arXiv subjects

Bingfei Yan

Publications and source records attributed to Bingfei Yan.

3 recordsLinked to original sources

arXiv2026

Onset of Radiatively Driven Convection in Ice-Covered Freshwater Lakes

This work investigates the formation and growth of Rayleigh-Taylor instabilities (RTIs) during the onset of radiatively driven convection (RDC) in seasonally ice-covered freshwater lakes. Two-dimensional direct numerical simulations (DNS) and linear analysis allow for the investigation of how environmental factors, including thermal stratification, water clarity, and solar forcing influence RTI formation. It is found that for strongly stratified lakes, there is a period of dormancy before the water column forms a gravitationally unstable layer that allows RTI growth. Conversely, for weakly stratified lakes the water column can become unstable almost immediately, allowing for rapid RTI growth. A linear analysis is performed to investigate the early RTI growth dynamics, and its results compare well with DNS. Notably, the wavelengths and depths of RTIs, and their associated time-dependent growth rates, are all captured by the linearised dynamics. Predictions of RDC onset obtained using the linear model show good agreement with DNS results. When the analysis is applied to field measurements of ice-covered lakes, it is found that weakly stratified lakes may take a few hours before RDC onset whereas strongly stratified lakes may not see RDC onset after a full day of clear-sky spring conditions.

physics.flu-dyn↗

arXiv2026

Vortex gust interactions with a freely-flying rigid airfoil

This study numerically investigates the interaction between an isolated vortex gust and a freely-flying airfoil, introducing a theoretical framework for interpreting the coupled lift and heave response. This complex and coupled dynamics is important for modern light-weight aircraft where gusts may easily perturb the wing, generating transient changes in trajectory and attitude. Here, the freely-flying airfoil is modeled with a single degree-of-freedom in heave, and is impacted by an isolated vortex gust generated upstream. Computational results demonstrate that the freely-flying airfoil reaches a maximum heave displacement after vortex impingement and subsequently rebounds with a comparable magnitude. The lift coefficient is then modeled by augmenting the lift from a corresponding stationary airfoil interaction with motion induced contributions associated with the induced angle of attack and added-mass. A comparison of the modeled lift with the simulation data confirms that the dynamics of the airfoil before impingement is dominated by these two terms, however the rebound after impingement is only partially explained by the model since it is also influenced by the gust-induced vortex shedding. Comparisons across various parameters show that the pre-impingement motion depends primarily on vortex rotation direction, whereas the post-impingement and induced shedding patterns vary with respect to angle of attack and vortex transverse position. With the lift coefficient of the corresponding stationary airfoil interaction as an input, the model can successfully predict the heave trajectory, thus providing a mechanism to assess the dynamic motion of an airfoil from experimental/computational data of gusts interacting with fixed airfoils.

physics.flu-dyn↗

arXiv2026

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

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.

physics.flu-dyn↗