Finite difference (FD) methods in mess-free discretization can be used for wave equation simulation in flexible computational domains, avoiding complex mesh generation. But artificial reflections from model boundaries are more complex and the near-gazing incident waves still exist. The complex frequency shifted perfectly matched layer (CFS-PML) has been demonstrated the absorption effectiveness in regular grids, especially for absorbing near-gazing incident waves. In mess-free discretization, we propose the unsplit CFS-PML method for piecewise smooth curved boundary based on an auxiliary differential equation (ADE) scheme. Scattered nodes in the objective zone is placed suitably with respect to irregular boundaries or model parameters without coordinate transformation, while nodes in absorbing zone is expanded straightforwardly based on sampled boundary nodes and their corresponding outward normal directions. It is important that the boundaries have arbitrary normal directions, which decide the attenuated directions of waves in absorbing zone. Finally, the numerical results indicate the effectiveness of our proposed method.


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