What is the effect on flow rate when the radius of a flow tube increases?

What is the effect on flow rate when the radius of a flow tube increases?

• A. Flow Rate Decreases
• B. Flow Rate Remains the Same
• C. Flow Rate Increases
• D. Flow Rate Becomes Zero

Answer: (C)

Increasing the radius of a flow tube dramatically raises the flow rate for a given driving pressure. In laminar flow through a circular tube, the flow rate is highly sensitive to radius: it scales with the radius to the fourth power. That means even a modest increase in radius makes the fluid move much more quickly—doubling the radius can increase flow by a factor of 16, tripling by 81, and so on. This happens because a larger radius provides more space for the fluid to pass and greatly reduces the viscous resistance along the walls, so more fluid can be carried per unit time. Therefore, the flow rate increases when the radius increases.

Increasing the radius of a flow tube dramatically raises the flow rate for a given driving pressure. In laminar flow through a circular tube, the flow rate is highly sensitive to radius: it scales with the radius to the fourth power. That means even a modest increase in radius makes the fluid move much more quickly—doubling the radius can increase flow by a factor of 16, tripling by 81, and so on. This happens because a larger radius provides more space for the fluid to pass and greatly reduces the viscous resistance along the walls, so more fluid can be carried per unit time. Therefore, the flow rate increases when the radius increases.