Abstract: A method for predicting if a flow over a smooth ramp surface will separate from the ramp surface, wherein the ramp surface has a slope that is everywhere non-positive along the length of the ramp surface relative to the flow at the inflow end of the ramp surface includes i) dividing the height of the ramp surface by the length of the ramp surface to determine a height-to-length ratio of the ramp surface, ii) identifying a maximum slope magnitude of the ramp surface, iii) calculating a maximum normalized slope by dividing the maximum slope magnitude of the ramp surface by the height-to-length ratio of the ramp surface, and calculating a critical ramp slope as a linear function of the height-to-length ratio of the ramp surface. If the maximum normalized slope is greater than the critical ramp slope, the method predicts the turbulent boundary layer will separate from the ramp surface.