HYD-07

Hazen–Williams velocity

SI form V = 0.849 C R^{0.63} S^{0.54}.

Reading speed

Pipe flowHazen–Williams 1905AWWA

Governing equation

V=0.849\,C\,R^{0.63}S^{0.54}

where

C: HW coefficient (—)
D: Diameter (m)
S: Hydraulic slope (—)
V: Velocity (m/s)
Q: Discharge (m³/s)

Lecture brief

Historical brief

Open-channel and pipe flow were written by Chezy, Manning, Darcy and Weisbach in the nineteenth century, then Bakhmeteff and Bélanger on the hydraulic jump. The sheets compute conveyance, head loss and gradually varied profiles. This sheet (HYD-07 — Hazen–Williams velocity) is the form associated with Hazen–Williams 1905 · AWWA. Working symbols: $C$ , $D$ , $S$ $\rightarrow$ $V$ , $Q$ . Hazen and Williams fitted water-distribution pipes with an exponential resistance law still used in municipal networks.

Purpose

Purpose: compute

V

Q

from

C

D

S

in Hydraulics via

V=0.849\,C\,R^{0.63}S^{0.54}

SI form V = 0.849 C R^{0.63} S^{0.54}. Use it when a real hydraulics question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

C = 130.000\,\mathrm{—}

D = 0.300\,\mathrm{m}

S = 0.004\,\mathrm{—}

, the governing relation

V=0.849\,C\,R^{0.63}S^{0.54}

yields

V = 1.095\,\mathrm{m/s}

Q = 0.077\,\mathrm{m^{3}/s}

. Water near 15 °C, circular full pipe, C is the HW coefficient. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

HW coefficient C130 —Diameter D0.3 mHydraulic slope S0.004 —

Outputs

Velocity V1.095 m/s
Discharge Q0.077 m³/s

Reading speed

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Narration of this film

Water near 15 °C, circular full pipe, C is the HW coefficient.

Hazen and Williams fitted water-distribution pipes with an exponential resistance law still used in municipal networks.

Reading speed

Watch on YouTube