Investigation of flow field of clap & fling motion using immersed boundary coupled lattice Boltzmann method

TL;DR

This study uses an immersed boundary coupled lattice Boltzmann method to analyze the flow dynamics of clap and fling motion, revealing key vortex interactions and aerodynamic performance at low Reynolds numbers.

Contribution

It introduces a computational approach combining immersed boundary and lattice Boltzmann methods to simulate clap and fling motion, providing new insights into vortex behavior and lift enhancement.

Findings

Low f, low J, high Re flow yields better aerodynamics

Leading edge vortices significantly enhance lift in unsteady regimes

Maximum lift coefficient decreases with increasing frequency, increases with Reynolds number

Abstract

This paper deals with the investigation of flow field due to clap and fling mechanism using immersed boundary coupled with lattice Boltzmann method. The lattice Boltzmann method (LBM), an alternative to Navier Stokes solver, is used because of its simplicity and computational efficiency in solving complex moving boundary problems. Benchmark problems are simulated to validate the code, which is then used for simulating flow over two elliptic wing of aspect ratio 5 performing clap and fling flapping motion for different flow parameters such as Reynolds number (Re = 75,100,150), advance ratio (J = 10E-3,10E-2,2) and frequency (f = 0.05Hz,0.25Hz). Numerical simulation is able to capture typical low Reynolds number unsteady phenomena such as, 'wake vortex wing interaction', 'Kramer effect' and 'delayed stall'. The results are both qualitatively and quantitatively consistent with experimental observation. The parametric study involving different combinations of Re, f and J depict distinctly different aerodynamic performances providing physical insights into the flow physics. It is observed that a combination of low f, low J and high Re flow results in better aerodynamic performance. Pronounced lift enhancement via leading edge vortices are obtained in unsteady regime (J<1) compared to quasi-steady regime (J>1). The role of leading edge vortices in enhancing lift are investigated by studying the size and strength of these vortices for different flow conditions. For a given Re, the magnitude of maximum lift coefficient decreases with increasing f irrespective of the value of J; while the same is enhanced with the increasing Re.