What is the flow in ft³/sec for wastewater flowing through a 42in diameter pipe at a rate of 6.5ft/sec?

To find the flow in cubic feet per second (ft³/sec) through a pipe, you can use the formula for the flow rate, which is the cross-sectional area of the pipe multiplied by the velocity of the wastewater.

First, calculate the cross-sectional area of the pipe, which is a circle given by the formula ( A = \pi r^2 ), where ( r ) is the radius of the pipe. The diameter of the pipe is 42 inches, so the radius is half of that, which is 21 inches.

Next, convert the radius into feet:

21 inches ÷ 12 inches/foot = 1.75 feet.

Now, substitute this value into the area formula:

[ A = \pi (1.75)^2 ]

[ A ≈ 3.14 (3.0625) ≈ 9.621 ft² ].

Given that the velocity of the wastewater is 6.5 feet per second, we can now calculate the flow rate:

[ Q = A \cdot v ]

[ Q ≈ 9.621 ft² \cdot 6.5 ft/sec ≈ 62.5 ft³/sec ].

So, when