Analysis of samara-wing decelerator steady-state characteristics

Crimi, Peter

doi:10.2514/3.45539

Cited by 26 publications

(16 citation statements)

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“…Rosen and Seter [6,7] have studied numerically the influence of different parameters on samara wing flight stability. Crirni [8] has studied a rotating body with only one wing for submunition applications, searching for a body that performed periodic movements. However, in these papers, there is no information about the behavior of a body with rotating wings like that presented here, and to the authors' knowledge, there is no other closely related information in the literature.…”

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confidence: 99%

Pararotor Dynamics: Center of Mass Displacement from the Blade Plane—Analytical Approach

Piechocki

Mora

Andres

2014

Journal of Aircraft

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The pararotor is a biology-inspired decelerator device based on the autorotation of a rotary wing whose main purpose is to guide a load descent into a certain atmosphere. This paper focuses on a practical approach to the general dynamic stability of a pararotor whose center of mass is displaced from the blade plane. The analytical study departs from the motion equations of pararotor flight, considering the center of mass displacement from the blade plane, studied over a number of simplifying hypotheses that allows determining the most important influences to flight behavior near equilibrium. Two practical indexes are developed to characterize the stability of a pararotor in terms of geometry, inertia, and the aerodynamic characteristics of the device. Based on these two parameters, a stability diagram can be defined upon which stability regions can be identified. It was concluded that the ability to reach stability conditions depends mainly on a limited number of parameters associated with the pararotor configuration: the relationship between moments of inertia, the position of the blades, the planform shape (associated with the blade aerodynamic coefficients and blade area), and the vertical distance between the center of mass and the blade plane. These parameters can be evaluated by computing practical indexes to determine stability behavior.

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confidence: 99%

Pararotor Dynamics: Center of Mass Displacement from the Blade Plane—Analytical Approach

Piechocki

Mora

Andres

2014

Journal of Aircraft

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“…It is worth mentioning that the samara autorotation in nature stimulated different engineering ideas and resulted in a samara type decelerator (Crimi, 1988) and an atmospheric autorotating imaging device (Burke,I 988).…”

Section: Introductionmentioning

confidence: 99%

Study of the Vertical Autorotation of a Singlewinged Samara

Seter

Rosen

1992

Biological Reviews

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Summary 1. Autorotation of a single‐winged samara is a highly nonlinear phenomenon that represents a delicate equilibrium between gravity, inertia and aerodynamic effects. Therefore, in order to analyse this phenomenon, an accurate detailed model is necessary. Such a model has not been presented in the past. Recently the authors derived a detailed model which is briefly described in the paper. 2. The aerodynamic contributions present the most complicated part of the phenomenon. These contributions are treated using the blade‐element/momentuin method, with certain improvements and additions. These improvements are necessary due to inherent differences between samara wings and other rotary wing systems (aircraft propellers, helicopter rotors, etc.). 3. The cross‐sectional aerodynamics of the samara is characterized by relatively small Reynolds numbers, high angles of attack and rough surfaces. While these characteristics are different from other rotary wings, they are typical of the wing cross‐sections of insects and birds. Therefore the lift and drag coefficients, which are necessary for the analysis, are obtained using available data for insect and bird wings. 4. The results of the theoretical model are compared with experimental results of tlvo kinds. The first kind includes results for a samara of an Acer platanoides that were reported in the literature. In addition, a special experimental model of a samiira was built and tested. This model offers a simple way of varying the configuration in order to study (experimentally) the effect of different geometric parameters on the autorotation. 5. In the light of the uncertainty in the aerodynamic coefficients, it can be concluded that there is quite a good agreement between the theoretical and experimental results. Thus, after LTalidation, the theoretical model is used for a parametric study to find the influence of different parameters on the autorotation. The important results of this study are outlined below. 6. The spanwise flolv component and the tangential component of the induced velocity have a very small influence and thus can be neglected. 7. It is important to include in the analysis the effects of the axial induced velocity, the tip effect, and the drag of the root region. 8. Since chordwise variations of the centre of pressure location, as a function of the angle of attack, were seen in the past (based on over simplified analyses) as the mechanism which is responsible for the samara stability, this effect is also added to the model. While the influence of this effect on the pitch angle is large and small on the sinking rate, it results in an increase in the deviation between the theoretical and experimental results. 9. Autorotation is sensitive to the cross‐sectional aerodynamic coefficients. This sensitivity is critical since the available data on these coefficients is, to say the least, unsatisfactory and require significant improvement.

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“…Among these last applications, there are the studies carried out by Crimi [1], who studied a rotating body with only one wing for submunition applications, and Karlsen et al [2], who also worked on winged bodies for submunition applications. They talked about the advantages of the pararotor over the parachute: lower sensitivity to lateral winds, parachute deployment problems, lower precession movements, and higher falling velocity.…”

Section: Introductionmentioning

confidence: 99%

Model of the Aerodynamic Behavior of a Pararotor

Nadal-Mora

Sanz-Andrés

Cuerva

2006

Journal of Aircraft

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A simple semi-empirical model for the aerodynamic behavior of a low-aspect ratio pararotor in autorotation at low Reynolds numbers is presented. The paper is split into three sections: Sec. II deals with the theoretical model derivation, Sec. III deals with the wind-tunnel measurements needed for tuning the theoretical model, and Sec. IV deals with the tuning between the theoretical model and the experimental data. The study is focused on the effect of both the blade pitch angle and the blade roughness and also on the stream velocity, on the rotation velocity, and on the drag of a model. Flow pattern visualizations have also been performed. The value of the free aerodynamic parameters of the semi-empirical model that produces the best fit with the experimental results agrees with the expected ones for the blades at the test conditions. Finally, the model is able to describe the behavior of a pararotor in autorotation that rotates fixed to a shaft, validated for a range of blade pitch angles. The movement of the device is found to be governed by a reduced set of dimensionless parameters.

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Analysis of samara-wing decelerator steady-state characteristics

Cited by 26 publications

References 1 publication

Pararotor Dynamics: Center of Mass Displacement from the Blade Plane—Analytical Approach

Pararotor Dynamics: Center of Mass Displacement from the Blade Plane—Analytical Approach

Study of the Vertical Autorotation of a Singlewinged Samara

Model of the Aerodynamic Behavior of a Pararotor

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