The paper analyses the double pendulum motion in the vertical plane interacting with the fluid (air or water) flow. The pendulum consists of two plates, fastened together with each other and with the foundation by the axes. The case was investigated where the fluid flows in a horizontal direction but the plates move around the pivots in the vertical plane. It is assumed that there is a laminar fluid flow. Double pendulum interaction with the flow is described as localized particles interaction with the plates, using the mass centre and angular momentum exchange theorems of mechanical systems. A system with two degrees of freedom is investigated. Interaction with fluid is approximated by a square step dependence on the flow relative velocity taking into account the direction of motion. The resulting system of equations is used to simulate the motion. The three cases of motion are analysed: free oscillations against a stationary fluid to determine experimentally all physical parameters of the interaction; auto vibration motion at a constant flow velocity; time variable flow induced oscillations. Some interesting results of the plate motion graphics are given.