Quantification of the boundary layer on a tripped generic submarine sail

Abstract: Boundary-layer transition to separation over the appendages of a submarine can affect manoeuvrability and drag. It is of interest to stimulate the boundary layer in model-scale testing so that it is more representative of the turbulent state at full scale. This paper explores the effect of Hama trips on boundary-layer transition by using a NACA0021 profile which matches the sail geometry of a generic benchmark submarine known as the BB2. The boundary layer is measured by a Pitot tube and flow transition is assessed by infrared thermography. Key results show that, with a suitable trip height and location, the fully turbulent boundary layer yields a reasonable collapse over a range of chord-length Reynolds numbers. The effectiveness of two different trip heights is presented in the form of a performance chart for Reynolds number vs trip location. Keywords: boundary layer, wind tunnel, infrared thermography