Vortical similarities across laminar and turbulent extreme gust encounters

Abstract

This study uncovers a striking similarity between massively separated laminar and turbulent flows that develop over a square wing during extreme vortex gust encounters. The evolving large-scale, vortical core structures responsible for significant transient lift variations exhibit remarkable similarity across Re = 600 and 10,000. The formation of these structures is attributed to a substantial gust-induced vorticity flux produced at the wing surface, resulting in shared large-scale topological features between the low- and high-Reynolds-number flows. Although fine-scale vortical structures quickly emerge in the Re = 10,000 case, the large-scale structures identified by scale decomposition of the turbulent flow resemble those observed at Re = 600. These findings suggest that large-scale vortical features present in laminar extreme aerodynamic flows provide key insights into their higher Reynolds number counterparts, potentially reducing the complexity of flow modeling and control for extreme aerodynamics.

Figures (7)

• Figure 1: (a) A square NACA0015 wing encountering a gust vortex. Q-criterion isosurface $Q=5$ is shown. (b) Computational domain and spatial discretization.
• Figure 2: (a) Lift history for the $G=2$ case at $Re=600$ (light red) and 10,000 (dark red). (b) Top-port view of the Q-criterion isosurface $Q=10$, colored in gray, at $\tau=\tau_1$ and $\tau_2$ noted in (a). The Q-criterion isosurface $Q=10$ of the large-scale structures extracted by the scale decomposition analysis with $\sigma/c=0.05$ in the $Re=$ 10,000 case is superposed in green.
• Figure 3: Same plot as figure \ref{['fig:fig2']} for the negative gust vortex case with $G=-2$.
• Figure 4: Spanwise slices of $C_p$ (color contours) with $\omega_z$ (line contours) along the root $z/c=0$ and near the tip $z/c=0.48$ at $\tau=\tau_1$ and $\tau_2$ for (a) $G=2$ and (b) $G=-2$. Dashed line contours indicate negative $\omega_z$.
• Figure 5: Spanwise slices of $L_e$ (color contours) with $\omega_z$ (line contours) at $Re=600$ and ${L_e}_{L,L}$ with $\widetilde{{\omega}}_{z_L}$ extracted with $\sigma/c=0.05$ in the $Re=$ 10,000 flow along the root $z/c=0$ and near the tip $z/c=0.48$ at $\tau=\tau_1$ and $\tau_2$ for (a) $G=2$ and (b) $G=-2$. Dashed contour lines indicate negative $\omega_z$ and $\widetilde{{\omega}}_{z_L}$.