Application of a modified variational formulation of the vector finite element method for modelling a harmonic electric field in areas with curved shields

Рассматриваются особенности применения модифицированной вариационной постановки векторного метода конечных элементов (ВМКЭ), основанной на замене тонких сильнопроводящих объектов токонесущими поверхностями, для моделирования гармонического электрического поля в областях с криволинейными экранами при различном типе возбуждения поля. Исследуется применимость модифицированной вариационной постановки в широком диапазоне частот Purpose. The paper addresses applicability of the modified variational formulation of vector FEM for the harmonic electric field to the media with cylindrical shields. Thin highly conductive objects are treated as surfaces with the equivalent surface current density. We consider the excitation of the field by a local source (current loop) located either inside or outside the cylindrical shield. Methodology. The simulations are carried out on unstructured tetrahedral meshes. Since the modified variational formulation treats thin highly conductive objects as surfaces, only the surface of a cylinder is discretized. The results yielded by the modified variational formulation are compared with the results of the classic vector FEM. Findings. For the frequency range between 100 KHz and 100 MHz, the modified variational formulation provides correct results when the field source is located outside the cylindrical shield. The modified variational formulation reduces computational cost, since the volume of the thin shield is not discretized. When the field source is located inside the shield, the modified variational formulation gives valid results only in the proximity of the source. Originality/value. The limitations for the application of the reduced variational formulation for the modelling of harmonic electric field in the media with hollow cylindrical shields are investigated

Magnetic field enhancement technique in the fluid flow gap of a single coil twin tube Magnetorheological damper using magnetic shields

Smart dampers in the automobile suspension system bring a precise balance between the ride comfort and stability through a controllable damping coefficient. Energy absorbed by a Magnetorheological (MR) damper is a dependent function of flux density in the fluid flow gap. In this paper, magnetic field enhancement technique in the form of a single cylindrical shield and sandwich cylindrical shield is incorporated in a twin tube single coil MR damper. The field strength in different configurations of MR damper having various type of shield configuration is computationally investigated. Further, the effect of shield thickness on field strength is investigated. A significant overall improvement in the magnetic field strength is observed in the MR damper configuration having copper alloy shield.

Numerical simulation of a sonic-underexpanded jet impinging on a partially covered cylindrical Hartmann whistle

The present study numerically investigates the effect of a partially covered cylindrical shield on the flow/shock oscillation characteristics of a Hartmann whistle when the pulsating jet exits through the two small openings, (a) close to the cavity inlet, and (b) away from the cavity inlet, of the cylindrical shield. The relevant parameters that modify the flow/shock oscillations of the Hartmann whistle are the stand-off distance, nozzle pressure ratio, cavity length, cavity shield, jet diameter, etc. The pulsating nature of flow in a partially shielded Hartmann whistle is investigated for various stand-off distances to understand its effect in achieving effective flow control. The velocity vectors indicate that the partly shielded Hartmann whistle operates in the jet regurgitant mode with different regurgitant phases. It also shows that some amount of the jet near the cavity inlet gets diverted towards the shield and gets attached to it, whereas some exits out through the two shield openings which can be injected into the flow to be controlled. The Mach number contours indicate the flow deceleration/reacceleration zones, shock-cell structures as well as fluid column oscillations in shock-cells/cavity regions. The present study reveals that the stand-off distance and the jet diameter are the crucial parameters, which control the oscillation mechanisms in a partially covered Hartmann whistle for achieving effective flow control. Thus, this paper sufficiently demonstrates the role of stand-off distances, openings in the shield as well as jet diameter in modifying the flow/shock oscillation characteristics of a partially shielded Hartmann whistle in achieving the finest flow control.

A plant for blood heat treatment of farm animals

The microwave installation for the cooking farm animals blood was designed. It consists of a cylindrical shield casing, inside which are the rotor; a plurality of cylindrical resonator chambers, rigidly fixed by the microwave generator so that the emitter is on its inside. Three microwave generators and an infrared heating sets (IR lamp) are installed alternately on the upper base of the cylindrical screening body to increase plant productivity. To fix the lower parts of the cylindrical resonator chambers in a vertical position there are a tension ring. It holds the resonator chamber to discharge the sector. The unit of start safety equipment was mounted on the side of the shield casing. There is a dispenser with a rotating shutter on the top shield frame, before the first microwave generator. Implementation of the gate with mounted along the shaft of the blades with scrapers is used for cleaning dispenser cap from entering blood. There is an unloading chute on the side of the shield casing. In its sector, there is a special stop element, contributing to overturn the resonating chambers and return them to the upright position. The cost effectiveness of microwave plant with a capacity of 60 kilogram per hour is about 1 million.