Active feedback control of effective mass density and sound transmission on elastic wave metamaterials

2021 ◽  
Vol 195 ◽  
pp. 106221
Author(s):  
Zhi-Hua He ◽  
Yi-Ze Wang ◽  
Yue-Sheng Wang
Keyword(s):  
Feedback Control ◽  
Elastic Wave ◽  
Effective Mass ◽  
Mass Density ◽  
Sound Transmission ◽  
Active Feedback ◽  
Active Feedback Control

Sound transmission tuned by active feedback control attached to elastic wave metamaterials immersed in water

2021 ◽  
pp. 1-28
Author(s):  
Zhi-Hua He ◽  
Yi-Ze Wang ◽  
Yue-Sheng Wang
Keyword(s):  
Feedback Control ◽  
Elastic Wave ◽  
Transmission Loss ◽  
Mass Density ◽  
Sound Transmission ◽  
Low Frequencies ◽  
Fluid Medium ◽  
Active Feedback ◽  
Active Feedback Control ◽  
Acoustic Responses

Abstract Elastic wave metamaterials have been widely exploited with their dynamic superior properties and outstanding acoustic responses. However, it is difficult to directly manipulate sound pressure in low frequencies. In this study, we propose a new kind of elastic wave metamaterial which consists of vertical and lateral resonators as well as orthogonal stiffeners. The active feedback control system is applied to extend to the tunable scope for both lower and higher frequency regions and change the characteristics of acoustic-structure coupling. Its effective mass density is also discussed with different feedback constants. In order to present effects of the fluid-solid interaction, we considered that the elastic wave metamaterial is immersed in different fluid medium and its sound transmission loss (STL) is calculated. This work provides a feasible method for creating mechanical/acoustic models with multi-functional potentials.

Active feedback control of elastic wave metamaterials

2017 ◽  
Vol 28 (15) ◽  
pp. 2110-2116 ◽  
Author(s):  
Yi-Ze Wang ◽  
Feng-Ming Li ◽  
Yue-Sheng Wang
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Elastic Wave ◽  
Effective Mass ◽  
Stop Band ◽  
Acoustic Properties ◽  
System Stability ◽  
Negative Effective Mass ◽  
Active Feedback ◽  
Active Feedback Control

As an important extension of periodic structures and phononic crystals, elastic wave/acoustic metamaterials can show negative effective parameters for special frequency regions. Although the active control method is widely applied to the vibration isolation and elastic wave propagation, little attention has been paid on changing elastic wave/acoustic properties of metamaterials. In this work, a new kind of elastic wave metamaterials combined with the automatic control system is presented. Propagation behaviors of the elastic wave are discussed. To demonstrate the effect of the active feedback control, the stop band properties, tunable negative effective mass and control system stability are considered. The results show that the negative acceleration feedback control can enhance the frequency region that creates the negative effective mass. Moreover, the stability of this periodic structure can be achieved.

scholarly journals Sound Transmission Comparisons of Active Elastic Wave Metamaterial Immersed in External Mean Flow

2021 ◽  
Author(s):  
Zhi-Hua He ◽  
Yi-Ze Wang ◽  
Yue-Sheng Wang
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Elastic Wave ◽  
Sound Transmission ◽  
Feedback Control System ◽  
Mean Flow ◽  
Transmission Properties ◽  
Active Feedback ◽  
Active Feedback Control ◽  
Equivalent Method

AbstractUsing the active feedback control system on the elastic wave metamaterial, this research concentrates on the sound transmission with the dynamic effective model. The metamaterial is subjected to an incident pressure and immersed in the external mean flow. The elastic wave metamaterial consists of double plates and the upper and lower four-link mechanisms are attached inside. The vertical resonator is attached by the active feedback control system and connected with two four-link mechanisms. Based on the dynamic equivalent method, the metamaterial is equivalent as a single-layer plate by the dynamic effective parameter. With the coupling between the fluid and structure, the expression of the sound transmission loss (STL) is derived. This research shows the influence of effective mass density on sound transmission properties, and the STL in both modes can be tuned by the acceleration and displacement feedback constants. In addition, the dynamic response and the STL are also changed obviously by different values of structural damping, incident angle (i.e., the elevation and azimuth angles) and Mach number of the external fluid with the mean flow property. The results for sound transmission by two methods are compared, i.e., the virtual work principle for double plates and the dynamic equivalent method corresponding to a single one. This paper is expected to be helpful for understanding the sound transmission properties of both pure single- and double-plate models.

