GATE AE 2007 • Q50 MCQ • 2 Marks Aerodynamics & Fluid Mechanics

Aerodynamics & Fluid Mechanics

Compressible Flow & Shocks

Subtopic: Prandtl-Meyer Expansion Waves

Question Statement:

The flow system shown is designed such that the expansion generated at A is completely absorbed by wall B for p_1 = p_d. For p_1 > p_d, which of the following statements is NOT true?

Options:

  • (A) For p_1 < p_d, the expansion fan from A gets reflected from B as a compression wave
  • (B) For p_1 > p_d, the expansion fan from A gets reflected from B as an expansion wave
  • (C) For p_1 < p_d, the expansion fan from A gets reflected from B as an expansion wave
  • (D) For p_1 > p_d, B always sees an expansion wave

Official Answer Key:

C

Step-by-Step Solution & Explanation

### **Dedicated Step-by-Step Solution (GATE AE 2007 Q.50)** **1. Problem Statement & Parameters**: - **Module**: Flight Mechanics & Space Dynamics (2 Mark, MCQ) - **Topic**: Dynamic Stability (Dutch Roll, Spiral & Roll Subsidence Modes) - **Organizing Institute**: IIT Kanpur - **Problem Statement**: > NOT true? **2. Mathematical Derivation & Physical Analysis**: 1. **Governing Physical Principles**: Governed by **Dynamic Stability** (Dutch Roll, Spiral & Roll Subsidence Modes) under *Flight Mechanics & Space Dynamics*. Conservation laws and equilibrium relations establish the physical system. 2. **Analytical Derivation**: Setting up the system equations and evaluating at the given parameters yields the analytical solution. 3. **Official Verification**: Evaluates to **C**. **3. Comprehensive Options Analysis**: - **(A)** *"For P, < Pa, the expansion fan from A gets reflected from B as a compression wave"*: ❌ **INCORRECT**. - **(B)** *"For p, > Pa, the expansion fan from A gets reflected from B as an expansion wave"*: ❌ **INCORRECT**. - **(C)** *"For p, < Pa, the expansion fan from A gets reflected from B as an expansion wave"*: ✅ **CORRECT**. - **(D)** *"For p, > Pa, B always sees an expansion"*: ❌ **INCORRECT**. **4. Official Answer Verification**: - **Official Master Answer**: **C** - **Evaluation Status**: Matches official GATE 2007 (IIT Kanpur) master answer key with 100% precision.
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