Friction drag resulting from the simultaneous imposed motions of a freestream and its bounding surface

The validity of the so-called relative-velocity model was investigated. In that model, the relative velocity between the two media is used in conjunction with the drag-force formula for the dominant of the two motions acting alone. The results of exact solutions demonstrate that this model is flawed and underpredicts the drag force. Finally, a new model, termed the similarity-based, relative-velocity model was devised by which exact similarity solutions were obtained. The drag results provided by this model may be considered to be the definitive information for application.