The well-known "ion wind"induced by a dielectric barrier discharge plasma actuator (DBD-PA) has been extensively used as an active flow control device in the boundary layer. Developing an accurate and efficient model for plasma-induced body force becomes the linchpin of the computational studies of DBD-PA-based flow control; both phenomenological and first-principle approaches have been largely investigated in the literature. In this research, a charged-particle model named Drift-Diffusion (D-D) model is employed to compute the body-force fields with ultra-high temporal resolution in a range of alternating voltage (peak-to-peak) from 7 kV to 20 kV. The analytical Suzen-Huang (S-H) model as an economical approach is also applied for comparison. Large-eddy simulations are employed to investigate the relationship between the DBD-PA-induced flow in quiescent air and the DBD-PA-controlled flow field over a stalled airfoil. The significance of body-force unsteadiness is well understood in the two flow fields by the model comparison. The results based on D-D model show good agreement with the corresponding experiments in both quiescent and separated flow fields, where the induced flow structure and separation control effect are carefully checked, respectively. As to the S-H model, the almost same magnitude but different location of the maximum wall-parallel induced velocity results in the stronger induced flow in quiescent field; however, the similar control effects in the separated flow. The present research provides a new approach to study the effect of DBD-PA-induced flow on separation control using the high-fidelity body-force field directly without any parametric calibration.