Question

Cusped airfoil is

• A. Stagnation point at trailing edge
• B. Unsymmetrical airfoil with more camber
• C. Upper and lower surfaces are parallel at trailing edge
• D. Blunt trailing edge

Hint:

A cusped trailing edge satisfies the Kutta condition and allows the flow to leave the trailing edge smoothly. \[ \boxed{ \text{Cusped airfoil} \Longrightarrow \text{Upper and lower surfaces are parallel at the trailing edge.} } \]

Answer 1

The Correct Option is C

Step 1: Recall the definition of a cusped airfoil. A cusped airfoil has a sharp trailing edge where the upper and lower surfaces meet smoothly. At the trailing edge, \[ \boxed{\text{the upper and lower surfaces are parallel.}} \]

Step 2: Identify the correct statement. Since the surfaces become tangent to each other at the trailing edge, \[ \boxed{\text{Upper and lower surfaces are parallel at the trailing edge}} \] is the defining characteristic of a cusped airfoil. Hence, \[ \boxed{(C)} \] is the correct answer.