This paper presents a hydraulic analysis of a fluid coupling which is designed to operate either in a forward or reverse mode when a set of turning vanes are respectively withdrawn or inserted into the flow between the driving and driven rotors. The flow path is subdivided into a set of streamtubes and an interative method is used to adjust the cross-sectional areas of these streamtubes in order to satisfy radial equilibrium. Though the analyis requires the estimation of a number of loss coefficients, it predicts coupling performance data which are in good agreement with that measured in NAVSSES tests of a large reversible coupling intended for use in a ship drive train
