Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session F30: Experimental Techniques: Wind Tunnel and Aerodynamic Measurements |
Hide Abstracts |
Chair: Jonathan Naughton, University of Wyoming Room: Georgia World Congress Center B402 |
Monday, November 19, 2018 8:00AM - 8:13AM |
F30.00001: Fan array wind tunnels: characterization, performance, and visualization Christopher Dougherty, Marcel Veismann, Morteza Gharib Fan array wind tunnels, FAWT, offer a versatile, configurable alternative to traditional wind tunnel design and testing. Utilizing an array of DC-powered off-the-shelf cooling fans (in place of one singular drive section) allows for greater flow control, overall decreased mixing lengths, and comparably large useable test section areas when compared with its effective footprint. The fan array itself is fully and individually software addressable, which translates to the capability of generating a variety of traditional and non-traditional spatially- and temporally- varying flows. Characterization of the 2.88m x 2.88m open-loop FAWT housed in the Center for Autonomous Systems and Technologies (CAST) at Caltech is accomplished through standard hot-wire anemometry as well as a multi-hole pitot probe system that provides real-time, visual feedback of time-averaged flow quantities. Standard 2D and volumetric flow reconstructions are presented to accurately quantify velocity variation, flow angularity, and turbulence intensity through the extent of the entire FAWT with in-plane spatial resolutions of less than 1mm. Steady uniform and shear flows will be highlighted. |
Monday, November 19, 2018 8:13AM - 8:26AM |
F30.00002: Novel aerodynamic testing paradigms for free-flying drones Flavio Noca, Guillaume Catry, Adrien Fleury Nowadays, drones are often tested by flying them freely outdoors. Aerodynamic characterization of these vehicles is fairly difficult and poor, as the drones are often quite distant from the observer and fly in atmospheric conditions that are largely unknown, unpredictable, and not repeatable. In 2015, inspired by the observation that some birds can hover stably in turbulent wind conditions over terrain, we imagined the concept of an open wind facility, which allows a vehicle to fly freely in a controlled flow environment while remaining stationary with respect to the laboratory frame. One realization of the idea makes use of fan array surfaces in conjunction with a Motion Capture system and/or drone onboard sensors intended to maintain the vehicle in a given spot or trajectory. The flow can be steady and laminar (as in a conventional tunnel, to simulate relative motion), but may also comprise gusts and shear. The wind speed in such a facility can be modulated in real-time using the instantaneous state of a freely-flying vehicle. The paradigm of aerodynamic characterization of a free-flying vehicle also requires re-evaluation. |
Monday, November 19, 2018 8:26AM - 8:39AM |
F30.00003: Concepts and engineering of wind & weather facilities based on fan arrays Guillaume Catry, Luca Jacopo Bardazzi, Sergio Márquez, Nicolas Bosson, Flavio Noca In 2015, we imagined a fan array wind facility that could generate spatially and temporally varying flowfields within which a free-flying vehicle (drone) could be tested. The concept of a fan array wind facility is not new and the idea of free-flying vehicles in an airstream has a long history. The novelty lies in the modular technology (WindShaperTM), enabling the shift from a permanent installation (such a conventional wind tunnel) to a completely flexible, tunable, small footprint, mobile wind generating facility, whose size and shape can be modified at will. The testing environment also includes a Motion Capture environment and/or onboard sensors that allow novel measurement paradigms on freely flying vehicles, which were unimaginable in the past with conventional sting-tethered models in constant speed wind tunnels. Weather (snow and rain) can be easily implemented. |
Monday, November 19, 2018 8:39AM - 8:52AM |
F30.00004: Performance of an Unsteady, Low-Speed Wind Tunnel with an Upstream Louver System for Longitudinal Velocity Modulation Daniel Sinner, Lucas Droste, Daniel Bateman, John A. Farnsworth The experimental simulation of unsteady flow can be obtained by moving a model relative to a flow or modifying the flow itself. In this study, the latter approach was used, utilizing the opening and closing of flow-impeding louvers at the far upstream end of a low-speed, open-return wind tunnel. These louvers can rapidly tune the flow speed in the test section without altering the blower speed. Fixing the louvers in the fully closed position results in a 53% to 60% drop in flow speed from fully open, with the larger reductions at faster blower speeds. During dynamic louver operation, the test section flow speed does not instantly track with louver position. Additionally, the flow speed responds more quickly as the shutters are closed, dropping the speed, than when opened at the same rate. When commanding louver motion with equal opening and closing times, the flow speed can spend as much as 62% more time accelerating than decelerating. This effect is most pronounced for faster louver motions and lower blower speeds. Ultimately, this project aims to accurately predict the flow speed in the test section for any arbitrary louver position schedule. |
Monday, November 19, 2018 8:52AM - 9:05AM |
F30.00005: Continuous Pseudorandom Longitudinal Velocity Perturbations in an Unsteady Low-Speed Wind Tunnel Lucas Droste, Daniel Sinner, Daniel Bateman, John A. Farnsworth Longitudinal velocity perturbations have been studied experimentally using active control methods over the last 75 years. To generate these perturbations in a wind tunnel, a system of counter-rotating louvers can be utilized to vary the blockage ratio and impose fluctuations in the test-section airspeed. Such a system has been implemented in the low-speed wind tunnel at the University of Colorado Boulder which can be commanded to produce pseudorandom, longitudinal velocity perturbations. A pseudorandom louver motion was prescribed such that the test-section air speed would have a predicted energy decay rate proportional to the Kolmogorov energy cascade. Experiments were conducted to investigate the fluid system response to these pseudorandom louver motions. For an input signal with a prescribed energy decay rate proportional to the Kolmogorov energy cascade, the test-section airspeed decayed at the same rate but was attenuated above 7 Hz. Future work will investigate the coupling of these velocity perturbations with passive turbulence generation grids in the test-section. |
