What is a consequence of shock-induced boundary layer separation?

What is a consequence of shock-induced boundary layer separation?

• A. It decreases drag and reduces buffet.
• B. It increases lift on the wing at all speeds.
• C. It increases drag and can cause flow unsteadiness or buffet.
• D. It has no impact on stall behavior.

Answer: (C)

When a wing operates near transonic speeds, a shock forms on the surface and pushes a strong adverse pressure gradient into the boundary layer. If the boundary layer can’t stay attached, it separates behind the shock. That separation creates a wake-like region with disrupted flow, so the wing’s lift effectiveness drops and the flow cannot follow the surface smoothly. The separated flow also causes a large pressure difference around the wing and a big rise in form (pressure) drag. Moreover, the interaction between the shock and the separated flow can be unstable, so the shock position and the separation region can oscillate, producing flow unsteadiness or buffeting. All of this aligns with the described consequence: increased drag and potential flow unsteadiness or buffet. This is not a scenario where lift reliably increases at all speeds, and it does affect stall behavior rather than being inconsequential.

When a wing operates near transonic speeds, a shock forms on the surface and pushes a strong adverse pressure gradient into the boundary layer. If the boundary layer can’t stay attached, it separates behind the shock. That separation creates a wake-like region with disrupted flow, so the wing’s lift effectiveness drops and the flow cannot follow the surface smoothly. The separated flow also causes a large pressure difference around the wing and a big rise in form (pressure) drag. Moreover, the interaction between the shock and the separated flow can be unstable, so the shock position and the separation region can oscillate, producing flow unsteadiness or buffeting. All of this aligns with the described consequence: increased drag and potential flow unsteadiness or buffet. This is not a scenario where lift reliably increases at all speeds, and it does affect stall behavior rather than being inconsequential.