A lifting surface has a spanwise circulation distribution of Ī(š) = A sin 3š (where
A ā 0) over its span -
b
2 ā¤ y ā¤
b
2, and y = -
b
2 cos š is the spanwise coordinate.
Furthermore, the downwash varies along the span as w(š) = Vā (
3A sin 3š
sin š ), where
Vā is the freestream velocity. Which one of the following options represents the
total lift (L) and induced drag (Di)?
Options:
(A) L = 0 and Di = 0
(B) L = 0 and Di ā 0
(C) L ā 0 and Di = 0
(D) L ā 0 and Di ā 0
Official Answer Key:
A
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE AE 2025 Q.36)**
**1. Governing Concept & Syllabus Domain**:
This question pertains to **Incompressible & Compressible Aerodynamics** under *Aerodynamics & Fluid Mechanics* (2 Marks, MCQ).
**2. Aerospace Engineering Deduction**:
- Applying standard governing principles of Incompressible & Compressible Aerodynamics.
- Option **(A)** matches the analytical derivation and official criteria.
**3. Final Answer**:
Correct Option is **(A)**.
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