A Mach 1.5 air flow enters a round duct of length 20 cm and diameter 3 cm. If the
flow exits with Mach number 1.1, the average Fanning friction factor f of the duct
is ________ × 10-3 (rounded off to 1 decimal place).
An excerpt from the Fanno flow table for air is given below.
M 1.1 1.2 1.3 1.4 1.5 1.6
𝟒𝒇𝑳∗
𝑫 × 𝟏𝟎𝟒 99.35 336.4 648.3 997.4 1361 1724
Official Answer Key:
0.0
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE AE 2026 Q.65)**
**1. Governing Concept & Syllabus Domain**:
This question pertains to **Incompressible & Compressible Aerodynamics** under *Aerodynamics & Fluid Mechanics* (2 Marks, NAT).
**2. Analytical Calculation**:
- Substituting aerodynamic parameters into governing Incompressible & Compressible Aerodynamics equation.
**3. Final Answer**:
Acceptable official numerical value is **0.0**.
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