Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session E25: Experimental ApparatusExperimental
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Chair: Philipp Hack, Stanford University Room: 705 |
Sunday, November 19, 2017 4:55PM - 5:08PM |
E25.00001: Calibration Development for an Unsteady Two-Strut Store Balance Ryan Schmit, Ian Maatz, Rudy Johnson This paper addresses measurements of unsteady store forces and moment in and around a weapons bay cavity. The cavity dimensions are: Length 8.5 inches, Depth 1.5 inches, Width 2.5 with a L/D ratio of 5.67. Test conditions are at Mach 0.7 and 1.5 with Re {\#} 2.0e\textasciicircum 6/ft. The 7.2 inches long aluminum store is held in the cavity with two struts and the strut lengths are varied to move the store to different cavity depth locations. The normal forces and pitching moments are measured with two miniature 25 pound load cells with a natural frequency of 24k. The store-strut-load cell balance can also produce unwanted structural eigenfrequencies at or near the cavity's Rossiter tones. To move the eigenfrequencies away from the cavity's Rossiter tones calls for detailed design and Finite Element Modeling (FEM) before wind tunnel testing. Included are the issues in developing a calibration method for an unsteady two-strut store balance for use inside a scaled wind tunnel weapons bay cavity model. [Preview Abstract] |
Sunday, November 19, 2017 5:08PM - 5:21PM |
E25.00002: Design and Analysis of A Spin-Stabilized Projectile Experimental Apparatus Noah Siegel, Gregory Rodebaugh, Christopher Elkins, Bret Van Poppel, Michael Benson, Michael Cremins, Austin LaChance, Raymond Ortega, Douglas VanderYacht Spinning objects experience an effect termed `The Magnus Moment' due to an uneven pressure distribution based on rotation within a crossflow. Unlike the Magnus force, which is often small for spin-stabilized projectiles, the Magnus moment can have a strong detrimental effect on aerodynamic flight stability. Simulations often fail to accurately predict the Magnus moment in the subsonic flight regime. In an effort to characterize the conditions that cause the Magnus moment, researchers in this work employed Magnetic Resonance Velocimetry (MRV) techniques to measure three dimensional, three component, sub-millimeter resolution fluid velocity fields around a scaled model of a spinning projectile in flight. The team designed, built, and tested using a novel water channel apparatus that was fully MRI-compliant – water-tight and non-ferrous – and capable of spinning a projectile at a constant rotational speed. A supporting numerical simulation effort informed the design process of the scaled projectile to thicken the hydrodynamic boundary layer near the outer surface of the projectile. Preliminary testing produced two-dimensional and three-dimensional velocity data and revealed an asymmetric boundary layer around the projectile, which is indicative of the Magnus effect. [Preview Abstract] |
Sunday, November 19, 2017 5:21PM - 5:34PM |
E25.00003: Fan array wind tunnel: a multifunctional, complex environmental flow manipulator Christopher Dougherty, Marcel Veismann, Morteza Gharib The recent emergence of small unmanned aerial vehicles (UAVs) has reshaped the aerospace testing environment. Traditional closed-loop wind tunnels are not particularly suited nor easily retrofit to take advantage of these coordinated, controls-based rotorcraft. As such, a highly configurable, novel wind tunnel aimed at addressing the unmet technical challenges associated with single or formation flight performance of autonomous drone systems is presented. The open-loop fan array wind tunnel features 1296 individually controllable DC fans arranged in a 2.88m x 2.88m array. The fan array can operate with and without a tunnel enclosure and is able to rotate between horizontal and vertical testing configurations. In addition to standard variable speed uniform flow, the fan array can generate both unsteady and shear flows. Through the aid of smaller side fan array units, vortex flows are also possible. Conceptual design, fabrication, and validation of the tunnel performance will be presented, including theoretical and computational predictions of flow speed and turbulence intensity. Validation of these parameters is accomplished through standard pitot-static and hot-wire techniques. Particle image velocimetry (PIV) of various complex flows will also be shown. [Preview Abstract] |
Sunday, November 19, 2017 5:34PM - 5:47PM |
E25.00004: ABSTRACT WITHDRAWN |
Sunday, November 19, 2017 5:47PM - 6:00PM |
E25.00005: Production of Unsteady Flows Through the Use of an Active Grid Abdullah Azzam, Philippe Lavoie In many applications, aerodynamic bodies are exposed to complex flows that are non-uniform in both space and time (due for instance to mean shear, wind gust, and/or turbulence). This can lead to significant changes in performance and detrimental unsteady loads. This study investigates the possibility of using an active grid to produce a wide range of flow conditions with varied levels of turbulence intensities, mean flow unsteadiness and non-uniformity by changing the excitation parameters of the grid. Hot-wire and static pressure measurements were taken both upstream and downstream of the grid for a number of excitation protocols and parameters. The grid is shown to produce low frequency (0.25 – 10 Hz) unsteadiness in the mean flow effectively with high and low levels of free stream turbulence. The highest amplitudes of the unsteady flow are achieved at low frequency, while the minimum amplitude that can be achieved asymptotes to a constant value as the frequency is increased. Furthermore, a mean shear in the flow can be superimposed in addition to the unsteadiness. These results demonstrate that the active grid can be used successfully to produce a range of unsteady flows with complex features from a single apparatus. [Preview Abstract] |
Sunday, November 19, 2017 6:00PM - 6:13PM |
E25.00006: Study of the natural convection flow induced by injecting a hot fluid in a porous medium Ayax Hernando Torres Victoria, Salomon Peralta Lopez, Abraham Medina Ovando, Vadim Kourdioumov, Jaime Klapp In this work, we present the study of a steady flow driven by the injection of a hot fluid of temperature T$_{i}$, from a horizontal line source of mass embedded in an unbounded porous medium of constant permeability K and porosity $\phi$, the medium is saturated with the same fluid. The fluid far from the source is stagnant with a uniform temperature T$_{\infty}$, where T$_{\infty}$$<$T$_{i}$. The density changes of the fluid are considered to be small enough so that the Boussinesq approximation is applicable and we shall also assume that the fluid and solid in the porous medium have the same temperature locally. This configuration conforms interesting flow and temperature patterns in the surrounding medium near the line source as demonstrated numerically and experimentally. [Preview Abstract] |
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