Longshore Current Speed Calculator

Longshore Current Speed Formula:

\[ V = \frac{5\pi}{16} \cdot \tan(\beta^*) \cdot \gamma_b \cdot \sqrt{g \cdot D} \cdot \sin(\alpha) \cdot \cos(\alpha)}{C_f} \]

Modified Beach Slope (β*):

Breaker Depth Index (γb):

Water Depth (D):

Wave Crest Angle (α):

rad

Bottom Friction Coefficient (Cf):

Longshore Current Speed (V):

m/s

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1. What is Longshore Current Speed?

Longshore Current Speed is the speed of a longshore current, which is a current that flows parallel to the shore within the zone of breaking waves. It plays a crucial role in coastal sediment transport and beach morphology.

2. How Does the Calculator Work?

The calculator uses the Longshore Current Speed formula:

\[ V = \frac{5\pi}{16} \cdot \tan(\beta^*) \cdot \gamma_b \cdot \sqrt{g \cdot D} \cdot \sin(\alpha) \cdot \cos(\alpha)}{C_f} \]

Where:

\( V \) — Longshore Current Speed (m/s)
\( \beta^* \) — Modified Beach Slope
\( \gamma_b \) — Breaker Depth Index
\( g \) — Gravitational acceleration (9.80665 m/s²)
\( D \) — Water Depth (m)
\( \alpha \) — Wave Crest Angle (radians)
\( C_f \) — Bottom Friction Coefficient

Explanation: This formula calculates the speed of longshore currents based on beach characteristics, wave properties, and bottom friction conditions.

3. Importance of Longshore Current Speed Calculation

Details: Accurate calculation of longshore current speed is essential for coastal engineering, beach erosion studies, sediment transport modeling, and coastal management planning.

4. Using the Calculator

Tips: Enter all required parameters with positive values. Modified Beach Slope and Breaker Depth Index should be dimensionless values. Water Depth should be in meters, Wave Crest Angle in radians, and Bottom Friction Coefficient is a dimensionless parameter.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for Longshore Current Speed?
A: Longshore currents typically range from 0.1 to 2.0 m/s, depending on wave conditions, beach slope, and other factors.

Q2: How is Modified Beach Slope determined?
A: Modified Beach Slope is derived from the actual beach slope and accounts for wave setup effects. It depends on beach slope and breaker depth index.

Q3: What is Breaker Depth Index?
A: Breaker Depth Index is the ratio of the wave height at breaking to the water depth at the breakpoint, typically ranging from 0.7 to 1.2.

Q4: Why is Wave Crest Angle important?
A: Wave Crest Angle determines the component of wave energy that drives the longshore current, with maximum current occurring at around 45 degrees.

Q5: How does Bottom Friction Coefficient affect the result?
A: Higher friction coefficients reduce the longshore current speed, as more energy is dissipated through bottom friction.