Computational Study of a NACA4415 Airfoil Using Synthetic Jet Control

Computational Study of a NACA4415 Airfoil Using Synthetic Jet Control
Author: Omar Dario Lopez Mejia
Publisher:
Total Pages: 384
Release: 2009
Genre:
ISBN:

Synthetic jet actuators for flow control applications have been an active topic of experimental research since the 90's. Numerical simulations have become an important complement of that experimental work, providing detailed information of the dynamics of the controlled flow. This study is part of the AVOCET (Adaptive VOrticity Control Enabled flighT) project and is intended to provide computational support for the design and evaluation of closed-loop flow control with synthetic jet actuators for small scale Unmanned Aerial Vehicles (UAVs). The main objective is to analyze active flow control of a NACA4415 airfoil with tangential synthetic jets via computational modeling. A hybrid Reynolds-Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) turbulent model (called Delayed Detached-Eddy Simulation-DDES) was implemented in CDP, a kinetic energy conserving Computational Fluid Dynamics (CFD) code. CDP is a parallel unstructured grid incompressible flow solver, developed at the Center for Integrated Turbulence Simulations (CITS) at Stanford University. Two models of synthetic jet actuators have been developed and validated. The first is a detailed model in which the flow in and out of the actuator cavity is modeled. A second less costly model (RSSJ) was also developed in which the Reynolds stress produced by the actuator is modeled, based on information from the detailed model. Several static validation test cases at different angle of attack with modified NACA 4415 and Dragon Eye airfoils were performed. Numerical results show the effects of the actuators on the vortical structure of the flow, as well as on the aerodynamic properties. The main effect of the actuation on the time averaged vorticity field is a bending of the separation shear layer from the actuator toward the airfoil surface, resulting in changes in the aerodynamic properties. Full actuation of the suction side actuator reduces the pitching moment and increases the lift force, while the pressure side actuator increases the pitching moment and reduces the lift force. These observations are in agreement with experimental results. The effectiveness of the actuator is measured by the change in the aerodynamic properties of the airfoil in particular the lift ([Delta]C[subscript t]) and moment ([Delta]C[subscript m]) coefficients. Computational results for the actuator effectiveness show very good agreement with the experimental values (over the range of -2° to 10°). While the actuation modifies the global pressure distribution, the most pronounced effects are near the trailing edge in which a spike in the pressure coefficient (C[subscript p]) is observed. The local reduction of C[subscript p], for both the suction side and pressure side actuators, at x/c = 0.96 (the position of the actuators) is about 0.9 with respect to the unactuated case. This local reduction of the pressure is associated with the trapped vorticity and flow acceleration close to the trailing edge. The RSSJ model is designed to capture the synthetic jet time averaged behavior so that the high actuation frequencies are eliminated. This allows the time step to be increased by a factor of 5. This ad hoc model is also tested in dynamic simulations, in which its capacity to capture the detail model average performance was demonstrated. Finally, the RSSJ model was extended to a different airfoil profile (Dragon Eye) with good results.

Adaptive Compensation of Nonlinear Actuators for Flight Control Applications

Adaptive Compensation of Nonlinear Actuators for Flight Control Applications
Author: Dipankar Deb
Publisher: Springer Nature
Total Pages: 129
Release: 2021-07-22
Genre: Technology & Engineering
ISBN: 9811641617

This book provides a basic understanding of adaptive control and its applications in Flight control. It discusses the designing of an adaptive feedback control system and analyzes this for flight control of linear and nonlinear aircraft models using synthetic jet actuators. It also discusses control methodologies and the application of control techniques which will help practicing flight control and active flow control researchers. It also covers modelling and control designs which will also benefit researchers from the background of fluid mechanics and health management of actuation systems. The unique feature of this book is characterization of synthetic jet actuator nonlinearities over a wide range of angles of attack, an adaptive compensation scheme for such nonlinearities, and a systematic framework for feedback control of aircraft dynamics with synthetic jet actuators.

Application of Active Flow Control Technology in an Unmanned Aerial Vehicle

Application of Active Flow Control Technology in an Unmanned Aerial Vehicle
Author: Gaurav
Publisher:
Total Pages:
Release: 2010
Genre:
ISBN:

