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Article
Publication date: 6 July 2015

He-yong Xu, Shi-long Xing and Zheng-yin Ye

The purpose of this paper is to investigate and improve a new method of unstructured rotational dynamic overset grids, which can be used to simulate the unsteady flows…

Abstract

Purpose

The purpose of this paper is to investigate and improve a new method of unstructured rotational dynamic overset grids, which can be used to simulate the unsteady flows around rotational parts of aircraft.

Design/methodology/approach

The computational domain is decomposed into two sub-domains, namely, the rotational sub-domain which contains the rotational boundaries, and the stationary sub-domain which contains the remainder flow field including the stationary boundaries. The artificial boundaries and restriction boundaries are used as the restriction condition to generate the entire computational grid, and then the overset grids are established according to the radius parameters of artificial boundaries set previously. The deformation of rotational boundary is treated by using the linear spring analogy method which is suitable for the dynamic unstructured grid. The unsteady Navier-Stokes/Euler equations are solved separately in the rotational sub-domain and stationary sub-domain, and data coupling is accomplished through the overlapping area. The least squares method is used to interpolate the flow variables for the artificial boundary points with a higher calculating precision. Implicit lower-upper symmetric-Gauss-Seidel (LU-SGS) time stepping scheme is implemented to accelerate the inner iteration during the unsteady simulation.

Findings

The airfoil steady flow, airfoil pitching unsteady flow, three-dimensional (3-D) rotor flow field, rotor-fuselage interaction unsteady flow field and the flutter exciting system unsteady flow field are numerically simulated, and the results have good agreements with the experimental data. It is shown that the present method is valid and efficient for the prediction of complicated unsteady problems which contain rotational dynamic boundaries.

Research limitations/implications

The results are entirely based on computational fluid dynamics (CFD), and the 3D simulations are based on the Euler equations in which the viscous effect is ignored. The current work shows further applicable potential to simulate unsteady flow around rotational parts of aircraft.

Practical implications

The current study can be used to simulate the two-dimensional airfoil pitching, 3-D rotor flow field, rotor-fuselage interaction and the flutter exciting system unsteady flow. The work will help the aircraft designer to get the unsteady flow character around rotational parts of aircraft.

Originality/value

A new type of rotational dynamic overset grids is presented and validated, and the current work has a significant contribution to the development of unstructured rotational dynamic overset grids.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 87 no. 4
Type: Research Article
ISSN: 0002-2667

Keywords

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Article
Publication date: 7 May 2019

Rupeng Yuan, Fuhai Zhang, Jiadi Qu, Guozhi Li and Yili Fu

The purpose of this paper is to propose an enhanced pose tracking method using progressive scan matching, focusing on accuracy, time efficiency and robustness.

Abstract

Purpose

The purpose of this paper is to propose an enhanced pose tracking method using progressive scan matching, focusing on accuracy, time efficiency and robustness.

Design/methodology/approach

The general purpose of localization algorithms is to dynamically track a robot instead of globally locating one. In this paper, progressive scan matching is used to promote the performance of pose tracking. Rotational and translational samples are separately generated to accelerate the calculation and to increase the accuracy. Progressive iteration of sample generation can ensure localization to achieve a specific precision. The direction of localization uncertainty is taken into consideration to increase robustness. Nonlinear optimization is adopted to achieve a more precise result.

Findings

The proposed method was implemented on a self-made mobile robot. Two experiments were conducted to test the accuracy and time efficiency of the method. The comparison with the basic Monte Carlo localization shows the advantages of the method. Another two experiments were conducted to test the robustness of the method. The result shows that the method can relocate a robot from an inaccurate place if the offset is moderate.

Originality/value

An enhanced pose tracking method is proposed to promote the performance by separately processing rotational and translational samples, progressively iterating the sample generation, taking the direction of localization uncertainty into consideration and adopting nonlinear optimization. The proposed method enables a robot to accurately and quickly locate itself in the environment with robustness.

