Center for Fluids at All Scales

Anderson, United States

Center for Fluids at All Scales

Anderson, United States
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McQuilling M.,Saint Louis University | McQuilling M.,Center for Fluids at All Scales | Potvin J.,Saint Louis University | Potvin J.,Center for Fluids at All Scales | And 2 more authors.
Journal of Aircraft | Year: 2011

This paper presents results from a Navier-Stokes finite volume flow solver simulating the flowfields around a platform and cargo configuration representative of platforms used for military parachute airdrops. The platform and cargo configuration consists of a flat-plate model with an aspect ratio (width/length) of 0.56 outfitted with a nose bumper, upon which a box representing cargo is placed. This combination is simulated in conditions approximating the fall of a container before and after parachute deployment and inflation, including a full 360° angle-of-attack range at Reynolds numbers of 2:94 × 106 and 9:80 × 106 (freestream velocities of 30 and 100 ft=s). The static simulations approximate those cases in which the tumbling and swinging of the container (mostly before parachute deployment or during descent) is slow enough to approximate near-steady-state flow conditions. Results include lift, drag, and moment coefficients over the range of flow conditions, as well as pressure contours to help elucidate relevant flow physics around the pallet-cargo configuration. Results show the flow orientation (into the nose bumper or flat side first) significantly affects the drag behavior, but not the lift or moment coefficients. Lift-curve slopes match well with previously published data on pallet and cargo geometries as well as flat plates with similar aspect ratios. Drag coefficients were significantly different between flow orientations and also exhibited asymmetry between positive and negative angles of attack. © 2011 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc.


McQuilling M.,Saint Louis University | McQuilling M.,Center for Fluids at All Scales | Lobosky L.,Saint Louis University | Lobosky L.,Center for Fluids at All Scales | And 2 more authors.
Journal of Aircraft | Year: 2011

Studying airdrop system aerodynamics is very challenging due to the coupling of aerodynamic forces and structural dynamics. Simplified models not containing the dynamic system coupling can yield information useful for fundamental understanding and advanced code validation. This paper presents steady-state results from a Reynolds-averaged Navier-Stokes flow solver simulating flow around a parachute model at a Reynolds number of 365,000 over five pitch angles of 0,-5,-8,-10, and-12-. The parachute model, rigid and hemispherical in shape, is similar to that of a ribbon parachute with four ribbons or rings. Pressure results are compared with experimental data to judge accuracy of the simulations. Additional results include pressure and vorticity contours, as well as computational oil-flow visualizations. These results illustrate the complex flow pattern in and around the ribbon parachute model, and they elaborate on existing data available for fluid-structure interaction code development. Copyright © 2010 by Mark McQuilling.


Bramesfeld G.,Saint Louis University | Bramesfeld G.,Center for Fluids at All Scales
Journal of Aircraft | Year: 2010

This paper explores at what point a further span increase, while maintaining a constant wing area and loading, results in a reduction in aerodynamic performance. Especially in the case of small and micro aerial vehicles, a span increase can be realized with only a minor weight penalty. Of particular interest are the maximum lift-to-drag ratio and the minimum power required. The existence of such extrema with respect to the aspect ratio is based on the notion that, while increasing the span decreases the induced drag, it also increases the profile drag as a result of the decreasing chord Reynolds number. The increasing profile drag eventually leads to a performance loss despite the growing aspect ratio. This behavior is investigated using an analytical and a computational approach. Whereas the analytical approach does not reveal distinct limits in beneficial aspect ratios, the computational approach indicates the existence of such limits, especially for lower flight masses below 500 g. The computations suggest, for a 100 g wing with fixed span, that doubling the aspect ratio from one to two results in a 20% endurance increase. Copyright © 2010.


Arko B.M.,Saint Louis University | Arko B.M.,Center for Fluids at All Scales | McQuilling M.,Saint Louis University | McQuilling M.,Center for Fluids at All Scales
Journal of Propulsion and Power | Year: 2013

This study uses a Reynolds-averaged Navier-Stokes finite volume flow solver to simulate the flowfields around a two-dimensional linear turbine cascade model at a Reynolds number of 25,000. Three blade profiles have been simulated, including the aft-loaded Pack B, which has a nominal Zweifel loading coefficient Zw equal to 1.15, the midloaded L1M (Zw = 1.33), and the front-loaded L2F (Zw = 1.59). All three blade profiles are known to be susceptible to varying degrees of laminar flow separation along the suction surface. Turbulence models used, which to the authors' knowledge have been applied for the first time here, are the Abe-Kondoh-Nagano linear low-Re k-ε as well as the Kato-Launder modification. Time-accurate simulations, including fully laminar computations, are compared with experimental data and higher-order computations to judge the accuracy of the results, where it is shown that Reynolds-averaged Navier-Stokes simulations with appropriate turbulence modeling can produce both quantitatively and qualitatively similar separation behavior as seen in experiments. However, large-scale vortical motions predicted by the turbulence models and laminar solver advect downstream and instigate flow reattachment, a result the authors believe would be attenuated to some degree by three-dimensional vortex breakdown. Results collectively show that characterization of transition to turbulence as judged by analysis of the Reynolds shear stress is not sufficient in two dimensions, and further analysis including spectral methods may be necessary to better predict transition at low Reynolds number. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc.

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