Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session M25: Flow Control VII: Actuator Design and Analysis |
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Chair: David Ashpis, NASA Room: 320 |
Tuesday, November 26, 2013 8:00AM - 8:13AM |
M25.00001: Single Dielectric Barrier Discharge Plasma Actuator Modelling using a Charge Transport Approach Theodore Williams, Thomas Corke Single dielectric barrier discharge (SDBD) plasma actuators have been used in active flow control due to their benefits of high response rate, no mechanical parts, and low cost. To effectively model the aerodynamic effects of a SDBD using computational fluid dynamics, a numerically efficient model of SDBD plasma actuator parameters is required. This work presents a charge transport model that is able to simulate the dynamic characteristics of an AC plasma actuator and calculate the time-dependent body force vector distribution. This work improves upon previous models by being able to simulate high-curvature electrode surfaces. Validation of this work is performed by comparison to experimentally measured thrust values. [Preview Abstract] |
Tuesday, November 26, 2013 8:13AM - 8:26AM |
M25.00002: SDBD Plasma Actuator and Geometric Optimization for Optimal Flow Control of Wind Turbine Blades Thomas Corke, Theodore Williams, Aleksandar Jemcov, John Cooney A Quantitative Design Optimization approach for active flow control using SDBD plasma actuators is presented. The approach couples passive geometric changes and plasma actuator design to produce a ``compliant flow'' that maximizes control authority. Aerodynamic shape optimization tools employed in this study make use of the adjoint formulation of the Navier-Stokes equations for incompressible flows. These are solved to obtain shape derivatives that are used in a gradient optimization procedure to produce aerodynamic shapes that are flow-control compliant. Coupling of compliant geometries and flow control devices are able to provide dynamic lift control to wind turbine blades. The effect of the plasma actuator is included as a body force distribution in the flow governing equations. The optimization seeks designs that effectively utilize a SDBD plasma actuator and are aerodynamically compliant to realize increased energy production on wind turbine blades. [Preview Abstract] |
Tuesday, November 26, 2013 8:26AM - 8:39AM |
M25.00003: Thrust Measurement of Dielectric Barrier Discharge (DBD) Plasma Actuators David E. Ashpis, Matthew C. Laun DBD plasma actuators generate a wall-jet that can be used for active flow control. We used an analytical balance to measure the thrust generated by the actuator, it is a common metric of its performance without external flow. We found that the measured force is afflicted by several problems; it drifts in time, not always repeatable, is unstable, and depends on the manner the voltage is applied. We report results of investigations of these issues. Tests were conducted on an actuator constructed of 1/4 inch thick high-density polyethylene (HDPE) dielectric with 100 mm long offset electrodes, with applied voltages up to 48 kV p-p and frequencies from 32 Hz to 2.5 kHz, and pure Sine and Trapezoidal waveforms. The relative humidity was in the range of 51-55{\%}, corresponding to moisture range of 10,500 to13,000 ppm mass. Force readings were up to 500 mg, (approximately 50 mN/m). We found that the measured force is the net of the positive thrust generated by the wall-jet and an ``anti-thrust'' acting in the opposite direction. We propose a correction procedure that yields the plasma-generated thrust. The correction is based on voltage-dependent anti-thrust measured in the low frequency range of 20-40 Hz. We found that adjacent objects in a test setup affect the measured thrust, and verified it by comparing experiments with and without a metal enclosure, grounded and ungrounded. Uncorrected thrust varied by up to approximately $\pm $100{\%}, and the corrected thrust variations were up to approximately 30{\%}. [Preview Abstract] |
Tuesday, November 26, 2013 8:39AM - 8:52AM |
M25.00004: Efficiency of Flow Control Actuators Avraham Seifert Bluff body flow control is an important and extensively studied branch of flow control. Bluff bodies can be found everywhere and mitigating its massively separated flow and associated penalties are extremely important from efficiency, vibration and noise considerations. Two distinct classes exist: one which involves separation control, i.e., where the flow can be reattached, and the other; control of massively separated flows, where the near wake is to be controlled. This paper reviews the state-of-the-art in actuators technology with the aim of providing a common ground for comparison and wise technology choices. Real-world aspects as well as fundamental challenges are identified and discussed. Actuators are sometimes considered, in a somewhat simplistic manner, as nominally 2D where high aspect ratio openings are assumed to lead to 2D excitation. This is clearly not the case and 3D effects always eventually prevail. The presentation will also discuss approaches not only to acknowledge and attempt to understand but also utilize 3D effects for effective and efficient flow control. [Preview Abstract] |
Tuesday, November 26, 2013 8:52AM - 9:05AM |