Details

Industrial Robot: the international journal of robotics research and application, vol. 46 no. 2
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 8 January 2018

Xiao-dong Yu, Lei Geng, Xiao-jun Zheng, Zi-xuan Wang and Xiao-gang Wu

Rotational speed and load-carrying capacity are two mutual coupling factors which affect high precision and stable operation of a hydrostatic thrust bearing. The purpose…

Abstract

Purpose

Rotational speed and load-carrying capacity are two mutual coupling factors which affect high precision and stable operation of a hydrostatic thrust bearing. The purpose of this paper is to study reasonable matching relationship between the rotational speed and the load-carrying capacity.

Design/methodology/approach

A mathematical model of relationship between the rotational speed and the load-carrying capacity of the hydrostatic bearing with double-rectangle recess is set up on the basis of the tribology theory and the lubrication theory, and the load and rotational speed characteristics of an oil film temperature field and a pressure field in the hydrostatic bearing are analyzed, reasonable matching relationship between the rotational speed and the load-carrying capacity is deduced and a verification experiment is conducted.

Findings

By increasing the rotational speed, the oil film temperature increases, the average pressure decreases and the load-carrying capacity decreases. By increasing the load-carrying capacity, the oil film temperature and the average pressure increases and the rotational speed decreases; corresponding certain reasonable matching values are available.

Originality/value

The load-carrying capacity can be increased and the rotational speed improved by means of reducing the friction area of the oil recess by using low-viscosity lubricating oil and adding more oil film clearance; but, the stiffness of the hydrostatic bearing decreases.

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Article
Publication date: 4 January 2011

Bingchang Ni and Constantinos Sourkounis

Wind energy plays a very important role in the future electrical power supply. With growing shares, the focus of the plant control will have to shift from maximum power…

Abstract

Purpose

Wind energy plays a very important role in the future electrical power supply. With growing shares, the focus of the plant control will have to shift from maximum power yield to grid friendly aspects, like stable power output despite fluctuating wind power. The purpose of this paper is to design a new operation management for wind energy converters that combines high‐energy yield, grid friendly power output characteristics and the ability to adapt to changing wind conditions.

Design/methodology/approach

An operation control based on stochastic dynamic optimization was developed for the special demands of variable speed wind energy converters. The task of the operation control is to set the appliance to the optimal operation point, following the above‐mentioned goals by adapting the control pattern to changing wind conditions.

Findings

It is shown that the novel control concept, the iterative self‐adapting system management with stochastic dynamic optimization, is able to control wind energy converters in such a way that the effect of the stochastic fluctuating wind energy supply on the output power fluctuation is smoothed while maintaining a high‐energy yield.

Originality/value

This non‐linear stochastic dynamic optimization structure has two special characteristics, first is the iterative self‐adaptation, and second is the optimization for an infinite process, while the optimization criteria are high‐power yield and low‐power output fluctuations. This will be of great value for further increase of wind energy converters in the electrical power supply.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 14 March 2019

Wei-Mon Yan, Hsu-Yang Teng, Chun-Han Li and Mohammad Ghalambaz

The electromagnetic field and cooling system of a high power switched reluctance motor (SRM) are studied numerically. The geometry of the motor and its main components are…

Abstract

Purpose

The electromagnetic field and cooling system of a high power switched reluctance motor (SRM) are studied numerically. The geometry of the motor and its main components are established using a computer-aided design software in the actual size. This study aims to evaluate the resulting thermal losses using the electromagnetic analysis of the motor.

Design/methodology/approach

In the electromagnetic analysis, the Joule’s loss in the copper wires of the coil windings and the iron losses (the eddy currents loss and the hysteresis loss) are considered. The flow and heat transfer model for the thermal analysis of the motor including the conduction in solid parts and convection in the fluid part is introduced. The magnetic losses are imported into the thermal analysis model in the form of internal heat generation in motor components. Several cooling system approaches were introduced, such as natural convection cooling, natural convection cooling with various types of fins over the motor casing, forced conviction air-cooled cooling system using a mounted fan, casing surface with and without heat sinks, liquid-cooled cooling system using the water in a channel shell and a hybrid air-cooled and liquid-cooled cooling system.

