Bistable flow dynamics of airfoil stall under varying angle of attack: A stochastic model with multiplicative noise

TL;DR

This paper introduces a stochastic model using a Langevin equation to capture the bistable flow dynamics of an airfoil during stall, accounting for varying angles of attack and reproducing key flow features.

Contribution

It presents a novel one-dimensional stochastic model with state-dependent noise that accurately captures flow bistability and bifurcations in airfoil stall dynamics.

Findings

Model reproduces the S-shaped lift curve.

Predicts flow bifurcations with changing angle of attack.

Aligns with observed flow statistics and dynamics.

Abstract

We focus on the intermittent bistable stall dynamics of an airfoil under varying angle of attack. We propose a one-dimensional Langevin equation where the stochastic forcing depends on the state of the system -- high-lift attached flow or low-lift detached flow -- and where the deterministic potential depends continuously on the angle of attack. The model, identified based on the flow statistics and dynamics, reproduces the S-shaped lift curve, as well as the flow dynamics. It also predicts the nature of the bifurcations that the flow undergoes as the angle of attack varies.