M25.00005: Numerical Simulation of Nanosecond Pulsed Dielectric Barrier Discharge Actuator for Flow Control J.G. Zheng, Z.J. Zhao, J. Li, Y.D. Cui, B.C. Khoo Recently, nanosecond pulsed dielectric barrier discharge (DBD) actuator has emerged as a promising active flow control means. In this study, numerical simulation is carried out to investigate fluid dynamics induced by nanosecond pulsed gas discharge. Two types of so-called phenomenological approaches reported in the literature are employed to model effects of plasma discharge. In the first methodology, the plasma region over covered electrode is modelled as preheated and pressurized gas layer. The second method is based on a quasi-one-dimensional self-similar, local ionization kinetic model. The plasma models are then coupled with compressible Navier-Stokes equations governing the external flow. The two models are validated against experimental data obtained for flow field arising from single voltage pulse discharge in quiescent air and proved to be valid. The numerical method is then applied to study flow separation control over NACA0015 airfoil with the actuator placed on the leading edge of airfoil. The goal is to numerically reproduce the formation and development of complex vortex structures due to plasma actuator induced shock propagation through the airflow. Special interest is focused on how the generated vortex interacts with and suppresses the separated shear layer. [Preview Abstract] |
Tuesday, November 26, 2013 9:05AM - 9:18AM |
M25.00006: Nonlinear model-order reduction for oscillator flows using POD-DEIM Miguel Fosas de Pando, Peter J. Schmid, Denis Sipp The design of control laws for fluid systems often relies on the prediction given by a reduced-order model of the response of the flow to actuations. Model-order reduction techniques have successfully been applied to flows exhibiting linear behavior. However, in many cases of practical interest the effect of nonlinearities must be incorporated to assess the dynamics of the flow. In this work, we present an extension to the POD-DEIM technique introduced by Chaturantabut and Sorensen (2010) to derive reduced-order models from flow solvers with minimal development effort. This technique will be demonstrated on the compressible flow around a NACA0012 airfoil featuring limit-cycle oscillations. Attention will then be focused on the accuracy and the robustness of the POD-DEIM reduced-order model at off-design conditions, and its application to flow control. [Preview Abstract] |
Tuesday, November 26, 2013 9:18AM - 9:31AM |
M25.00007: Structural Sensitivity for Estimating Actuator and Sensor Placement for Flow Control Mahesh Natarajan, Jonathan Freund, Daniel Bodony A control strategy is developed for the modification of the growth rates of global modes. The method is based on an analysis of the structural sensitivity of the baseflow, which uses the forward and adjoint global modes of the steady baseflow to estimate effective locations of actuation. Linear feedback is used to modify the eigenstructure of the linearized system for reduction/stabilization of amplification rates using different control-feedback pairs. This procedure provides an assessment of the effectiveness of different modes of actuation and different quantities to sense. The method is demonstrated for the case of a separated boundary layer in a Mach 0.7 diffuser and the eigensystem senstivity to perturbation is evaluated for different cases. An error analysis of the predicted and computed eigenvalues as a function of the control amplitude establishes the limit of applicability of the linear description. Direct numerical simulations demonstrate the efficacy of a linear feedback controller based on mass injection with density feedback. [Preview Abstract] |
Tuesday, November 26, 2013 9:31AM - 9:44AM |
M25.00008: Increasing Wind Turbine Power Generation Through Optimized Flow Control Design John Cooney, Theodore Williams, Thomas Corke A practical, validated methodology is outlined for implementing flow control systems into wind turbine designs to maximize power generation. This approach involves determining optimal flow control strategies to minimize aerodynamic losses for horizontal axis wind turbines during Region II operation. A quantitative design optimization (QDO) process is completed for the wind turbine utilized in the Notre Dame Laboratory for Enhanced Wind Energy Research. QDO utilizes CFD simulations and shape optimization tools to maximize effectiveness of flow control. Here, only flow control schemes that could be retrofitted on the existing turbine were explored. The final geometry is discussed along with accompanying validations of the predicted performance from wind tunnel experiments at full-scale conditions. Field data from the wind energy laboratory is included. [Preview Abstract] |
Tuesday, November 26, 2013 9:44AM - 9:57AM |
M25.00009: Closed-loop turbulence control with machine learning methods Bernd R. Noack, Thomas Duriez, Laurent Cordier, Marc Segond, Markus Abel, Steven Brunton, Marek Morzynski, Jean-Charles Laurentie, Vladimir Parezanovic, Jean-Paul Bonnet We propose a machine learning control strategy for arbitrary turbulent flow configurations with finite number of actuators and sensors. This method designs and optimizes closed-loop control laws automatically detecting and exploiting linear to strongly non-linear actuation mechanisms. Presented examples range from a simple analytical model to the TUCOROM mixing layer control demonstrator. [Preview Abstract] |
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