Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session E9: Aerodynamics I |
Hide Abstracts |
Chair: Kamran Mohseni, University of Florida Room: 25B |
Sunday, November 18, 2012 4:45PM - 4:58PM |
E9.00001: Aerodynamic Improvements to Cargo Carrying Rail Cars due to Roof Modifications Robert Condie, Daniel Maynes The aerodynamic drag associated with the transport of commodities by rail is becoming increasingly important as the cost of diesel fuel increases. We provide an assessment of the influence of the roof structure on aerodynamic performance of two dissimilar rail cars, namely automobile carrying cars and coal carrying cars. Currently, the roof material for automobile carrying rail cars is corrugated steel, with the corrugation aligned perpendicular to the direction of travel. Coal cars are currently left uncovered for loading convenience and on the return leg from the power plant are empty. Aerodynamic drag data have been obtained through wind tunnel testing on 1/29 scale models to understand the savings that may be realized by judicious modification to the tops of both these car types. For the automobile-carrying cars, testing is performed for the corrugated and smooth roof configurations. This modification alone has the potential of reducing the car drag coefficient by nominally 25{\%}. A broader study is performed for the coal cars, with data being acquired for coal filled models, empty models, and several cover prototype configurations. The results reveal that implementation of a cover may yield reductions in the aerodynamic drag for both coal filled (nominally 7{\%}) and empty coal cars (nominally 30{\%}). [Preview Abstract] |
Sunday, November 18, 2012 4:58PM - 5:11PM |
E9.00002: Flow over a Ram-Air Parachute Canopy Ali Eslambolchi, Hamid Johari The flow field over a full-scale, ram-air personnel parachute canopy was investigated numerically using a finite-volume flow solver coupled with the Spalart-Allmaras turbulence model. Ram-air parachute canopies resemble wings with arc-anhedral, surface protuberances, and an open leading edge for inflation. The rectangular planform canopy had an aspect ratio of 2.2 and was assumed to be rigid and impermeable. The chord-based Reynolds number was 3.2 million. Results indicate that the oncoming flow barely penetrates the canopy opening, and creates a large separation bubble below the lower lip of canopy. A thick boundary layer exists over the entire lower surface of the canopy. The flow over the upper surface of the canopy remains attached for an extended fraction of the chord. Lift increases linearly with angle of attack up to about 12 degrees. To assess the capability of lifting-line theory in predicting the forces on the canopy, the lift and drag data from a two-dimensional simulation of the canopy profile were extended using finite-wing expressions and compared with the forces from the present simulations. The finite-wing predicted lift and drag trends compare poorly against the full-span simulation, and the maximum lift-to-drag ratio is over-predicted by 36\%. [Preview Abstract] |
Sunday, November 18, 2012 5:11PM - 5:24PM |
E9.00003: Flow in the near wake of hemispherical parachute shapes Jeffrey Young, Maria-Isabel Carnasciali, Mike Kandis A CFD study was conducted using ANSYS to investigate the pitch-stability of several hemispherical parachute geometries at varying Reynolds numbers. In actuality, the parachute itself is not a rigid body and large variations in the parachute geometry can occur due to the flexibility of the parachute fabric. This factor combined with flow through gaps/open areas provide for a much more complex wake than that of a simple bluff body like a disc or sphere. In some cases, Vortex Shedding or alternating vortices are generated which cause oscillations in the axial (i.e., drag force) and normal (i.e., lift force) forces that lead to pitching/oscillations. This study investigated the flow in the near wake of hemispherical parachute shapes (assumed to be rigid) having various sized gaps/open areas positioned at distinct locations to determine which designs resulted in ``less severe'' Vortex Shedding. The design features (i.e., size and location of the gaps) that provided the smallest variation/fluctuation in the normal forces were identified and compared to actual parachute designs. [Preview Abstract] |
Sunday, November 18, 2012 5:24PM - 5:37PM |
E9.00004: A lifting surface approximation for roll stall of Micro Aerial Vehicles Matt Shields, Kamran Mohseni The lateral stability of Micro Aerial Vehicles (MAVs) has been known to be adversely affected by the low aspect ratio (LAR) nature of these aircraft. While this has typically been attributed to the small moments of inertia about the plane of symmetry, recent experimental results display the development of a significant roll stability derivative ($C_{l,\beta}$) for flat plate (0\% camber) wings. The roll moment can be attributed to the asymmetric development of the tip vortices of a yawed wing and the resulting deviation from the wing loading at zero sideslip. Furthermore, results indicate that a harmonic yaw oscillation at increasing angular velocities results in a delay effect as the formation of the tip vortex is affected by the rotation of the wing; that is, the roll moment does not reach its steady value at a given yaw angle until after the model yaws past the angle. A model based on modified lifting surface theory is developed to determine the influence of the induced velocities of the skewed tip vortices on the lateral loading of both the static and oscillating wing; experimentally determined parameters are used to compensate for the separated flow experienced by MAV wings and not considered in conventional lifting surface methods. [Preview Abstract] |
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