1. What is Mach Number?

Definition: Mach number is a dimensionless quantity representing the ratio of flow velocity to the speed of sound in the surrounding medium.

Purpose: It's used in aerodynamics to characterize high-speed flows and determine compressibility effects.

2. How is Mach Number Calculated?

The calculator uses the formula:

Where:

• \( M \) — Mach number (dimensionless)
• \( V \) — Flow velocity (m/s)
• \( \gamma \) — Heat capacity ratio (1.4 for air)
• \( R \) — Specific gas constant (287 J/kg·K for air)
• \( T \) — Absolute temperature (K)

Explanation: The denominator represents the speed of sound in the medium. Mach number compares the object's speed to this speed.

3. Importance of Mach Number

Details: Different flow regimes are characterized by Mach number:

• Subsonic: M < 0.8
• Transonic: 0.8 ≤ M ≤ 1.2
• Supersonic: 1.2 < M < 5
• Hypersonic: M ≥ 5

4. Using the Calculator

Tips: Enter velocity in m/s, heat capacity ratio (default 1.4 for air), gas constant (default 287 J/kg·K for air), and temperature in Kelvin. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the significance of γ = 1.4?
A: 1.4 is the heat capacity ratio (Cp/Cv) for diatomic gases like air at standard conditions.

Q2: Why is temperature in Kelvin important?
A: Speed of sound varies with temperature, so accurate temperature measurement is crucial.

Q3: What's a typical Mach number for commercial aircraft?
A: Most commercial jets cruise at Mach 0.78-0.85 (subsonic).

Q4: How does Mach number affect aerodynamics?
A: As M approaches 1, shock waves form, dramatically changing pressure distribution and drag.

Q5: What's the difference between true Mach and indicated Mach?
A: Indicated Mach is what instruments show; true Mach accounts for instrument errors and actual conditions.