Volumetric Flow Rate
Volume of fluid passing per unit time.
Formula
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Example
Wider pipe, more flow
How it works
This formula says how much fluid moves past a cross-section each second: if you know the area of the opening and how fast the fluid is moving, you can find the flow rate. It works because in one unit of time, the fluid travels a distance equal to its velocity, so the amount that passes through is the cross-sectional area multiplied by that distance. In other words, a larger opening or a faster speed both increase the volume carried through.
When to use it
Use this when analyzing fluid moving through pipes, channels, hoses, or ducts, especially when the flow is fairly steady. It is also useful in engineering and physics problems involving water supply, blood flow, air flow, or pump and fan performance.
Worked example, step by step
A pipe has a cross-sectional area of 0.020 m^2 and water flows through it at 3.5 m/s. Use Q = Av Q = 0.020 × 3.5 Q = 0.070 m^3/s So the volumetric flow rate is 0.070 m^3/s, which is 70 liters per second.
Common mistakes to avoid
- Using the pipe’s length instead of its cross-sectional area
- Forgetting to convert units so area and velocity are in compatible SI units
- Mixing up volumetric flow rate with mass flow rate
Did You Know?
Flow rate equals velocity times cross-sectional area, the starting point for designing any pipe network.
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