1. What is Mach Number?

The Mach number is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound. It's named after Austrian physicist Ernst Mach.

2. How Does the Calculator Work?

The calculator uses the Mach number equation:

Where:

• \( M \) — Mach number (dimensionless)
• \( v \) — Velocity of the object (m/s)
• \( \gamma \) — Specific heat ratio (dimensionless)
• \( R \) — Gas constant (J/kg·K)
• \( T \) — Temperature (K)

Explanation: The Mach number compares the object's speed to the speed of sound in the surrounding medium, which depends on the medium's properties and temperature.

3. Importance of Mach Number

Details: Mach number is crucial in aerodynamics. Different flow regimes occur at different Mach numbers:

• Subsonic: M < 0.8
• Transonic: 0.8 < M < 1.2
• Supersonic: 1.2 < M < 5
• Hypersonic: M > 5

4. Using the Calculator

Tips:

• For air at standard conditions, γ ≈ 1.4 and R ≈ 287 J/kg·K
• Temperature must be in Kelvin (K = °C + 273.15)
• All values must be positive numbers

5. Frequently Asked Questions (FAQ)

Q1: What is the speed of sound at sea level?
A: Approximately 343 m/s (1,235 km/h) in air at 20°C (293.15 K).

Q2: Why does Mach number matter in aviation?
A: Aircraft experience different aerodynamic effects as they approach and exceed the speed of sound (M=1).

Q3: How does temperature affect Mach number?
A: Higher temperatures increase the speed of sound, decreasing Mach number for a given velocity.

Q4: What's the difference between true Mach and indicated Mach?
A: Indicated Mach is what instruments show; true Mach accounts for actual atmospheric conditions.

Q5: Can Mach number be used for liquids?
A: While possible, it's rarely used as compressibility effects are minimal in liquids compared to gases.