Monday, November 19, 2018 9:05AM - 9:18AM |
F30.00006: Contraction Effects on Turbulent Inflow Produced by an Active Grid Christopher Rumple, Jonathan W Naughton Applications such as wind energy have provided motivation for generating realistic turbulent inflows in wind tunnels. Facilities with the ability to produce such inflows allow for studies of the interaction between the inflow turbulence and the flow of interest. An example flow is the effect of atmospheric turbulence on the behavior of a wind turbine wake. Active grids – systems of actively driven elements - have the ability to tailor the inflow turbulence quantities (e.g. turbulence intensities, integral length scale, and turbulence spectrum). An active grid with 40 independent axes located within the forward contraction of a low speed, open return wind tunnel has been developed with the intent to allow the generated turbulence to evolve before entering the test section thereby producing a better conditioned turbulent inflow. The effects of the contraction on the turbulent inflow is thus of interest. Surveys using hot-wire anemometry within the contraction have been conducted to investigate the evolution of the turbulence as it propagates downstream. The turbulence characteristics at the grid and those at the test section entrance will be compared. |
Monday, November 19, 2018 9:18AM - 9:31AM |
F30.00007: Integrated sensing and actuation of unsteady flow-induced membrane deformations Jillian Bohnker, Kenneth Breuer The ability to monitor flow-induced deformation of a membrane in real time provides first-order insight into the surrounding flow field. Simple first-order quantities such as the mean camber can be linked to aerodynamic forces acting on the membrane, as well as flow field information such as the frequency and timing of vortex shedding. Coupling this with the ability to dynamically adjust membrane tension provides an opportunity for closed-loop flow control of membrane wings. In this work, a dielectric elastomer actuator is used as the wing membrane, actuated using a high voltage to dynamically vary the tension and camber of the wing. Either independently or simultaneously, the capacitance of the membrane is measured in real time using a recursive least squares (RLS) adaptive filter. Because the membrane is incompressible, the capacitance can be used to calculate in-plane strain, which in turn can be used to estimate the wing camber. The performance of the system acting solely as a sensor and as an integrated sensor/actuator is quantified in a series of benchtop and wind tunnel experiments. |
Monday, November 19, 2018 9:31AM - 9:44AM |
F30.00008: Design and Testing of a Multi-Hole Probe Geometry Insensitive to Manufacturing Variance Grant T. Dunbar, John A. Farnsworth Multi-hole probes are aerodynamic instruments that measure pressure at various points on their geometry. This array of pressures is used to estimate airspeed and flow angles through an established mathematical relationship. For existing multi-hole probes, this relationship is highly sensitive to the particular geometry of the probe. Due to manufacturing variances, each probe requires a unique calibration for its specific geometry, which is expensive and time consuming. Typical multi-hole probe configurations include hemispherical, conical, and pyramidal tip geometries. This project considers six probes spanning these common configurations and seeks to identify which geometry is least sensitive to manufacturing variance utilizing Reynolds-Averaged Navier-Stokes computational fluid dynamic simulations. These probes are tested for a range of simulated manufacturing variances, including non-uniform scaling, pressure port displacement, bumps and dips on the surface, and skewed geometries. The consistency of the pressure measurements from these probe geometries is compared for equivalent manufacturing variances. In future work, the least sensitive probe geometry will be manufactured through a stereolithographic additive manufacturing technique and evaluated experimentally. |
Monday, November 19, 2018 9:44AM - 9:57AM |
F30.00009: Just my two “sense”: A novel sensor design for two-component velocity measurements Matthew Fu, Clayton Byers, Yuyang Fan, Marcus Hultmark A unique system for measuring multiple velocity components is proposed. The system relies on the Nanoscale Thermal Anemometry Probe (NSTAP) developed at Princeton, which can be operated in two distinct modes for measuring velocity: constant current hot-wire anemometry (CCA) and a new strain-based, velocity measurement technique called elastic filament velocimetry (EFV). The individual operating modes can be achieved using the same circuitry, however each mode is sensitive to a different component of the flow velocity. By switching between these modes at a sufficiently high frequency, measurements of the two velocity components can be obtained. The switching is characterized and shown to have a sufficiently high bandwidth to obtain unattenuated turbulence measurements. |
Monday, November 19, 2018 9:57AM - 10:10AM |
F30.00010: 2d-LCA – a new sensor for highly resolved turbulence in liquids Jaroslaw Puczylowski, Joachim Peinke The 2d-LCA (2d-Laser-Cantilever-Anemometer) has originally been developed as a robust alternative to hot wire anemometry. It utilizes the laser pointer principle of a scanning-force microscope to measure the velocity and the angle of attack of fluid flows. The sensing element is a self-developed cantilever (bending beam) of 150µm (or 400µm) in length that is set into the flow. Several cantilever designs with different geometries and properties have been developed to fit various flow situations and demands. The working principle of the 2d-LCA has been proven in various experiments under laboratory and atmospheric conditions. Recently, we have succeeded to modify the 2d-LCA in order to perform measurements in water. In a first attempt we have measured a turbulent water flow that was generated using an obstacle with a sampling frequency of 20kHz. The measurements have been performed in the water channel of the University of Southern California (USC). Unlike hot-wires or hot-films, the resolution power of the 2d-LCA does not decrease with increasing flow velocity, making it particularly suitable for measurements in high-speed flows. In the recent past a lot of effort has been invested in order to make the 2d-LCA a portable and easy to use measurement device. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700