Flow Patterns
•Inlet area often chosen to minimize external acceleration during takeoff •So that external deceleration occurs during level-cruise operation
•External deceleration requires less internal pressure rise •Hence, less severe loading of the boundary layer
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External acceleration raises the inlet velocity and lowers the inlet pressure thereby increasing the internal pressure rise across the diffuser.  If this pressure increase is too large, the diffuser may stall because of boundary layer separation.  Stalling usually reduces the stagnation pressure of the stream as a whole.