Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session A16: Flow Control: General |
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Chair: Mingjun Wei, Kansas State University Room: 144 |
Sunday, November 20, 2022 8:00AM - 8:13AM |
A16.00001: Aerodynamic Characteristics of a NACA 0010 Airfoil with Rotating Cylinders Alejandro D Carrizales, Cesar A Leos, Stephen W Crown, Robert A Freeman, Isaac Choutapalli The aerodynamics and flow field characteristics of a NACA 0010 airfoil with rotating cylinders near the leading-edge were investigated in flow with a freestream turbulence intensity of 4%. A NACA 0010 airfoil was modified so that 5 micro-DC motors fit within the airfoil body at 14.6% of chord length from the leading edge. Cylinders with a diameter of 0.75 inches and a width of 0.5 inches were attached to the motor shafts with only 3mm of the cylinders being exposed to the incoming flow. Experiments were carried out on the NACA 0010 airfoil with and without the rotating cylinders. The cylinders were driven by micro-DC motors with 12 volts, which translates to 3400 RPM, with the cylinder rotation being counter-clockwise to the direction of the flow. The Reynolds number varied from 173,400 to 218,900. The angle of attack was varied within the range of 0 to 24 degrees. The forces and torque experienced by the airfoil are measured using two 9105-TIF-DELTA ATI 6-axis force/torque transducers. From the results, it was shown that the airfoil with the cylinders rotating experienced a maximum lift coefficient increase of 45 percent when compared to results from an unmodified baseline airfoil. |
Sunday, November 20, 2022 8:13AM - 8:26AM |
A16.00002: Gust mitigation of a plunging-pitching airfoil by an adjoint-based approach Bolun Xu, Mingjun Wei, John T Hrynuk Gust encounters during the flight of Micro-air vehicles (MAVs) can be detrimental and an effective method for gust mitigation is highly desirable to help MAVs operating under extreme conditions. In this study, facing the problem's large control space, an adjoint-based approach is developed to achieve the gust mitigation of a heaving-pitching airfoil. Two kinds of gust are considered: the horizontal gust by changing the velocity of incoming flow, and the vertical gust by inducing an additional flow from the bottom. Mitigation is realized by first designing an objective function to assess force difference before and after gusts, then using an adjoint-based approach to minimize the function. Two different adjoint-based algorithms are developed: one uses direct numerical simulation (DNS) and its adjoint simulation of an incompressible flow, and the other uses a Galerkin-projection reduced-order model (ROM) and its adjoint ROM. It is shown that both adjoint-based algorithms can effectively mitigate the influence of gusts by tuning the motion of airfoil accordingly. The adjoint-based DNS algorithm is a high-fidelity method with reasonable computational cost, and the adjoint-based ROM algorithm is a low-fidelity method but its online computation is fast enough for real-time control. |
Sunday, November 20, 2022 8:26AM - 8:39AM |
A16.00003: Data-Driven Controller Design and Sensor Selection for Flow Around a Circular Cylinder Yasuo Sasaki, Taku Nonomura We propose a data-driven method to design feedback controllers and select sensor positions for real-time particle image velocimetry (PIV). The proposed method is divided into two steps. First, we acquire data of an optimal feedback controller that is designed based on the Navier-Stokes equations. Second, we derive a sparse map between the flow velocity field and the optimal control input from the data. The sparse map is regarded as a real-time feedback controller. This feedback controller uses information of the flow velocity at so a few points that PIV processing can be implemented in real time. The processing points are selected via a greedy algorithm that is developed for a simultaneous optimization problem of controller gain and processing point positions. The greedy algorithm takes into account that PIV measures two components of a flow velocity vector per processing point. We deal with a benchmark problem of flow around a circular cylinder at the Reynolds number 100 to verify the effectiveness of the proposed method. A numerical simulation reveals that a controller that is designed with the proposed method successfully mitigates vortex shedding by the feedback of the flow velocity at only a few dozen points. |
Sunday, November 20, 2022 8:39AM - 8:52AM |
A16.00004: Stabilizing cylinder flow at supercritical Reynolds number using surface velocity perturbations and momentum forcing Ernold Thompson, Andres Goza The stabilization of the vortex shedding behind a cylinder has been a classical breeding ground for development of flow control rooted in linear stability/sensitivity analysis techniques. We extend prior efforts by probing two new classes of actuation: surface velocity perturbations in the local normal direction, and spatio-temporally varying momentum forcing throughout the flow domain. The former is motivated by advances in materials science, which enable realizable actuation on the body surface, and the latter is an extension of studies that focused on time steady, spatially localized actuation. We use adjoint-based optimization to inform an actuation protocol that drives the unsteady flow at a Reynolds number of 100 to the flow's unstable base state. For the surface actuation protocol, we will assess the effect of the horizon optimization window, which was shown in tangential actuation to affect the reduction in temporal oscillations. For the full-domain actuation, we will compare the mechanisms for mitigating vortex shedding to those shown via sensitivity analysis for small, stationary secondary cylinders, possibly providing further insights into how the wake can be further manipulated towards a desired control outcome. |
