1. What is a Propeller Thrust Calculator Under Water?

Definition: This calculator estimates the thrust generated by a propeller operating underwater based on water density, propeller area, velocity, and thrust coefficient.

Purpose: It helps marine engineers, naval architects, and boat designers determine propeller performance in underwater applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( T \) — Thrust (Newtons)
• \( \rho \) — Water density (kg/m³)
• \( A \) — Propeller disc area (m²)
• \( v \) — Velocity of water (m/s)
• \( C_T \) — Thrust coefficient (dimensionless)

Explanation: The thrust is proportional to water density, propeller area, and the square of water velocity, scaled by the thrust coefficient.

3. Importance of Thrust Calculation

Details: Accurate thrust estimation ensures proper vessel propulsion system design, efficiency optimization, and performance prediction.

4. Using the Calculator

Tips: Enter water density (default 1025 kg/m³ for seawater), propeller area, water velocity, and thrust coefficient (default 0.5). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical thrust coefficient value?
A: Most propellers have C_T between 0.3 and 0.7, with 0.5 being a common default value.

Q2: How do I calculate propeller area?
A: Area = π × (propeller diameter/2)². For a 0.5m diameter propeller: A = π × (0.25)² ≈ 0.1963 m².

Q3: Why does water density matter?
A: Thrust is directly proportional to density. Seawater (1025 kg/m³) produces more thrust than freshwater (1000 kg/m³) at same conditions.

Q4: What velocity should I use?
A: Use the water velocity relative to the propeller, which is typically the boat speed plus propeller slip velocity.

Q5: How accurate is this calculation?
A: This provides theoretical maximum thrust. Real-world factors like cavitation, efficiency losses, and hull drag will reduce effective thrust.