Wind tunnel test results of heavy rain effects on airfoil performance

Bezos, Gaudy M.; Dunham, R. E.; Gentry, G. L.; Melson, W. Edward

doi:10.2514/6.1987-260

Cited by 10 publications

(7 citation statements)

References 2 publications

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“…But this phenomenon is not well understood. No other researcher like Dunham [10], Campbell and Bezos [12], Bezos et al [13,14], Valentine [21], and Valentine and Decker [22,23] predicted lift and stall angle increment at high AOA in heavy rain conditions in their studies. For our studies, the stall angle is 15 deg.…”

Section: Simulation and Resultsmentioning

confidence: 99%

“…For a rainfall rate of 200 cm∕h, a decrease in lift up to 30%, an increase in drag up to 25%, and decrease in stall angle of attack up to 6 deg were estimated. In the early 1980s, an experimental research program was established at NASA Langley Research Center to determine the heavy rain effects on the aerodynamic efficiency of NACA 64210, NACA 0012, and NACA 23015 airfoils [10][11][12][13][14]. The results of these programs indicated an increase in drag, decrease in lift, and earlier onset of the stall for the airfoils in heavy rain environment.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Study of Aerodynamic Efficiency of a Wing in Simulated Rain Environment

Ismail

Cao

et al. 2014

Journal of Aircraft

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In this study, heavy rain effects on the aerodynamic efficiency of a NACA 0012 wing with an aspect ratio of 2 have been anticipated at a Reynolds number of 2.2 × 10 6 . In the numerical simulation, the preprocessing software Gridgen has been used for creation of the geometry and generation of the mesh, and Fluent software is used as a solver. Discrete phase modeling in a Langrangian frame of reference has been used to simulate the rain particles dispersed in the continuous phase using a two-phase flow approach. The coupling between the two phases and its impact on both phases has been included. In this study, significant decrease in aerodynamic efficiency of the NACA 0012 threedimensional wing has been observed. The lift and lift to drag ratio decreased up to ∼15-18% for liquid water content of 30 and 39 g∕m 3 , respectively. The maximum decrease in lift has been observed for angle of attack of 6-14 deg, at which airplanes usually perform takeoff and landing. It is found that the heavy rain causes premature boundary-layer transition at low angle of attack and separation due to increase of shear stresses at high angle of attack. The water film layer formed on the surface of the wing and the splashed particles into the air are the main causes of the degradation in aerodynamic efficiency of the three-dimensional wing. The results obtained in the numerical study are compared with the experimental results, and they are in good agreement. This study will be useful for aviation engineers and scientists to design airplanes and unmanned aerial vehicles capable of flying in severe weather conditions.

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Section: Simulation and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical Study of Aerodynamic Efficiency of a Wing in Simulated Rain Environment

Ismail

Cao

et al. 2014

Journal of Aircraft

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“…In this paper, a thunderstorm heavy rain with N0=1400, n=3, and m=0.21 referred in Ref. 29 and R=1500 mm/h referred in Ref. 20 are selected as the simulated rain conditions.…”

Section: Theoretical Developmentmentioning

confidence: 99%

Helicopter flight dynamics with simulated rainfall

Cao

2022

Proceedings of the Institution of Mechanical Engineers, Part G:

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Sustaining flight operation that encounters with rainfall might be a challenge to a pilot due to lacking of understanding flight dynamics in the rain conditions. This paper, combined with a computational fluid dynamics (CFD) technique, develops a nonlinear flight dynamics model in the rain conditions that can be capable of exploring UH-60A single-rotor helicopter flight dynamics in the rain conditions, including trim, stability, and controllability. Firstly, in order to obtain a data-driven basis relating to multiple working conditions of the blades, a CFD-based method of simulation of the blade airfoil in the conditions of the angles of attack ranging from −26° to 26° and under a thunderstorm heavy rain scenario when the rate of rainfall is 1500 mm/h is developed. Then, these data are incorporated into a nonlinear flight dynamics model in the form of coefficient increments. Numerical simulations are conducted in the range of the flight velocities from 0 knots to 160 knots. The quantitative results indicate that rainfall degrades the blade airfoil aerodynamic performance and increases the rotor torque and required power, affecting the helicopter trim, stability, and controllability. More importantly, helicopter that flies in a small or moderate flight velocity and that encounters rainfall might be a relative serious case, which should be paid attention to.

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“…The mass reception rate is dependent on the liquid water content of the air, the free‐stream airspeed and the local collection efficiency. (3) The roughness change by raindrop impact and surface stress [3]. The effect of water on surface roughness includes three aspects.…”

Section: Introductionmentioning

confidence: 99%

Marking function of Stokes number on airfoils’ aerodynamic penalties in a gas–solid flow

Jin

Guo

et al. 2021

IET Renewable Power Gen

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This paper aims to employ the Stokes number to mark aerodynamic penalties of airfoils caused by particles, which is crucial to implement their scaling experiments in a gas‐solid flow. Each Stokes number is associated with a series of approximate aerodynamic penalties which are obtained at the same Reynolds number with different chord lengths. In the process, two phenomena which go against the mark are discussed and their mechanisms are revealed. The results show they occur at smaller and larger ranges of Stokes number, respectively. The effect of gravity is the leading cause and a larger chord length or diameter particle can strength its effect. The application scope of the mark, meanwhile, is ascertained. A chord length smaller than 1.5 m is advised at Re = 1.00 × 106 and those at other Reynolds numbers are also presented. As Stokes number decreases from 3, the aerodynamic penalty increases exponentially first at the advised chord length and reaches up to their peak values at the Stokes number of 0.050. In addition, the change of the aerodynamic penalty with Stokes number is dominated by the momentum exchange in the direction of gravity in the region between the particle injection plane and the airfoil.

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Wind tunnel test results of heavy rain effects on airfoil performance

Cited by 10 publications

References 2 publications

Numerical Study of Aerodynamic Efficiency of a Wing in Simulated Rain Environment

Numerical Study of Aerodynamic Efficiency of a Wing in Simulated Rain Environment

Helicopter flight dynamics with simulated rainfall

Marking function of Stokes number on airfoils’ aerodynamic penalties in a gas–solid flow

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