Numerical simulation of the effect of rain on aerodynamic performance and aeroacoustic mechanism of an airfoil via a two
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Numerical simulation of the effect of rain on aerodynamic performance and aeroacoustic mechanism of an airfoil via a two‑phase flow approach Hossein Fatahian1 · Hesamoddin Salarian1 · Majid Eshagh Nimvari2 · Jahanfar Khaleghinia1 Received: 16 January 2020 / Accepted: 2 April 2020 / Published online: 9 April 2020 © Springer Nature Switzerland AG 2020
Abstract In the present study, two complex physical phenomena have been completely simulated and discussed in detail to predict the aerodynamic degradation and aeroacoustic mechanism of a NACA 0012 airfoil in both dry and heavy rain conditions. For this purpose, a CFD-based multiphase model was adopted to numerically investigate the process of formation of the water film layer on the airfoil surface by coupling the Lagrangian Discrete Phase Model (DPM) and the Eulerian Volume of Fluid (VOF) models. The Ffowcs Williams–Hawkings (FW–H) method was used to predict the aerodynamic noise of the airfoil in a heavy rain condition. The results showed that there were significant degradations of the airfoil aerodynamic performance because of water film formation especially at lower angles of attack. The maximum value of lift-to-drag ratio degradation was 56% at the angle of attack of 2°. Also, the Sound Pressure Level (SPL) increased due to the rain condition. The SPL was sensitive to the raindrop impact on airfoil surface and caused to increase SPL especially in the frequency region less than 2000 Hz. By increasing the angle of attack, the SPL increased especially in the high-frequency region higher than 2500 Hz in rain condition. Keywords Eulerian–lagrangian · Heavy rain · Aerodynamic degradation · Aeroacoustic · Sound pressure level (SPL) Nomenclature μ Air dynamic viscosity c Airfoil chord length α Angle of attack ρD Density of droplets ρ Density of fluid phase Y+ Dimensionless wall distance δ(f ) Dirac delta function ε Dissipation rate CD Drag coefficient β Drag force μT Eddy viscosity un Flow velocity normal to the surface (f = 0) ui Fluid phase velocity in i direction gi Gravitational acceleration H(f ) Heaviside function
Eim Impact energy CL Lift coefficient Mex Momentum exchange NACA National Advisory Committee for Aeronautics up Parcel phase velocity in i direction P Pressure Re Reynolds number Cf Skin friction coefficient σw Surface tension of water vn Surface velocity component normal to the surface vi Surface velocity in i direction UT Terminal velocity p′ The far-field sound pressure Tij The Lighthill tensor α0 The sound velocity in the far-field
* Hossein Fatahian, [email protected] | 1Department of Mechanical Engineering, Nour Branch, Islamic Azad University, Nour, Iran. 2Faculty of Engineering, Amol University of Special Modern Technologies, Amol, Iran. SN Applied Sciences (2020) 2:867 | https://doi.org/10.1007/s42452-020-2685-4
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Research Article
SN Applied Sciences (2020) 2:867 | https://doi.org/10.1007/s42452-020-2685-4
δbl Thickness of the boundary layer t Time k Turbulent kinetic energy
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