Active Feedback Control on Sound Radiation of Elastic Wave Metamaterials

AIAA Journal ◽  
2019 ◽  
Vol 57 (10) ◽  
pp. 4536-4547 ◽  
Author(s):  
Zhi-Hua He ◽  
Yi-Ze Wang ◽  
Yue-Sheng Wang
Keyword(s):  
Feedback Control ◽  
Elastic Wave ◽  
Sound Radiation ◽  
Active Feedback ◽  
Active Feedback Control

Feedback Control of Turbulence

1994 ◽  
Vol 47 (6S) ◽  
pp. S3-S13 ◽  
Author(s):  
Parviz Moin ◽  
Thomas Bewley
Keyword(s):  
Feedback Control ◽  
Turbulent Flows ◽  
Systems Approach ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Small Scale ◽  
Flow Equations ◽  
Active Feedback ◽  
Active Feedback Control ◽  
Mathematical Techniques

A brief review of current approaches to active feedback control of the fluctuations arising in turbulent flows is presented, emphasizing the mathematical techniques involved. Active feedback control schemes are categorized and compared by examining the extent to which they are based on the governing flow equations. These schemes are broken down into the following categories: adaptive schemes, schemes based on heuristic physical arguments, schemes based on a dynamical systems approach, and schemes based on optimal control theory applied directly to the Navier-Stokes equations. Recent advances in methods of implementing small scale flow control ideas are also reviewed.

Nonlinear Control of Axisymmetric Swirling Flows in a Long Finite-Length Pipe

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Lei Xu ◽  
Zvi Rusak ◽  
Shixiao Wang ◽  
Steve Taylor
Keyword(s):  
Reynolds Number ◽  
Feedback Control ◽  
High Reynolds Number ◽  
Vortex Breakdown ◽  
Basin Of Attraction ◽  
Swirling Flows ◽  
Active Feedback ◽  
Active Feedback Control ◽  
High Reynolds ◽  
Control Methodology

Feedback stabilization of inviscid and high Reynolds number, axisymmetric, swirling flows in a long finite-length circular pipe using active variations of pipe geometry as a function of the evolving inlet radial velocity is studied. The complicated dynamics of the natural flow requires that any theoretical model that attempts to control vortex stability must include the essential nonlinear dynamics of the perturbation modes. In addition, the control methodology must establish a stable desired state with a wide basin of attraction. The present approach is built on a weakly nonlinear model problem for the analysis of perturbation dynamics on near-critical swirling flows in a slightly area-varying, long, circular pipe with unsteady changes of wall geometry. In the natural case with no control, flows with incoming swirl ratio above a critical level are unstable and rapidly evolve to either vortex breakdown states or accelerated flow states. Following an integration of the model equation, a perturbation kinetic-energy identity is derived, and an active feedback control methodology to suppress perturbations from a desired columnar state is proposed. The stabilization of both inviscid and high-Re flows is demonstrated for a wide range of swirl ratios above the critical swirl for vortex breakdown and for large-amplitude initial perturbations. The control gain for the fastest decay of perturbations is found to be a function of the swirl level. Large gain values are required at near-critical swirl ratios while lower gains provide a successful control at swirl levels away from critical. This feedback control technique cuts the feed-forward mechanism between the inlet radial velocity and the growth of perturbation's kinetic energy in the bulk and thereby enforces the decay of perturbations and eliminates the natural explosive evolution of the vortex breakdown process. The application of this proposed robust active feedback control method establishes a branch of columnar states with a wide basin of attraction for swirl ratios up to at least 50% above the critical swirl. This study provides guidelines for future flow control simulations and experiments. However, the present methodology is limited to the control of high-Reynolds number (nearly inviscid), axisymmetric, weakly nonparallel flows in long pipes.

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