Evaluation of closed cracks is the most serious issue for safety of important structures such as power plants or air planes. To overcome the problem, subharmonics in nonlinear ultrasound is particularly useful because of the excellent selectivity for closed cracks and high temporal resolution, which has been verified by the subharmonic phased array for crack evaluation (SPACE), developed by the authors. In this study, we propose the first two dimensional (2D) model to reproduce subharmonic generation at closed cracks using damped double nodes (DDN). Numerical simulation using finite difference time domain (FDTD) method was performed using DDN and time frequency analysis was performed based on the wavelet analysis. The results were able to reproduce essential features observed in the experiments.