Numerical simulation of flow over an airfoil in heavy rain

Numerical simulation of flow over an airfoil in heavy rain via a two-way coupled Eulerian–Lagrangian approach

Highlights

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A new two-way momentum coupled Eulerian–Lagrangian approach is developed.

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Scaling laws are implemented for raindrop particles.

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A random walk dispersion approach is adopted.

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Raindrop impacts, splash-back and formed water film are modelled.

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Airfoil aerodynamic performance degradation in heavy rain is studied.

Abstract

Airfoil performance degradation in heavy rain has attracted many aeronautical researchers’ eyes. In this work, a two-way momentum coupled Eulerian–Lagrangian approach is developed to study the aerodynamic performance of a NACA 0012 airfoil in heavy rain environment. Scaling laws are implemented for raindrop particles. A random walk dispersion approach is adopted to simulate raindrop dispersion due to turbulence in the airflow. Raindrop impacts, splash-back and formed water film are modelled with the use of a thin liquid film model. The steady-state incompressible air flow field and the raindrop trajectory are calculated alternately through a curvilinear body-fitted grid surrounding the airfoil by incorporating an inter-phase momentum coupling term. Our simulation results of aerodynamic force coefficients agree well with the experimental results and show significant aerodynamic penalties at low angles of attack for the airfoil in heavy rain. An about 3° rain-induced increase in stall angle of attack is predicted. The loss of boundary momentum by raindrop splash-back and the effective roughening of the airfoil surface due to an uneven water film are testified to account for the degradation of airfoil aerodynamic efficiency in heavy rain environment.

Keywords

• Multiphase flow; 
• Eulerian–Lagrangian; 
• Airfoil; 
• Heavy rain; 
• Water film; 
• Aerodynamic degradation.