Finite Numerical Method Research Articles

Experimental and numerical investigations of aluminum foam-filled auxetic circular tubular metamaterials with elliptical cells

Aluminum foam-filled circular auxetic metamaterials were designed, fabricated and investigated in this work. Firstly, the mechanical properties and deformation modes of the proposed aluminum foam-filled auxetic tubes (AFFAT) were analyzed using experimental and finite numerical methods. The load capacity of the AFFAT is larger than the sum of the load for the auxetic tube and aluminum foam. Secondly, the effect of aluminum foam’s density on the mechanical properties of AFFAT was studied. The results show that the energy contribution ratio of the interaction between the aluminum foam and auxetic tube improves with the aluminum foam’s density. Then, the effect of unit cell size on the mechanical properties of AFFAT was investigated. It can be concluded that the compression load efficiency of AFFAT with the ratio of the elliptical major axis to the minor axis increases. Finally, the study of tube type’s effect on the mechanical properties of AFFAT was carried out. Among the investigated composite structures, the AFFAT has the highest compression load efficiency. Due to their unique structural design and excellent mechanical properties, the AFFAT has great potential for applications in aerospace, vehicle crashworthiness and protective infrastructure.

Calculation and Analysis of the Strands Short-Circuit in Stator Transposition Bar for Large Generators

The transposition of the stator bar is an important technique in the large generator design. Under the excitation of vibration and thermal effect, the insulation of strand is easily damaged, which leads to short-circuiting fault, and adversely impacts the generator’s secure operation. To better protect the generator, there is a need for detailed research of the characteristics of stator transposition bar under the strands short-circuit condition. In this paper, we proposed a 3D finite numerical method (FEM) for calculating the strand short-circuit current. In the proposed method, the whole model of stator transposition bar is divided into multiple piecewise segments, and each segment is coupled together by the circuit. Based on this method, the electromagnetic properties of the 308° stator transposition bar under the strands short-circuit fault condition are analyzed. Then, the properties of the strand short-circuit current is studied. Finally, the calculated results are compared with the measured data. The results show that the calculation of the strand short-circuit current with high precision and the strand short-circuit current jump is one of the characteristics of strands short-circuit fault in stator transposition bar.

The Dynamic Analysis of Municipal Pipeline Under Shield Tunneling Construction Based on the ABAQUS Software

Shield tunneling construction is the modern popular used model in underground pipelines. In this paper, finite numerical method based on ABAQUS software has been used to simulate the effect of shied tunneling construction on the underground pipelines, the effect between the pipeline and soil interface had been considered, the dynamic effect and response have been simulated for underground pipelines. Numerical results show that the tunnel depth, propelling force, pipe’s diameter and pipe’s depth have greater influence on the pipeline’s displacement. The rules and conclusions drawn in the paper can provide reference for the pipeline protection in similar projects in the future.

ALARMING SYSTEM FOR SHIFTING WILD ANIMALS FROM FOREST DURING FLOOD USING DTED AND FINITE NUMERICAL METHODS

Abstract. The paper presents a methodology to develop a three dimension model of any area using DTED data and mapping toolbox of MATLAB. This three dimension model is further use to calculate the volume from minimum bottom level using finite numerical methods and hence to classifying the area based on level and volume of water occupying upto particular level. This data is used to create the alarming system for shifting of wild animals from area based on volume and elevation data during flood. Further based on these results, areas are determined which are going to flood if water comes either through rain or through Tsunami.. Simulations are performed to compare the results between mathematical formulations and numerical methods.

A Frequency-Domain Near-Field-to-Far-Field Transform for Planar Layered Media

We report a frequency-domain near-field-to-far-field transform (NFFFT) for the numerical modeling of radiation and scattering in planar multilayered spaces. Although the results are equivalent to those of Demarest (1996), the formulation is more compact, more stable, and applicable to observation angles in the lower half space. Furthermore, the results are presented in a vector-potential formalism that is more easily adaptable to existing free-space implementations. The NFFFT algorithm can be used in any differential-equation-based finite numerical method, including but not limited to the finite-difference time-domain (FDTD) method and the finite-element method (FEM).

Augmented control strategies for radiant floor heating systems

A dynamic model of a radiant floor heating (RFH) system useful for control analysis is developed. The overall model consists of a boiler, distribution system, an embedded tube floor slab and building enclosure. The overall model is described by non-linear differential equations which were solved using finite numerical methods. Two control strategies for improving the temperature regulation in RFH systems are proposed. These are: a multistage on–off control and an augmented constant gain control (ACGC). Simulation results show that the multistage control maintains zone air temperature close to the setpoint better than the existing on–off control scheme does. Likewise, ACGC gives good zone temperature control compared to the classical proportional control. The ACGC is shown to be robust to changes in weather conditions and internal heat gains. The advantage of the control strategies proposed is that they eliminate the use of outdoor temperature sensors required in some existing control schemes. Being simple and robust, the proposed control schemes are good candidate controls for RFH systems. Copyright © 2002 John Wiley & Sons, Ltd.

Augmented control strategies for radiant floor heating systems

A dynamic model of a radiant floor heating (RFH) system useful for control analysis is developed. The overall model consists of a boiler, distribution system, an embedded tube floor slab and building enclosure. The overall model is described by non-linear differential equations which were solved using finite numerical methods. Two control strategies for improving the temperature regulation in RFH systems are proposed. These are: a multistage on–off control and an augmented constant gain control (ACGC). Simulation results show that the multistage control maintains zone air temperature close to the setpoint better than the existing on–off control scheme does. Likewise, ACGC gives good zone temperature control compared to the classical proportional control. The ACGC is shown to be robust to changes in weather conditions and internal heat gains. The advantage of the control strategies proposed is that they eliminate the use of outdoor temperature sensors required in some existing control schemes. Being simple and robust, the proposed control schemes are good candidate controls for RFH systems. Copyright © 2002 John Wiley & Sons, Ltd.

Estimating vacuum tunneling rates

In Euclidean field theories, a rigorous upper bound on the action of the bounce with the least action can be obtained by finite numerical methods because the bounce with the least action is the global minimum of the action in an open space. The corresponding lower bound on the tunneling rate is easily computed by a new method of “reduction”.

Calculation of zero phase sequence impedance for power transformers using numerical methods

This paper aims to demonstrate an approach to the calculation of zero phase sequence impedance for power transformers using finite numerical methods. Specifically concentrating on 3-limb, core type, YNyn connected transformers where no accurate solution is available. An understanding of the physical factors affecting the calculation have been considered. Actual test results are presented. >