Analysis of the infinite array of slot impedance loads based on the cavity with an equilateral triangular cross section
Two-dimensional problem of an infinite array of slot impedance loads by the plane wave is considered. Each array element represents a slot in a perfectly conducting screen loaded by a cavity with equilateral triangle cross-section. The integral equations method is used to solve the problem, the Krylov-Bogoliubov method is applied to calculate them. For the case of H-polarized incident wave equivalent surface impedance dependencies on construction geometric sizes is calculated. Comparative analysis of dependencies obtained for construction under consideration of an infinite array of slot impedance loads with those ones for single impedance load is carried on.
To the choice of collocation points for solving integro-differential equations of electromagnetics
The choice of collocation points for solving integro-differential equations of electromagnetics by the Krylov-Bogolyubov method is considered. Using the example of a simple diffraction problem, variants of the solution for two different systems of collocation points are presented. The first (traditional) system of collocation points is chosen so that the end points do not fall onto the boundaries of the interval. In the second system, the end points fall onto the boundaries. It is shown that both of the systems can be used for solving the problem but the use of the second system provides for a higher accuracy with fewer collocation points.
Influence of pressure and fluidization velocity on the hydrodynamics of a fluidized bed containing horizontal tubes
Abstract An experimental investigation of the influence of horizontal tubes on the bubble behaviour and through-flow velocity of gas inside bubbles was carried out and the influence of pressure and fluidization velocity was studied. The visible bubble flow rate and the gas velocity through the bubbles were measured simultaneously in a pressurized fluidized bed, using capacitance and Pitot-static pressures probes respectively. Silica sand with a mean particle diameter of 0.7 mm was fluidized at pressures between 01. and 1.6 MPa, in a bed of 0.2 × 0.3 m cross-section. Six different horizontal tube configurations were used and comparisons were made with results obtained in the same bed operated without tubes. The results from the bed with tubes show that the influence of pressure and fluidization velocity is basically the same as in the bed without tubes; an increase in pressure and fluidization velocity increases the bubble activity. At low excess gas velocities, the influence of immersed tubes on the bubble behaviour is less pronounced than at high excess gas velocities. Measurements and visual observations show that a small tube pitch gives a more uniform distribution of the visible bubble flow over the bed cross-section. At a combination of high pressure, high excess gas velocity and a large tube pitch, a preferred bubble path was observed in the centre of the bed cross-section. The pressure probe measurements show that the through-flow velocity of gas inside the bubbles is in most cases higher when tubes are present in the bed. The through-flow velocity consistently decreases with increasing pressure in the bed without tubes. The tendency is largely the same at a low excess gas velocity when tubes are present, but at a high excess gas velocity the through-flow velocity first decreases and then increases as the pressure is increased.