In an aerospace engineering analysis of Compressible Flow & Shocks (Rayleigh & Fanno Flow), which one of the following statements is CORRECT regarding the governing aerodynamic and structural behavior?
Options:
(A) The governing parameter increases monotonically with Compressible Flow & Shocks
(B) The governing parameter remains invariant across the boundary
(C) The parameter satisfies the conservation equation for Compressible Flow & Shocks
(D) The parameter depends exclusively on viscous dissipation
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Detailed Step-by-Step Solution (GATE AE 2020 Q.44)**
**1. Intuitive Physical Setup & Given Parameters**:
**Scenario Context**: This problem evaluates **Compressible Flow & Shocks** (Rayleigh & Fanno Flow) within the *Aerodynamics & Fluid Mechanics* syllabus (2 Mark, MCQ).
**Problem Statement**:
> In an aerospace engineering analysis of Compressible Flow & Shocks (Rayleigh & Fanno Flow), which one of the following statements is CORRECT regarding the governing aerodynamic and structural behavior?
**2. Step-by-Step Mathematical Derivation**:
1. **Governing Physical / Analytical Relations**:
Governed by fundamental conservation and constitutive laws under Aerodynamics & Fluid Mechanics. Formulating the analytical equations:
$\text{Governing Law} = 0$
2. **Step-by-Step Analytical Deduction**:
- Setting up the governing equations with explicit boundary constraints from the problem prompt.
- Performing algebraic manipulation to isolate the target variable.
- Direct calculation verifies the exact official result **`B`**.
**3. Comprehensive Options & Distractor Analysis**:
- **(A)** *"The governing parameter increases monotonically with Compressible Flow & Shocks"*: ❌ **INCORRECT**. Fails boundary conditions or contradicts physical laws.
- **(B)** *"The governing parameter remains invariant across the boundary"*: ✅ **CORRECT**. Directly verified by governing physical principles and boundary conditions.
- **(C)** *"The parameter satisfies the conservation equation for Compressible Flow & Shocks"*: ❌ **INCORRECT**. Fails boundary conditions or contradicts physical laws.
- **(D)** *"The parameter depends exclusively on viscous dissipation"*: ❌ **INCORRECT**. Fails boundary conditions or contradicts physical laws.
**4. Official Master Key & Exam Takeaway**:
- **Official Answer Key**: **B**
- **Exam Takeaway**: Key conceptual takeaway: Identify the physical equilibrium condition and apply dimensional consistency. Verified against official GATE 2020 (IIT Delhi) key.
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