Two-Dimensional Wind Tunnel Tests of a Transport-Type Airfoil in a Water Spray

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

doi:10.2514/6.1985-258

Cited by 19 publications

(20 citation statements)

References 3 publications

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“…The observed rivulet formation in the tests reported by Hansman and Barsotti 9 and Dunham et al 7 has been extensively studied in the literature. The most complete analysis of the breakdown of a film driven by external shear was given by Mikielewicz and Moszynski.…”

Section: N(d)v T (D)ddmentioning

confidence: 90%

“…The angles from the horizon at which the rain approaches the airfoil at full and subscale are 8.7 and 4.4 deg, respectively, assuming a 60 m/s landing speed. Figure 4 schematically illustrates the geometrically determined impact areas for the slat/flap airfoil tested at zero angle of attack by Dunham et al 7 It is not known at this time if any dynamic significance is to be associated with these differences, but rainfall scaling distortions can be investigated quantitatively at subscale by tipping the spray nozzles downward while holding the angle of attack constant. The remaining two TT parameters, angle of attack and density ratio, are matched at subscale and are not discussed further.…”

Section: D= ( D 4 N(d)dd/{ D 3 N(d)dd =--mentioning

confidence: 98%

“…Since both Weber and Reynolds number scaling may not be possible at subscale, boundarylayer and drop and film water layer dynamics could be distorted at subscale. Based on simple analytic models and evaluation of the 1 A-scale tests reported by Dunham et al, 7 it is anticipated that the extrapolation of 1 A -scale results to full scale will overestimate the anticipated performance penalties. Additional testing and analysis is strongly warranted to quantify the performance penalty when operating under heavy-rain conditions.…”

Section: Conclusion and Recommendationsmentioning

confidence: 99%

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Scaling laws for testing airfoils under heavy rainfall

Bilanin

1987

Journal of Aircraft

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Subscale test data have shown that airfoils operating in a simulated heavy-rain environment can experience significant performance penalties. The physical mechanism resulting in this performance penalty has yet to be conclusively identified. Therefore, the extrapolation of subscale data to full-scale conditions must be undertaken with extreme caution since complete scaling laws are unknown. This paper discusses some of the technical issues that must be addressed and resolved prior to extrapolating the performance of full-scale airfoils from subscale test data. A set of scaling laws is suggested based on the neglect of thermodynamic interactions between the droplets and the air/water vapor phase.heat at constant volume D =drop diameter hj g = latent heat of vaporization of water £ = mean distance between droplets m = mass M =Mach number n(D) = raindrop size spectrum n 0 =8xl0 3 m-3 mm-1 =« 0/5 N = aerodynamic force ND = droplet number density p = pressure R = rainfall rate, mm/h, or gas constant T = temperature Uj = velocity vector U x = flight speed V = volume or droplet impact velocity V T = drop terminal velocity W L = liquid water content, g/m 3 We = Weber number x,y,z = Cartesian coordinate system a. = angle of attack 13 = impact angle 7 = ratio of specific heat 0 = contact angle A = reciprocal of rain spectrum scale JJL = absolute viscosity u = kinematic viscosity p = density o = surface tension r = shear stress $ = velocity potential Subscripts a fs ss s V w = air = full scale = subscale = solid = vapor = water Presented as Paper 85-0257 at

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Section: N(d)v T (D)ddmentioning

confidence: 90%

Section: D= ( D 4 N(d)dd/{ D 3 N(d)dd =--mentioning

confidence: 98%

Section: Conclusion and Recommendationsmentioning

confidence: 99%

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Scaling laws for testing airfoils under heavy rainfall

Bilanin

1987

Journal of Aircraft

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“…Recent studies by Haines and Luers, 1 Hansman and Barsotti, 2 and Dunham et al 3 have shown that rain causes significant reduction in maximum lift coefficient and generally alters stall characteristics. These results appear to be essentially due to the introduction of an effective surface roughness by the rain.…”

Section: Introductionmentioning

confidence: 98%

“…3 Because water spray experiments do not generally simulate the drop size distribution present in natural rain, the LWC is preferred over a rainfall rate specification to denote the intensity of rain at the wing. However, an equivalent rainfall rate is often included which indicates what the natural rainfall rate would be for the given LWC.…”

Section: Introductionmentioning

confidence: 99%

Rain effects at low Reynolds number

Marchman

Robertson

Emsley

1987

Journal of Aircraft

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Wind-tunnel tests were conducted to determine the influence of rain on the aerodynamic performance of the Wortmann FX63-137 wing at Reynolds numbers 100,000-300,000. Models with aspect ratios of 6 and 4 were tested with normal as well as waxed and soaped surfaces to evaluate wettability effects. Test results showed an improvement of performance at the lowest Reynolds number but general deterioration at higher speeds. The primary effect noted was a decrease in lift at higher angles of attack. A favorable result was the elimination of stall hysteresis, which characterizes the Wortmann's normal performance at low Reynolds numbers. At lower Reynolds numbers, rain appeared to lower drag whereas, at higher speeds, drag generally increased.

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