Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session S26: Flow Control: Plasma Actuation B |
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Chair: Jesse Little, University of Arizona Room: 608 |
Tuesday, November 26, 2019 10:31AM - 10:44AM |
S26.00001: Active flow control of the laminar separation bubble on a plunging airfoil near stall Jesse Little, Mark Agate, Arth Pande The effects of small amplitude, high frequency plunging motion on the X-56A airfoil are examined experimentally at Re$=$200,000 for 12 degrees angle of attack. The purpose of this research is to study the aerodynamic influence of structural motion when the wing is vibrating close to its eigenfrequency near static stall. Specific focus is placed on the laminar separation bubble (LSB) near the leading edge and its control via plasma actuation. In the baseline case, the leading edge bubble bursts during the oscillation cycle causing moment stall. A collaborative computational effort has shown that small amplitude forcing at a frequency that is most amplified by the primary instability of the LSB generates coherent spanwise vortices that entrain freestream momentum, thus reducing separation all while maintaining a laminar flow state. Results (PIV and surface pressure) indicate that a similar control mechanism is effective in the experiments. This is significant given the existence of freestream turbulence in the wind tunnel which has been shown to limit the efficacy of this active flow control technique in a model problem using direct numerical simulation. The implications of these results are discussed. [Preview Abstract] |
Tuesday, November 26, 2019 10:44AM - 10:57AM |
S26.00002: Viscous Drag Reduction on a NACA 63012A Airfoil Katherine Yates, Alan Duong, Thomas Corke, Flint Thomas A series of wind tunnel experiments were performed in which an array of flush mounted pulsed-DC plasma actuators were utilized to reduce the skin friction drag on a NACA 63012A airfoil over a Mach number range of $0.20 \leq M_{\infty} \leq 0.50$ at zero angle of attack. The array of plasma actuators were designed to inhibit the lift-up and subsequent break-up of the low-speed wall streak structure to prevent the formation of streamwise vortices; a key element in wall-bounded turbulence generation. Experiments were done with two sets of actuator arrays: 1) with the electrodes aligned in the mean flow direction and 2) with the electrodes oriented 5 degrees offset to the oncoming flow. The aerodynamic load (viscous drag) was measured directly using an integrated floating element force balance. Viscous drag reduction of up to 47\% was observed depending on the operating parameters of the plasma actuators. Net power savings were also achieved across the range of Mach numbers tested. [Preview Abstract] |
Tuesday, November 26, 2019 10:57AM - 11:10AM |
S26.00003: Active Turbulent Boundary Layer Drag Reduction using Pulsed-DC DBD Plasma Actuators Alan Duong, Thomas Corke, Flint Thomas Experiments were performed involving the use of an active flow control scheme designed to inhibit the lift-up and subsequent break-up of the low-speed wall streak structure to reduce skin friction drag in a turbulent boundary layer. The flow control utilized an array of pulsed-DC plasma actuators that was designed to produce a steady span-wise velocity component on the order of $u_{\tau}$ in order to reduce the mean flow distortion caused by the quasi-steady wall streak structure first observed by Kline \textit{et al} (1967). This flow control method has been successful in reducing the viscous drag over a decade of Mach numbers and is capable of reducing the skin friction coefficient up to 68\% while maintaining net power savings. The work presented here investigates the underlying flow physics of a pulsed-DC drag reduced boundary layer in a controlled, low-speed environment. The plasma actuator array in this paper was successful in reducing the skin friction velocity by 37\%, which corresponds to a decrease of 50\% in the skin friction coefficient, measured directly by means of a floating element force balance. Detailed two-component velocity measurements were done with xwire hotwires in the wallnormal and spanwise directions downstream of the actuator. [Preview Abstract] |
Tuesday, November 26, 2019 11:10AM - 11:23AM |
S26.00004: On spatial arrangement of vortex-generator type plasma actuator for separation control of airfoil flow Makoto Sato, Chinatsu Kobayashi LESs on separation control flows around a NACA4418 have been conducted. In the separation control, a vortex-generator type plasma actuator (VG-PA) has been adapted. The flow conditions and the configurations of the plasma actuator are set based on the previous experimental study The Reynolds number is 85000 with angle of attack 18 deg. The effects of spanwise spacing of the VG-PA have been mainly investigated. The spacing of the VG-PA is set as 0.05$c$, 0.1$c$, 0.2$c$, 0.3$c$, and 0.4$c,$ where $c$ means the chord length. The maximum lift is attained in the case with 0.1$c$. On the other hand, a streamwise vortex generated by the VG-PA in a boundary layer flow has been investigated to clarify the distribution of the vortex. The streamwise vortex is distributed from the actuator to 0.1$c$ away from the actuator in the induced flow direction. It means that the most effective control for the lift increase can be achieved for the case that the streamwise vortex generated by the VG-PA collides with the opposite streamwise vortex. In addition, from the results of 0.05$c$ and 0.1$c$, the location of the streamwise vortex collision is also important factor for the effective control. [Preview Abstract] |
