Generation of an isolated vortex gust through a heaving and pitching foil

Abstract

This study introduces a vortex gust generation method for isolated vortices impacting a downstream airfoil that is applicable to both numerical simulations and experiments. The vortex gust is generated by a symmetric airfoil undergoing a rapid pitching maneuver during a prescribed heaving motion. The resulting vortices propagate along trajectories nearly parallel to the incoming flow, while the associated wake extends obliquely from the vortex core. Despite differences in Reynolds number, rapid pitching duration and detailed vortex structure between simulations and experiments, consistent trends are observed in how the vortex rotation orientation, strength, and position vary with the prescribed motion parameters. Analysis of the lift response of the downstream airfoil shows that the aerodynamic influence associated with the wake does not persist over extended time scales. These results demonstrate that the proposed method enables the controlled generation of vortex gusts with prescribed characteristics, providing a flexible approach for systematic studies of vortex-airfoil interaction.

Figures (12)

• Figure 1: Schematic of the airfoil geometry and vortex-gust generation setup. The upstream airfoil undergoes prescribed heaving and pitching motions to generate vortex gusts, while a stationary downstream airfoil is positioned $5c$ downstream. Flume walls are present only in the experimental configuration.
• Figure 2: Foil kinematics during the vortex-generation maneuver. (a) Foil position colored according to the profiles shown in (b). (b) Kinematic profiles, with timing and geometric parameters defined in Eqs. \ref{['eqn:vortex_profile_theta']} and \ref{['eqn:vortex_profile_alpha']}. Also shown are $T_\mathrm{total}$ and $T_\mathrm{v}$ from Eq. \ref{['eqn:tauv']}.
• Figure 3: Computational mesh layout used in the numerical simulations. (a) Overall computational domain. (b) Intermediate region where unstructured cells connect the near-airfoil meshes to the outer structured grid. (c) Body-fitted structured mesh near the upstream airfoil.
• Figure 4: Experimental setup. The upstream symmetric airfoil serves as the vortex generator and is mounted on a traverse system. Two cameras arranged in a side-by-side configuration acquire PIV measurements in the measurement plane. A stationary downstream airfoil is positioned to measure the forces induced by the incoming vortex gust.
• Figure 5: Time evolution of vorticity contours during the formation of counter-clockwise and clockwise vortices. Simulation results are shown for cases S06_CCW (panels a--d) and S01_CW (e--h), and experimental results for cases E06_CCW (i--l) and E01_CW (m--p).