1. What is Wetted Perimeter?

The wetted perimeter is the length of the channel cross-section that is in contact with water. For a trapezoidal channel, it includes the bottom width and the two sloped sides.

2. How Does the Calculator Work?

The calculator uses the formula for trapezoidal wetted perimeter:

Where:

• \( P \) — Wetted perimeter (m)
• \( b \) — Bottom width (m)
• \( l \) — Side length (m)
• \( h \) — Height (m)

Explanation: The formula accounts for the bottom width plus twice the length of each sloped side, calculated using the Pythagorean theorem.

3. Importance of Wetted Perimeter

Details: Wetted perimeter is crucial in hydraulic calculations for determining flow resistance, channel efficiency, and in the calculation of hydraulic radius.

4. Using the Calculator

Tips: Enter all dimensions in meters. Ensure all values are positive numbers. The calculator will compute the total wetted perimeter of the trapezoidal channel.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between wetted perimeter and hydraulic radius?
A: Hydraulic radius is the cross-sectional area divided by the wetted perimeter, representing the efficiency of the channel shape.

Q2: How does wetted perimeter affect flow rate?
A: Generally, a smaller wetted perimeter for a given area means less friction and higher flow rates.

Q3: Does this formula work for partially full pipes?
A: No, this is specifically for trapezoidal channels. Circular pipes have different wetted perimeter calculations.

Q4: What are typical values for trapezoidal channels?
A: Side slopes typically range from 1:1 to 4:1 (horizontal:vertical) depending on material and application.

Q5: How accurate is this calculation?
A: The calculation is mathematically exact for ideal trapezoidal shapes. Real-world applications may require adjustments for irregularities.