Tuesday, November 26, 2019 11:23AM - 11:36AM |
S26.00005: Effects of the Layout of DBD Plasma Actuators on its Anti-/De-Icing Performance for Aircraft Icing Mitigation Cem Kolbakir, Haiyang Hu, Yang Liu, Hui Hu An experimental study was performed to evaluate the effects of different layouts of DBD plasma actuators on their anti-/de-icing performances for aircraft icing mitigations. An array of DBD plasma actuators were designed and embedded on the surface of a NACA0012 airfoil/wing model in different layout configurations (i.e., different alignment directions of the plasm actuators (e.g., spanwise vs. streamwise), width of the exposed electrodes and the gap between the electrodes). The experimental study was carried out in the Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT). While the dynamic anti-icing operation is recorded by using a high-resolution imaging system, a high-speed Infrared (IR) thermal imaging camera is used to quantitatively map the temperature distributions over the surface of the airfoil model during the anti-/deicing processes. The findings derived from the present study are very helpful to explore/optimize design paradigms for the development of novel plasma-based anti-/de-icing strategies tailored specifically for aircraft inflight icing mitigation to ensure safer and more efficient aircraft operation in atmospheric icing conditions. -/abstract- Cem Kolbakir, Haiyang Hu, Yang [Preview Abstract] |
Tuesday, November 26, 2019 11:36AM - 11:49AM |
S26.00006: Transient flow control effect of Quasi-DC filamentary plasma in Mach 2 and Mach 4 supersonic flows Yasumasa Watanabe, Skye Elliott, Alec Houpt, Sergey Leonov This study explores the effect of pulse-periodic quasi-DC filamentary plasma on the flow structure over 15-degree compression ramp in Mach 2 and Mach 4 airflows. A major attention is focused on transient phenomena related to plasma-flow interaction. Experiments were conducted in supersonic wind tunnel SBR-50 at the University of Notre Dame. Pulse-periodic plasma generator, operating at the frequency ranging from 250 to 5000 Hz, was installed flush-mounted crossflow in front of the compression ramp. Flow stagnation pressure and temperature were varied as 1-4 bar and 300-600K respectively. The transient flow structure and plasma filament behavior were visualized with schlieren method and high speed camera. The surface pressure distribution on the wall surface and at the ramp was measured with fast pressure transducers. The plasma generated upstream of the compression ramp shifts the shock position from the ramp to the electrode location, subsequently forming a separation zone and resulting in pressure change behind electrodes and over the ramp surface both in cases of Mach 2 and Mach 4 flows. Pressure change was characterized as a function of flow/plasma parameters. [Preview Abstract] |
Tuesday, November 26, 2019 11:49AM - 12:02PM |
S26.00007: Numerical, Experimental and Analytical Investigation of the Planar Electrohydrodynamic Wall Jet Patrick Fillingham, Yifei Guan, Ravi Sankar Vadi, Igor Novosselov Classical laminar wall jet theory is used for the examination of the flow induced by Electrohydrodynamic (EHD) actuators. The planar EHD wall jet, induced by both corona discharge and dielectric barrier discharge (DBD), is investigated experimentally and computationally. The thrust generated by the actuators is measured while the velocity profiles downstream of the cathode are measured using hot-wire anemometry. A multiphysics computational model couples the Navier-Stokes, electrical field, and ion transport equations. Experimental investigations of EHD actuators in the literature are used for model validation. The wall jet resulting from both DBD and Corona actuators was found to adhere to the analytical solution for a planar laminar wall jets; allowing for the calculation of the momentum generated by EHD actuators with only information about the downstream maximum velocity. The model allows for characterization of the thrust generated by any EHD actuator attached to a wall using only two velocity measurements.~ [Preview Abstract] |
Tuesday, November 26, 2019 12:02PM - 12:15PM |
S26.00008: Drag reduction on a three-dimensional model vehicle by a wire-to-plate DBD plasma actuator Dongri Kim, Zhi Wu, Hyungrok Do, Haecheon Choi We apply a wire-to-plate DBD plasma actuator to a three-dimensional model vehicle (Ahmed body) for drag reduction. With a thin wire (diameter of 11 $\mu$m) as an exposed electrode, the performance and efficiency enhance far more than those of the conventional plate-to-plate actuator. By varying the actuator length in the spanwise direction, the drag reduction up to 10\% is obtained at the Reynolds number of 96,000 based on the free-stream velocity and model height. With surface-pressure and PIV measurements, it is shown that drag reduction occurs mainly due to entrainment induced by streamwise momentum addition and flow changes at the actuator ends, which significantly modify the evolution of the flow in the center region and corner vortices at the lateral sides of the slanted surface of the model. Other configurations of plasma actuator are being tested and their results will be also given in the presentation. [Preview Abstract] |
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