An approach to turbulent incompressible separation under adverse pressure gradients

A separation criterion is developed, relating the maximum pressure-recovery ratio at separa- tion to the skin-friction coefficient at the start of the adverse gradient. This criterion shows very good agreement with six experimental points. A method of computing the skin fric- tion is also given, and it has been applied to three experimental runs; the agreement is good in two cases and poor in the third. The present theory indicates that separation will move upstream with increasing Reynolds number, therefore affecting the scaling procedures from model test to prototypes. The theory also indicates that inviscid pressure profiles must be considered in relation to the desired operational Reynolds number, since the effective pressure gradients and the pressure-recovery ratios will change. The theory is based on the assump- tions of dissipative-region similarity under any pressure gradient and of a constant total-head line at a fixed distance from the wall under adverse pressure gradients.