Generation of underwater object motion by internal interactions

Abstract. The paper analyses the closed frame object translated motion in the horizontal directions interacting with the fluid (air or water). The object consists of two rigid bodies, fastened together with each other by a spring. The first small body is located inside the large second body, which is isolated from the fluid. As a motion generator internal harmonica or adaptive force control is used. The case is investigated where internal interactions can be with collisions. External interaction of the second body with the fluid flow is nonlinear like absolute velocity in square. Additionally, different drag coefficients are used, depending on the velocity direction of the large body. It is assumed that there is a laminar fluid flow. A system with two or three degrees of freedom is investigated. Interaction with fluids is approximated by a square resistance force dependence on the flow relative velocity taking into account the direction of motion. The resulting system of equations is used to simulate the motion by two programs: Mathcad and Working Model 2D. The three tasks of motion are analysed: – motion with harmonica internal interaction by Mathcad; – motion with adaptive internal interaction by Mathcad; – motion with harmonica internal interaction by Working Model 2D. Some results of the object part motion graphics are given. The main conclusion of the given results is that it is possible to generate closed object motion inside fluid by motion control of another internal body. The results of the investigations can be used for synthesis of new propulsion systems.