A numerical wave flume is developed to simulate the hydrodynamic resonance in a narrow gap formed between twin bodies of identical dimensions. The numerical wave flume is based on the Navier-Stokes equations and CLEAR-Volume of Fluid method in the frame of Finite Element Method. Comparisons of the present numerical results and the experimental data available in literature show that the present numerical wave flume works well in predicting the well-known hydrodynamic resonance in narrow gaps. It is found that the amplitudes of the free surface oscillations in the narrow gap are not as large as those predicted by the potential theory and are rather limited. The influence of non-dimensional incident wave frequency on the resonance is examined using the numerical wave flume.