scholarly journals A Review on Generation and Mitigation of Airfoil Self-Induced Noise

2021 ◽  
Vol 90 (1) ◽  
pp. 163-178
Author(s):  
Mohamed Ibren ◽  
Amelda Dianne Andan ◽  
Waqar Asrar ◽  
Erwin Sulaeman
Keyword(s):  
Parametric Design ◽  
Acoustic Scattering ◽  
Feedback Mechanism ◽  
Flow Topology ◽  
Trailing Edge ◽  
Airfoil Surface ◽  
Design Concepts ◽  
Acoustic Control ◽  
Passive Acoustic ◽  
And Control

A review on passive acoustic control of airfoil self-noise by means of porous trailing edge is presented. Porous surfaces are defined using various terms such as porosity, permeability, resistivity, porosity constant, dimensionless permeability, flow control severity and tortuosity. The primary purpose of this review paper is to provide key findings regarding the sources and mitigation techniques of self-induced noise generated by airfoils. In addition, various parametric design concepts were presented, which are critically important for porous-airfoil design specifications. Most research focus on experimentation with some recent efforts on numerical simulations. Detail study on flow topology is required to fully understand the unsteady flow nature. In general, noise on the airfoil surface is linked to the vortex shedding, instabilities on the surface, as well as feedback mechanism. In addition, acoustic scattering can be minimized by reducing extent of the porous region from the trailing edge while increasing resistivity. Moreover, blowing might also be another means of reducing noise near the trailing edge. Ultimately, understanding the flow physics well provides a way to unveil the unknowns in self-induced airfoil noise generation, mitigation, and control.

Unsteady aerodynamic modeling and control of the wind turbine with trailing edge flap

2018 ◽  
Vol 10 (6) ◽  
pp. 063304 ◽  
Author(s):  
Wenguang Zhang ◽  
Yifeng Wang ◽  
Ruijie Liu ◽  
Haipeng Liu ◽  
Xu Zhang
Keyword(s):  
Wind Turbine ◽  
Trailing Edge ◽  
Modeling And Control ◽  
Aerodynamic Modeling ◽  
Unsteady Aerodynamic ◽  
Trailing Edge Flap ◽  
And Control

Paper 20. Improvement of Control by Special Devices

1972 ◽  
Vol 14 (7) ◽  
pp. 150-154
Author(s):  
H. Ritter
Keyword(s):  
Large Angle ◽  
Leading Edge ◽  
Rotating Cylinder ◽  
Practical Significance ◽  
Trailing Edge ◽  
Stall Angle ◽  
Lift Control ◽  
And Control

The paper discusses hydrodynamic devices for improving manoeuvring and control. Two hydrodynamic concepts are shown to be of practical significance for large craft: control of hydrofoil lift independent of incidence, and deflection of the propulsion jet through a large angle by means of a simple hydrofoil. Lift control independent of incidence is illustrated by the jet flap and the trailing edge rotating cylinder. Improved deflection of the propeller slipstream involves extending the rudder stall angle, and it is shown how this may be achieved by fitting the rudder with a leading edge rotating cylinder.

Model-Based Simulation to Examine Command and Control Issues with Remotely Operated Vehicles

2008 ◽  
pp. 199-218 ◽  
Author(s):  
Sasanka Prabhala ◽  
Subhashini Ganapathy ◽  
S. Narayanan ◽  
Jennie J. Gallimore ◽  
Raymond R. Hill
Keyword(s):  
Cognitive Model ◽  
Command And Control ◽  
Simulation Models ◽  
High Fidelity ◽  
Remotely Operated Vehicles ◽  
Design Concepts ◽  
Model Based ◽  
Critical Issues ◽  
Commercial Applications ◽  
And Control

With increased interest in the overall employment of pilotless vehicles functioning in the ground, air, and marine domains for both defense and commercial applications, the need for high-fidelity simulation models for testing and validating the operational concepts associated with these systems is very high. This chapter presents a model-based approach that we adopted for investigating the critical issues in the command and control of remotely operated vehicles (ROVs) through an interactive model-based architecture. The domain of ROVs is highly dynamic and complex in nature. Hence, a proper understanding of the simulation tools, underlying system algorithms, and user needs is critical to realize advanced simulation system concepts. Our resulting simulation architecture integrates proven design concepts such as the model-view-controller paradigm, distributed computing, Web-based simulations, cognitive model-based high-fidelity interfaces and object-based modeling methods.

scholarly journals A Time Domain Passivity Control Scheme for Bilateral Teleoperation

Electronics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 325 ◽  
Author(s):  
Long Sheng ◽  
Usman Ahmad ◽  
Yongqiang Ye ◽  
Ya-Jun Pan
Keyword(s):  
Time Domain ◽  
Parametric Design ◽  
Switching Time ◽  
Experimental Results ◽  
Division Problem ◽  
Bilateral Teleoperation ◽  
Safe Operation ◽  
Guaranteed Stability ◽  
Control Scheme ◽  
And Control

Conventional time domain passivity control inevitably embodies division. Zero division can occur under a tiny force or velocity, which may be inevitable, and will be the cause of control crash. To avoid the zero division problem and control crash, we propose a switching dissipation controller for guaranteed stability. The parametric design of the proposed approach is discussed. The switching time domain passivity control is then applied to teleoperation and safe operation is achieved. Simulation and experimental results are demonstrated to validate the effectiveness of the proposed control scheme.