Sunday, November 20, 2022 8:52AM - 9:05AM |
A16.00005: Closed-loop Feedback based Adaptive Model Predictive Control of a Bluff-Body Wake Calin Gaina Ghiroaga, Christopher R Morton, Robert J Martinuzzi Achieving robust closed-loop feedback control of turbulent bluff-body wakes poses challenges due to the non-linear response of the wake dynamics to actuation. A strategy based on Model Predictive Control (MPC) with a Long Short-Term Memory (LSTM) Neural Network model to achieve closed-loop control of a bluff-body wake is outlined and its performance assessed experimentally. |
Sunday, November 20, 2022 9:05AM - 9:18AM |
A16.00006: Drag reduction of a slanted Ahmed body with many actuators using the explorative gradient method Yiqing Li, Zhigang Yang, Bernd R Noack
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Sunday, November 20, 2022 9:18AM - 9:31AM |
A16.00007: Controlling the Instability at the Interface of Supersonic Streams Within a Modern Rectangular Jet Nozzle Seth W Kelly, Carl W Kjellberg, Matthew A Qualters, Amanda M Stafford, Mark N Glauser Modern jet nozzle designs for next-generation aircraft often exhibit distinct features such as multiple flow streams or non-axisymmetric exits. This study expands upon extensive experimental and computational research on a Multi Aperture Rectangular Single Expansion Ramp Nozzle, characterized by core (M=1.6) and bypass (M=1.0) streams that merge behind a splitter plate and exit onto an aft deck meant to simulate air frame integration. Preliminary research has determined that the region where the two streams meet produces an unwanted tone ubiquitous within the flowfield. To mitigate this tone that results from the complex shedding instability, flow control techniques are applied experimentally. A spanwise wavenumber is introduced to the splitter plates trailing edge (SPTE) as a means to passively affect the mixing in the shear layer. Additionally an array of microjets are introduced just below the SPTE region and actuated to provide a more tuned active control approach to affecting the instability. Experiments are performed within an anechoic chamber utilizing simultaneous near and far-field pressure measurements as well as schlieren imaging to quantify the efficacy of the control methods and observe changes to the spectral characteristics as well as shock behavior of the system. |
Sunday, November 20, 2022 9:31AM - 9:44AM |
A16.00008: A method for generating arbitrary wind patterns in fan array wind tunnel facilities Ioannis M Mandralis, Alejandro Stefan-Zavala, Richard M Murray, Morteza Gharib Fan array wind tunnels are a novel technology that promises to revolutionize testing of aerodynamic components by providing fine-grained control over the type of wind patterns that can be generated. However, general methods for producing desired wind patterns using fan array wind tunnels have yet to be elaborated. Here we present a gradient-based optimization algorithm for shaping the mean streamwise velocity distribution by modifying the fan rotational rates based on feedback of velocity information. The algorithm is tested experimentally on a fan array wind tunnel coupled with a grid of spatially distributed Pitot sensors which measure the velocity field. Results show that the proposed method can accurately produce user-specified wind shapes, opening new possibilities for the testing of low Reynolds number fliers in experimentally simulated atmospheric conditions. |
Sunday, November 20, 2022 9:44AM - 9:57AM |
A16.00009: Cyclone negative pressure pump for efficient purification of airborne contaminants Gihyun Song, Hyoungsoo Kim The medical facility needs a negatively pressurized room to treat respiratory disease patients such as COVID-19. These days, the conventional negative pressure pump typically has low-speed suction flow and no active control. These flow conditions could not efficiently purify airborne contaminants and it could be disorganized by the movement of medical staff in a hospital, and therefore airborne pathogens could be remained and mixed indoors. In this study, we developed a negative pressure pump having a cyclone flow at the inlet, which was numerically investigated. Firstly, the particle purification efficiency of the conventional and the cyclone negative pressure pump was compared in the case of patients covered with the contaminants. The pollutants covering the patient were collected faster for the cyclone pressure pump. Secondly, the purification efficiency was tested for the case of the patient's breathing and coughing case. We observed that for both cases the cyclone negative pressure pump would be more efficient to purify the contaminants. Furthermore, we tried to optimize the position of cyclone pumps for better performance. As a result, we demonstrated that the airborne aerosol or saliva droplets could be efficiently and effectively collected by controlling indoor airflow. |
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