The main objective of the present study is to propose a numerical scheme to model irregular wave systems through a Lagrangian, particle-based numerical method, namely, Smoothed Particle Hydrodynamics (SPH). A numerical wave generator tank, which can generate desired irregular waves is modeled by the SPH method. The fluid motion is governed by continuity and Navier-Stokes equations where Weakly Compressible SPH (WCSPH) approximation is employed for the numerical discretization of the problem domain. To generate the irregular wave spectrum, a flap-type wave generator is adopted into the computational domain which yields to the modeling of moving boundary conditions on the problem domain. As benchmark studies, JONSWAP and Pierson-Moskowitz wave spectrums are simulated to validate the obtained wave characteristics with the theoretical results. The performances of the wave maker are tested under different peak wave frequency values. Fast Fourier Transformation (FFT) analysis is conducted to scrutinize the distribution of wave energy spectrum in the frequency domain. In the light of sufficiently long-term simulation results, it can be said that a good agreement is obtained between the numerical and theoretical results, which indicates that the presented SPH scheme can be utilized in further free-surface hydrodynamics studies related to the irregular wave regimes