Mechanism and Control of the Trailing Edge in Intermittent Slot Die Coating

2020 ◽  
Vol 59 (35) ◽  
pp. 15758-15767
Author(s):  
Penghui Tan ◽  
Simian Diao ◽  
Tianlun Huang ◽  
Zhiming Yang ◽  
Huamin Zhou ◽  
...  
Keyword(s):  
Trailing Edge ◽  
Slot Die Coating ◽  
Slot Die ◽  
And Control

On the mechanism of high-incidence lift generation for steadily translating low-aspect-ratio wings

2017 ◽  
Vol 813 ◽  
pp. 110-126 ◽  
Author(s):  
Adam C. DeVoria ◽  
Kamran Mohseni
Keyword(s):  
Vortex Pair ◽  
Tip Vortex ◽  
Mean Flow ◽  
Flow Topology ◽  
Trailing Edge ◽  
Negative Contribution ◽  
High Incidence ◽  
The Mean ◽  
Stall Angle ◽  
Strong Vorticity

High-incidence lift generation via flow reattachment is studied. Different reattachment mechanisms are distinguished, with dynamic manoeuvres and tip vortex downwash being separate mechanisms. We focus on the latter mechanism, which is strictly available to finite wings, and isolate it by considering steadily translating wings. The tip vortex downwash provides a smoother merging of the flow at the trailing edge, thus assisting in establishing a Kutta condition there. This decreases the strength/amount of vorticity shed from the trailing edge, and in turn maintains an effective bound circulation resulting in continued lift generation at high angles of attack. Just below the static lift-stall angle of attack, strong vorticity is shed at the trailing edge indicating an increasingly intermittent reattachment/detachment of the instantaneous flow at mid-span. Above this incidence, the trailing-edge shear layer increases in strength/size representing a negative contribution to the lift and leads to stall. Lastly, we show that the mean-flow topology is equivalent to a vortex pair regardless of the particular physical flow configuration.

New Design Concepts for Direct Reader Measurement Electronics

1988 ◽  
Vol 42 (6) ◽  
pp. 961-972 ◽  
Author(s):  
V. Karanassios ◽  
G. Horlick
Keyword(s):  
Integrated Circuits ◽  
Atomic Emission ◽  
Atomic Emission Spectrometry ◽  
Emission Spectrometry ◽  
Single Chip ◽  
Direct Reading ◽  
Design Concepts ◽  
Distributed Intelligence ◽  
And Control ◽  
Intelligence Approach

A dual-processor, distributed-intelligence approach toward the computerization of a direct-reading polychromator for atomic emission spectrometry is described. Emphasis is placed on a “zero based design” of the PMT current integration electronics of a direct-reader channel using microprocessor bus architectures, programmable support chips, data domain conversion integrated circuits, and inexpensive single-board microcomputers. Traditional analog integration of the current signal is replaced by domain conversion of the current to a frequency, and integration/digitization is achieved with the use of single chip software programmable counters. Each channel can be independently addressed, configured, cleared, preset, and read, as the channels are autonomous units on the bus of the data acquisition and control microcomputer.

Acoustic Control Modeling of Conical Bores With Actuating Boundary Conditions

2001 ◽  
Author(s):  
Kevin M. Farinholt ◽  
Donald J. Leo
Keyword(s):  
Boundary Conditions ◽  
Driving Forces ◽  
State Space Model ◽  
Linear Quadratic Regulator ◽  
Mode Shapes ◽  
Linear Quadratic ◽  
Acoustic Control ◽  
Average Control ◽  
The One ◽  
And Control

Abstract An investigation of the natural frequencies and mode shapes associated with sealed conical bores having actuating boundary conditions is presented. Beginning with the one dimensional wave equation for spherically expanding waves, modal characteristics are developed as functions of cone geometry and actuator parameters. This paper presents both analytical and experimental comparisons for the purpose of validating model and development techniques. An investigation of the orthogonality and adjointness of the solution is presented. A discussion of incorporating driving forces in the system model for the purpose of coupling control actuators with internal acoustics is also included. Including these driving forces, a state space model of the system is developed for the purpose of applying modern feedback control. This paper concludes with a study on applying Linear Quadratic Regulator techniques to this system, relating tradeoffs between spatially averaged pressure and control voltages. The results of our simulations indicate that pressure reductions of 30% are attainable with average control voltages of 14.4 volts, given an example geometry.

Flow topology and noise modeling of trailing edge serrations

2020 ◽  
Vol 168 ◽  
pp. 107423
Author(s):  
Huijing Cao ◽  
Mingming Zhang ◽  
Chang Cai ◽  
Ziliang Zhang
Keyword(s):  
Flow Topology ◽  
Trailing Edge ◽  
Noise Modeling ◽  
Trailing Edge Serrations
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