Findings

The results of the electromagnetics analysis show that the low rotational speed of the motor induces higher currents in coil windings, which in turn, it causes higher copper losses in SRM coil windings. For higher rotational speed of SRM, the core loss is higher than the copper loss is in SRM due to the higher frequency. An air-cooled cooling system is used for cooling of SRM. The results reveal when the rotational speed is at 4,000 rpm, the coil loss would be at the maximum value. Therefore, the coil temperature is about 197.9°C, which is higher than the tolerated standard temperature insulation material. Hence, the air-cooled system cannot reduce the temperature to the safe temperature limitation of the motor and guarantee the safe operation of SRM. Thus, a hybrid system of both air-cooled and liquid-cooled cooling system with mounting fins at the outer surface of the casing is proposed. The hybrid system with the liquid flow of Re = 1,500 provides a cooling power capable of safe operation of the motor at 117.2°C, which is adequate for standard insulation material grade E.

Originality/value

The electromagnetic field and cooling system of a high power SRM in the presence of a mounted fan at the rear of the motor are analyzed. The thermal analysis is performed for both of the air-cooled and liquid-cooled cooling systems to meet the cooling demands of the motor for the first time.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 June 2000

A. Savini

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic…

Abstract

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 6 August 2019

Mohammad Haji Mohammadi and Joshua R. Brinkerhoff

Turbomachinery, including pumps, are mainly designed to extract/produce energy from/to the flow. A major challenge in the numerical simulation of turbomachinery is the…

Abstract

Purpose

Turbomachinery, including pumps, are mainly designed to extract/produce energy from/to the flow. A major challenge in the numerical simulation of turbomachinery is the inlet flow rate, which is routinely treated as a known boundary condition for simulation purposes but is properly a dependent output of the solution. As a consequence, the results from numerical simulations may be erroneous due to the incorrect specification of the discharge flow rate. Moreover, the transient behavior of the pumps in their initial states of startup and final states of shutoff phases has not been studied numerically. This paper aims to develop a coupled procedure for calculating the transient inlet flow rate as a part of the solution via application of the control volume method for linear momentum. Large eddy simulation of a four-blade axial hydraulic pump is carried out to calculate the forces at every time step. The sharp interface immersed boundary method is used to resolve the flow around the complex geometry of the propeller, stator and the pipe casing. The effect of the spurious pressure fluctuations, inherent in the sharp interface immersed boundary method, is damped by local time-averaging of the forces. The developed code is validated by comparing the steady-state volumetric flow rate with the experimental data provided by the pump manufacturer. The instantaneous and time-averaged flow fields are also studied to reveal the flow pattern and turbulence characteristics in the pump flow field.

Design/methodology/approach

The authors use control volume analysis for linear momentum to simulate the discharge rate as part of the solution in a large eddy simulation of an axial hydraulic pump. The linear momentum balance equation is used to update the inlet flow rate. The sharp interface immersed boundary method with dynamic Smagorinsky sub-grid stress model and a proper wall model is used.

Findings

The steady-state volumetric flow rate has been computed and validated by comparing to the flow rate specified by the manufacturer at the simulation conditions, which shows a promising result. The instantaneous and time averaged flow fields are also studied to reveal the flow pattern and turbulence characteristics in the pump flow field.

Originality/value

An approach is proposed for computing the volumetric flow rate as a coupled part of the flow solution, enabling the simulation of turbomachinery at all phases, including the startup/shutdown phase. To the best of the authors’ knowledge, this is the first large eddy simulation of a hydraulic pump to calculate the transient inlet flow rate as a part of the solution rather than specifying it as a fixed boundary condition. The method serves as a numerical framework for simulating problems incorporating complex shapes with moving/stationary parts at all regimes including the transient start-up and shut-down phases.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 December 2020

Rupeng Yuan, Fuhai Zhang, Yili Fu and Shuguo Wang

The purpose of this paper is to propose a robust iterative LIDAR-based pose tracking method assisted by modified visual odometer to resist initial value disturbance and…

Abstract

Purpose

The purpose of this paper is to propose a robust iterative LIDAR-based pose tracking method assisted by modified visual odometer to resist initial value disturbance and locate a robot in the environments with certain occlusion.

