GATE 2021 AE – Question 25
Which statements about the Kutta condition are correct?
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Show answer and explanation
Correct answer: (A) It determines circulation around an airfoil.; (B) It applies to airfoils with a sharp trailing edge.; (D) The flow leaves the trailing edge smoothly.
Explanation
The **Kutta condition** fixes the circulation around a lifting airfoil in potential flow.
- **A. It determines the circulation.** True. Out of the infinite possible values, the Kutta condition selects the one for which the flow leaves the trailing edge smoothly. ✓
- **B. It applies to airfoils with a sharp trailing edge.** True. ✓
- **C. The trailing edge must always be a stagnation point.** False. For a cusped trailing edge the velocity is finite and non-zero, so it need not be a stagnation point (for a finite-angle trailing edge it is).
- **D. The flow leaves the trailing edge smoothly.** True. ✓
Answer **A, B and D**.