Coupled dynamic and thermal simulation of airfoil flap movement in turbulent flow using the lattice Boltzmann method
Authors: Saffarzadeh Hamed , Djavareshkian Mohammad Hassan 
Published: November 2023

The study introduces an innovative approach that combines dynamic and thermal lattice Boltzmann simulations utilizing the ghost fluid boundary detection method for enhanced flow stability during flapping oscillation. This novel methodology is applied to large-eddy simulations of a flapping airfoil, aiming to capture the complex dynamics of oscillatory vortices and their impact on aerodynamics, while also allowing control over aerodynamic responses through airfoil surface temperature modulation. The investigation involves integrating the ghost fluid method into the lattice Boltzmann framework, synchronized with each time step to accurately model both the airfoil's oscillatory and boundary-induced movements. The advancement of specific fluid domain nodes due to boundary motion is managed using a recharging and force imposition scheme, estimating energy, and density function distributions on these nodes. Variations in lift and drag coefficients resulting from dynamic viscosity changes and thermal effects are observed due to airfoil surface temperature adjustments. A nonreflecting boundary condition is introduced to regulate flow velocity upper and lower near the domain boundary, facilitating smooth flow transfer from the boundary to the oscillating airfoil flow and minimizing transverse interference. Changes in energy exchange lead to delayed boundary layer separation, suggesting enhanced performance with reduced airfoil temperature. It is shown that decreasing the airfoil temperature by 100 K compared to the fluid temperature reduces the drag coefficient by 34% and increases the lift coefficient by 14%, while with an increase in 100°, the drag coefficient increases by 14.9% and the lift coefficient decreases by 4%. The proposed approach offers computational simplicity, concise solvable equations, and high accuracy, eliminating the need for mesh size adjustments when simulating different Reynolds numbers. Additionally, its ability to accommodate heat transfer-induced alterations within the aerodynamic context is highlighted. Comparative analysis with the finite volume method validates its effectiveness, demonstrating potential applications for controlling aerodynamic coefficients through controlled thermal interventions. In conclusion, the study presents a comprehensive methodology that integrates dynamic and thermal lattice Boltzmann simulations with the ghost fluid boundary detection method for enhanced flow stability during flapping oscillation. The insights gained contribute to a deeper understanding of complex aerodynamic phenomena, with implications for aerospace and fluid dynamics research, where accurate prediction and control of airfoil behavior are crucial. In summary, this study offers a groundbreaking strategy that seamlessly integrates dynamic and thermal lattice Boltzmann simulations, leveraging the ghost fluid boundary detection method for enhanced stability in flapping oscillatory motion. The outcomes contribute to a deeper understanding of intricate aerodynamic phenomena, thus holding promise for broader applications in aerospace and fluid dynamics research.