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Keywords
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Aerodynamic performance, Airfoil, Flow separation, Leading-edge slat, Rainy conditions
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Abstract
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This study investigated the effects of rainfall on flow separation and the aerodynamic performance of single elementandslattedNACA0012airfoilsbyusingamathematicalmodel
developedwiththe commercialcomputationalfluiddynamicssolverANSYSFLUENT18.2.
Atwo-way momentumcoupled Eulerian–Lagrangianmultiphaseapproach wasusedto
simulate the formation ofthe waterfilmlayer onthe airfoil’ssurface. Accordingto the
results, verylow valuesofthe lift-to-drag ratio atlow anglesofattackreflected severe
degradationofthe aerodynamicperformanceofthe airfoilin the presenceofwateraccu-mulatedonits surface. Theimpact ofrain dropletsonthe leading-edge slat surface led
to less wateraccumulatingonthe mainsectionofthe airfoil.In particular,the maximum
waterfilmmassconcentratedonthe airfoilsurfacedecreasedfrom 15gto 1gcompared
withthe singleelementairfoil.Hence,the thickness ofthe waterfilmlayer wasnotsuf-ficientlylarge to significantlyaffectthe aerodynamiccoefficientsofthe slattedairfoil,es-peciallythe maximumlift coefficient,comparedwiththe thicker waterfilmlayer onthe
singleelementairfoil.In addition,the useofslatsclearlyenhancedthe aerodynamicco-efficientsandincreased the stallanglefrom 13°to 22°in dryconditions,andfrom 16°to
24°in rainyconditions.Slatsalsosignificantlydecreasedtheboundarylayer thicknessand
delayedthe separationathigheranglesofattack.
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