Transom Flow Elevations in the Partially Ventilated Condition

Predicting separation from a transom stern presents a problem for potential flow calculations. As the vessel speed increases, the transom flow elevation progressively deviates from the static condition. In the absence of viscosity, potential theory is not able to adequately capture this process. Without a priori information regarding the transom flow elevation, potential flow calculations either under or over-predict the resistance. The under-prediction results from placement of the wake sheet at the static condition waterline, and over-prediction results from placement of the wake sheet at the transom/keel intersection (the fully ventilated condition). This paper expands the investigation of transom flow elevations by experimentally measuring the deflection of the flow from the static condition for five different transom configurations ranging from round bilge to deep-vee sections. The models use a common forebody of the vessel. The models were effectively fixed in sinkage and trim. High definition video was used to capture the flow elevations for a range of speeds. This paper presents the findings in terms of the transom Froude number and ventilation factors, and makes comparisons to prior empirical equations. Model data is also provided.