Equivalent edge currents for the time-domain analysis of reflector antennas

The paper discusses the parallelization of a novel explicit harmonic balance Navier-Stokes solver for wind turbine unsteady aerodynamics. For large three-dimensional problems, the use of a standard MPI parallelization based on the geometric domain decomposition of the physical domain may require an excessive degree of partitioning with respect to that needed when the same aerodynamic analysis is performed with the time-domain solver. This occurrence may penalize the parallel efficiency of the harmonic balance solver due to excessive communication among MPI processes to transfer halo data. In the case of the harmonic balance analysis, the necessity of further grid partitioning may arise because the memory requirement of each block is higher than for the time-domain analysis: it is that of the time-domain analysis multiplied by a variable proportional to the number of complex harmonics used to represent the sought periodic flow field. A hybrid multi-level parallelization paradigm for explicit harmonic balance Navier-Stokes solvers is presented, which makes use of both distributed and shared memory parallelization technologies, and removes the need for further domain decomposition with respect to the case of the time-domain analysis. The discussed parallelization approaches are tested on the multigrid harmonic balance solver being developed by the authors, considering various computational configurations for the CFD analysis of the unsteady flow field past the airfoil of a wind tubine blade in yawed wind.

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THE TIME DOMAIN ANALYSIS ON MOORED SHIP MOTIONS

Coastal Engineering Proceedings ◽

10.9753/icce.v21.219 ◽

1988 ◽

Vol 1 (21) ◽

pp. 219 ◽

Cited By ~ 2

Author(s):

Masayoshi Kubo ◽

Naokatsu Shimoda ◽

Shunsaku Okamoto

Keyword(s):

Time Domain ◽

Integral Method ◽

Time Domain Analysis ◽

Domain Analysis ◽

Ship Motions ◽

Convolution Integral ◽

Quay Wall ◽

Calculation Results ◽

The Time Domain

The ship refuge inside a harbor in storm requires the analysis of moored ship motions along a quay wall. In this case the time domain analysis with the convolution integral method becomes effective. But the calculation accuracy is not enough and must be improved to analyze actual moored ship motions. In this paper some methods of the improvement are proposed and their efficiency is verified by comparing the calculation results with the experimental ones.

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The Time Domain Analysis of the Flutter of Wind Turbine Blade Combined with Eigenvalue Approach

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.860-863.342 ◽

2013 ◽

Vol 860-863 ◽

pp. 342-347

Author(s):

Hao Wang ◽

Jiao Jiao Ding ◽

Bing Ma ◽

Shuai Bin Li

Keyword(s):

Wind Turbine ◽

Turbine Blade ◽

Time Domain ◽

Time Domain Analysis ◽

Domain Analysis ◽

Wind Turbine Blade ◽

Eigenvalue Approach ◽

Characteristic Roots ◽

Eigenvalue Method ◽

The Time Domain

The aeroelasticity and the flutter of the wind turbine blade have been emphasized by related fields. The flutter of the wind turbine blade airfoil and its condition will be focused on. The eigenvalue method and the time domain analysis method will be used to solve the flutter of the wind turbine blade airfoil respectively. The flutter problem will be firstly solved using eigenvalue approach. The flutter region, where the flutter will occur and anti-flutter region, where the flutter will not occur, will be obtained directly by judging the sign of the real part of the characteristic roots of the blade system. Then the time domain analysis of flutter of wind turbine blade will be carried out through the use of the four-order Runge-Kutta numerical methods, the flutter region and the anti-flutter region will be gotten in another way. The time domain analysis can give the changing treads of the aeroelastic responses in great detail than those of the eigenvalue method. The flap displacement of wind turbine blade airfoil will change from convergence to divergence, and change from divergence to convergence extremely suddenly. During the flutter region, the flutter of wind turbine blade will occur extremely dramatically. The flutter region provided by the time domain analysis of the flutter of the blade airfoil accurately coincides with the results of eigenvalue approach, therefore the simulation results are reliable and credible.

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A Frequency Domain Analysis of Learning Control

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.2899278 ◽

1994 ◽

Vol 116 (4) ◽

pp. 781-786 ◽

Cited By ~ 19

Author(s):

C. J. Goh

Keyword(s):

Frequency Domain ◽

Time Domain ◽

Linear Time ◽

Planning Horizon ◽

Time Domain Analysis ◽

Learning Control ◽

Domain Analysis ◽

Frequency Domain Analysis ◽

Convergence Criterion ◽

The Time Domain

The convergence of learning control is traditionally analyzed in the time domain. This is because a finite planning horizon is often assumed and the analysis in time domain can be extended to time-varying and nonlinear systems. For linear time-invariant (LTI) systems with infinite planning horizon, however, we show that simple frequency domain techniques can be used to quickly derive several interesting results not amenable to time-domain analysis, such as predicting the rate of convergence or the design of optimum learning control law. We explain a paradox arising from applying the finite time convergence criterion to the infinite time learning control problem, and propose the use of current error feedback for controlling possibly unstable systems.

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