In this paper, the movement of a gas-fluid flow in a plane channel with an oscillating wall was investigated. The aim of the research is to increase the efficiency of separation equipment by imposing the vibration impact on a gas-liquid flow. This purpose was achieved by applying the phenomenon of selective coagulation of a dropping liquid. The novelty of the proposed approach concerns creating the mathematical model for determination of analytical dependences between the efficiency of the hydromechanical process and initial parameters of the separation device. As a result, quantitatively and qualitatively sufficient approximations for the scalar pressure and vector velocity fields were obtained with a permissible relative error in comparison with the results of numerical simulation. The presence of biharmonic fluctuation of particles was proved; besides, related dependencies for the calculation of vibration characteristics were obtained. Additionally, the paper presents the dependencies for identifying a range of thickness for a near-wall area. The system of dimensionless criteria was proposed for determining flow modes and relative trajectories of liquid droplets in a gas-fluid flow. The numerical simulation approach and related methodology of engineering calculations were proposed on the example of a plane channel of the separation device. Finally, the distance between adjacent zones of the pressure minimum was determined. As a result, it was found that this distance is equal to the wavelength of the vibrating impact to the flow that is an initial justification of further coagulation process of liquid droplets in a gas-liquid flow in a separation device.