Testing-Based Approach to Determining the Divergence Speed of Slung Loads
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 uncer...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2018-02-01
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| Series: | Aerospace |
| Subjects: | |
| Online Access: | http://www.mdpi.com/2226-4310/5/1/24 |
| _version_ | 1811260906071392256 |
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| author | Narayanan Komerath Nandeesh Hiremath Dhwanil Shukla |
| author_facet | Narayanan Komerath Nandeesh Hiremath Dhwanil Shukla |
| author_sort | Narayanan Komerath |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-04-12T18:54:39Z |
| format | Article |
| id | doaj.art-52219795eee9463bbda4a191398f118c |
| institution | Directory Open Access Journal |
| issn | 2226-4310 |
| language | English |
| last_indexed | 2024-04-12T18:54:39Z |
| publishDate | 2018-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Aerospace |
| spelling | doaj.art-52219795eee9463bbda4a191398f118c2022-12-22T03:20:22ZengMDPI AGAerospace2226-43102018-02-01512410.3390/aerospace5010024aerospace5010024Testing-Based Approach to Determining the Divergence Speed of Slung LoadsNarayanan Komerath0Nandeesh Hiremath1Dhwanil Shukla2School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USASchool of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USASchool of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USAWhen 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.http://www.mdpi.com/2226-4310/5/1/24slung loadscontinuous rotationFourier seriesbluff bodywind tunnelsimulationdivergenceamplificationphase |
| spellingShingle | Narayanan Komerath Nandeesh Hiremath Dhwanil Shukla Testing-Based Approach to Determining the Divergence Speed of Slung Loads Aerospace slung loads continuous rotation Fourier series bluff body wind tunnel simulation divergence amplification phase |
| title | Testing-Based Approach to Determining the Divergence Speed of Slung Loads |
| title_full | Testing-Based Approach to Determining the Divergence Speed of Slung Loads |
| title_fullStr | Testing-Based Approach to Determining the Divergence Speed of Slung Loads |
| title_full_unstemmed | Testing-Based Approach to Determining the Divergence Speed of Slung Loads |
| title_short | Testing-Based Approach to Determining the Divergence Speed of Slung Loads |
| title_sort | testing based approach to determining the divergence speed of slung loads |
| topic | slung loads continuous rotation Fourier series bluff body wind tunnel simulation divergence amplification phase |
| url | http://www.mdpi.com/2226-4310/5/1/24 |
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