What is the coefficient of a smooth and rounded outlet hydrant?

What is the coefficient of a smooth and rounded outlet hydrant?

• A. .70
• B. .80
• C. .90
• D. .97

Answer: (C)

Discharge coefficient reflects how actual flow compares to ideal flow after losses from the outlet geometry and fittings are included. A smooth, rounded hydrant outlet minimizes flow separation and turbulence at the exit, so the losses are lower and the discharge coefficient is relatively high compared with rough or irregular outlets. In typical ITM practice, a smooth rounded outlet is given a higher coefficient within the normal range, representing better discharge performance, though it’s still below a perfect, lossless case. That’s why the correct choice corresponds to the higher end of the options, while much lower values would apply to rougher outlets and a near-perfect coefficient isn’t achievable in real hydrants.

Discharge coefficient reflects how actual flow compares to ideal flow after losses from the outlet geometry and fittings are included. A smooth, rounded hydrant outlet minimizes flow separation and turbulence at the exit, so the losses are lower and the discharge coefficient is relatively high compared with rough or irregular outlets. In typical ITM practice, a smooth rounded outlet is given a higher coefficient within the normal range, representing better discharge performance, though it’s still below a perfect, lossless case. That’s why the correct choice corresponds to the higher end of the options, while much lower values would apply to rougher outlets and a near-perfect coefficient isn’t achievable in real hydrants.