This paper presents a computationally efficient actuator line-based CFD approach for simulations of diffuser-augmented wind turbines (DAWTs) using the OpenFOAM framework. A pressure-based actuator line model is applied to both the rotor and the diffuser, enabling accurate representation of rotor–diffuser interaction without explicitly resolving the diffuser geometry. Numerical simulation results demonstrate that the proposed framework accurately predicts DAWT performance and captures diffuser-induced flow acceleration and pressure redistribution. The method provides a computationally efficient and physically consistent tool for engineering-oriented DAWT analysis, parametric studies, and design optimization.