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active absorption of Perforated Plate Based on Airflow

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Journal of Donghua University(English Edition) 2022年第6期39卷 590-596页

作者： ZHANG Renqi ZHU Congyun DING Guofang HUANG Qibai School of Mechatronics Engineering Zhongyuan University of TechnologyZhengzhou 450007China School of Mechanical Science&Engineering Huazhong University of Science and TechnologyWuhan 430074China

The theory of active absorption of the perforated plate is proposed in this *** perforated plate is used as the material of active absorption and the depth of the cavity behind the perforated plate is changed according to the resonant frequency of the perforated *** rigid wall is moved to produce resonance so that the absorption coefficient can reach the maximal *** is shown from the numerical calculation that when the perforated plate resonates,the moving distance is large at low frequencies,and the absorption coefficient is low under certain *** plate resonance is effective for single frequency of incident sound wave,which is difficult for the wide frequency,so active absorption based on airflow is posed,and the numerical calculation and experiment are carried *** results denote that this method of active absorption is practical.

关键词： airflow perforated plate resonance absorption coefficient active absorption

An iterative re-weighted least-squares algorithm for the design of active absorbing wavemaker controller

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Journal of Hydrodynamics 2016年第2期28卷 206-218页

作者：杨洪齐李木国柳淑学陈芳梅 State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology The Department of Electronic Engineering Tsinghua University

In physical model tests for highly reflective structures, one often encounters a problem of multiple reflections between the reflective structures and the wavemaker. Absorbing wavemakers can cancel the re-reflective waves by adjusting the paddle motion. In this paper, we propose a method to design the controller of the 2-D absorbing wavemaker system in the wave flume. Based on the first-order wavemaker theory, a frequency domain absorption transfer function is derived. Its time realization can be obtained by de- signing an infinite impulse response （IIR） digital filter, which is expected to approximate the absorption transfer function in the least- squares sense. A commonly used approach to determine the parameters of the IIR filter is applying the Taylor expansion to linearize the filter formulation and solving the linear least-squares problem. However, the result is not optimal because the linearization cha- nges the original objective function. To improve the approximation performance, we propose an iterative reweighted least-squares （IRLS） algorithm and demonstrate that with the filters designed by this algorithm, the approximation errors can be reduced. Physical experiments are carried out with the designed controller. The results show that the system performs well for both regular and irregu- lar waves.

关键词： wavemaker active absorption infinite impulse response (IIR) digital filters optimization methods

A Piston-Type active Absorbing Wavemaker System with Delay Compensation

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China Ocean Engineering 2015年第6期29卷 917-924页

作者：杨洪齐李木国柳淑学张群王静 State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology

Physical model tests with highly reflective structures often encounter a problem of multiple reflections between the structures and the wavemaker. This paper presents a piston-type active absorbing wavemaker system which can absorb most of the reflections. Based on the first-order wavemaker theory, a frequency domain absorption transfer function is modeled. Its time realization can be achieved by designing an IIR digital filter, which is used to control the absorbing wavemaker system. In a real system, time delays often exist in the wave making process. Thus a delay compensation term to the transfer function is proposed. Experimental results show that the system performs well for both regular and irregular waves with periods from 0.6 s to 2.0 s, and the absorption capability is larger than 96.5% at target wave fields.

关键词： wavemaker active absorption IIR digital filter time delay

active Control of A Piston-Type Absorbing Wavemaker with Fully Reflective Structure

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China Ocean Engineering 2020年第5期34卷 730-737页

作者： Saeed MAHJOURI Rasoul SHABANI Ghader REZAZADEH Peyman BADIEI Department of Mechanical Engineering Faculty of EngineeringUrmia UniversityUrmiaIran South Ural state University ChelyabinskRussian Federation cDepartment of Civil Engineering Tehran UniversityTehranIran

Multiple reflections of the waves between structure and wavemaker in hydraulic flumes could change the frequency content of the desired incident wave or result in resonance. A prominent approach to avoid multiple reflections is active control of the wavemaker. This paper proposes a simple and practical active control algorithm for piston-type wavemaker. The block diagram of the control system is presented in real time domain. It is shown that there is no need to use any transfer function or filter in the feedback and feed forward loops and the use of constant gains can yield acceptable results. In the operating frequency range(0.25-2 Hz), it is revealed that the proposed system is very effective at suppressing the excitation of resonant sloshing for regular wave. In the case of irregular waves, it is depicted that the experimental waves agree quite well with the desired wave elevation in frequency domain. In addition, comparison of the results obtained both with and without absorption discloses the good characteristics in time domain.

关键词： wave flume piston-type wavemaker active absorption mathematical modeling reflective waves