1. What is Dimensionless Fetch?

Dimensionless Fetch for the empirical prediction methods is the distance over water that the wind blows in a single direction, normalized by friction velocity and gravitational acceleration. It is a key parameter in wave prediction models.

2. How Does the Calculator Work?

The calculator uses the Dimensionless Fetch formula:

Where:

• \( X' \) — Dimensionless Fetch
• \( [g] \) — Gravitational acceleration (9.80665 m/s²)
• \( X \) — Straight Line Distance over which Wind Blows (m)
• \( V_f \) — Friction Velocity (m/s)

Explanation: The formula normalizes the wind fetch distance using friction velocity and gravitational acceleration to create a dimensionless parameter used in wave prediction models.

3. Importance of Dimensionless Fetch Calculation

Details: Dimensionless Fetch is crucial for accurate wave prediction and modeling in oceanography and coastal engineering. It helps in predicting wave height, period, and energy based on wind characteristics over water surfaces.

4. Using the Calculator

Tips: Enter the straight line distance over which wind blows in meters and friction velocity in meters per second. Both values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is friction velocity?
A: Friction Velocity, also called shear velocity, is a form by which a shear stress may be re-written in units of velocity. It represents the velocity scale related to turbulent flow near boundaries.

Q2: Why is dimensionless fetch important in wave prediction?
A: Dimensionless fetch allows for the normalization of wind-wave relationships across different scales and conditions, making wave prediction models more universally applicable.

Q3: What are typical values for dimensionless fetch?
A: Values can vary widely depending on wind conditions and fetch length, typically ranging from 10² to 10⁶ in practical applications.

Q4: How is friction velocity measured or estimated?
A: Friction velocity can be measured directly using specialized instruments or estimated from wind speed profiles using logarithmic wind law relationships.

Q5: What are the limitations of this calculation?
A: The calculation assumes steady wind conditions over a uniform water surface and may not account for complex coastal geometries or varying wind patterns.