the optimal channel configuration was determined. Particular attention is paid to the study of the influence on the amplitude of pressure fluctuations of the shape and size of the nozzle - the hole in the front cover. There were measured the following processes: the pressure drop across the nozzle, to calculate the speed of the jet at the chamber entrance, and the parameters of pressure fluctuations in the chamber, to plot the amplitude-frequency spectra. There were made certain observations of a jet tone appearance and acoustic modes excitation at the natural frequency of the chamber-resonator with a smooth increase in the jet velocity. The relationship between the jet tone and the resonant in the chamber is noted. Recommendations for designing a Helmholtz jet oscillator are presented.

A Green’s Function Solution for Acoustic Attenuation by a Cylindrical Chamber With Concentric Perforated Liners

In this study, a Green’s function-based semi-analytical method is presented to predict the transmission loss (TL) of a circular chamber having concentric perforated screens. Initially, the Green’s function is developed for a single-screen configuration as the summation of eigenfunctions of the inner pipe in the absence of the mean flow. The inlet and the outlet ports are modeled as oscillating piston sources. A transfer matrix is formulated from the velocity potential generated by the piston sources. The results obtained from the proposed method are validated with the numerical and analytical models and with the experimental results available in the literature. Later, the method has been extended to the double-screen configuration. The effect of the additional perforated screen on the TL is studied in terms of the surface impedance of the chamber. Along with grazing flow considerations, guidelines are provided to incorporate more concentric perforated screens into the formulation.

On Small Oscillations Inside a Volcano Feeding System

A simple analytical model representing one of the possible mechanisms for the occurrence of low-frequency oscillations in a feeding system of volcano has been developed. The model is presented for a cylindrical chamber filled with magma with Maxwell rheology. It is shown that damped harmonic oscillations in the magma flow velocity can occur in the volcanic chamber. These damped harmonic oscillations can appear as a reaction to remote seismic events or seismic events in the volcanic feeding system. The dependence of the oscillation frequency on the physical characteristics of the magmatic melt and the geometric dimensions of the volcano chamber is shown. The occurrence of magmatic oscillations can be observed near the surface as a volcanic tremor. The model is applied to the measurements result of low-frequency oscillations for the magma chamber of the Elbrus volcanic center.

Performance Assessment of Multi-Electrodes Reactors for Scaling-up Microbial Fuel Cells

The microbial fuel cells (MFCs) represent an emerging technology for converting directly organic waste into electricity. In recent years, the application of MFCs to the energy recovery from wastes has been widely explored. The main aspect that limits the development and implementation of this technology on a larger-scale is the possibility of realizing its scaling-up. In order to overcome this critical factor, it is useful to analyze novel MFCs configurations based on compact reactors with multiple electrodes.In this paper, single chamber MFCs provided with multiple fiber brush anodes and a single air-cathode were designed and realized by using a 3D printer. The reactors had a cubic shape, with a cylindrical chamber of 350 mL in volume. The mineral medium added with sodium acetate (0.25 M), as sole source of carbon and energy to sustain exoelectrogenic bacteria metabolism, were used. Anodes biofilms were prepared from a mix of compost and sodium acetate dissolved in phosphate buffer solution (0.2M), in a 1:3 ratio. The performances of two MFCs provided with two and three anodes were assessed in terms of voltage, current density and power density. These performances were compared to those of a smaller cubic MFC (30mL).