Computational Aerodynamic Analysis for the Formation Flight for Aerodynamic Benefit Program

Slotnick, Jeffrey P.

doi:10.2514/6.2014-1458

Cited by 25 publications

(18 citation statements)

References 11 publications

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“…20 This was tested because it was used in a few OVERFLOW studies involving full aircraft. 21,22 The dissipation levels were nearly the same as the SA DES case, the time to dispersion just slightly longer than SA DES but still much less than SST DES and SSTV DES. …”

Section: B Inviscid Convecting Vortex Machmentioning

confidence: 80%

Simulating Aircraft Wake Vortices with OVERFLOW

Schauerhamer

2015

33rd AIAA Applied Aerodynamics Conference

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Low dissipation methods were used to simulate wake vortex generation using the OVER-FLOW computational fluid dynamics solver. The study involved varying parameters such as grid spacing, time step, high order spatial and temporal methods, turbulence modeling, and automatic grid adaption. A two-dimensional inviscid vortex was analyzed to assess numerical dissipation, then the practices learned were applied to a finite wing and a full aircraft. Comparisons were made to idealized vortex models, the finite wing compared closest to the Hallock-Burnham model and the full aircraft to the the Proctor model.

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Section: B Inviscid Convecting Vortex Machmentioning

confidence: 80%

Simulating Aircraft Wake Vortices with OVERFLOW

Schauerhamer

2015

33rd AIAA Applied Aerodynamics Conference

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“…A “snapshot” of the velocity distribution at

t =

10 seconds is used in the CFD atmosphere of the SoS level to propagate wakes to the entire field. Given the relative location of a leading aircraft, the following aircraft must travel through consecutive sections of the wake while maintaining a safe distance [Halaas et al., ; Slotnick et al., ].…”

Section: Methods Used: Analysis and Optimization Modulesmentioning

confidence: 99%

Application of Multidisciplinary Systems‐of‐Systems Optimization to an Aircraft Design Problem

Subramanian

DeLaurentis

2016

Systems Engineering

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A generic mathematical formulation for Systems‐of‐Systems (SoS) optimization problems is presented. SoS optimization problems resemble the structure of a tree of Multidisciplinary Design Optimization (MDO) problems with additional unique features. The framework for solving such problems involves features from evolutionary computing, platform‐based design, and evolving design spaces. One important aspect of SoS Engineering, often overlooked, is the role it plays in improving the design of individual systems. In this vein, this work has sought to exemplify such a synergistic approach for aircraft design. A large‐scale SoS optimization problem for designing noise‐optimal aircraft and improved procedures for the approach phase is studied. Modules involving Computational Fluid Dynamics (CFD), noise modeling, multifidelity analysis, topology optimization, and autotuned control systems are used to obtain optimal solutions.

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“…In the tandem wing experiments of Insawa et al, 17 maximum advantage of lift-to-drag ratio was also observed when the wings were overlapped in the spanwise direction. Additionally, a comprehensive multi-fidelity computational analysis of formation flight has been provided by Slotnick et al 18 Most notably, trimmed aerodynamic benefit maps were developed to uncover the best formation positioning for optimal performance, and the Reynolds Averaged Navier-Stokes (RANS) computational method coupled with a wake evolution solver was found to yield comparable timeaveraged quantities to flight test data. Despite advances in the basic prediction and demonstration of the benefits of formation flight, significant challenges still exist in the understanding and implications of the unsteady loading and flow structure incurred from formation flight before this technology becomes a viable and safe operational capability.…”

Section: Introductionmentioning

confidence: 98%

Transient Encounters of a NACA0012 Wing with a Streamwise-Oriented Vortex

Garmann

Visbal

2015

45th AIAA Fluid Dynamics Conference

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A high-fidelity numerical study has been conducted to examine the unsteady interactions resulting from a finite wing maneuvering into a streamwise-oriented vortex as a representative problem of wake encounters. A NACA0012 wing at an angle of α = 4 • and operating at a Reynolds number of Re = 2.0 × 10 5 is dynamically maneuvered into the path of a stationary vortex, and the transient encounter is analyzed for three side-slip velocities corresponding to 10%, 20%, and 40% of the free stream. The wing is shown to traverse a range of flow regimes, including instances of vortex pairing of the tip and incident vortices that lead to mutual induction and attenuation of the pair, tip vortex suppression as the impingement passes inboard of the wingtip, and induced separation that precipitates an abrupt transition at the leading edge. The overall flow structure is mostly consistent among the wing speeds examined, indicating an almost quasi-stationary response with relative vortex position. However, a notable lag is observed in the development of a spiraling instability in the incident vortex just upstream of the wing. With slower encounter speeds, the vortex core exhibits a pronounced spiraling undulation that persists farther upstream earlier in the motion. The advanced development is attributed to prolonged exposure to the adverse pressure gradient from stagnation on the underside of the wing that decelerates the core axial flow below known stability bounds of the vortex. Additionally, a dynamic loading effect is identified prior to the vortex crossing inboard of the wingtip, whereby the incident structure's relative position at peak loading shifts outboard with increased wing speed. The peak magnitudes of lift, pitching moment, and rolling moment coefficients are also shown to scale proportionally with the wing's side-slip speed as they are predicated upon an enhanced tip vortex development. In all cases as the wing approaches the vortex, an upstream progression of separation, transition, and reattachment over the leading edge leads, which forward tilts the force vector and reduces the drag. Once the vortex is brought inboard, however, the drag saturates, and the other quantities exhibit a nearly quasi-stationary response with vortex position as the wingtip unloads.

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Computational Aerodynamic Analysis for the Formation Flight for Aerodynamic Benefit Program

Cited by 25 publications

References 11 publications

Simulating Aircraft Wake Vortices with OVERFLOW

Simulating Aircraft Wake Vortices with OVERFLOW

Application of Multidisciplinary Systems‐of‐Systems Optimization to an Aircraft Design Problem

Transient Encounters of a NACA0012 Wing with a Streamwise-Oriented Vortex

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