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The average velocity in vertical is calculated using a reduction factor multiplied by the surface velocity of the river. This provides a more accurate estimation of the water flow rate throughout the water column.
The calculator uses the formula:
Where:
Explanation: The reduction factor accounts for the velocity profile in vertical direction, where surface velocity is typically higher than the average velocity throughout the water column.
Details: Accurate velocity estimation is crucial for hydraulic calculations, sediment transport studies, flood forecasting, and water resource management.
Tips: Enter the reduction factor (typically between 0.85-0.95 for natural channels) and surface velocity measured at the river surface. Both values must be positive numbers.
Q1: What is a typical value for the reduction factor?
A: For natural rivers, the reduction factor typically ranges from 0.85 to 0.95, depending on channel roughness and flow conditions.
Q2: How is surface velocity measured?
A: Surface velocity can be measured using floats, current meters, or modern techniques like radar or acoustic Doppler instruments.
Q3: Why is average velocity different from surface velocity?
A: Due to friction with the channel bed and banks, velocity is highest at the surface and decreases toward the bottom, making average velocity lower than surface velocity.
Q4: Can this formula be used for all flow conditions?
A: This is a simplified approach. For precise calculations, detailed velocity profiling across the entire cross-section is recommended.
Q5: How does channel shape affect the reduction factor?
A: Wider and deeper channels typically have higher reduction factors, while narrow, shallow channels with rough beds have lower reduction factors.