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Linyuan Che

Publications and source records attributed to Linyuan Che.

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Unsteady flow predictions around an obstacle using Geometry-Parameterized Dual-Encoder Physics-Informed Neural Network

Machine learning-based flow field prediction is emerging as a promising alternative to traditional Computational Fluid Dynamics, offering significant computational efficiency advantage. In this work, we propose the Geometry-Parameterized Dual-Encoder Physics-Informed Neural Network (GP-DE-PINN) with a dual-encoder architecture for effective prediction of unsteady flow fields around parameterized geometries. This framework integrates a geometric parameter encoder to map low-dimensional shape parameters to high-dimensional latent features, coupled with a spatiotemporal coordinate encoder, and is trained under the Navier-Stokes equation constraints. Using 2D unsteady flow past petal-shaped cylinders as an example, we evaluate the model's reconstruction performance, generalization capability, and hyperparameter sensitivity. Results demonstrate that the GP-DE-PINN significantly outperforms the PINN with direct geometric input in flow field reconstruction, accurately capturing vortex shedding structures and pressure evolution, while exhibiting superior generalization accuracy on unseen geometric configurations. Furthermore, sensitivity analyses regarding geometric sampling and network width reveal the model's robustness to these hyperparameter variations. These findings illustrate that the proposed framework can serve as a robust and promising framework for predicting unsteady flows around complex geometric obstacles.

physics.flu-dyn

Sequential water wave reconstruction in VOF-based numerical wave tanks with the EnKF approach

Existing phase-resolved wave reconstruction methods are mostly based on potential flow theory, which limits their ability to capture strongly nonlinear phenomena such as wave breaking dynamics. In such cases, the importance of multiphase incompressible Navier--Stokes solvers becomes particularly evident. These solvers form the foundation of the widely used numerical wave tanks in marine, ocean, and coastal engineering. However, the high dimensionality of the state variables in such systems often hinders the efficiency of data assimilation. The POD method is applied to reduce the order of the state vector in ensemble-based data assimilation, where instantaneous snapshots are naturally available. Given the unsteady nature and random phase combinations of irregular waves, the effectiveness of single data assimilation is limited. Sequential data assimilation is thus adopted to continuously update the wave profile as it evolves, ensuring that the wave field matches the real-world conditions. Therefore, inflation is needed to mitigate the ensemble collapse. Unlike single-phase flows without any interface, where the background error covariance can be inflated directly, to preserve physical constraints, when inflating for the phase field, the velocity field is simultaneously updated by incorporating potential flow formulas. Three representative cases-regular waves, irregular waves, and plunging waves-are used to validate the proposed method and assess its performance. The effect of assimilation parameters is also examined. The results demonstrate that the sequential data assimilation strategy achieves accurate free-surface reconstruction for a VOF-based numerical wave tank.

physics.flu-dyn