Navier-Stokes-Based Dynamic Simulations of Sling Loads

Prosser, Daniel; Smith, Marilyn J.

doi:10.2514/6.2013-1922

Cited by 5 publications

(3 citation statements)

References 23 publications

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“…Given these two large uncertainties, one cannot be sure if there are other difficulties. Computational work on problems relevant to slung loads includes the work published by Bonhaus et al, Theron et al, Mantri et al and Prosser et al [78][79][80][81]. Free-swinging dynamic behavior on the CONEX container in the wind tunnel was reported in [82], correlating to earlier published data.…”

Section: Computational Analysesmentioning

confidence: 63%

Testing-Based Approach to Determining the Divergence Speed of Slung Loads

2018

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When a rotorcraft carries an external slung load, flight speed is often limited by the fear of divergent oscillations, rather than vehicle performance. Since slung objects can be of any shape, incorporating the aerodynamics with sufficient accuracy to predict safe speed has been a problem. The uncertainty forces certifying authorities to set conservative limits on speed to avoid divergence. Obtaining the aerodynamic coefficients of bluff bodies was excessively time-consuming in experiments, and impractical in computations. This review traces the evolution of progress in the area. Prior thinking was to use computations for prediction, with the computational codes validated using a few samples of experiments. This approach has not led to valid general predictions. Data were sparse and a-priori predictions were rarer. A continuous rotation approach has enabled swift measurements of 6-degrees-of-freedom aerodynamic load maps with high resolution about several axes of rotation. The resulting knowledge base in turn permits a swift determination of dynamics up to divergence, with wind tunnel tests where necessary to fill interpolation gaps in the knowledge base. The essence of efficient and swift dynamics simulation with a few well-tested assumptions is described. Under many relevant conditions, the vehicle flight dynamics can be safely decoupled from those of the slung load. While rotor wake swirl causes the payload to rotate at liftoff and landing, this effect can be incorporated into the simulation. Recent success in explaining two well-documented flight test cases provides strong evidence that predictions can be made for most missions swiftly.

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Section: Computational Analysesmentioning

confidence: 63%

Testing-Based Approach to Determining the Divergence Speed of Slung Loads

2018

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“…The details of the solver, grids, and conditions for the computation of quasi-steady aerodynamic coefficients for 3D rectangular prism and cylinder geometries have been presented previously (Refs. 17,21). These computations have been demonstrated to be some of the most accurate in the literature to date (Refs.…”

Section: Quasi-steady Aerodynamicsmentioning

confidence: 94%

“…In this work, HRLES data validated for turbulent bluff body flows including dynamic cases (Refs. 17,[21][22][23][24][25][26] have been employed to generate the quasi-steady data set. The details of the solver, grids, and conditions for the computation of quasi-steady aerodynamic coefficients for 3D rectangular prism and cylinder geometries have been presented previously (Refs.…”

Section: Quasi-steady Aerodynamicsmentioning

confidence: 99%

A Physics-Based, Reduced-Order Aerodynamics Model for Bluff Bodies in Unsteady, Arbitrary Motion

Prosser¹,

Smith²

2015

J Am Helicopter Soc

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A novel reduced-order model for the simulation of bluff bodies in unsteady, arbitrary motion has been developed. The model is physics-based, meaning that it is derived from known fundamental aerodynamic phenomena of bluff bodies instead of response fitting of experimental data. This physics-based approach is essential to ensure that the model is applicable to new, untested configurations. We describe the development of a physics-based model, including detailed explanations of the fundamental aerodynamic phenomena and how they are modeled in simulation. The reduced-order model is evaluated by application to rotorcraft-tethered loads and validated against much more expensive high-fidelity computational fluid dynamics simulations and flight tests. Excellent correlation in the predictions of aerodynamic forces and moments, as well as the dynamic response, is observed, while the computational cost has been reduced by several orders of magnitude relative to high-fidelity computational-fluid-dynamics-based simulations. Additionally, the important role that unsteady aerodynamics play in bluff body dynamics and instability is demonstrated.

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Autorotation dynamics of a low aspect-ratio rectangular prism

Greenwell¹,

Garcia

2014

Journal of Fluids and Structures

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Navier-Stokes-Based Dynamic Simulations of Sling Loads

Cited by 5 publications

References 23 publications

Testing-Based Approach to Determining the Divergence Speed of Slung Loads

Testing-Based Approach to Determining the Divergence Speed of Slung Loads

A Physics-Based, Reduced-Order Aerodynamics Model for Bluff Bodies in Unsteady, Arbitrary Motion

Autorotation dynamics of a low aspect-ratio rectangular prism

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