Design/methodology/approach

At first, an iterative LIDAR-based pose tracking method is proposed. The LIDAR information is filtered and occupancy grid map is pre-processed. The sample generation and scoring are iterated so that the result is converged to the stable value. To improve the efficiency of sample processing, the integer-valued map indices of rotational samples are preserved and translated. All generated samples are analyzed to determine the maximum error direction. Then, a modified visual odometer is introduced for error compensation. The oriented fast and rotated brief (ORB) features are uniformly sampled in the image. A local map which contains key frames for reference is maintained. These two measures ensure that the modified visual odometer is able to return robust result which compensates the error of LIDAR-based pose tracking method in the maximum error direction.

Findings

Three experiments are conducted to prove the advantages of the proposed method. The proposed method can resist initial value disturbance with high computational efficiency, give back credible real-time result in the environment with abundant features and locate a robot in the environment with certain occlusion.

Originality/value

The proposed method is able to give back real-time pose tracking results with robustness. The iterative sample generation enables the robot to resist initial value disturbance. In each iteration, rotational and translational samples are separately generated to enhance computational efficiency. The maximum error direction of LIDAR-based pose tracking method is determined by principle component analysis and compensated by the result of modified visual odometer to give back correct pose in the environment with certain occlusion.

Details

Sensor Review, vol. 41 no. 1
Type: Research Article
ISSN: 0260-2288

Keywords

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Article
Publication date: 1 February 2004

Janusz Szosland

Shedding without dynamic warp loading is done by a loom using assemblies of polygonal shedding disks and disks for increasing weft density. The multiphase rotational loom…

Abstract

Shedding without dynamic warp loading is done by a loom using assemblies of polygonal shedding disks and disks for increasing weft density. The multiphase rotational loom allows completely new woven fabric structures to be manufactured, which until now was impossible to achieve using conventional looms. Woven fabrics can be manufactured with the use of warp and weft threads with extremely low tenacities, loose structures, and strong developed surfaces; as can grid structures and woven structures with pile loops. The possibility of utilizing unspinnable fibres, roving, and selvedges was demonstrated on a model of a multiphase rotational loom specially constructed for the tests.

Details

Research Journal of Textile and Apparel, vol. 8 no. 1
Type: Research Article
ISSN: 1560-6074

Keywords

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Article
Publication date: 8 August 2019

Ahmed Abou El-Azm Aly and Wagdi G. Habashi

Computational fluid dynamics (CFD) simulation of the flow field around marine propellers is challenging because of geometric complexity and rotational effects. To capture…

Abstract

Purpose

Computational fluid dynamics (CFD) simulation of the flow field around marine propellers is challenging because of geometric complexity and rotational effects. To capture the flow structure, grid quality and distribution around the blades is primordial. This paper aims to demonstrate that solution-based automatic mesh optimization is the most logical and practical way to achieve optimal CFD solutions.

Design/methodology/approach

In the current paper, open water propeller performance coefficients such as thrust and torque coefficients are numerically investigated. An anisotropic mesh adaptation technique is applied, believed for the first time, to marine propellers and to two computational domains.

Findings

The current study’s performance coefficients are compared with other previously published CFD results and improvements in terms of accuracy and computational cost are vividly demonstrated for different advance coefficients, as well as a much sharper capture of the complex flow features.

Originality/value

It will be clearly demonstrated that these two improvements can be achieved, surprisingly, at a much lower meshing and computational cost.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 9
Type: Research Article
ISSN: 0961-5539

Keywords

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