A low speed wind tunnel experimental investigation was conducted to determine the effectiveness of the leading edge pulsed blowing and the trailing edge jet blowing/ Gurney flap on the improvement of aerodynamic performance of an unmanned aerial vehicle at low Reynolds numbers. The wind tunnel tests for the leading edge pulsed jet blowing were conducted at 10%, 30% and 50% location of the chord length from the leading edge at a free stream velocity of 20 m/s. The jet momentum coefficient and the non-dimensional pulser frequency had been varied independently to investigate the effectiveness of the leading edge pulsed blowing. The trailing edge jet blowing tests were conducted at free stream velocity of 20 m/s at different jet momentum coefficients. The leading edge pulsed blowing showed a strong dependency of the actuator effectiveness on the jet momentum and the pulser frequency. The leading edge pulsed blowing had delayed the flow separation over the airfoil from an angle of attack of 17° to 22° with a docile stall for jet emanating at 10% location of the chord length for a jet momentum coefficient of 0.0275. The pulsed blowing at 50% chord location generated higher lift compared to the 10% location of the pulser with an abrupt stall at 19°. There was no evidence of the lift augmentation in the pre-stall angle of attack regime. The experimental results showed that the trailing edge jet flap was capable of generating significant roll moment at realistic jet momentum coefficients. The fluidic actuators were then integrated into the wings of a scale Extra 330 model airplane. The wind tunnel results for the leading edge pulsed blowing on the scale model indicated a delay in the stall of the airplane from an angle of attack of 12° to 21° with a 13% increase in the lift at take-off and landing speed of 17 m/s. The trailing edge jet actuators were also able to augment lift and demonstrate the roll control authority at low angle attacks at a cruising speed of 30 m/s.

Flow Control Techniques and Applications

Flow Control Techniques and Applications
Author: Jinjun Wang
Publisher: Cambridge University Press
Total Pages: 293
Release: 2019
Genre: Science
ISBN: 1107161568

Master the theory, applications and control mechanisms of flow control techniques.

Robust Nonlinear Estimation and Control Applications Using Synthetic Jet Actuators

Robust Nonlinear Estimation and Control Applications Using Synthetic Jet Actuators
Author: Natalie Ramos Pedroza
Publisher:
Total Pages: 294
Release: 2018
Genre: Drone aircraft
ISBN:

Limit cycle oscillations (LCO), also known as flutter, cause significant challenges in flight control of small unmanned aerial vehicles (SUAVs), and could potentially lead to structural damage and catastrophic failures. LCO can be described as vibrational motions in the rocking, pitching and plunging displacements of an aircraft wing. To address this, the use of synthetic jet actuators (SJAs) in UAV flight control systems is becoming popular as a practical alternative and to mechanical deflection surfaces. Synthetic jet actuators are promising tools for LCO suppression systems in small UAVs due to their small size, ease of operation, and low cost. Uncertainties inherent in the dynamics of the synthetic jet actuators present significant challenges in the synthetic jet actuator-based control design. Specifically, the input-output characteristic (voltage-virtual deflection angle relationship) of the synthetic jet actuators is nonlinear and contains parametric uncertainty. Further control design challenges exist in situations where multiple actuators lose effectiveness. This dissertation focuses on the suppression of limit cycle oscillations on small unmanned air vehicles using synthetic jet actuators. A brief description on how wind gust affects aircraft tracking control is presented. It shows an extension to a paper by adding the wind gust model to the system while also varying the uncertain synthetic jet actuator parameters using a Monte Carlo method. Next, a robust nonlinear control method is presented, which achieves simultaneous aircraft tracking control and limit cycle oscillation suppression using these synthetic jet actuators and a robust controller. Following that, a nonlinear LCO regulation method is presented, which uses a bank of dynamic filters to eliminate the need for pitching and plunging LCO rate measurements. Finally, an alternative method of LCO regulation control is presented, which utilizes a sliding mode observer in lieu of a bank of filters to estimate the pitching and plunging LCO rates.

Design of Synthetic Jet Actuator for Flight Control of Small UAV

Design of Synthetic Jet Actuator for Flight Control of Small UAV
Author: Priyanka Pagadala
Publisher:
Total Pages: 130
Release: 2015
Genre: Actuators
ISBN:

The main idea of this project is to develop a prototype SJA - Synthetic Jet Actuator to embed into a small UAV with modified Glauert wing cross-section for Active Flow Control. Apart from lift enhancement, drag reduction, or separation control, etc; LCO suppression might be possible by modifying the boundary layer through the use of these actuators. For initial investigation, a wing section with span of 12.4 cm and chord of 14 cm was fabricated and tests were conducted in the subsonic wind tunnel at the free stream velocities of 5 and 10 m / s. From these experiments, lift curves for two different cases (with and without the actuator) were compared. Two models of actuators, one with circular orifice and the other with rectangular slot, were developed using Gallas LEM tool. Effect of orifice shapes on the performance of the actuator is also investigated. Numerical analysis of 3D model was done in Ansys Fluent with k-E turbulence model. Hot Wire Anemometer experiments were conducted to obtain frequency response plots to be validated with the similar plots obtained from the LEM tool. Due to the time consuming nature of CFD simulations, high accuracy reduced order models play a prominent role in quickly understanding the performance parameters that affect the jet. Further research is recommended for building or improving the current mathematical model and numerical tool to allow more sophisticated design configurations and optimization procedures.